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PostPosted: Fri Apr 12, 2013 7:33 pm 
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I think the confusion about venting comes from there being only one vent tube used for each valve box, with an exposed [EDIT - silly forum censors n a k e d !!] fill pipe. This is shall we say unconventional but not a disaster assuming the 'unused' vent stub is properly sealed to the pipe, and the single tube meets the free cross-section specs (it probably does). Through venting is preferable to avoid gas trap and condensation.

But where is the tee for the two tank fill lines to the single filler? I'd fail it on inspection if that's exposed within the boot.

That's pretty moot though, I'd fail it on filler mounting anyway, it looks to be impossible to fill without spilling gas into the boot space.

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PostPosted: Fri Apr 12, 2013 8:21 pm 
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TVR owner, you really are rather obnoxious and arrogant, what you have achieved after presumably spending much cash, is a system which is significantly less accurate and sophisticated than the standard off the shelf gas systems.
Perhaps you should consider that as a rank newcomer to fuelling engines on lpg, you don't know more than all the guys that have been doing it for many years or indeed, the manufacturers of more or less every modern gas system currently available?


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PostPosted: Fri Apr 12, 2013 8:40 pm 
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Just noticed another one. CoP 11 says:

Pending the adoption of the common European filling system, the "Bayonet" fitting (see fig.l) should be used for cars and light commercial vehicles. This should be fitted with the axis of the fitting horizontal and with the bayonet pins horizontal. (3 o'clock and 9 o'clock).

So having the filler mounted vertically isn't allowed either.

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PostPosted: Fri Apr 12, 2013 11:28 pm 
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Wow I'm really surprised at all the negativity at the end of my project.

Especially seeing as it's been such a success.

When I first came on here people told me to piggyback the 14CUX, really!!

How in God's name can manipulating a petrol injector signal that's completely wrong for LPG in the first place be better than creating a specific correctly formulated LPG map is beyond me?

Piggyback ECUs only exist to make a LPG installers life easier when converting a petrol car, if the car was manufactured as LPG only you wouldn't need a piggyback at all.

And amazingly people are still suggesting to put a Tornado chip in the 14CUX, honestly my sides are splitting :lol:

Then, when I presented the Canems system people told me it wouldn't work.

Ignored that too.

Finally we completed the project, which works really well, and people are spending their evening sifting through an advisory system to find statements to discredit what we've done.

At best that's small minded, at worst its plain sad.

I'm left thinking "Boy what a friendly forum", NOT!

I worked with a highly respected LPG engineer, an extremely experienced electronics engineer / ECU manufacturer, & two engineers with degrees in automotive engineering to put this together.

I'm inclined to trust these people and their skills, over people of dubious qualification on a forum, people I've never met.

I smell sour grapes, sprinkled liberally with a large dose of a refusal to believe things can be done differently.

Stupidly I thought people might be interested in my project, perhaps it's just hard for some people to break away from piggybacks that are carefully designed to hold the hand of the installer?

Never mind, I'm extremely happy with the end result.

And I didn't even have to put a Gems engine in my TVR :lol:

I'll leave the post up for the benefit of a broader minded & less critical audience.

But for me, It's Topic Closed!


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PostPosted: Sat Apr 13, 2013 1:21 am 
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ChimponGas wrote:
Wow I'm really surprised at all the negativity at the end of my project.
Not negativity, but more a concern that you have gone to an awful lot of time, experimentation and expense to achieve something that, while being an interesting project, could have been achieved far simpler but would still have given you the same end result.
ChimponGas wrote:
How in God's name can manipulating a petrol injector signal that's completely wrong for LPG in the first place be better than creating a specific correctly formulated LPG map is beyond me?
Piggyback ECUs only exist to make a LPG installers life easier when converting a petrol car, if the car was manufactured as LPG only you wouldn't need a piggyback at all.
Because you are manipulating it, that's the whole point. If a car was manufactured to only run on LPG then no, it wouldn't need a second ECU but I know what you are getting at. You have to start from somewhere, you could simply generate fixed length pulses 4 times for each engine revolution and then fit a piggyback ECU that manipulates those fixed length pulses to give a perfect map. It doesn't matter whether you start with a petrol map, an incorrect gas map or a basic map that wouldn't even allow an engine to run, you manipulate it until it is right. Alternatively, you do as you have and generate the map from scratch. It doesn't matter how you achieve it, the end map will be the same.
ChimponGas wrote:
And amazingly people are still suggesting to put a Tornado chip in the 14CUX, honestly my sides are splitting :lol:
No, I suggested you could put a GEMS or Thor engine in instead of the 14CUX and fit a Tornado chip if you wanted a cheap increase in power.
ChimponGas wrote:
Then, when I presented the Canems system people told me it wouldn't work.
I don't think anyone said it wouldn't work, what was said was that there was concern that it might not work as well as it could due to the lack of gas temperature compensation.
ChimponGas wrote:
Finally we completed the project, which works really well, and people are spending their evening sifting through an advisory system to find statements to discredit what we've done.
I didn't have to sift and I wasn't trying to discredit anything you have done. Simply pointing out a couple of areas where I consider it doesn't comply. The fuel filler is very neat although having owned cars with the petrol filler in a similar place I've lost count of the number of times the petrol pump nozzle has emptied it's contents over the bodywork before I've got it near to the filler. I'm surprised the boot doesn't get a regular filling with petrol. You won't do that with LPG but you will get vapour falling into the boot. Although it is advisory, it is the Code of Practice that you need to comply with in order for the installation to be accepted on the UKLPG register. Without which, depending on your insurance company, you may or may not be able to get insurance cover. It's primary focus is on safety and personally I wouldn't consider filling the boot with Propane vapour every time I filled the tank to be particularly safe.
ChimponGas wrote:
I worked with a highly respected LPG engineer, an extremely experienced electronics engineer / ECU manufacturer, & two engineers with degrees in automotive engineering to put this together.
But you could just as easily have worked with just an LPG engineer and got the same end result, in a fraction of the time and cost. Yes, what you achieved is good as an experiment and all those involved should be congratulated on a good job well done but it's a hell of an effort to go to. How good it will be in the depths of winter or in the middle of summer without temperature compensation is a different matter. It may be fine, the effects may not be sufficient to be noticeable or you may need a cold weather map, an average weather map and a stinking hot weather map
ChimponGas wrote:
I smell sour grapes, sprinkled liberally with a large dose of a refusal to believe things can be done differently.
No sour grapes here, each to his own, but it does make me ponder the question, how do you make love? Standing in a hammock? You do seem to go about things in the most complicated way possible. I'd much rather stick to the KISS principle. Keep it simple, there's less to go wrong and when it does you can pick up the required bits or knowledge anywhere.
ChimponGas wrote:
And I didn't even have to put a Gems engine in my TVR :lol:
If it was me doing it and spending the amount of money that you obviously have, I wouldn't put a GEMS in either, I'd go the next step and put the Thor with the vastly superior Bosch ECU, cross bolted bottom end and longer intake tracts to give more torque. But are you saying you've left the 14CUX dodgy distributor in there? Even if the Canems ECU takes over the ignition timing you're still at the mercy of the inferior quality distributor cap and rotor arm that are all you can get these days. Seems to me that the priorities are a bit skewed.

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PostPosted: Sat Apr 13, 2013 2:06 am 
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ChimponGas wrote:
When I first came on here people told me to piggyback the 14CUX, really!!

Yup, you did ask what your options were, and that remains the easiest/cheapest one.
Easy/cheap isn't the be-all of course, but it is a strong driver for most other LPG installs.

ChimponGas wrote:
How in God's name can manipulating a petrol injector signal that's completely wrong for LPG in the first place be better than creating a specific correctly formulated LPG map is beyond me?

No-one claimed it was better; it's just as good. I can fully understand you wanted to improve on the CU14X/dizzy, I've no doubts at all Canems will do that. But that's a complete aside to adding LPG to either system.
The apparent drawback here is that the Canems doesn't seem to do the fuel density corrections necessary for gaseous fuel accuracy. There's no fundamental reason why that can't be developed if striving for perfection.

ChimponGas wrote:
Piggyback ECUs only exist to make a LPG installers life easier when converting a petrol car, if the car was manufactured as LPG only you wouldn't need a piggyback at all.

Yes. If your TVR was like a modern car where the engine management chats away and handshakes with multiple transmission, security and dashboard systems you would appreciate why piggyback is a practical idea.

ChimponGas wrote:
Finally we completed the project, which works really well, and people are spending their evening sifting through an advisory system to find statements to discredit what we've done.

Yes, that usually happens when folk post pictures etc. of installs that appear to breach safety guidelines. Those issues remain unaddressed, aren't you even interested in discussing them with your engineer?

ChimponGas wrote:
At best that's small minded, at worst its plain sad.

As you like. "They" even make us have airbags in new cars and evereyfink ;)

ChimponGas wrote:
I smell sour grapes, sprinkled liberally with a large dose of a refusal to believe things can be done differently.

But what's "different"? At the front end it's just another dual-mapped engine management system. It does indeed seem to avoid doing some established gas practice - the fuel density correction. No-one has explained why that would make it 'better', or even as good. I suspect it is indeed very nearly as good - it's not going to show up in rolling road testing - but that kinda deflates the whole point about supposed "compromises".

At the back end we're just looking at basic safe gas handling, mechanical issues, not ground breaking stuff.

ChimponGas wrote:
Stupidly I thought people might be interested in my project

From all the postings its clear we are interested !

ChimponGas wrote:
perhaps it's just hard for some people to break away from piggybacks that are carefully designed to hold the hand of the installer?

For both pros and DIYers, ease of install is a valid consideration. That is not a Bad Thing of itself. To make it difficult to install e.g. requiring rolling road setting up, requires good cause. You had a good cause, that of generally upgrading the engine management; but thats precious little to do with LPG or piggyback methods of itself.

Some folk will make polished stainless brackets etc. for the "coo" factor and that's fine. It doesn't mean bent perforated strips don't work just as well for less cost/time. They're not even a compromise - but an an equally effective solution within differing budget/cosmetic requirements.
Perhaps its hard for some people to accept there's more than one way to do things and still do it properly ... ah, that's where we came in :)

ChimponGas wrote:
Never mind, I'm extremely happy with the end result.

Good ! But please excuse us where we point out things you may just have missed.

Praps we're just at cross purposes; let me set out my current view of the project overall:
1) Move on from CU14X/dizzy to Canems - well that's a great update for sure, if you can afford the kit and r/road time etc. it'd be a great improvement to a pride'n'joy
2) Getting Canems to do LPG as well - technically very interesting (even if it is reinventing wheels). Just be sure not lose a spoke along the way.
3) Getting acceptable tankage in that awkward frame - most interesting solution, the custom tank fab is a big investment, but good job. But again watch out for that ha'perth of tar.

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PostPosted: Sat Apr 13, 2013 8:23 am 
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I took an interest in this project because I want to do something along the same lines. I had been looking at using MS with its switchable dual map. As both petrol and gas injectors are both 3ohm there would have been no issue with resistance compatibility, the big problem for me is all the features that would have been lost by not using a LPG ECU. My only answer left them would be to keep to the two maps to optimise the ignition for both fuels.

You came along with your ECU with the promise that it is specialy made for running both petrol and LPG. The idea sounded great to me so I had a look at pricing. Adding the LPG option to the camens adds a lot more cost than using a seperate LPG ECU. To then find out that the Camens does not actualy do what it is supposed to do and is still missing the fuel pressure and temperature corrections is a real disapointment. When I come to do my project I will not be using the Camens petrol/lpg ecu but one of teh better known mapable systems and combine that with a LPG ECU to get the best of both worlds.

There are other programable systems that would be capable of doing exactly the same job but do not claim to be a petrol/lpg ecu. The only way you could make that system work perfectly is to use liquid LPG injection as with the pump temprature and pressure are almost constant.


I do actualy like the tank installation and the fabrication is grate. If the car was mine I would have probably kept the filler in the same place if I have moved teh petrol tank as you have done. However I would have fitted a drain to stop it either filling or it dumping its contents into the boot.


To me it seems like you can be deaf to advice and can not accept any constructive critasism. Anyone reading this thread should be able to see the pros and cons of the experimental installation you have done and be fully aware of all advantages and disadvantages in the way the conversion has been made.

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PostPosted: Mon May 15, 2017 2:10 pm 
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Four years and tens of thousands of miles have passed since I started this post, and I'm pleased to say my LPG TVR Chimaera is still delivering exceptional performance, drivability, reliability and fuel economy.

Anyone considering converting a performance vehicle that runs carburetors or as in the case of my TVR Chimaera is burdened with the rather antiquated and virtually unmappable Lucas 14CUX and a distributor may be interested in this project and the Canems duel fuel engine management system. Given we live in a world of cost driven LPG conversions on everyday cars using piggy back LPG ECUs spliced into the vehicle's OEM engine management system I can see why people on this forum struggled to absorb the unique objectives and drivers behind my project, however for those who understand the benefits behind the latest trend of updating classic cars with a petrol engine management system should understand what sets my conversion apart from the normal work-a-day LPG installation.

For me this project was very much an exercise in deep diving engine management systems, mapping, and understanding the unique behaviors of burning LPG in it's gaseous state in a V8 sports car without ruining the car's character and exhilarating performance, as such we start by understanding the benefits of converting a petrol only TVR Chimaera/Griffith to a directly mappable stand alone engine management system, those benefits being performance, fuel economy, throttle response and drivability. These benefits are all well understood and accepted so the trend of fitting stand alone engine management systems to such cars continues to grow with TVR specific kits now available from V8 Developments (MegaSquirt), Canems, Emerald, MBE and many others besides. Owners of older 911 Porsches which have rocketed in price recently are also on this bandwagon, not to mention the likes of Eagle with their wonderful £250,000 Omex equipped improved E-Type and Frontline's £85,000 MGB for the modern world that also uses an Omex ECU. These engine management conversions are never going to be cheep but they are becoming increasingly popular within the classic car community, and it's not just for those cars that ran carbs originally either. Even though the Chimaera & Griffiths of the 1990's came with fuel injection more and more people in TVR circles are accepting the old Lucas 14CUX injection system and especially the ancient distributor ignition system it was paired with can be greatly improved upon by installing a more modern and user mappable engine management system with 3D fuel & ignition control.

With all that out of the way we can now understand the Canems dual fuel ECU simply takes this trend for fitting stand alone engine management systems one step further, this system delivers all the benefits of updating to full engine management on petrol but adds the option of extending the same advantages to run the vehicle on LPG too. Almost halving your fuel costs on your thirsty TVR or classic car at the flick of a switch becomes a very appealing proposition indeed, because the one unavoidable part of owning an older performance car or classic car will always be it's considerable thirst for fuel especially when compared with a modern vehicle.

I make no secret of the fact this has not been a cheap conversion especially when compared with say converting an old Range Rover to LPG, I could have used a kit designed to be used on such a V8 Discovery or Range Rover running the antiquated 14CUX system but that would have been missing the point, a TVR is a performance car so deserves and demands a much better system than that. With Chimaeras and Griffiths going up in price every year more TVR enthusiasts than ever see spending £3k plus to implement an updated stand alone engine management as small potatoes, this also puts paying a little extra for the dual fuel features offered by the Canems duel fuel system into perspective. Of course LPG continues to suffer the stigma of poor drivability, reliability and a loss of performance so given a TVR Chimaera/Griffith is a drivers car it's understandable why anyone looking at such a conversion might be more than a little skeptical.

The good news is people shouldn't be concerned, the benefits offered by the Canems system to directly map both the fuel and especially 3D the ignition tables eliminates the traditional negatives of running gas on such older vehicles that do not benefit from a sophisticated OEM engine management systems with knock control and the convenient connectivity of an OB2 port. Switching to gas on the Canems duel fuel system not only activates the LPG safety solenoids, turns off the petrol injectors and turns on the LPG injectors like an LPG piggyback ECU does butrather than then trying to twist the petrol injector durations for LPG uniquely switches you to your unique LPG fuel and spark tables. We have proved through careful mapping and analysis using a very accurate hub dyno that the ignition advantage is significant, firstly LPG being 110 allows for and demands a lot more ignition advance, but it's the shape of the map where the real improvements are found. The rate of ignition advance required is radically different, close analysis of where peak torque is found at different load and rpm sites within the table eventually serves to build a very different 3D map than the one that delivers best results on petrol.

Of course such systems can only deliver their true potential if a skilled operator using an accurate dyno is involved in the complex mapping process, people should therefore not confuse the Canems duel fuel system with the kind of OBD plug in LPG piggyback ECU designed for the average mechanic to install and get working quickly. I accept this is a niche market product but do respect and acknowledge the experience of some in the LPG world so throughout the process of fine tuning the system on my TVR I've remained open to suggestions, as such I and the ECU designer at Canems have implemented and extensively tested gas pressure and gas temperature correction strategies. On my request David Hampshire of Canems engine management systems implemented both these data inputs taken from a Bosch pressure temp sensor (Prins filter housing mounted), lots of hub dyno time and real world road testing followed with my final conclusions being:

1. Gas pressure correction: This was proven to be a completely unnecessary feature, firstly the flexible nature of a user configurable fuel tables offered by the Canems system (open loop) combined with fast acting wide lambda closed loop feedback serves to provide exceptionally accurate fueling under all load/rpm conditions without resorting to using the pressure correction table, and secondly because my Prins vaporizer has been observed to deliver extremely consistent pressures even under violent WOT acceleration events.

2. Gas temperature correction: While largely unnecessary for the same reasons outlined under gas pressure correction I have found it mildly useful in fine tuning cold starts and the warm up phase on LPG. The effects of temperature on LPG volume and so AFRs is present but not as significant as some would have you believe, the correction requirement is very similar to and in most cases follows inducted air temp, as I already have the benefit of air temperature correction the implementation of gas temperature correction can be considered a nice-to-have rather than essential, as I say I have only really found it offers a small benefit during LPG cold starts and during warm up.

I hope people can now understand the unique nature of this project and the Canems dual fuel system, it is and never will be an alternative to an LPG piggyback ECU and was never designed as such. This post was not intended to present the benefits of the Canems system over an LPG piggyback although there are clearly many if you're considering converting a vehicle that traditionally ran a carb or even one of the earlier half way house engine management systems like the Lucas 14CUX, which as we know only controls fueling and idle management and plays no part in influencing the ignition curve. I must also say if I was looking to convert a Rage Rover/Disco with a more modern engine management system like the GEMs system then I would have simply choosne one of the excellent and cost effective OB2 complaint LPG piggybacks available on the market.

But on a TVR Chimaera/Griffith that runs 14CUX or any classic that originally ran carbs for that matter, the Canems dual fuel system is definitely the way to go, especially if you want to enjoy the considerable cost advantages of LPG while still retaining performance and even improving drivability over the same car running petrol on it's original fuel delivery ignition management system. I've ended up with a TVR that starts on the button and drives perfectly from stone cold in the winter on LPG, delivers 248hp and 263ft/lbs of torque on LPG proving a zero power loss over petrol, created an LPG vehicle that gets from 0-60 in 4.8 seconds and romps on to an easy 153mph. Best of all I've created a TVR that delivers considerably better drivability on LPG than it did burning petrol when running the old Lucas 14CUX & distributor.

And so that finally leads us to my economy results, I left this until last because being a true drivers car if my TVR Chimaera LPG conversion had lost me performance and drivability it would have been a completely pointless exercise, the good news is the project has delivered benefits and improvements in all areas including the cost of fueling the car. Formerly the car consumed petrol at an average rate of 23mpg measured accurately and logged over some 14,000 miles before I ripped out the old Lucas system and embarked on this conversion, following the conversion the car now consumes LPG at 21.3mpg. As we all know due to the differences in petrol & LPG calorific values (by mass) a typical LPG conversion will see fuel consumption drop by 20% (sometimes more), a really good conversion may get this economy drop down to 18% so I have to say I'm delighted with my chemistry defying 7.5%. This 7.5% drop stands as further proof of the benefits of ignition tuning on LPG and the efficiency of the Canems duel fuel system, and to put the cost savings into perspective my 4.0 litre V8 TVR thay once cost me £0.22p a mile to fuel on petrol now costs a mere £0.12p a mile running on LPG and with no disadvantages whatsoever.

I've spent more on this project than most reading this forum would consider acceptable but I'm please to say my £0.10p a mile saving has finally paid for the whole exercise leaving me with a TVR that delivers the average petrol cost equivalent of 45mpg. Best of all it's been a hugely rewarding deep dive into engine management systems, mapping, and the chemistry, burn rates and temperature behaviors of this cheap and readily available low carbon high octane fuel.

I hope all this proves of interest to someone?

Dave.


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PostPosted: Tue May 16, 2017 12:52 pm 
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Dave, first off I'm pleased to hear the results are satisfactory and that, above all, you are happy that the effort was worth it. I also appreciate you were approaching things from a different angle and, despite the hard work, managed to get it all to come together. But, and there had to be a but I'm afraid, you are still comparing what you have now with what you had before. You were running the 14CUX which hasn't been fitted to the LR V8 since 1994. The petrol injection was batch fired per bank so not even sequential and, as you very rightly say, there was no ignition mapping, just a very antiquated distributor with the timing adjusted by springs and weights. The GEMS was an improvement but still far from perfect, and only used from 1995 to 1999, while the Bosch Motronic on the Thor engine was superior still. Comparing what you have with a properly mapped piggyback system on a Motronic and the differences would be far less. A reduction in economy of 8-10% would be more realistic in that case.

Why do TVR owners still insist on running the old 14CUX and not upgrading to a later, vastly superior system anyway? I'm running a V8 Developments engine in my P38 Range Rover and some of the options they offer are far better.

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PostPosted: Tue May 16, 2017 1:47 pm 
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I agree with all the points and sentiments (including the positive sentiments of course) in the two quotes below.

classicswede wrote:
I took an interest in this project because I want to do something along the same lines. I had been looking at using MS with its switchable dual map. As both petrol and gas injectors are both 3ohm there would have been no issue with resistance compatibility, the big problem for me is all the features that would have been lost by not using a LPG ECU. My only answer left them would be to keep to the two maps to optimise the ignition for both fuels.

You came along with your ECU with the promise that it is specialy made for running both petrol and LPG. The idea sounded great to me so I had a look at pricing. Adding the LPG option to the camens adds a lot more cost than using a seperate LPG ECU. To then find out that the Camens does not actualy do what it is supposed to do and is still missing the fuel pressure and temperature corrections is a real disapointment. When I come to do my project I will not be using the Camens petrol/lpg ecu but one of teh better known mapable systems and combine that with a LPG ECU to get the best of both worlds.

There are other programable systems that would be capable of doing exactly the same job but do not claim to be a petrol/lpg ecu. The only way you could make that system work perfectly is to use liquid LPG injection as with the pump temprature and pressure are almost constant.


I do actualy like the tank installation and the fabrication is grate. If the car was mine I would have probably kept the filler in the same place if I have moved teh petrol tank as you have done. However I would have fitted a drain to stop it either filling or it dumping its contents into the boot.


To me it seems like you can be deaf to advice and can not accept any constructive critasism. Anyone reading this thread should be able to see the pros and cons of the experimental installation you have done and be fully aware of all advantages and disadvantages in the way the conversion has been made.

Gilbertd wrote:
Dave, first off I'm pleased to hear the results are satisfactory and that, above all, you are happy that the effort was worth it. I also appreciate you were approaching things from a different angle and, despite the hard work, managed to get it all to come together. But, and there had to be a but I'm afraid, you are still comparing what you have now with what you had before. You were running the 14CUX which hasn't been fitted to the LR V8 since 1994. The petrol injection was batch fired per bank so not even sequential and, as you very rightly say, there was no ignition mapping, just a very antiquated distributor with the timing adjusted by springs and weights. The GEMS was an improvement but still far from perfect, and only used from 1995 to 1999, while the Bosch Motronic on the Thor engine was superior still. Comparing what you have with a properly mapped piggyback system on a Motronic and the differences would be far less. A reduction in economy of 8-10% would be more realistic in that case.

Why do TVR owners still insist on running the old 14CUX and not upgrading to a later, vastly superior system anyway? I'm running a V8 Developments engine in my P38 Range Rover and some of the options they offer are far better.


Gas pressure and temperature correction while not always strictly necessary are always an improvement, I know pretty much how pressure stable the Prins reducers are (and limitation of 335bhp), the Prins system itself compensates for vapour pressure and temperature, we can see the correction percentage on screen in Prins software and the range of fluctuation is usually around 5% as you drive around.. not bad for a reducer but this 5% still represents a 5% margin for fuelling error which your system cannot directly compensate for, so represents an instant 5% margin of error for fuelling (and this is after the reducer has reached temperature). If your system doesn't compensate for pressure your whole setup could be compromised simply by turning the pressure adjuster screw on the front of the reducer but even without turning that screw the pressure will be different in different conditions anyway, e.g. the pressure is often a bit higher when the reducer is still warming up than it is when it is up to temperature, this will be due to a few reasons such as tension of the rubber diaphragm being greater when cold than when warm so helping to resist the reducer's spring pressure. Cheaper and maybe better results could be obtained running an engine management system such as MS with a slave LPG ECU but if such a system were compared to your results (the only fair comparison) the most likely outcome would be near identical results under most conditions with the MS slave LPG system performing better under circumstances when gas temp correction and pressure correction are more important such as cold weather or hot under bonnet temp after idling on a sunny day. The MS with slave LPG system would at least have the advantage of automatically switching back to petrol when you've run out of gas, run out of gas condition detected when gas vapour pressure falls.

I do take exception to some points in this
ChimponGas wrote:
Of course such systems can only deliver their true potential if a skilled operator using an accurate dyno is involved in the complex mapping process, people should therefore not confuse the Canems duel fuel system with the kind of OBD plug in LPG piggyback ECU designed for the average mechanic to install and get working quickly. I accept this is a niche market product but do respect and acknowledge the experience of some in the LPG world so throughout the process of fine tuning the system on my TVR I've remained open to suggestions, as such I and the ECU designer at Canems have implemented and extensively tested gas pressure and gas temperature correction strategies. On my request David Hampshire of Canems engine management systems implemented both these data inputs taken from a Bosch pressure temp sensor (Prins filter housing mounted), lots of hub dyno time and real world road testing followed with my final conclusions being:

1. Gas pressure correction: This was proven to be a completely unnecessary feature, firstly the flexible nature of a user configurable fuel tables offered by the Canems system (open loop) combined with fast acting wide lambda closed loop feedback serves to provide exceptionally accurate fueling under all load/rpm conditions without resorting to using the pressure correction table, and secondly because my Prins vaporizer has been observed to deliver extremely consistent pressures even under violent WOT acceleration events.

2. Gas temperature correction: While largely unnecessary for the same reasons outlined under gas pressure correction I have found it mildly useful in fine tuning cold starts and the warm up phase on LPG. The effects of temperature on LPG volume and so AFRs is present but not as significant as some would have you believe, the correction requirement is very similar to and in most cases follows inducted air temp, as I already have the benefit of air temperature correction the implementation of gas temperature correction can be considered a nice-to-have rather than essential, as I say I have only really found it offers a small benefit during LPG cold starts and during warm up.

I hope people can now understand the unique nature of this project and the Canems dual fuel system, it is and never will be an alternative to an LPG piggyback ECU and was never designed as such. This post was not intended to present the benefits of the Canems system over an LPG piggyback although there are clearly many if you're considering converting a vehicle that traditionally ran a carb or even one of the earlier half way house engine management systems like the Lucas 14CUX, which as we know only controls fueling and idle management and plays no part in influencing the ignition curve. I must also say if I was looking to convert a Rage Rover/Disco with a more modern engine management system like the GEMs system then I would have simply choosne one of the excellent and cost effective OB2 complaint LPG piggybacks available on the market.
Dave.


I'm a full time LPG installer, I regard myself as an expert in the field, I don't often get involved with general mechanics. I'm not an average mechanic trying to get a vehicle to run on LPG as quickly as possible, nor do I use LPG system self tuning facilities or connect LPG ECU's to vehicle OBD ports.
1. I've already mentioned importance of pressure correction and it's advantages not only in terms of accurate fuelling but also in allowing the system to know when to switch back to petrol. If you at some point implemented such system, why not leave it in place and active? If your current reducer ever fails and you fit an identical Prins reducer, and you set it's pressure exactly the same at idle as your current Prins reducer, it's pressure response may still be slightly different to your current reducer. Without pressure correction you'd need to go back to the rolling road after changing such component, may need to go back to the rolling road for tuning as the reducer's response changes with it's age and in different weather etc anyway. Law of physics - if you have an injector nozzle of a certain size and put gas through it at a certain pressure it will flow more gas if you increase the pressure and vice/versa.
2. Even if you can feed an injector with gas at a very stable pressure the temperature is still relevant. Increase the temperature and you decrease the mass of gas injected and vice/versa. The 'some who would have you believe' is anyone who knows the law of physics that relates to this, probably most people. Again the temps on the rolling road will be different to on the road in varying weather conditions.

What you've done is fairly unique and it's an achievement that you pulled it off. Like Gilbert though I have some further buts - Correct to say it is best suited to engines that ran carbs or very old petrol injection systems because a more modern engine might use a 32bit engine management system that not only runs the ignition and fuel injection but also controls fly by wire throttle, boost pressure, VVT, etc etc. If this is aimed at kit cars and the like, the kit car owner might want to weigh up whether to upgrade the engine management and on the same stoke add LPG to an old skool engine at a cost of £3k as a DIY prospect (and then still probably need to come to you for calibration?), or just fit a more modern engine complete with it's loom and engine management system straight out of a scrapyard car and then add a normal sequential LPG system. My mate has a Capri, could have spent thousands on increasing the power and efficiency of the original engine, instead he just fitted a Lexus V8 complete with loom and ECU out of a scrap Lexus, and then added an LPG conversion. Total cost much less than £3k, no messing mapping the petrol side of things, engine makes the big power far more reliably and economically than the original engine ever could (on either fuel), this would still be true even if the original engine had it's fuelling and sparks optimised but the Lexus engine sparks weren't quite optimised on LPG. For under £100 could then even add a system to help get sparks more optimised for LPG, I'm not talking a standalone sparks controller like Megajolt but doesn't need to be... it sits between the CPS and engine management system and simply sends a suitably advanced CPS signal to the engine management system, they are programmable so sparks can be advanced by varying amounts for various rpm ranges. No need to fit the sparks processor right away, could easily be fitted at any time. That's if there was need for a timing advance processor... the Lexus engine has knock sensors which the original petrol ECU uses to automatically advance timing to suit the fuel.

If this project cost you £3k and involved so much time and effort, how much would you charge a customer to supply and calibrate? Presumably the customer could then expect to collect his car from you and it would be set up perfectly on both fuels and remain like that? So what sort of warranty is offered, i.e. is correct fuel mixture covered in case the customer has an exhaust gas analyser and notices mixture is incorrect at any point in the rpm/load range any time after installation (presuming your system doesn't have a MIL light that will come on in case mixture is incorrect)? Or, is this only offered as a DIY project, in which case it is up to the customer to make sure they set the system up to deliver correct mixture and drive-ability under all vehicle operating conditions?

Simon

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PostPosted: Tue May 16, 2017 6:31 pm 
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Thanks for your comments chaps, firstly a couple of points on gas pressure & temp:

1. I implemented both and still have these features

2. Extensive on road and hub dyno evaluation proves them to be largely unnecessary

Horsepower and torque outputs along with carefully monitored AFRs at all temperatures, throttle openings and engine loads prove this. I'm working with accurate feedback data in real time and using a sophisticated hub dyno (superior to a rolling road) to measure exactly whats going on, the environment is closer to a lab testing cell than you might imagine. However, studying the chemical makeup and temperature induced volume change behaviors of propane I could certainly see why the temperature correction might be beneficial, this (and only this) is why I bothered to implement it at all. But like anything theory is one thing, you can have all the theory in the world but it's not until you test it and analyze the data that you find the truth under real world operating conditions.

Personally I just don't understand what the advantage there would be in running a stand alone ECU (MegaSquirt in your example) spliced into another piggyback LPG ECU when I have a far neater one box stand alone ECU solution in my Canems Dual Fuel ECU that does it all anyway. There seems to be a fixation in the LPG industry with splicing slave ECUs to the master ECU, lets be honest with ourselves here chaps this practice only exists because a petrol car is being converted (tricked) into metering a fuel the master ECU was never designed to control. If an OEM manufacturer's engine management design team was to set out to create a dual fuel vehicle from scratch they would start with a clean sheet of paper, they certainly wouldn't be cobbling two ECU's together in some sort of Heath Robinson workaround hash-up.

We must also accept a considerable amount of processing power on a LPG piggyback ECU is set aside for the express purpose of fooling the OEM ECU into believing the vehicle is still running on petrol, emulation this & that... call it what you will but it's all just tricking the OEM ECU so it doesn't throw a code and go into limp home mode. Nobody could argue the need for all this master ECU trickery is a good thing, and no one would design a system this way if they had half a chance to do things properly with a clean sheet of paper approach. It's no surprise to me LPG has such a bad reputation and presents so many engine management warning light events with such systems relying on what is fundamentally a process of tricking one computer with another. With engine management systems so sophisticated these days the process of making LPG conversions work must be like an arms race where emulation after emulation strategies must be implemented just to make the car run and to ensure fault codes aren't thrown up right left and centre.

Of course my TVR is very different animal, burdened from birth with the archaic Lucas 14CUX and worse still it's prehistoric distributor ignition, literally anything in the world of engine management would be better. Indeed when you boil it all down all the Canems system is, is straight up & down early nineties engine management technology with a user friendly inteface, it's batch fired port injection operating the Ford EDIS type wasted spark ignition for heavens sake so it's really no more sophisticated than a 1990 Mk3 Ford Fiesta, indeed it uses the very same coil packs (two of them obviously) from said Mk3 Fiesta. Like most entry level stand alone ECUs the Canems system uses technology that in engine management terms is as old as the hills, you couldn't even begin to compare it to something even from the year 2000 let alone what we have now, as I've said before if the car started life with even a slightly more up-to-date engine management system there would indeed be a strong argument for just slapping an LPG piggyback on the OEM ECU and having done with it, but that's not the animal we're dealing with here.

TVR used the 14CUX from the days of the V8s model introduced in 1990 and stuck with it right to the end of Chimaera production in 2003 (yes that's 2003!), by 1994 Land Rover had already moved on but TVR were stuck with that old 14CUX right up to 2003 by which time the system was comically out of date. The 14CUX is of course virtually unmappable, Mark Adams makes some pretty bold claims for what he can do with it and there are others who've had some recent success hacking the code, but at the end of the day with the ignition side handled by a completely separate device there's only so much you can do with fuel to make any kind of meaningful difference.

What I can tell you is there are people out there working with Mark Adams on converting their TVR Chimaera to the Bosch Motronic (Thor) system but it's more a complicated exercise than you might think, TVR themselves ran a test mule Chimaera in the late nineties on the GEMs system but Land Rover wouldn't supply the ECU ect so that one fell at the first hurdle, LR probably wanted to get shot of their stock of old 14CUX systems gathering dust in a Solihul shed that realistically would only have just been scrapped without TVR using them up. So with all TVR Chimaera & Griffith owners stuck with the 14CUX/distributor setup and the Bosch Motronic conversion presenting certain challenges owners of these Rover V8 TVRs wanting to update and improve tend to choose a plug & play (with loom) stand alone ECU kit from Emerald, MBE (TVR Power exclusive), MegaSquirt (kits from various sources), Canems (Lloyd Specialist Developments) and many others.

Like I say all you're really getting with these kits is mid nineties engine management technology that offers user friendly mapping software as part of the package, of course a mid nineties tech ECU you can map is infinitely better than the locked down 14CUX and 3D mappable wasted spark ignition is light years ahead of a distributor so this is why people are happy spend £3,000 plus fitting such systems to their Rover V8 engined TVRs. To be honest a TVR Chimaera or Griffith would be far easier to tune if it was on a carb which is why you find people on a budget and suffering 14CUX issues tend to slap a Holly on top and have done with it.

All I've done with my Chimaera is do what so many op for which is to fit a mid nineties tech stand alone engine management system, as such it's still ancient technology but it is way way better than the 14CUX & distributor, the real difference in selecting Camem's duel fuel ECU model over their slightly cheaper petrol only offering is at a flick of a switch I can can give my old school V8 analogue muscle/sports car 45mpg (petrol cost equivalent) fuel economy, while still retaining it's visceral, brutal and intoxicating performance. The fact is also drives way nicer on LPG than it ever did on the locked down 14CUX is just a nice bonus, I guess you either get TVRs or you don't.

It's all about a raw back to basics driving experience we've all lost in modern cars, this combined with an AC Cobra sound track ringing in your ears as you live out your Le Man fantasies as you blast past another anodyne and sterile Porsche Boxster or BMW Z4, personally I love all that but what really makes me smile is knowing as I smoke these modern dullards I'm doing it for a lot less fuel cost than they would ever achieve or believe.

Do you get me now boys?

Dave :twisted:


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PostPosted: Tue May 16, 2017 8:26 pm 
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I got it all along and agree that sticking a piggy back system on a 14CUX equipped motor would not only be a waste of time and money but wouldn't work particularly well either. My only query is that I would have thought it would be cheaper and simpler to upgrade to a Thor with the Motoronic petrol ECU and piggy back that. Mark Adams does a stand alone Thor ECU already fitted with the Tornado chip for 500 notes specifically so that engine can be used in a TVR or similar. That gets around the problem of using one from a P38 Range Rover or Discovery when it needs a data stream from the rest of the car to turn off the immobiliser. I would have thought that would be a viable way forward, particularly if tied in with one of these http://www.v8developments.co.uk/product ... ndex.shtml

It doesn't surprise me that LR wanted to shift the old 14CUX motors to TVR as I assume the TVR isn't imported to the US. They insisted on full OBD2 compliance from 1996 and even the GEMS struggled to meet the requirements as it isn't fully OBD2 compliant (while it can be read by a generic code reader some things give some very odd readings). When it became mandatory in Europe in 2000, swapping to the Motronic would have made perfect sense. Not only have you got a superior system but it is fully OBD2 compliant too (and used in no end of other cars from numerous manufacturers with a fairly simple change to the firmware).

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PostPosted: Tue May 16, 2017 9:57 pm 
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There seems to be plenty lack of understanding, or at least lack of thinking around the toipic, appearing in this thread all of a sudden.

OEM ECUs will OBDB compliant because of outside regulation. This means that a mechanic unfamiliar with that particular car can quickly ascertain what is causing a particular fault. For this instal, the user/owner can plug in a laptop and interrogate and alter the ECU settings directly - this isn't an option to the average garage mechanic and the user/owner is in a much better postion with his CANEMS or Megasquirt or GEMS ECU than anyone simply restricted to OBDB type information. Some of these aftermarket systems are way more powerful and sophisticated than the limited functionality accessible on an OEM setup.

The user/owner here isn't a professional nor a member of the trade body who wrote cop11. As such, he's not bound by it nor obliged to follow the guidance given in cop11, subject to his insurance company's opinions. Earlier in the thread, the cop11 language was quoted as "should be" and then this was used as evidence for "isn't allowed". If the trade body wanted to say "isn't allowed" they could have done that, but they didn't, so it's simply wrong to impute that. Furthermore, given that this installation isn't new, the appropriate test, were it to be appropriate to apply at all, would be to check against the wording cop11 had at the time the car was converted.

Temperature and pressure adjustments:- the system clearly works so these are obviously not deal breakers. For gas pressure, with a system referenced to manifold vacuum, the reducer will largely self adjust as the spring loaded diaphragm belches gas into the rail containing the injectors. The typical range of over/under pressure over the life of a tankful of lpg will be plus/minus 3 per cent of the injection time. It'll be rich on overrun when the throttle is snapped shut as the reducer can't take back gas that isn't being used but other than that it is almost self adjusting. For gas temperature, this doesn't quite follow air temperature (which the ECU will adjust for) but the two will broadly be affected by the same factors, namely being bottled up in stop-go traffic versus running in free air, which will see both numbers rise by ~30'c. Once again, it is partially factored in again by proxy.

One poster has expressed a very negative view as though the original poster is more of an ingenue than an engineer. It should be pointed out that the original poster has built and programmed a working system from scratch and not fitted a piggy-back self calibrating kit.

I'd challenge everyone who wants to criticise to have a go at it from first principles without using a car ECU or even a fuelling map as a starting point.

kind regards
Marek


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PostPosted: Wed May 17, 2017 9:33 am 
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Marek, I think you may be taking my comments out of context. I'm in admiration of what has been done but I only mentioned the OBD2 compliance as a starting point. The OP has stared off with a car that was using the very old 14CUX petrol injection system and didn't go down the piggy back route as the existing petrol injection system is very crude. It isn't sequential and batch fires the petrol injectors per bank while the ignition is dealt with by a distributor that adjusts the timing using springs and weights. It also uses an ignition amplifier which is notoriously unreliable with a habit of failing without warning when it feels like it (I used to carry a spare in the boot of my 14CUX equipped Classic Range Rover for that just in case moment). My comments are that if the starting point had been a vastly superior modern petrol injection system such as the Mototronic, particularly one that has been re-mapped by Mark Adams or similar, then a piggy back system would have achieved the same results. The petrol system would be far better in the first place so the manipulation would only need to be done within the LPG ECU. The fact that it is OBD2 compliant is irrelevant but it shows the progress made by OEM systems.

As for the wording of CoP11, you need to remember that it is a generic standard written to cater for an install in any vehicle. Each installation is going to be different so to stipulate that something must be done in a certain way isn't always going to apply. If something is done that is outside the 'should be' as long as it can be shown that the way it has been done is as safe or safer than doing it the way the guidance says, then an inspector should pass it for insurance purposes. Without going back through the whole thread I think the main thing I didn't approve of, and that also didn't meet CoP11, was the location of the filler which allowed spilt gas from removing the filler nozzle to pool in the boot. I recently saw a Romanian registered Peugeot filling up where the filler nozzle was mounted under the rear parcel shelf inside the boot so the boot had to be opened to access it. The owner filled up, removed the nozzle and then left the boot open while he went to pay for the fuel so the bootful of vapour could dissipate. Not ideal if you are in a hurry and the precise reason why CoP11 says the filler should be external.

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PostPosted: Wed May 17, 2017 10:15 am 
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Mine and Gilberts posts nearly crossed, still I don't see a reason to edit my post below except to add here that I agree with Gilbert's 'out of context' point.

I don't know if anyone else has put any emphasis on importance of OBD2 and COP11, I haven't. No need for OBD2, the only reason I mentioned OBD2 is that on vehicles with it the engine warning light comes on to alert the driver if fuelling isn't right, which relates to my warranty point below.

Just because something works doesn't mean it wouldn't work better with a few changes, here I'm talking about temperature and pressure correction. With hindsight in my last post I should have asked Champongas to comment on what I said about different pressure through same size nozzle effecting fuelling and gas temperature variance effecting fuelling... In fact I'll ask you to comment now. You said yourself that gas temperature isn't directly related to air temperature (I'd say of course it isn't), do you believe in the law of physics which says a gas is more dense when it is cooler? A system that doesn't compensate for gas temperature variances therefore has that margin of error on mixture? My findings agree with the law of physics, this is what we should expect because findings that don't agree with laws of physics are wrong.

I don't know if it's posted anywhere that the Prins reducer has been referenced to manifold pressure, Prins reducers generally are not referenced to manifold pressure, they don't come supplied with a manifold pressure connection even lol.. Not that it makes much difference regards the type of reducer pressure fluctuation that I was talking about. Where do you get +-3% over the tank full of LPG pressure correction from? How can you quote pressure fluctuations for a reducer that you're clearly not familiar with? Unless your intended meaning is that there is some sort of self compensation going on because gas temp and air temp may rise and fall together most of the time, what is factored in by proxy? There is little correlation between gas temp and air temp, gas temp starts off immediately at air temp when first switching to gas from a cold (but warming) engine, depending on coolant changeover temperature gas temp may then fall below air temp but it will quickly rise to way above air temp, under most engine loads gas temp will be way above air temp but when booting it gas temp will fall, you cannot accurately predict gas temp because it is affected by many factors including temperature of the liquid gas in the tank and air temperature.

The OP has done well with what he's done but has spent £3k on changing the engine management system, though this does include the combined LPG system. To be fair to myself and others posting here, the OP has at times seemed to wave this in our face as a superior way of doing things... but some of us, while we can appreciate the achievement, are far from convinced it is superior.

In the last paragraph of my last post I asked questions about whether the OP would be willing to supply and fit this system for customers with a warranty, a warranty that would allow customers to come back for retune if they noticed fuelling changed in different operating conditions (which with the absence of a MIL light will mean the customer noticing incorrect fuelling by other means such as monitoring lambda themselves). If this was running the Thor petrol ECU (as per Gilbert's point) and was fitted with an aftermarket LPG controller, any LPG installer in the land would supply and fit including a warranty that would allow the customer to return for it sorting if the Mil light ever came on. I am aware Mil lights don't come on on UK spec Rangerovers but that's rather beside the point because it would be the same story with any LPG conversion of any engine, not just conversions of the very forgiving old-skool Rover V8.

I wouldn't have much of a problem doing the fuelling map on an aftermarket petrol ECU to suit a Rover V8, some of the LPG ECU's I fit make a record of the petrol map as you drive around on petrol.. It would be fairly simple to interpret such data and then enter it directly into an aftermarket petrol ECU.

Simon

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PostPosted: Wed May 17, 2017 10:53 am 
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I don't have a problem with either of the last two posts. Cop11 is a very useful document and it is of great assistance to the amateur who gets an insight into how a professional is to be asked to approach a conversion. Similarly, any diagnostic tools that can be made available to the end user are an asset. The context of my OBDB comment is primarily that the fitment of an aftermarket ECU (e.g. Megasquirt) will typically give the end user much more than just OBDB information. I often have a second digital dashboard attached and datalog whole journeys - it's too easy and it's free.

The piggy-back approach is well suited to converting new cars which have no issues when running petrol but are a less certain starting point when using semi life expired components or a poor petrol ECU (or perhaps even carburettors). This would likely entail far more work and research than any off of the shelf solution.

My comments on gas pressure and temperature variation are based from looking at datalogs which show how much percentage adjustment is being made to injection pulsewidth at any particular time. There is remarkably little by way of variation. It isn't zero, but neither is it moving like a yo-yo. The only significant movement in the gas pressure adjustment comes when the throttle is snapped shut which results in the engine being overfuelled for about 0.8seconds. (A piggy-back system may well have a "fuel cut on overrun" at this point if the petrol ECU makes it so.)

You are more than welcome to download a free copy of Megalogviwer and look at a typical datalog - just pm me your email details.

The original poster's car has been running lpg for about three years now, so presumably he has done something right somewhere. It is clearly in a different category to a stack-em-high sell-em-cheap done-in-a day conversion for an end user who simply wants to halve the price of a fillup.

kind regards
Marek


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PostPosted: Wed May 17, 2017 12:26 pm 
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Merek makes some good points, people should understand this project was a personal deep dive into engine management first principles, it's as far off slapping an LPG piggyback ECU on my ancient original 14CUX ECU as you could imagine, and unsurprisingly the results are in a different galaxy to such a crude approach. Admittedly what I have is still an early nineties tech batch fired port injection system with wasted spark but people need to understand this is a map from scratch exercise using a stand alone ECU on a performance car all be it one using the venerable old skool Rover V8.

If any of the contributors on this post have mapped a vehicle with a stand alone ECU they will understand whats involved, it's infinitely more complex work than calibrating an LPG piggy back ECU which are essentially designed to be up and running with minimum fuss within an hour of fitting. I've reviewed a number of LPG piggyback systems and the software they use, the newer breed of these systems are very clever indeed but the real cleverness centres around how the ECU designers have made them so easy for an average mechanic to get up and running without the need for years of engine management knowledge and engine mapping experience.

A stand alone ECU is a very different animal, the complete control over every parameter allows the mapper ultimate flexibility, but in the hands of the inexperienced this total control is a very dangerous thing indeed. LPG piggyback ECU designers know this and they understand their market aren't true engine mappers but guys trying to make a living out of price driven LPG installation that must work perfectly within 30 minutes or so of being fitted. This is why LPG piggyback ECU designers invest so much of their energies in self calibration algorithms and strategies designed to essentially use processor power to calibrate itself with little more required from the installer than a few clicks of his mouse and 30 minutes or so of driving the vehicle.

Its all very different in the case of my Canems Duel Fuel stand alone ECU system, all mapping work must start from scratch with none of the hand holding provided by LPG piggybacks on offer, of course all this mapping work demands a skilled mapper be involved and must also be done twice because there are two very different fuel types requiring very unique calibrations. There's no twisting the wrong petrol information to try and make it right for LPG here, you must start from scratch to build perfect fuel and ignition maps on each fuel, as such its at least four times the work requiring considerably more knowledge, skill and time than the calibration of a typical LPG piggyback that's been expressly designed with ease and speed of calibration in mind.

Does all this make the Canems dual fuel system better than an LPG piggyback system, well that very much depends on the vehicle and the generation of the petrol engine management system it's already running. And this is the point I think most are missing here, if I'd started with a vehicle that had a more up-to-date engine management system than the dreadfully antiquated and rather crude fuel only narrow band controlled Lucas 14CUX then things would start to swing towards splicing in one of the excellent modern LPG piggyback ECUs, but that's just not the case with my TVR.

It's really important people reading this post understand the Canems Dual Fuel system is not and was never designed as a competitor to the many excellent an LPG piggyback ECUs available specifically designed for more modern vehicles, it isn't even an option for those seeking to cheaply convert something like a 14CUX equipped Rangie or Disco because the cost of it would probably be twice the value of the whole vehicle being converted. To help understand why the Canems system even exists you need to forget the whole LPG element for a minute, if we just focus on petrol the Canems ECUs are just like any other popular stand alone ECU from Emerald, MegaSquirt, MBE, DTA, Omex ect ect. These systems are designed for people running a classic on carbs who are looking to implement injection/distributorless ignition which as I've said before is a huge trend in the old car world these days, these stand alone ECUs are also ideal for owners of vehicles fitted with mechanical injection or even early electronic fuel injection systems (like the 14CUX) who want to improve performance, reliability, drivability and fuel economy.

Like so many classic car owners these days Merek is converting his originally carburetored E-Type to engine management, on petrol alone he will see huge benefits using his MegaSquirt ECU over how the car functioned on carbs and a distributor, it's a brilliant project and we should all be behind him offering encouragement & support. I've been involved in many such engine management conversions and can assure you a correctly mapped classic car running such a stand alone engine management systems will always be completely transformed, it's easy to forget what it was like back in the days of carburetors and I suspect many reading this post are even too young to have experienced the pish poor cold starts, flat spots, poor fuel economy and drivability carbs deliver when compared with fuel injection. The whole LPG element Merek and I have chosen to take on is really just a logical extension of this practice, Merek is going his own way by using a MegaSquirt ECU while I chose to short cut many of the challenges I'm sure he's faced by using a system specifically designed by an engine management expert to deliver a true dual fuel solution from the word go. In the case of both projects which in many respects are frighteningly similar there will inevitably be the requirement for development work, I just chose the Canems path to shortcut a huge amount of this development work because David Hampshire of Canems Engine Management Sytems had already done 98% of it for me.

The MegaSquirt product is very feature rich offering way more features and user configuration than my Canems system, but the truth is many of these complex features you just don't need, these additional complexities can just as easily get you in a muddle as help you deliver the right result because it's all too easy to end up layering conflicting correction strategies over correction strategies. The Canems system takes a slightly different approach, David Hampshire's design brief for his products being to only give you the features you really need. Don't get me wrong there are still hundreds of features and strategies, it's just they're the ones that make a real difference and are then presented in a way that makes for less opportunity to tie yourself in knots, because even mapping a simple stand alone ECU from scratch is a complex business indeed. The Canems Duel Fuel ECU then scores it's final goal by offering LPG functionally straight out of the box, so rather than hours of soldering to build your own bespoke dual fuel MegaSquirt ECU you get all that done for you in a proven package that doesn't require the skills of an experienced electronics engineer to construct.

I have the upmost respect for those like Merek who is building his own bespoke dual fuel MegaSquirt ECU, it must be a deeply rewarding project, I just selected the Canems path because I'm all too aware of how much time and effort David Hampshire had already put into developing the system. Going Canems meant I was able to short cut a lot of this development work so I could concentrate on the not to be underestimated task of mapping the system on both fuels. That's not to say I didn't get involved in further developing the system, with only two other Canems duel fuel ECUs out there functioning when I selected it (one being David Hampshire's own and the other running on Lloyd Specialist Development's Range Rover) I knew there would be some tweaks along the way.

But because so much of the development work was done already I was able to get the system working brilliantly on my TVR in very short order, I then waited over 3 years during which time the car has performed flawlessly before I chose to return to this post and reveal my results. I feel over 3 years of consistent use over tens of thousands of miles unquestionably and conclusively proves it's reliability, performance and efficiency. Like I've said countless times the Canems Dual Fuel system is not for everyone, but for someone with a classic car on carbs who's looking to move to engine management it's absolutely perfect, and equally ideal for someone with a more modern classic from the 70's or 80's with an early injection system.

Hopefully placing the project in this context helps to give the perspective it deserves, evaluated by someone who understands the potential benefits of such a system on an traditional classic or modern classic car I trust the results speak for themselves and this post proves it's worth to anyone considering a similar project. I think my only mistake may have been to post my project on an LPG forum where modern vehicles being converted with modern piggyback LPG ECUs are the primarily topic of discussion, perhaps I should have chosen a classic car forum where the project may well have been better received?

Thanks to everyone who followed this post, even the Doubting Thomas', Nay Sayers and the people who comically suggested I should cobble an LPG piggyback ECU on the old 14CUX system TVR originally inflicted on my beautiful and very rapid modern classic Chimaera.

I genuinely hope you've all found it of interest?

Dave.


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PostPosted: Thu May 18, 2017 2:22 pm 
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I am glad you are happy with how it all turned out and is all working as you want.

If going down this path I would have still chosen Megasquirt over anything else based on knowing it works and price.

The problem using a lesser known system is will the support be there in years to come?

There are still a couple of safety issues as pointed out but as long as you are happy with the risk yourself then that is fine.

There are many cars out there with a stand alone ecu running both gas and petrol since way before you did this so yes you are right that there is a demand for this type of conversion

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PostPosted: Thu May 18, 2017 7:16 pm 
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ChimponGas wrote:
Admittedly what I have is still an early nineties tech batch fired port injection system with wasted spark
Huh? are you saying that after all this effort it's still only batch firing and not fully sequential?
ChimponGas wrote:
LPG piggyback ECU designers know this and they understand their market aren't true engine mappers but guys trying to make a living out of price driven LPG installation that must work perfectly within 30 minutes or so of being fitted. This is why LPG piggyback ECU designers invest so much of their energies in self calibration algorithms and strategies designed to essentially use processor power to calibrate itself with little more required from the installer than a few clicks of his mouse and 30 minutes or so of driving the vehicle.
Yet even with all this the quick self calibration will only ever get it close, to get it correct takes much longer and does involve an understanding of mapping.
ChimponGas wrote:
Does all this make the Canems dual fuel system better than an LPG piggyback system, well that very much depends on the vehicle and the generation of the petrol engine management system it's already running. And this is the point I think most are missing here, if I'd started with a vehicle that had a more up-to-date engine management system than the dreadfully antiquated and rather crude fuel only narrow band controlled Lucas 14CUX then things would start to swing towards splicing in one of the excellent modern LPG piggyback ECUs, but that's just not the case with my TVR.
Which is why I've asked why you didn't go down the route of updating the petrol system to a Motronic in the first place? The actual engines are interchangeable with only very minor differences (crank nose length and cam sprocket being the main differences) and with the benefit of a much stronger bottom end.
ChimponGas wrote:
These systems are designed for people running a classic on carbs who are looking to implement injection/distributorless ignition which as I've said before is a huge trend in the old car world these days, these stand alone ECUs are also ideal for owners of vehicles fitted with mechanical injection or even early electronic fuel injection systems (like the 14CUX) who want to improve performance, reliability, drivability and fuel economy.
But if using the LR V8, ignoring the LPG side of things for the moment, the same could be achieved with a Motronic. You'd also have the benefit of a decent system if you did decide to upgrade to LPG with an off the shelf piggy back system.
ChimponGas wrote:
it's easy to forget what it was like back in the days of carburetors and I suspect many reading this post are even too young to have experienced the pish poor cold starts, flat spots, poor fuel economy and drivability carbs deliver when compared with fuel injection.
I'm easily old enough to remember all those things as well as carb icing in the winter, stuck needle valves causing fuel to pour out of every orifice and vapour locks caused by the petrol boiling in the fuel lines before it even gets to the carb. I'm wholeheartedly behind you in updating to injection and I for one would never want to go back to running a car on carbs.
ChimponGas wrote:
I think my only mistake may have been to post my project on an LPG forum where modern vehicles being converted with modern piggyback LPG ECUs are the primarily topic of discussion, perhaps I should have chosen a classic car forum where the project may well have been better received?
No I don't think you did post in the wrong place. It has been followed with interest by a number of people with varying levels of experience. The reason piggy back systems are the primary topic is because that is what the vast majority run and many of the posts on here are from people that have these systems, have a problem and come here for help and advice. Most of what you posted will have gone completely over their heads as their only understanding of LPG systems is that they make their car cheap to run and have no interest in how or what lives under the bonnet. That, unfortunately, is how many people regard a car these days, even manufacturers are starting to describe them as white goods, something to be used and replaced, rather than repaired, when it goes wrong. Try buying something as basic as a gasket set, let alone a set of big end shells, for a modern engine these days.

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PostPosted: Fri May 19, 2017 6:13 pm 
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Marek, Light heartedly mate... I look at fuel trims enough as part of making a living and certainly wouldn't want a digital dash constantly feeding me info that takes me right back to work mode . I have a mate who has one, other mates tell him it's a bit geeky :lol:

Champongas, not having a go, what you've done is a good achievement, but again got to nod to some of what Gilbert's said.

Batch firing is a bit of a compromise for petrol because in certain conditions it is more likely to wet manifolds and cannot offer the same per cylinder control over enrichment in acceleration; When it comes to LPG manifold wetting is never an issue but there can be a worse issue concerning the extra latency of LPG injectors over petrol injectors, which can ultimately lead to less accurate fuelling (the latency concern is doubled with batch firing).

LPG ECU's are piggyback because it is the only way that they could possibly be on modern vehicles - Unless you can set Canems up to talk on canbus to gearbox ECU's, dash ECU's, body ECU's, immobiliser system, control aspects of modern engines such as VVT / Valvetronic / boost control / EGR / flexfuel / multiple wideband lambdas on the same cylinder bank (e.g. Toyota) / change of injection strategy (Mazda, or you might not get enough fuelling at high load), fuel pressure monitoring with variable fuel pump control (e.g. Ford), fly by wire throttle, cruise control, idle air control, evap purge valve control (with anticipation of extra air and fuel vapour effecting trims, e.g. Ford V8 supercharged), aircon clutch control with idle speed correction, traction control. I don't see any shortfalls to the piggy back idea, it makes absolute total sense for converting modern vehicles. Half of the piggy back ECU's processing power isn't wasted on emulation, the only emulation necessary is as simple as closing a resistor across petrol injector wiring, but even if half of a piggy back ECUs processing power was wasted on emulation it would still likely have many times more processing power remaining than Canems. Some modern vehicle ECU's have more than one processor chip, two ECUs built into one housing which can share data across a chipbus. When we add a piggyback ECU the only data that needs to be transferred is petrol injector pulse duration, so in a very similar way to some manufacturer's petrol ECU's we have two ECUs sharing data, the only difference is now we have two ECUs in separate boxes and the datastream between them is all in one direction.. it is all that is necessary.

Better installers don't use gimmicky self tuning facilities built into some piggyback ECU's, we 'map' them properly. This isn't a standalone map, it is a map which interprets petrol injector pulses into correct pulse width for the LPG injectors (and the ECU automatically controls the peak and hold characteristics). What would be the sense in disabling the petrol ECU (which combines all the above mentioned features, plus runs the ignition), and then having to re-invent those same features again in an aftermarket ECU like Canems, when all the LPG ECU has to do is factor in a twiddle factor to the length of the petrol injector pulse duration.. There is a perfectly good map built into the petrol ECU by the manufacturer of the vehicle who probably spent £millions on the ECU with the vehicle and all it's systems and other ECU's/modules in mind. Sure if you change the design of the engine or chuck on a big turbo that map might be wrong and you might have to start again, but faster and better results still might be possible remapping the original ECU than trying to redo from start.. and if you're adding a big turbo or building the engine to handle 10000rpm you probably won't want to use batch firing, especially if an LPG conversion is in mind.

Simon

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