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PostPosted: Tue Jan 25, 2011 10:47 pm 
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Thought it may be of interest to jot down a few things about the up and coming front end swap on our 1996 Discovery, from a BRC Just Heavy system fitted in 2003, to a new OMVL DreamXXI N system.

First problems with the JH system occured after a spot of welding and a dead ECU was diagnosed. This was fixed by a friend of my wife for a few drinks and continued to work well for another couple of months until a flat battery one morning. After a jump start it would not run on gas again, and considerably more damage was evident inside the ECU - this time not repairable. As the (same) battery did not lose charge again, and no lights were left on I can only assume the meltdown within the ECU flattened the battery.

On with a replacement ECU which came from a 6 cylinder car and hence needed setting up for a V8. After a 140 mile round trip to the specialist they got it running on 1 bank, but a new stepper motor was needed to get back on all 8. This was duly found and fitted, and after a short period (self learning?) all was reasonably well again, although slightly down on power and rough to idle. There was also the Yellow/Green/Red fault code corresponding to a faulty lambda sensor - we put this down to the imbalance between the two steppers which ideally should be a matched pair.

Then the seals in the vaporiser failed, so I rebuilt that and the system seemed better. As we planned to do a lot of towing I thought it wise to take it back to the specialist for a check to see whether they could raise the idle speed and make sure the stepper imbalance was not causing it to run dangerously lean on one bank. They did make it clear to me that they couldn't promise an improvement, and that they would recommend removing the Just Heavy system to fit a single point mixer system instead. This I declined as it would cost significantly more than an hour of their diagnostic time!

So by the time they finished with the car they tell me they've tried various different maps, and also altered the speed of the self learning setting, but all this made things worse. So my original map was put back in, and it just needed a run on the open road to re-learn parameters (they were unable to do this due to Christmas traffic).

We were then left with a car that would idle (just) on gas but not rev above 1500rpm. Upon phoning them back after about 20 miles of trying to switch to gas whilst running (as advised) they told me that there was nothing more they could do without substituting parts (which they didn't have) as the gas pressure was too low. They also did not have a suitable 8 cylinder map, suggesting that the ECU was still on its original 6 cylinder map!

After too many miles of heavy towing whilst on petrol we made the decision to change the system for something to hopefully give long term reliability. We settled on the OMVL system mainly due to the close proximity of the importers, and their excellent response to email and phone queries - customer service is not dead yet!

I've now started taking out the old system and am shocked by the standard of installation. I'd already tidied up a few dodgy crimped connections (under the bonnet, where COP11 stipulates soldered joints although this may have been done since the original installation) and fitted a fuseholder rather than spade connections directly to a blade fuse resting on the battery. But all the cables though the bulkhead were run without a protective grommet, the RPM signal from the coil was made up of 3 different offcuts of wire (3 different colours!), and the system was not connected to either lambda sensor!!! How it ran as well as it did is a mystery, although it does rather explain the lambda fault code...

I'm rather looking forwards to doing the job properly - I've taken next week off work so I can devote some time to it. At least I will know where all the connections are, that they will be done well and I'll have the software to be able to carry out diagnosis.

More info and possibly pictures to come over the next week or so, together with feedback on the system.

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PostPosted: Mon Feb 07, 2011 11:00 pm 
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Well, got the system installed although the initial photos aren't the best.

Started off by connecting to both lambdas under the dash.

Image

I planned to thread the new nozzles into the existing tapped holes in the inlet manifold. What should have been an easy job of removing the old nozzles wasn't, when one of them decided to shear off rather than unscrew. Bugger.

Off with the inlet manifold then for drilling out and retapping. Unfortunately, taking off the inlet manifold could be easier, but fortunately I had a gasket on the shelf and it kept me out of the pub I suppose!

Image

I was pleased to see that the engine looked in very good condition internally - Rover V8s are a bit of a 'dirty' engine in that they are prone to sludging up if not looked after.

Image

Next was the underbonnet wiring. I wanted to avoid the messy looking plug in looms that take the signal from the petrol injectors, so I cut the injector signal wires and spliced in the wires to the gas ECU.

Image

Note that I decided against mounting the injector rails on the bulkhead, both for noise and also to keep the hose length short - although space was a little limited for ideal placement on the throttle butterfly side

Image

In making up the bracket for the vaporiser/AFM/K&N air filter...

Image

...I had a little 'accident'. I was angle grinding next to a battery that I had inadvertently left on charge. Next thing I knew there was an almighty bang, a flash, and my face started to sting. This is what was left of the battery, and fortunately the stinging was only brief and minor...

Image

I've got it switching over to gas successfully, but in doing the autocalibration it tells me the nozzle size is too large. After speaking to the kit supplier it seems like the correct size (with my HP reducer) is 1.75mm, but unfortunately they have no stock. They have suggested soldering up the existing nozzles and redrilling, which I'll probably have a go at on Wednesday. The other option I thought about was reducing the pressure, but their advice was to reduce the nozzle size before altering any pressures.

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PostPosted: Tue Feb 08, 2011 12:10 pm 
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Sounds like you were very lucky with the battery! :shock:

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PostPosted: Tue Feb 08, 2011 4:37 pm 
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Yes, let that be a lesson to me! Annoyingly it was a newish battery that I had put on charge after storage so I could put it on a car. Doh! Made a hole in the garage roof too. :(

Regarding the injector size, a little bit of searching on here has led me to this post, which implies maybe I should adjust the pressure before nozzle size. For a given injector time the only 2 variables I can see affecting the amount of gas being injected are pressure and nozzle size - is there any preference to which would be best to try first? My logic tells me that a high pressure and a small nozzle will mean a faster gas speed, hence the pulses will reach the inlet manifold faster which will be better as the injector pipes are a bit on the long side (getting on for 300mm which is the maximum recommended). Or am I thinking too deeply?

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PostPosted: Tue Feb 08, 2011 6:39 pm 
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The battery reminds me of when some of the locals lit a fire underneath my battery :shock: .Fortunatly only soot and melted paint resulted.

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PostPosted: Tue Feb 08, 2011 6:55 pm 
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whenyou autocalibrate, the injector size settng will tell you wether they are the right size nozzles. Bear in mind this is an indication only and does not have to be adhered to.
set the pressure to around 1.1 bar and calibrate the system.
you are more interested in the injection times.
the petrol injection times should be the same on gas as they are on petrol.
you have the lambdas wired in so these will also give you an indication of how the system is running and if the nozzles are about right.
on the setup page select the 2 lambdas option, as this will give you two sets of injector times (each bank)
an indication of wether the nozzle sizes are big enough is to monitor the petrol injector times and while on petrol give it short sharp revs to see what the max injector times go to. then do the same on gas and again see what the petrol injector times go to as a max value. if they will reach the same point as when on petrol then the nozzles sizes are fine (as long as you haven't had to remove gas through the carb setup page)


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PostPosted: Tue Feb 08, 2011 10:47 pm 
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Thank you Tommo. That makes a lot of sense - to try and ensure the petrol ECU isn't constantly having to make on the fly adjustments to the fuelling. At least if I drop the pressure by taking out the larger spring from the reducer (the HP is around 1.7 bar, the MP (minus spring) is supposed to be 1.2), it's an easily undone modification. Assuming that puts the nozzle size into the 'acceptable' band, I can then fine tune the pressure to try and get the petrol injector times constant regardless of fuel.

I've already set up both lambdas, and yes it is running rich. It will sort itself out after a short period of steady speed running, but that's obviously no good for on the road.

Not sure what you mean by
Quote:
as long as you haven't had to remove gas through the carb setup page

but that could just be me being dense... :oops:

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PostPosted: Wed Feb 09, 2011 12:58 am 
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When the nozzles are too big, you get hot idle injection times below the minimum sensible operating time of whatever injector type you have fitted. Symptoms: rough idle, hunting.

When the nozzles are too small, you get injection times that are too long to fit in an engine cycle at high rpm and large demand. Symptoms: either like hitting a brick wall when drag racing, or secretively switching back to petrol temporarily, depending on the system software.

Obviously there's an acceptable band in between the extremes, and the art is to balance nozzles/pressure to get in the band, and allow the electronic calibration and manual software tweaks to do the fine delivery matching to petrol.

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PostPosted: Wed Feb 09, 2011 9:29 am 
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run the autocal and see what values you get, look at the injector nozzle size bit and see what it says, this will give you an indication if you are close or not.
while on idle running on petrol see what the petrol injector times are, then switch to gas and see what the petrol injector times are, they should be the same, look at the gas injection times, these should be roughly 110-120% of the petrol times.

As rossko syas, if the nozzles are too big the injection times will be too small for the system to control properly. if they are too small they will more than the 120% range that you are looking for.

Only change one thing at a time, ie if you adjust the pressure leave the nozzle size, if you change nozzle size leave the pressure setting. only change one variable at a time otherwise you could get yourself in a right mess.

The carb setup page gives you 8 boxes where wou can add or remove gas, this gives you some room to fine tune. If you have a dongle you can open the full map but, this is not usually required for most installs.


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PostPosted: Wed Feb 09, 2011 9:47 am 
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tommo2009 wrote:
The carb setup page gives you 8 boxes where wou can add or remove gas, this gives you some room to fine tune. If you have a dongle you can open the full map but, this is not usually required for most installs.

Ah, I see. The latest software doesn't need a dongle so I've got full access, but not going to adjust the map unless I have to!

When I did the autocalibrate at the weekend this is what I got

Image
(lambdas switching between 0 & 1V on petrol)

and the kit supplier suggested 1.75mm nozzles would be what I need, which they didn't have (on back order :roll: ). He suggested soldering/drilling the existing ones to 1.75mm, which I'm a bit nervous about, especially with it all being brand new!

Idle is pretty smooth, almost but not quite identical to petrol. If I raise the revs slowly no problems but if I blip the throttle there is a moments hesitation and if I really blip it sharply there is a small exhaust backfire (which I would normally think meant I was running lean :? )

Will try pressure first at the weekend, and see where I get, thanks for the advice guys. :)

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Last edited by mat_fenwick on Mon Dec 03, 2012 12:27 pm, edited 1 time in total.

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PostPosted: Wed Feb 09, 2011 9:04 pm 
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Just to add a bit about that "too big / too small" gauge. The software has no idea what nozzles are actually fitted, nor what they should be.
The gauge is just showing the ratio between petrol/gas times in a simple way, and makes an assumption that something around 120% is a Good Thing, as described by tommo. (It's a reasonable assumption for most cars, including this one, but can mislead if the car has exotic petrol injectors or even non-standard gas injectors.) I think the exact target ratio is determined by what type of injectors you tell the software about.

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PostPosted: Thu Feb 10, 2011 1:51 am 
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rossko wrote:
Just to add a bit about that "too big / too small" gauge. The software has no idea what nozzles are actually fitted, nor what they should be.

Yes, I thought that but it's good to have my thoughts confirmed by someone 'in the know'. To simplify things for my tiny mind, my understanding is (now) as follows: I want to get the petrol injector times similar whichever fuel is actually being used, with gas injector times approximately 20% longer (and hence the too big/too small indicator sat in the middle(ish). But how this is actually achieved (pressure or nozzle size) doesn't really matter, so long as idle is OK and I don't run out of go at long injector times.

I'm now starting to see that the statement "calibration process should typically take between 2 -5 minutes" should perhaps be taken with a little pinch of salt...

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PostPosted: Thu Feb 10, 2011 1:58 am 
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mat_fenwick wrote:
I'm now starting to see that the statement "calibration process should typically take between 2 -5 minutes" should perhaps be taken with a little pinch of salt...

It's based on an assumption that the correct vap/injectors/nozzles were supplied in the first place ;)

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PostPosted: Thu Feb 10, 2011 2:07 am 
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:lol: Yeah, and we all know where assumption gets you! From what I'm starting to understand, the system as supplied seems more suited to a sequential petrol set up, where I've read you need a larger nozzle size. Not ecstatic about it, but I'm learning, which is a good thing. I hate having any kind of mechanical system where I don't understand what is going on.

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PostPosted: Thu Feb 10, 2011 10:31 pm 
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Right, now we might be getting somewhere!

Took the larger spring out of the reducer which dropped the pressure to around 1.15bar. Changed the software setting to MP reducer and did the autocalibrate again.

Image

Nozzles are still too big (or pressure still too high), but it runs a lot better - only a trace of 'fluffiness' when you blip the throttle and no backfiring. But the injector times are puzzling me - they are WAY more than 120% of the petrol times, more like 230% looking at the values above at idle. But petrol injector times are similar! And surely if the nozzle size is too big, then the gas injector times would shorten to less than ideal.

So if I decrease the size, the gas injector times will have to increase, but they are already too long. Or am I missing a trick here? :? :oops:

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PostPosted: Mon Feb 14, 2011 10:47 am 
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Almost got it cracked I think. I soldered up the nozzles and drilled them out to 1.75mm, which was almost OK - just in the correct band. But full throttle power was down so I took them out and drilled them to 1.85mm. Almost bang in the middle, with very similar petrol injector times, Lovely and smooth at all revs/loads. (I had a bit of puzzlement trying to set it up after the nozzle change, but that *may* have been down to me leaving a petrol injector disconnected after removing the connector to get at the nozzle I'd just dropped and forgetting to put it back :oops: ).

But when changing over from cold there was a distinct loss of power and backfiring, disappearing after a short while (seconds). I assumed this was down to the reducer not being hot enough so upped the changeover temperature to 35°C. Unfortunately (according to my wife) it still did the same thing this morning, even though the point at which it changed fuels was hotter than the temperature at which it started behaving on my test run. There is an option in the software to pressurise the gas system in advance of changeover, so I will try that and see if slow pressure build up is the cause. Perhaps if this has no effect, I could select changeover in deceleration rather than acceleration. Plenty for me to play with!

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PostPosted: Wed Feb 16, 2011 11:05 am 
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Aha, it appears as though my wife was leading me to the wrong tree to bark up! (Or I'd misunderstood, but it's always easier to blame it on someone else isn't it? :wink: ) The "Backfiring just after changeover" actually lasts for 30 seconds or so, so is obviously nothing to do with pressurisation prior to changing fuels (I should have asked her how long it lasted :oops: ) and must be to do with temperature. Especially as it is worse on cold mornings, and almost OK on her drive home.

This, coupled with the statement yesterday "The heater takes ages to warm up" suggests the thermostat is on its way out. When I've driven it the heater had seemed fine, and engine temperature would sit in the middle of the gauge. But thinking back, most of the recent drives I've had are when I've been setting up the LPG system, and hence the engine is already warm. Wish I'd changed it with the inlet manifold off... :roll:

Update and hopefully some finished photos at the weekend. Still not 100% happy with my 'mount' for the vapour filter - looks a bit of a bodge job to me but seemed better than just letting it hang.

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PostPosted: Thu Feb 17, 2011 1:28 am 
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There will be some underlying setup or configuration cause here, most Disco will switch over without drama. It could well be as simple as bust thermostat leading to brief overfuelling until the lambdas sort that out.

I expect the pictures will reveal, but it is worth fitting the gas injectors as upright as possible, so that any stray oily heavy ends can drain out into the engine. Else there is a risk of congealing into wax when cold.

The vapour filter also serves a hidden purpose as an expansion trap when cold. Again, mounting orientation can affect this, horizontal-ish should work best for inline types.

Given that this is a reworked install, confident that wiring has been reinstated from previous install e.g. no extra emulators left in petrol circuit, lambda wires restored (no cuts, only tees)?

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PostPosted: Thu Feb 17, 2011 8:21 am 
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If it is the thermostat I now have one to change if required, and it is looking more like that. I think it's more a question of "Why is it taking so long to warm up?" as now I've set the changeover temperature to 45°C, there is no hesitation (but a small drop in power). But it takes a couple of miles to reach that, admittedly half of that is downhill but even so...

Wiring is 100% OK - I initially thought there was no lambda connection to the JH system, as it had been teed into under the bonnet and then cut off! It was then found to be teed under the dash (to one side) but strangely, there was another T into both lambda wires, which again had been cut and left bare. :roll: I thought it a good idea to check continuity from the lambdas back to the ECU after seeing that mess.

When you say injectors upright, do you mean shafts upright (to minimise wear)? That's how they are, with the outlet at the bottom although horizontal. Could heavy ends build up potentially be a problem after only a few hours running on gas? I think I have some fuzzy pictures on my phone, which I can post up soon.

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PostPosted: Thu Feb 17, 2011 9:44 am 
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OK, here is a fuzzy photo!

Image

The RH bank of injectors is tilted down slightly - more in the interests of a smoother pipe run than anything else. It would be fairly easy to tilt them both a little more downwards if this is likely to help, without suffering too much with injector wear?

The vapour filter I have mounted next to the AFM - on the following picture you can see the semicircular cut out for it on the left of the AFM mounting bracket.

Image

All I have done was to put a stud through the bracket, and zip tie the filter to that. I might have an old style coil mounting bracket with which I could do a neater job, but lets get the thing working properly first!

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