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PostPosted: Wed Feb 01, 2017 8:24 pm 
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Joined: Wed Apr 17, 2013 6:13 pm
Posts: 20
Hi all

I wonder if the MPG computer works the same way when its on gas than when it was on petrol

Despite the fact that it is showing 20.7mpg overall since the last reset when I filled up a full tank of gas of 50 ltrs. It only lasted 145 miles to be precise.

so if I was to work out in the same manner (50ltr = 11 gallons) , 145 miles / 11 gallon = 13.18 MPG, which is a whole world different to indication.

Regards

J


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PostPosted: Wed Feb 01, 2017 8:39 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
Posts: 2943
Location: Yorkshire
Must be talking about the car which is the subject below...

Josewick & LPGC wrote:
josewick
Message subject: Re: LPG conversionFolder: Inbox
I wish i haven't bothered with this car on gas as this is not the easiest car or perfect car to do I do not think

Attached photos

Regards

Image

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Sent: Wed Jan 25, 2017 5:51 pm
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josewick
Message subject: Re: LPG conversionFolder: Inbox
Thanks for your reply.

I will send you a photo in the day and that explains better.

It is kind if annoying that this is my second car of lpg and his first job was good with no come back on a BRC system and this time round I have kind of lost faith in him.

Now the engine is running fine, I come across a second problem and of cos it would not be noticed until you are low or out of gas.

I am not too familiar with the stag Ac control yet but the 4 green light round the ring is not counting down as the gas gets lower and with the 62 ltr tank, I can only fill up about 40 ltr then the filling pump can't get any more in and started to make noise and vibration. So I think something is not right with the filling up and stopping it from filling to full capacitor and may have caused the leveler not monitoring, so yes another trip back to the installer next week.

Regards

Joe
Sent: Sat Jan 21, 2017 9:29 pm
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LPGC
Message subject: Re: LPG conversionFolder: Sent messages
From how you've described it Joe it would seem the installer correctly identified and sorted the problem. But it is a pity you had to mess with coils/plugs etc yourself before the installer realised their mistake.

Whether a blockage between an injector and inlet manifold affects idle or top end power most will depend on where exactly the blockage is..

If it is very close to the injector it has the same effect as fitting a smaller nozzle in the injector (which effects the amount of gas flowed by the injector for any given pulse length and pressure) so effects fuelling at all engine loads, and since fuelling accuracy is more important at idle than at high loads in this case it is usually idle that is effected most.

If it is close to the manifold then it *might* not effect how much gas the injector meters for a given pulse length and pressure unless pressure builds between the injector and the blockage. Pressure won't build between the injector and the blockage at low engine loads because the engine vacuum suck all the gas past the blockage before the injector pulses again, so at low loads the engine will receive the same amount of gas as it would if there was no blockage except it will get more of a constant stream of gas rather than the same amount of gas in pulses, this might not effect how the engine idles on gas at all. But such blockage *might* still restrict the flow of gas at high engine loads, because now more gas is needed to flow past the blockage, leading to pressure between the injector and the blockage rising towards injector feed pressure.. If pressure due to blockage ever equalled injector feed pressure this scenario would flow no more gas regardless of how much longer the injector was pulsed for, but even well before this point is reached injector flow will be smaller compared to unaffected injectors... thus leaning the mixture to the effected cylinder at medium/high loads perhaps to the extent of a problem that is noticeable.

Of course, a blockage that doesn't effect flow under any conditions effectively wouldn't be a blockage, so out of the two *mights* above, one is a certainty!

Simon
Sent: Sat Jan 21, 2017 6:44 pm
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josewick
Message subject: Re: LPG conversionFolder: Inbox
Hi Simon

Thank you for your reply.

The car was misfiring on number 3 when lightly accelerating especially around the 2-2500 rpm mark, but fine at full load. the installer was blaming to be ignition related. So swapped the plugs and coil pack of 3 to 2, see if the Mil code swapped. No it didn't i kind of convinced its not my car but the install. I took it back and it was narrowed down to a partial blockage of the T piece that joins the fuel and lube to number 3 , after the injector, had that changed and touch wood so far it is running sweet.

What puzzled me before was that if it was fuel related, should it suffer more under full load when its higher fuel demand, ? Then I was thinking about it and I think I have got it.

so when light or normal cruising when injectors were part opened probably giving just enough fuel to the inlet, and any partial blockage will cos a significant change to fuel delivery...
however if it was under full load, the injector is fully opened and possibly chucking loads and more than enough fuel into the inlet, which a partial blockage is not as significant with the fuel delivery, hence did not notice the problem..

It would be nice to be confirmed by professional like you, and I appreciated your kindness in replying to my previous post

Regards

Joe
Sent: Fri Jan 20, 2017 2:10 pm
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LPGC
Message subject: Re: LPG conversionFolder: Sent messages
Hi Joe,

What seems to be the problem with your new LPG ocnversion?

Simon
Sent: Fri Jan 20, 2017 10:52 am
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josewick
Message subject: Re: LPG conversionFolder: Inbox
Dear Simon

I have been away and got back the new,it has an extremely long story and bad timing and possibly blaming on the inbox system (and I did email you directly once) but since we missed each other (was kind of assuming that you might not be too interested, but not realising that you might not even had got the pm), I took a pinch again and had it done locally to me. It was not for any financial reason as he was in fact charging more.

I had just picked the car up yesterday and the install was not as neat as your Cayenne but its done, in an acceptable level, AND with a running problem.

I find it rude to ask you since you did not do the work and have to look at someone else's mess up (I would not say a mess up just yet but could be easy to an experienced installer) but I do like to find out more before I dump the car back for him to sort out, so that I know he is not talking @!## to me.

But if you do not mind to share your extensive knowledge to help up an user, i would be appreciated.

Regards

Joe
Sent: Wed Jan 18, 2017 6:04 pm
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LPGC
Message subject: Re: LPG conversionFolder: Sent messages
Joe, I sent you a PM reply shortly after you sent me your PM, but it appears you haven't read my reply.

Are you still interested in converting your car?

Hope to hear.

Regards,

Simon, LPGC, 07816237240
Sent: Fri Jan 06, 2017 1:39 am
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LPGC
Message subject: Re: LPG conversionFolder: Sent messages
Hi Joe,

Here's the thread you started on the subject, I quoted £1400.
viewtopic.php?f=27&t=14157&p=109783

I could do your conversion early in the new year.

Regards,

Simon
Sent: Sat Dec 24, 2016 6:39 pm
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josewick
Message subject: LPG conversionFolder: Inbox
Dear Simon

I enquired about a conversion last month or so on a touareg. Now I have taken delivery of the car and is looking into getting it done.

However I am not sure if it's a forum upgrade or else, I have lost all the pm in inbox and outbox and cannot find tour previous quote and details.

I learned that BRC has ceased trading in uk so I am not sure what system you are recommending to fit in my 3.2 v6 touareg.
I watched your cayenne conversion and is impressed with the work.

I would love to get it done sooner rather than later , the 2004 petrol touareg unfortunately does not have much of a market value and my wife has been nagging spending half the value of the car on a conversion kit.

If you can tell me again the cost supplied and fitted that will be appreciated. Also do I require a lube kit? I would want a spare wheel tank and discreet filling point behind the petrol flap.

It would be nice to be able to do it in the new year on your return

Regards

Joe


The latest issue you've noticed is probably due to the system not being calibrated properly, it could even involve parts that aren't well suited... Either situation might be expected if the installer is used to fitting BRC but then has a go at fitting Stag. It is a pity you seemed to have a problem getting in touch with me right before you chose to go with the other installer - I will be able to sort out your problems if you bring the car in but will have to charge for it...

Simon

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Last edited by LPGC on Wed Feb 01, 2017 8:45 pm, edited 1 time in total.

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PostPosted: Wed Feb 01, 2017 8:45 pm 
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Joined: Wed Apr 17, 2013 6:13 pm
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sorry simon,

yes it is the toureg..

At last its fully up and running.. trying to learn it now..

Regards

Joe


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PostPosted: Wed Feb 01, 2017 8:52 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
Posts: 2943
Location: Yorkshire
Toureg or Towrag? :lol:

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Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
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2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240


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PostPosted: Wed Feb 01, 2017 8:54 pm 
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Joined: Wed Apr 17, 2013 6:13 pm
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LPGC wrote:
Toureg or Towrag? :lol:


You are not wrong there mate, might as well be a Towrag lol

Car is nice but the amount of grief is unreal.


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PostPosted: Wed Feb 01, 2017 11:05 pm 
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Joined: Mon Jan 23, 2012 12:21 pm
Posts: 864
Location: Milton Keynes
On the BRC front the previous distributor (BRCGB) has gone bust, but the good news from that is that Tinley Tech are now the BRC distributor instead as per one of their recent posts here.


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PostPosted: Thu Feb 02, 2017 11:24 am 
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Joined: Wed Apr 09, 2008 9:00 am
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Location: Peterborough
Using the trip computer when running on gas won't show the actual fuel consumption but can give you an indication that the calibration of the gas system is correct or not. The trip computer doesn't measure the amount of fuel you use but calculates it from the fuel trims. With the car running on petrol, reset the trip computer and go for a drive. Preferably 20 or 30 miles of mixed driving and at the end check the mpg figure it is displaying (this, in theory, should be accurate). Then reset the trip computer and do the exact same journey only running on gas this time. The displayed mpg figure should be the same. If it says you are doing more miles per gallon, then the petrol ECU is having to lean the mixture off (make the fuel trims go negative) so the gas ECU is adding too large a correction, if it says you are doing less miles per gallon, the petrol ECU is having to increase the petrol injector pulse lengths to get the mixture correct (make the fuel trims go positive) because the LPG controller isn't adding enough.

In either case though the figure displayed will not be the same as you are actually doing on gas. You can usually expect to use about 10% more gas than you would petrol.

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PostPosted: Thu Feb 02, 2017 11:36 am 
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Agreed Gilbert, that's how it is with most vehicles anyway, though there are some that work a bit differently (e.g., fuel trims aren't involved).

If you drive with the same amount of throttle (especially true on a vehicle that uses a traditional throttle cable rather than drive by wire, which can adjust the actual throttle without driver input) the instant mpg reading should stay the same, though to remain at the same speed you might need to press ever so slightly further on the throttle when running on LPG, in which case instant mpg reading will go down a little anyway. Calorific value and stochiometric ratio play there part here too, with these two factors slightly offsetting each other but still steering displayed figure to be slightly above actually attained mpg. Then there's the fact fuel computers aren't always very accurate in the first place.

Simon

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Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240


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PostPosted: Fri Feb 03, 2017 1:27 pm 
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Joined: Wed Apr 17, 2013 6:13 pm
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thank you for your reply. So its figures cannot be taken into account but as an indication if its using more or less than my reference figure (say overall if I get 20mpg, i get 140 miles from a tank) so if i get 22mpg effective i should be expecting to see 10% more miles from the tank.

cos with published figures that car does 15mpg round down and if I can get 20, something is not right, as the published figure is always higher than fact anyway lol

Good to know BRC is obtainable. That never let me down and give me grief in my first LPG'd car...

Regards


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PostPosted: Fri Feb 03, 2017 5:23 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
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Location: Yorkshire
If fuel computer jumps from 20mpg to 22mpg without you moving your foot on the throttle (regardless of vehicle slowing down or speeding up) it is likely that your LPG system, at least at this specific combination of engine rpm and engine load, is calibrated 10% rich. There are other scenarios, including that there is some issue with your petrol system, but the above 10% rich scenario is most likely.

Grief has been brought on for the customers of some installers, installers who might have at one time only fitted such as Prins / BRC systems but have since tried their hands at fitting a wider range of systems. Not because Prins / BRC are any better, but because with Prins / BRC they won't have had to match components to suit the vehicle or get as involved in calibration. This, so far, may still read like Prins / BRC are the best bet (because at this point it will read as though Prins / BRC are more plug n play and will work work on any vehicle) but this isn't true... Better results can be had by an installer fitting a different system than are possible with Prins / BRC, as long as the installer knows the job properly. The emphasis should be placed on the latter part of the last sentence... Many times I have seen results of Prins / BRC installers fitting different systems, the choice of components, the way of installation and the calibration have all seemed very random, amateurish and seemingly demonstrated a lack of understanding of even basic concepts. A lack of understanding of basic fuel injection concepts and LPG system methodology may be what all this boils down to - and it may be telling that both Prins and BRC had a policy of recruiting installers at 'established garages'. Established garages by definition are generally the places that have been around a long time fitting clutches etc, not always staffed by mechanics who have great understanding of fuel injection on modern vehicles. I know a lot of such mechanics that packed in shortly after carbs were replaced in the mainstream with fuel injection and/or when vehicles generally became more reliable, they trained as mechanics, they don't want to know about electronics or pulse duration of electronic injectors etc... but there may have been a time when they might have considered becoming a Prins / BRC dealer and got away with converting vehicles to LPG even if they didn't otherwise want to be involved with fuel injection. As engine electronics and fuel injection become more complicated, and as the systems they are used to have gone from being among the best around to mediocre systems perhaps at best, they start to have more and more problems converting vehicles properly to LPG. Then, if they try fitting anything else, if the engine is a design where they can't get away with fitting stuff in an easy to access position, if they start to have to match suitable LPG components to the vehicle, if they have to fiddle with calibration that involves more than now involves changing more than just a couple of numbers... their shortfalls can really start to show. This is what I see and put right on a fairly regular basis.

Simon

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Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240


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