Those who run LPG converted 2.2's

[FreitasS6]

Hi, why haven`t you used a Liquid Injection system?

It's perfect for Turbocharged engines (the transition from liquid to gas is endothermic and cools the charged air big time, almost like an nitrous sistem) and super easy to tune and install. BTW it's easier to get more power and torque from those systems than from petrol, and the economy is very similar ( like 5% less ).

I have a 4.0 Cherokee running on LPG (Liquid SI) with great results, and i'am thinking if i should convert my urS6... not totally convinced yet as she only have 70.000Miles, is 100% original and have a fully stamped Audi service book.

hope you sort all the remaing gremlins with your Avant!

Best from Portugal.

[prj]

BTW it's easier to get more power and torque from those systems than from petrol, and the economy is very similar ( like 5% less ).

Everything was looking fine until you made that claim.
There is no perpetual motion machine in existence.

LPG is 26 MJ/L whereas gasoline is 34.2 MJ/L. That is a difference of 30%.
In the areas where the fuel economy is realized an ICE is not knock limited on gasoline, so that is a moot point.
The only thing there is, is that you can run LPG lean burn up to about lambda 1.3 and somewhat reduce pumping loss - but unless you know how to make your ECU do that it is not going to happen.

Liter per liter, even if you make the perfect optimizations LPG is going to have AT LEAST 25% worse fuel efficiency.

[hunker7]

Everything was looking fine until you made that claim.
There is no perpetual motion machine in existence.

LPG is 26 MJ/L whereas gasoline is 34.2 MJ/L. That is a difference of 30%.
In the areas where the fuel economy is realized an ICE is not knock limited on gasoline, so that is a moot point.
The only thing there is, is that you can run LPG lean burn up to about lambda 1.3 and somewhat reduce pumping loss - but unless you know how to make your ECU do that it is not going to happen.

Liter per liter, even if you make the perfect optimizations LPG is going to have AT LEAST 25% worse fuel efficiency.

Mine is currently about 30% worse off on LPG. Prj, what's the best way to calibrate LPG for someone who's knowledge is very limited in such area?

[FreitasS6]

Hunker7, the best way is pay someone that knows how to do it!

As reffered here it s also mandatory to have a AFR (i have a PLX device on my Jeep 4.0)

About my claim, prj i must say that everything is still looking fine! as you said there is no perprtual motion machine. And when we're talking on internal combustion engines it's even worse...

IF we were talking of WOT and only a set RPM you are 100% right. But we are not. We are talking of a machine that works with very diferent levels of efficiency with lots of different variables, only one is the energy density in the fuel.

A LPG car is going to use more fuel than a petrol one, yes. But you can do several things to improve that. First of all is Liquid Injection.

On a atmosferic engine ou can also bump the compression to levels the petrol can only safely idle... but let's not go there. let's stay focused here. just keep in mind that i use 17L of GPL to do 100km and if i use petrol i use minimum 15,5L. again, that looks very fine indeed for me! :-)

( and sorry for the hijack hunker7!)

Hunker7 you should really pay someone to do it, with a afr meter it should be easy. I had to tune my car 3 times to make it perfect. When it is ok then you should reprogram the motronic! why? because, as you know know the motronic don't care if you use petrol lgp cng or whatever. it only knows that it will trim fuel to the full extent of it's ability to reach the stipulated AFR. so in order to get the best results you should tune your motronic in such a way that it works perfectly with LPG and at least usable ( if you can´t get any LPG for example ) and does not ruin your engine internals.

Also 30% off with your injection kit it's not far off... the levels of efficiency i talk about are only obtainable with liquid injection.

[hunker7]

Liquid injection was too expensive of an option, and gas injection works for my driving style. Even with 30% loss in efficiency, LPG costs £0.48 per liter whereas premium unleaded, which I always used, is £1.10. 470 miles cost me £50 on LPG compared to £80 on unleaded.

When it comes to calibration, I simply don't trust anyone with my car. I called up local LPG fitting place, and they told me getting rid of mixture adaptation error is impossible, that put me off "professionals". I fitted wideband, and being complete novice I got rid of it within 5 minutes of connecting laptop. With help from Des, I have managed to get her running pretty well, just few little things needs adjusting, but for that I need to be in charge of laptop and someone else driving.

I know PRJ has done work on LPG cars, so I was wondering if there are any changed that can/need to be done to Motronic to further improve LPG system performance.

[prj]

IF we were talking of WOT and only a set RPM you are 100% right. But we are not. We are talking of a machine that works with very diferent levels of efficiency with lots of different variables, only one is the energy density in the fuel.

I think you need some schooling on the first law of thermodynamics.
None of your yadda is going to change a thing about it.

Also 30% off with your injection kit it's not far off... the levels of efficiency i talk about are only obtainable with liquid injection.

It makes no difference if it is liquid or gas at the areas where efficiency is concerned.
It makes a lot of difference on WOT, but that's about it.

Nothing of what you say is true. Your claims are either made up or your engine is detuned on gasoline (4.0 cherokee has **** mapping from factory).

It will always be 20-25% worse on fuel given proper mapping on both fuels, end of.
Why? Because you can not get out more than you put in. And in case of LPG you put in 30% less per liter. You can gain some back running it lean burn, but that is below 5%.

[hunker7]

I think you need some schooling on the first law of thermodynamics.
None of your yadda is going to change a thing about it.

It makes no difference if it is liquid or gas at the areas where efficiency is concerned.
It makes a lot of difference on WOT, but that's about it.

Nothing of what you say is true. Your claims are either made up or your engine is detuned on gasoline (4.0 cherokee has **** mapping from factory).

It will always be 20-25% worse on fuel given proper mapping on both fuels, end of.
Why? Because you can not get out more than you put in. And in case of LPG you put in 30% less per liter. You can gain some back running it lean burn, but that is below 5%.

What do you mean by "running lean burn"?

[FreitasS6]

Hunker7, i totally get you man. I seldom let anybody tinker with my cars. but there are somethings that are best left for the guys that know how to do it. i think that you just need to find the right guys, the ones you did are clearly not the ones for the job!

But dont let that speak for every guy in the business, there should be one that can help you!

If not, and you prefer to do it by yourself ( which i applaud ) maybe you could get some info from the source ( the guys that have built the kit ).

Hope you sort your Avant, let us know how it goes!

best of luck to you!

[hunker7]

Is there a way to log AFR against RPM? Currently can only do against time which isn't great.

[hunker7]

This is AFR and it is running super rich at points and too lean at others. Before I try and get it right, At any gear at WOT I shouldn't be seeing more than 12.5 to 13.2 AFR?

[diesel des]

Is this on petrol or Lpg. Get a graph of both on a third gear pull from 2 k rpm to 7 k and overlay them.

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[hunker7]

Is this on petrol or Lpg. Get a graph of both on a third gear pull from 2 k rpm to 7 k and overlay them.

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that's a quick run on LPG on 2nd and 3rd. I'll try and do that as soon as I can. I can feel car not running properly at higher speeds.

[diesel des]

The very lean points could be when you change gear or are on the overrun?

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[hunker7]

The very lean points could be when you change gear or are on the overrun?

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those very very lean are when I change gear yeah. But on WOT it sometimes runs at 15-18 AFR, and in second at around 5k it starts juddering and looking at the data it goes to 11.5AFR.

I am going back to London next Sunday, and dad will be with me, so I want to get it calibrated on the way as I will have 200 miles of M1

[hunker7]

It seems it's running rich on petrol too, goes to about 10.5 AFR and it shouldn't be less than 12. Have last exam tomorrow, so will get log for lpg and petrol in 3rd form 2000-7000 rpm