Discussion
Does anybody have any experience with LPG conversions? I'm considering the implications of both single and multipoint systems and the effect that they would have when running on a 2.0l 4 pot supercharged engine. Throttle is located before the compressor, (Which is centrifugal). Any advice?
Don't do it!!!
Which engine is it? VW G-lader, Lancia Volumex or something else? Apparently modern ECU controlled engines are easier to convert than older Carb engines.
I've had my V6 cavalier done a couple of months ago, and it's still not sorted. A lot of people seem to have misfiring problems with a new LPG installation which can damage your induction system.
I've got noticably less top end power on LPG compared to petrol, but that might be because it's still not properly set up? I'm currently getting about 15mpg on gas cf 25mpg for petrol. My goal is 20mpg on gas.
Which engine is it? VW G-lader, Lancia Volumex or something else? Apparently modern ECU controlled engines are easier to convert than older Carb engines.
I've had my V6 cavalier done a couple of months ago, and it's still not sorted. A lot of people seem to have misfiring problems with a new LPG installation which can damage your induction system.
I've got noticably less top end power on LPG compared to petrol, but that might be because it's still not properly set up? I'm currently getting about 15mpg on gas cf 25mpg for petrol. My goal is 20mpg on gas.
I had a lot of grief when I converted my Nissan Primera. The installer then went bust. I wouldn't do it again to be honest, although I'm told by the specialist who finally fixed it, no, made it tolerable (two days before I sold it 
), that the injection systems you describe are much more effective than the older (and still most common) carburetted systems. Have to say, if I'd known at the time it would be a carb I wouldn't have had it done. I didn't ask enough questions, just assumed that this heavily developed and promoted technology would be fine. There's a life lesson.
Performance didn't seem to be affected except at the very bottom end, eg trickling through traffic. I never really explored the very top end in that car, although full bore acceleration wasn't significantly different. Got regular power loss, stalling problems, heavier than expected fuel consumption (As low as 22 on gas but ended up with 27 gas, vs 34 petrol). I would be very reluctant to do it again.
I'm told that older engine designs lend themsleves better to conversion, which is why so many Range Rover/Discovery V8s and Jeep Cherokees get it done.
I'd suggest that if you're going to do it, make sure that the installer has done the same conversion to other cars with the same engines, and get references from those customers. Go and see / get a ride in their cars if you can.
>> Edited by JohnL on Wednesday 5th February 11:20
), that the injection systems you describe are much more effective than the older (and still most common) carburetted systems. Have to say, if I'd known at the time it would be a carb I wouldn't have had it done. I didn't ask enough questions, just assumed that this heavily developed and promoted technology would be fine. There's a life lesson. Performance didn't seem to be affected except at the very bottom end, eg trickling through traffic. I never really explored the very top end in that car, although full bore acceleration wasn't significantly different. Got regular power loss, stalling problems, heavier than expected fuel consumption (As low as 22 on gas but ended up with 27 gas, vs 34 petrol). I would be very reluctant to do it again.
I'm told that older engine designs lend themsleves better to conversion, which is why so many Range Rover/Discovery V8s and Jeep Cherokees get it done.
I'd suggest that if you're going to do it, make sure that the installer has done the same conversion to other cars with the same engines, and get references from those customers. Go and see / get a ride in their cars if you can.
>> Edited by JohnL on Wednesday 5th February 11:20
Hm, my comment about older engines seems to be completely at odds with Danhay's.
Land Rover / Jeep are of course ECU controlled engines, not carburetted ones, albeit of an older design. My Primera was definitely a modern engine design with an ECU. Anyone converted a Rover V8 TVR?
Apparently the very basic gas ECU read the petrol-request signal from the main ECU, and delivered the anount of gas it considered equivalent to that. I suppose if the original engine has a carb and no ECU that wouldn't be possible.
Land Rover / Jeep are of course ECU controlled engines, not carburetted ones, albeit of an older design. My Primera was definitely a modern engine design with an ECU. Anyone converted a Rover V8 TVR?
Apparently the very basic gas ECU read the petrol-request signal from the main ECU, and delivered the anount of gas it considered equivalent to that. I suppose if the original engine has a carb and no ECU that wouldn't be possible.
My bro used to do these conversions a while back working for someone else.
The biggest problem is that the quality of the systems is so varied.
Some are extremely well made , others are crap.
I had all sorts of problems trying to diagnose one of these fitted to a peugeot.
It was running continually rich to the point of black smoke coming out the exhaust at idle.
Eventually traced to the gas system putting both petrol and gas injectors on at the same time.
The basic system is pretty simple, but the problems can occur when feeds are taken from lambda sensors etc and modified by the gas ecu, causes skitzo operations....
The biggest problem is that the quality of the systems is so varied.
Some are extremely well made , others are crap.
I had all sorts of problems trying to diagnose one of these fitted to a peugeot.
It was running continually rich to the point of black smoke coming out the exhaust at idle.
Eventually traced to the gas system putting both petrol and gas injectors on at the same time.
The basic system is pretty simple, but the problems can occur when feeds are taken from lambda sensors etc and modified by the gas ecu, causes skitzo operations....
Thanks for the advice guys.
Engine in question will be a 2.0l zetec lump with s/c and charge cooler etc installed by myself. Not too worried about afr problems as the engine will be running on Emerald, giving the ability to have a map for petrol and a different map for gas. The choice is whether to use a single point gas injection system before the throttle or a multi point set up directly into the inlet manifold. Anybody know what sort of pressure the gas is held at with multipoint system, i.e. is it comparable to petrol fuel pressure of say 3 - 4 bar?
Engine in question will be a 2.0l zetec lump with s/c and charge cooler etc installed by myself. Not too worried about afr problems as the engine will be running on Emerald, giving the ability to have a map for petrol and a different map for gas. The choice is whether to use a single point gas injection system before the throttle or a multi point set up directly into the inlet manifold. Anybody know what sort of pressure the gas is held at with multipoint system, i.e. is it comparable to petrol fuel pressure of say 3 - 4 bar?
A mate of mine had a corsa converted to LPG. (1.2 16v)
From what I gathered it work perfectly, made very very little difference to the performance and cut fuel bills by a about 2/3rds.
As the previous posts show though it looks like it really depends on the engines suitability and the quailty of the fitting.
From what I gathered it work perfectly, made very very little difference to the performance and cut fuel bills by a about 2/3rds.
As the previous posts show though it looks like it really depends on the engines suitability and the quailty of the fitting.
JohnL said: Hm, my comment about older engines seems to be completely at odds with Danhay's.
John, I think there's room for us both to be right. My point was that computer managed fuel systems are easier to convert (in theory!). That's not to say that an older engine design doesn't respond well when properly set up. Best bet may be an old design engine that has modern computer management e.g. the V8 in a Discovery?
viper said: doesn't the current tax ruling finish on LPG the end of this year? No doubt it will be then priced up closer to unleaded, the government won't want to miss out on a few coffers
I reckon they'll keep it cheap for another year or two, until it becomes really mainstream, then they'll start to "subtly" put up the tax on it. It probably will stay cheaper to run on than petrol because of the alleged environmental benefits, but I'd expect the gap to narrow.
I got my Range rover converted to gas last year, its transformed the car!!!. Use it all the time for long and short trips, I can't remember the last time I stood at petrol pump with that depressing 'here we go again' feeling.
Did a lot of research and got a professional conversion from a Land Rover man. You get what you pay for!!!
Not had any problems so far. Its a 4.6 auto if there was any power loss it wouldn't notice (240 bhp).
It may only be running at 12mpg but who cares when its 30p a litre!!.
But whats the point of converting little engined cars??
The newer multipoint system are supposed to stop the ignition problems but cost more, general problem seems to be the unburnt gas mixture in the inlet manifold, if you ignition system isn't perfect you get backfires etc!!.
Got a big car that drinks petrol, convert it!!!.
Got a little engine car?, well buy a big one and convert it!!!.
>> Edited by SLiller on Thursday 6th February 13:10
Did a lot of research and got a professional conversion from a Land Rover man. You get what you pay for!!!
Not had any problems so far. Its a 4.6 auto if there was any power loss it wouldn't notice (240 bhp).
It may only be running at 12mpg but who cares when its 30p a litre!!.
But whats the point of converting little engined cars??
The newer multipoint system are supposed to stop the ignition problems but cost more, general problem seems to be the unburnt gas mixture in the inlet manifold, if you ignition system isn't perfect you get backfires etc!!.
Got a big car that drinks petrol, convert it!!!.
Got a little engine car?, well buy a big one and convert it!!!.
>> Edited by SLiller on Thursday 6th February 13:10
SLiller said: I got my Range rover converted to gas last year, its transformed the car!!!. Use it all the time for long and short trips, I can't remember the last time I stood at petrol pump with that depressing 'here we go again' feeling.
No, it's the poor buggers queuing behind you that have the "Here we go feeling"! Filling up with LPG seems to be unbelievably slow, I waited behind a Range Rover for what must have been a good ten minutes. Unfortuanetly the only super unleaded is on the same pump at my local station.
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