LPG conversions in sporty cars
Discussion
Only worth doing a conversion if you are doing a lot of mileage to offset the cost of the conversion.
In my experience, engines do not perform as well when running on LPG - less power and less MPG (someone will probably disagree with this, but this is just my experience)
You don't get back very much of the investment of the conversion when you sell the car. And a conversion to the wrong sort of car might even devalue the vehicle.
They will switch almost unnoticeably between petrol and LPG. When you start the engine, it always starts on Petrol and then switches over to LPG shortly after. You can generally manually switch back to Petrol of you want.
In my experience, engines do not perform as well when running on LPG - less power and less MPG (someone will probably disagree with this, but this is just my experience)
You don't get back very much of the investment of the conversion when you sell the car. And a conversion to the wrong sort of car might even devalue the vehicle.
They will switch almost unnoticeably between petrol and LPG. When you start the engine, it always starts on Petrol and then switches over to LPG shortly after. You can generally manually switch back to Petrol of you want.
Had my Griff converted just over a year ago (Avon Autogas in Bedminster who have done loads of 'sporty car' conversions) - its already nearly paid for itself .....
Very little difference in power and mpg just half price fuel....
Lots of info. here from Dave with his Chimaera:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Very little difference in power and mpg just half price fuel....
Lots of info. here from Dave with his Chimaera:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
I know it's a different kettle of fish but I have a V8 range rover that is LPG converted. There is absolutely no difference in power or running on LPG over petrol. The only difference is when I really boot it to go for some speed it flicks over to petrol, then flicks back to LPG when the maneovre (sp) is complete...
Engine wear depends on the engine - some aren't suited to LPG and will suffer valve seat erosion. What are you thinking about converting?
There's no reason you should lose power on a properly tuned LPG conversion, but as another poster has already said you will lose MPG as LPG contains less energy per litre than petrol. There are compromise setups available with newer systems where petrol is injected to make up the defecit under load but if you set up an LPG system for equvalent power you will lose 20 to 30% of MPG compared to running on petrol. No big deal, but it does affect the maths when working out how long it takes to break even on the conversion.
You can compensate by tuning the system to run leaner on LPG than on petrol for better economy - but that means less power and if taken too far (especially under load) will cause engine damage over time. That's why it's vital to have the system mapped by someone who knows what they're doing, and personally I'd want to keep an eye on the long term fuel trims - a cheap OBC reader is all you need.
There's no reason you should lose power on a properly tuned LPG conversion, but as another poster has already said you will lose MPG as LPG contains less energy per litre than petrol. There are compromise setups available with newer systems where petrol is injected to make up the defecit under load but if you set up an LPG system for equvalent power you will lose 20 to 30% of MPG compared to running on petrol. No big deal, but it does affect the maths when working out how long it takes to break even on the conversion.
You can compensate by tuning the system to run leaner on LPG than on petrol for better economy - but that means less power and if taken too far (especially under load) will cause engine damage over time. That's why it's vital to have the system mapped by someone who knows what they're doing, and personally I'd want to keep an eye on the long term fuel trims - a cheap OBC reader is all you need.
Ozzie Osmond said:
pjac67 said:
Very little difference in power and mpg
I'm not convinced. There's much less energy in a gallon of LPG - only about three quarters as much - so expect mpg to be down by about 25%HOW MANY LPG CARS HAVE YOU OWNED ?
I've owned at least 10 - currently own 2
With a decent multipoint kit I cannot tell the difference in power and whilst there may be a small difference in mpg it's so slight it's not worth worrying about - perhaps 2mpg
They also add to resale - try to buy an LPG car !
I have managed to buy LPG yanks but most of the LPG cars have done rocketship mileages or are so overpriced I've bought a car and then converted it.
OK so its not a sports car, but I've had my 1986 Range Rover 3.5EFi on LPG for over 12 years.
You will get less MPG on LPG - I average just over 13mpg on LPG, towing & fully loaded or empty. BUT take into account that LPG is about 1/2 the price per gallon then you need to multiply the LPG mpg by 2 to get the cost equivalent. This is what people fail to realise or take into account. What it means is that I am going around 26 miles for the COST of a gallon of petrol. That's what I would expect of the same vehicle with a factory fit LR diesels
The main issue is the loss of loadspace to accomodate the tank - in my case I have sill tanks so no issue.
LPG burns slower than petrol. Advancing the timing will give it a better burn & the power difference is then pretty much undetectable. There are electronic gizmos on the market which will alter the timing automatically so it will run on either fuel.
You can't take an LPG car on the Channel Tunnel.
Some insurers won't touch LPG cars at all, some require an inspection, some couldn't care less as long as you tell them.
Cars that require leaded fuel may suffer from valve erosion - but that would be the case running it on unleaded.
I note on mine that the oil stays a lot cleaner - dipstick oil is always clear, although oil changes still come out black - so less crap in the engine.
You will get less MPG on LPG - I average just over 13mpg on LPG, towing & fully loaded or empty. BUT take into account that LPG is about 1/2 the price per gallon then you need to multiply the LPG mpg by 2 to get the cost equivalent. This is what people fail to realise or take into account. What it means is that I am going around 26 miles for the COST of a gallon of petrol. That's what I would expect of the same vehicle with a factory fit LR diesels
The main issue is the loss of loadspace to accomodate the tank - in my case I have sill tanks so no issue.
LPG burns slower than petrol. Advancing the timing will give it a better burn & the power difference is then pretty much undetectable. There are electronic gizmos on the market which will alter the timing automatically so it will run on either fuel.
You can't take an LPG car on the Channel Tunnel.
Some insurers won't touch LPG cars at all, some require an inspection, some couldn't care less as long as you tell them.
Cars that require leaded fuel may suffer from valve erosion - but that would be the case running it on unleaded.
I note on mine that the oil stays a lot cleaner - dipstick oil is always clear, although oil changes still come out black - so less crap in the engine.
Edited by paintman on Thursday 6th March 09:04
p1tse said:
On some cars its proven that super unleaded can give more power so I wander how LPG stacks up
That's down to how the petrol management is mapped. If the base map is set for 98RON and uses a knock sensor to pull the timing back for 95, then - yep - it'll give more power on 98. But since LPG is around 100-105RON, pinking is the least of your concerns. If you're setting it up as LPG-only, you can take advantage of that and regain the power lost to the lower calorific content.Twice the servicing? Hardly - it's only a couple of filters and they don't need doing often. As for complexity yes it does add some pipework, injectors, an ECU and an evaporator so there is more to go wrong there, there's no denying that. Twice the complexity is pushing it though. Losing load space/spare wheel well is just an unfortunate fact of life with it.
As for why it's cheap - tax.
Not all garages sell it, it requires specific tanks and pumps so it's quite an investment.
Manufacturers have offered it, but for reasons best known only to themselves tend to put it on generic 1.6 litre hatchbacks which are quite good on fuel already rather than on cars where it would really make a difference. It's the usual chicken/egg thing.
Unless it's on something really, really thirsty LPG doesn't really make sense unless you do a lot of miles, but then nor does diesel.
As for why it's cheap - tax.
Not all garages sell it, it requires specific tanks and pumps so it's quite an investment.
Manufacturers have offered it, but for reasons best known only to themselves tend to put it on generic 1.6 litre hatchbacks which are quite good on fuel already rather than on cars where it would really make a difference. It's the usual chicken/egg thing.
Unless it's on something really, really thirsty LPG doesn't really make sense unless you do a lot of miles, but then nor does diesel.
skyrover said:
Twice the servicing, twice the complexity, twice the chance of something going wrong
Well yes, but how much servicing and complexity does your petrol fuel tank and delivery system require and how often does it go wrong? Replacing two filters every five years instead of one is hardly a huge cost. 
TooMany2cvs said:
... since LPG is around 100-105RON, pinking is the least of your concerns. If you're setting it up as LPG-only, you can take advantage of that and regain the power lost to the lower calorific content.
And that's where my interest starts to kick in. Given the high RON (106), an LPG-only engine could be built with a very high compression ratio and better ignition advance which would give huge power, wonderful torque and decent economy - and it would run on cheap fuel. The only downside is that it would ONLY run on LPG, with no option of a reserve petrol tank. Has anyone ever done this?
Oli.
Depending on how sporty the car - if it's a common and fairly affordable sporty car then fair enough. If it's something half-way rare or exotic then it'll probably be both a massive red flag for any future buyer and with most exoticish cars the fuel costs although high are backed up by high other running costs such as servicing/parts/consumeables etc.
Nobody wants to buy a Ferrari that has been modified by a previous owner to save money, and furthermore nobody wants a converted car unless there's already a strong track record of that engine not suffering adverse consequences from conversions.
Nobody wants to buy a Ferrari that has been modified by a previous owner to save money, and furthermore nobody wants a converted car unless there's already a strong track record of that engine not suffering adverse consequences from conversions.
I'v also had a lot of LPG cars, currently own 2, a Jeep & a Jag.
Neither are particularly "sporty", but the Jaguar is the 4.2. V8, in a Jaguar X350. So is respectably quick. I don't notice any power difference. I don't find having the 2 filters changed every 12k much of a ball ache either. Re resale, I sold my previous LPG Jag (1996 with 325k miles) almost immediately for £1500 about 4 years ago. As someone else said, try finding a LPG car, they usually have a premium, and also most have very high miles, as people who buy or convert cars usually do as they are expecting to do high miles. I would have no hesitatioon in converting a high performance car, or classic, the key is a good installer. i have previously owned an old Silver Shadow on gas, and only last week was chatting to a guy at the LPG pump with an Audi W12, LPG converted. He'd had it since 10k, now over 100k, all on LPG.
Re last post, I would be the man who would buy a Ferrari, or XJ-S, 928 etc running on LPG !
Neither are particularly "sporty", but the Jaguar is the 4.2. V8, in a Jaguar X350. So is respectably quick. I don't notice any power difference. I don't find having the 2 filters changed every 12k much of a ball ache either. Re resale, I sold my previous LPG Jag (1996 with 325k miles) almost immediately for £1500 about 4 years ago. As someone else said, try finding a LPG car, they usually have a premium, and also most have very high miles, as people who buy or convert cars usually do as they are expecting to do high miles. I would have no hesitatioon in converting a high performance car, or classic, the key is a good installer. i have previously owned an old Silver Shadow on gas, and only last week was chatting to a guy at the LPG pump with an Audi W12, LPG converted. He'd had it since 10k, now over 100k, all on LPG.
Re last post, I would be the man who would buy a Ferrari, or XJ-S, 928 etc running on LPG !
Gassing Station | EV and Alternative Fuels | Top of Page | What's New | My Stuff