Discussion
I think there was an LPG Chimera or Griff. Don't see why you couldn't do this, swap the injectors for LPG ones and install a mapable ECU.
I've often thought about this as I run a 5 litre Rover V8 engined car on dedicated (i.e. no petrol)LPG. Even in a mild state of tune and running old-skool LPG components this produces 220HP at the wheels.
Its something I may look at for the Cerbera.....
There is a reasonable amount of mis-information about LPG, some of of it right here on PH
, but it is a good fuel (apart from its cost) due to its octane rating and clean burning (good for the environment and your engine life). The drawbacks are bulky fuel tank and less (about 85%) calorific value compared to petrol.
I've often thought about this as I run a 5 litre Rover V8 engined car on dedicated (i.e. no petrol)LPG. Even in a mild state of tune and running old-skool LPG components this produces 220HP at the wheels.
Its something I may look at for the Cerbera.....
There is a reasonable amount of mis-information about LPG, some of of it right here on PH
, but it is a good fuel (apart from its cost) due to its octane rating and clean burning (good for the environment and your engine life). The drawbacks are bulky fuel tank and less (about 85%) calorific value compared to petrol.
I think someone put an LPG system on a Dodge Viper, but he was running the LPG+petrol at the same time for more power.
I've had loads of LPG powered cars, no problems with them at all so when I bought the Cerb, said to the wife "we could LPG this?" Her reply was - "What the F**k would you want to do that for?"
I've had loads of LPG powered cars, no problems with them at all so when I bought the Cerb, said to the wife "we could LPG this?" Her reply was - "What the F**k would you want to do that for?"
Byff said:
I think someone put an LPG system on a Dodge Viper, but he was running the LPG+petrol at the same time for more power.
I've had loads of LPG powered cars, no problems with them at all so when I bought the Cerb, said to the wife "we could LPG this?" Her reply was - "What the F**k would you want to do that for?"
Your wife is a smart cookie!!!!!I've had loads of LPG powered cars, no problems with them at all so when I bought the Cerb, said to the wife "we could LPG this?" Her reply was - "What the F**k would you want to do that for?"
tofts said:
The short answer is you could LPG any petrol car.
But why would you want to, 100% lpg looses somewhere in the region of 5-10% power and the headache of fitting it can be enormous, not to mention you would have no boot space at all.
All in all, I don't think its work it.
Not sure I agree with that. Valve seats have been a major problem on some engines, later Saabs had major issues despite OEM kits being offered. Flashlube isn't a universal cure. But why would you want to, 100% lpg looses somewhere in the region of 5-10% power and the headache of fitting it can be enormous, not to mention you would have no boot space at all.
All in all, I don't think its work it.
I'd be loath to fit LPG on an AJP or a SP6 or AJP8 unless you know someone who has run one without problems. Less of an issue on LS or RV8 engines where lots have used LPG, especially RV8's in Landies and RR's.
The power loss depends on the engine tbh - I had a five pot turbo Volvo and it boosted harder on gas.
How funny, this thread caught my eye and I see that I responded to it 11 years ago! LPG is a good fuel, I still have my cerbera but haven't converted it as I don't do the miles these days. Still have the 5 litre rover, it was repatriated to the UK last year from New Zealand where I'm from. Just need to get it registered. Since my original reply, I've got married, had a child and my wife's car is an old D2 Audi A8 4.2 V8 on LPG. It's a very smooth system, so I think a S6 or V8 cerbera would be fine with a modern gas injection system. Jus be prepared for some development work, like any cerbera modification. 
Simon Sparrow
Simon Sparrow
I'd be happy to advise anyone genuinely considering converting their Cerbera to LPG.
I spent over a year planning the dual fuel conversion of my TVR Chimaera, and the last three years honing and refining my installation and system.
I came to to project with a good working knowledge of LPG systems and approached the project with the express objective of designing out all the traditional pitfalls and compromises associated with LPG conversions.
The key elements of my design brief were:
1. My TVR should give away no external clues to reveal it is running on LPG
2. My TVR should suffer no power loss when running on LPG
3. My TVR should deliver equal drivability on LPG as it does on petrol
4. Luggage space and the ability to still fit the targa roof panel in the boot should be retained
5. The car should absolutely retain the character, sound and driving experience of a TVR
These five design brief rules have remained the constant drivers behind the project, while my experience of gaseous fuel systems was good, having worked on both LPG and CNG systems in the UK and New Zealand, I used this LPG project to deep drive into the chemistry of the fuel and to design a system that eradicated all the well known pitfalls and compromises associated with this fuel.
Some key FACTS about LPG people should understand from the outset:
1. LPG is a mix of propane & butane - butane is added to improve the behaviour of propane during cold ambient temperatures - the percentage of this mix will change by country and season - as such the combustion properties can vary slightly so a dynamic air fuel ratio compensation strategy (wide band closed loop) should be considered
2. LPG in it's gaseous state has a lower calorific value than petrol - the percentage is somewhere between 15-20% lower by volume dependent of the proportion of butane present
3. LPG only has a lower calorific value to petrol by volume when it's in the gaseous state - LPG in it's liquid state actually has a higher calorific value than petrol
4. The lower calorific value of LPG in it's gaseous state will have an inevitable impact on fuel economy, dependant on many variables you must accept even the best systems will experience somewhere between a 15-20% increase in fuel consumed over the same given distance travelled on petrol
5. The increased fuel consumption must be compensated for by an increase in fuel capacity by the same percentage if the vehicle's range is to be retained - 20% increase in fuel consumed = 20% increase in fuel capacity
6. Packaging - A 20% increase in fuel capacity will result in a 20% loss of luggage space if the original petrol capacity is to be retained
7. Weight - A 20% increase in fuel capacity will result in a 20% increase in weight - LPG is stored in the vehicle in it's compressed liquid state - pressure figures are actually quite low as LPG becomes a liquid at 140psi (at room temperature) but still requires (by law) tanks that are capable of holding pressures well in excess of this figure (600psi) - this pressure requirement means the tanks are manufactured from steel which is heavy compared with the aluminium used by TVR for the Cerbera petrol tank - overall and if the original petrol capacity is to be retained those considering an LPG conversion must accept a 25% increase in the vehicle's fuel weight (including tank weight increase) will be inevitable - clearly this can be mitigated by reducing the petrol capacity and using the space/weight saved to store the LPG
8. If the vehicle is designed to consume LPG in it's gaseous state a system to manage the process of converting the fuel stored in it's liquid state to that of a gas must be implemented - this system must also be capable of accurately managing the significant drop in pressure during the fuel state transition - during the process of changing from a liquid to a gas LPG will actually boil at -42°C this cold energy must be effectively managed
9. Pressure management - As previously stated pressure management is critical, on a petrol injection system fuel is delivered at a fairly fixed pressure by the high pressure fuel pump, the pressure to the petrol injectors is then ultimately very accurately managed by the fuel pressure regulator - in an LPG system fuel pressure and delivery is dictated by the pressure held inside the LPG tank or tanks - unlike a high pressure petrol injection fuel pump, the pressure inside an LPG tank will vary significantly dependant on a combination of LPG level and ambient temperatures - a system that accurately manages the pressure at the LPG injectors is essential, this system must also allow for a very rapid increase in pressure when accelerating
10 LPG injectors - When injecting a gaseous fuel an injector type must me selected that is capable of delivering a far higher volume of fuel than an injector designed to deliver a liquid fuel - petrol injectors known as "saturated" injectors are not capable of delivering a gaseous fuel in the volumes required as such "peak & Hold" injectors must be used - Peak & Hold injectors require different injector drivers to those that run your petrol injectors, and unlike saturated petrol injectors these Peak & Hold injectors also create a lot of heat at their drivers - this resistive heat must me managed to ensure injector driver reliability and longevity
11. LPG has an octane rating of 110 Ron, it is therefore far more tolerant to detonation making it ideal for high compression engines or those functioning on forced induction - the auto ignition temperature of LPG is 450°C, the auto ignition temperature of petrol is far lower at 247–280°C.
12. Ignition timing - To take advantage of the far higher octane rating of LPG and its far greater resistance to detonation (see auto ignition temp difference above) an efficient system must have the ability to alter the ignition timing when you switch to LPG - an efficient LPG ignition map will look very different to an efficient petrol map - in simple term you need more advance earlier on LPG but slightly less timing at the upper end of engine speed - additional variables include engine load, air temperature, fuel temperature, fuel pressure ect - as such a sophisticated 3D mappable ignition system is required for optimum efficiency
13: Ignition continued - LPG is harder to strike than petrol, to ignite LPG you need a healthy and powerful ignition system ideally capable of longer ignition durations - this increases the load on all ignition components namely coils, HT leads & spark plugs, as such the very best ignition components should be selected and the frequency of maintenance/replacement schedules considered
14. Delivered in it's gaseous state LPG is very sensitive to small changes in ambient and under bonnet temperatures - the volume of LPG in its gaseous state may increase and decrease by as much as 28% over the range of normal operating or environmental temperatures
15. IMPORTANT: Fluctuations in fuel pressure and volume will have a significant effect on air fuel ratios - as such a fast responding strategy must be implemented to compensate for the inevitable challenges presented by fuel volume changes during normal operating conditions it should also be noted LPG vapour density is 1.6 times that of air - A post combustion compensation strategy such as wide band closed loop fuelling is essential, further benefits can be gained by implementing pre-combustion strategies referencing LPG temperature and pressure at the injectors
SUMMARY
So you can see there's a lot to consider, LPG is mostly implemented on the cheap by people who have little or no knowledge of fuel chemistry or the true behaviour of gaseous fuels. Most if not all vehicles are converted with the express objective of saving money, as such corners are cut, cheap components are used.
Hopefully all this serves to explain why LPG has a bad reputation, the fuel is actually excellent but the understanding, systems and components used are very often woefully poor.
My TVR meets or exceeds all my design brief objectives, indeed it is more powerful, nicer to drive and way way more economical than a standard 4.0 litre Chimaera.
The end result is a better car in all respects that is capable of delivering petrol equivalent fuel economy in excess of 53mpg while remaining every bit a TVR.
The moral of the story is you can have your cake and eat it but you need to accept converting any vehicle to LPG is a project that must be approached with care and intelligence.
Hope this helps?
Dave.
I spent over a year planning the dual fuel conversion of my TVR Chimaera, and the last three years honing and refining my installation and system.
I came to to project with a good working knowledge of LPG systems and approached the project with the express objective of designing out all the traditional pitfalls and compromises associated with LPG conversions.
The key elements of my design brief were:
1. My TVR should give away no external clues to reveal it is running on LPG
2. My TVR should suffer no power loss when running on LPG
3. My TVR should deliver equal drivability on LPG as it does on petrol
4. Luggage space and the ability to still fit the targa roof panel in the boot should be retained
5. The car should absolutely retain the character, sound and driving experience of a TVR
These five design brief rules have remained the constant drivers behind the project, while my experience of gaseous fuel systems was good, having worked on both LPG and CNG systems in the UK and New Zealand, I used this LPG project to deep drive into the chemistry of the fuel and to design a system that eradicated all the well known pitfalls and compromises associated with this fuel.
Some key FACTS about LPG people should understand from the outset:
1. LPG is a mix of propane & butane - butane is added to improve the behaviour of propane during cold ambient temperatures - the percentage of this mix will change by country and season - as such the combustion properties can vary slightly so a dynamic air fuel ratio compensation strategy (wide band closed loop) should be considered
2. LPG in it's gaseous state has a lower calorific value than petrol - the percentage is somewhere between 15-20% lower by volume dependent of the proportion of butane present
3. LPG only has a lower calorific value to petrol by volume when it's in the gaseous state - LPG in it's liquid state actually has a higher calorific value than petrol
4. The lower calorific value of LPG in it's gaseous state will have an inevitable impact on fuel economy, dependant on many variables you must accept even the best systems will experience somewhere between a 15-20% increase in fuel consumed over the same given distance travelled on petrol
5. The increased fuel consumption must be compensated for by an increase in fuel capacity by the same percentage if the vehicle's range is to be retained - 20% increase in fuel consumed = 20% increase in fuel capacity
6. Packaging - A 20% increase in fuel capacity will result in a 20% loss of luggage space if the original petrol capacity is to be retained
7. Weight - A 20% increase in fuel capacity will result in a 20% increase in weight - LPG is stored in the vehicle in it's compressed liquid state - pressure figures are actually quite low as LPG becomes a liquid at 140psi (at room temperature) but still requires (by law) tanks that are capable of holding pressures well in excess of this figure (600psi) - this pressure requirement means the tanks are manufactured from steel which is heavy compared with the aluminium used by TVR for the Cerbera petrol tank - overall and if the original petrol capacity is to be retained those considering an LPG conversion must accept a 25% increase in the vehicle's fuel weight (including tank weight increase) will be inevitable - clearly this can be mitigated by reducing the petrol capacity and using the space/weight saved to store the LPG
8. If the vehicle is designed to consume LPG in it's gaseous state a system to manage the process of converting the fuel stored in it's liquid state to that of a gas must be implemented - this system must also be capable of accurately managing the significant drop in pressure during the fuel state transition - during the process of changing from a liquid to a gas LPG will actually boil at -42°C this cold energy must be effectively managed
9. Pressure management - As previously stated pressure management is critical, on a petrol injection system fuel is delivered at a fairly fixed pressure by the high pressure fuel pump, the pressure to the petrol injectors is then ultimately very accurately managed by the fuel pressure regulator - in an LPG system fuel pressure and delivery is dictated by the pressure held inside the LPG tank or tanks - unlike a high pressure petrol injection fuel pump, the pressure inside an LPG tank will vary significantly dependant on a combination of LPG level and ambient temperatures - a system that accurately manages the pressure at the LPG injectors is essential, this system must also allow for a very rapid increase in pressure when accelerating
10 LPG injectors - When injecting a gaseous fuel an injector type must me selected that is capable of delivering a far higher volume of fuel than an injector designed to deliver a liquid fuel - petrol injectors known as "saturated" injectors are not capable of delivering a gaseous fuel in the volumes required as such "peak & Hold" injectors must be used - Peak & Hold injectors require different injector drivers to those that run your petrol injectors, and unlike saturated petrol injectors these Peak & Hold injectors also create a lot of heat at their drivers - this resistive heat must me managed to ensure injector driver reliability and longevity
11. LPG has an octane rating of 110 Ron, it is therefore far more tolerant to detonation making it ideal for high compression engines or those functioning on forced induction - the auto ignition temperature of LPG is 450°C, the auto ignition temperature of petrol is far lower at 247–280°C.
12. Ignition timing - To take advantage of the far higher octane rating of LPG and its far greater resistance to detonation (see auto ignition temp difference above) an efficient system must have the ability to alter the ignition timing when you switch to LPG - an efficient LPG ignition map will look very different to an efficient petrol map - in simple term you need more advance earlier on LPG but slightly less timing at the upper end of engine speed - additional variables include engine load, air temperature, fuel temperature, fuel pressure ect - as such a sophisticated 3D mappable ignition system is required for optimum efficiency
13: Ignition continued - LPG is harder to strike than petrol, to ignite LPG you need a healthy and powerful ignition system ideally capable of longer ignition durations - this increases the load on all ignition components namely coils, HT leads & spark plugs, as such the very best ignition components should be selected and the frequency of maintenance/replacement schedules considered
14. Delivered in it's gaseous state LPG is very sensitive to small changes in ambient and under bonnet temperatures - the volume of LPG in its gaseous state may increase and decrease by as much as 28% over the range of normal operating or environmental temperatures
15. IMPORTANT: Fluctuations in fuel pressure and volume will have a significant effect on air fuel ratios - as such a fast responding strategy must be implemented to compensate for the inevitable challenges presented by fuel volume changes during normal operating conditions it should also be noted LPG vapour density is 1.6 times that of air - A post combustion compensation strategy such as wide band closed loop fuelling is essential, further benefits can be gained by implementing pre-combustion strategies referencing LPG temperature and pressure at the injectors
SUMMARY
So you can see there's a lot to consider, LPG is mostly implemented on the cheap by people who have little or no knowledge of fuel chemistry or the true behaviour of gaseous fuels. Most if not all vehicles are converted with the express objective of saving money, as such corners are cut, cheap components are used.
Hopefully all this serves to explain why LPG has a bad reputation, the fuel is actually excellent but the understanding, systems and components used are very often woefully poor.
My TVR meets or exceeds all my design brief objectives, indeed it is more powerful, nicer to drive and way way more economical than a standard 4.0 litre Chimaera.
The end result is a better car in all respects that is capable of delivering petrol equivalent fuel economy in excess of 53mpg while remaining every bit a TVR.
The moral of the story is you can have your cake and eat it but you need to accept converting any vehicle to LPG is a project that must be approached with care and intelligence.
Hope this helps?
Dave.
There are other issues at play here with this type of car though.
Firstly, it is likely to diminish the market for potential purchasers as many will see it as a downside on this type of car.
Secondly, no matter what kit you have, it's another thing to service and another thing to potentially go wrong.
Finally the clincher for most - who does the mileage to make it worth the conversion??
Firstly, it is likely to diminish the market for potential purchasers as many will see it as a downside on this type of car.
Secondly, no matter what kit you have, it's another thing to service and another thing to potentially go wrong.
Finally the clincher for most - who does the mileage to make it worth the conversion??
JezF said:
There are other issues at play here with this type of car though.
Firstly, it is likely to diminish the market for potential purchasers as many will see it as a downside on this type of car.
In response my point would be people don't convert to LPG to increase their vehicle's market value, what they are doing is making it cheaper to own and enjoy, as such any decline in resale value is greatly compensated for in the fuel savings over a calculated period.Firstly, it is likely to diminish the market for potential purchasers as many will see it as a downside on this type of car.
Those seriously considering investing in an LPG conversion do so on the understanding the car will be retained for an extended period in order to recoup the costs of the installation.
JezF said:
Secondly, no matter what kit you have, it's another thing to service and another thing to potentially go wrong.
Gaseous LPG systems are very much a known entity, if a quality kit is procured and installed correctly the reality is very little if any additional maintenance is required, indeed a vehicle consuming LPG can enjoy extended oil changes due to the clean burning nature of the fuel.JezF said:
Finally the clincher for most - who does the mileage to make it worth the conversion??
I would like to award a prize for stating the obvious but this seems as pointless as your comment, anyone lacking the intelligence to complete a simple return on investment calculation deserves to be left in a financially negative position.FINALLY
I have provided a 15 point overview of LPG, it is by no means anywhere near as comprehensive as I could make it but I wanted to present the facts as they stand in a simplified and condensed way everyone could understand.
You may also have noticed I omitted the subject of valve seat erosion, this is intentional as it is very much a subject in it's own right warranting a more detailed response based on the specific vehicle in question.
The subject of LPG always seems to attract the comments of doubters and naysayers, these people typically expose their own ignorance to the truthful facts surrounding LPG by the very statements they make. Many have had bad experiences with LPG and many more pass on these tales of woe in a way that would have you believe its fact, the truth is if you take the time to unpick the facts behind every case you will always find deficiencies in knowledge, components used or fuel delivery/ignition management systems.
There a over 250,000 LPG converted vehicles traveling millions of combined miles every year in the UK alone, and we dont even use LPG that much here compared with other countries. Across the world from Brazil to Japan, from Holland to Turkey and out to New Zealand and Australia there are literally millions and millions of vehicles happily consuming LPG with no issues at all.
Ignorance is common in all walks of life but the subject of LPG for some reason seems to be a magnet for it here in the UK, modern LPG delivery and management systems are extremely sophisticated and reliable and should not be confused with what was used even just 10 years ago.
My recommendation to anyone genuinely considering converting their vehicle to LPG, is to take advice from someone who truly understands the chemistry and behavior of this fuel. They should avoid falling in the trap of listening to the naysayers who are most likely just repeating something they heard down the pub.
LPG is an excellent fuel and in many areas actually offers advantages over petrol beyond the cost saving element, the fact its half the price of petrol is really just down to European taxation rules that support the lower rate of tax due to this fuel's significantly lower impact on the environment, this will not change and is replicated by every government across the globe.
LPG is here to stay; if you understand the way the fuel behaves, use the right modern components and install everything correctly, LPG represents an excellent alternative fuel that delivers significant cost improvements over petrol but environmental and engine life benefits too.
Like anything else in life, if you ignorantly blunder into converting your vehicle to LPG and try to do it on an inadequate budget you will quickly get your fingers burnt, but ask yourself honestly if this was the fault of LPG itself or the way you approached your conversion?
Edited by ChimpOnGas on Tuesday 1st March 10:23
JezF said:
Hey - you got any toys left in your pram???
I ran a car on LPG for 75,000 miles. A car I chose to have converted using a BRC system.
I'm fully aware of the benefits and of the drawbacks.
Lol, bless you Jez, my apologies... I'm on my period this week I ran a car on LPG for 75,000 miles. A car I chose to have converted using a BRC system.
I'm fully aware of the benefits and of the drawbacks.
Edited by JezF on Tuesday 1st March 10:28
Hope you enjoyed those 75,000 miles?
How did the BRC system and installation treat you?
I would imagine 75,000 miles is plenty enough to get your ROI... plus some?
Share your experiences good and bad, and reveal the car in question.
Lets be LPG friends
Dave.Xxx
ChimpOnGas said:
Lol, bless you Jez, my apologies... I'm on my period this week
Hope you enjoyed those 75,000 miles?
How did the BRC system and installation treat you?
I would imagine 75,000 miles is plenty enough to get your ROI... plus some?
Share your experiences good and bad, and reveal the car in question.
Lets be LPG friends
Dave.Xxx
Lol Dave! Hope you enjoyed those 75,000 miles?
How did the BRC system and installation treat you?
I would imagine 75,000 miles is plenty enough to get your ROI... plus some?
Share your experiences good and bad, and reveal the car in question.
Lets be LPG friends
Dave.Xxx
It was on a Volvo 850R, a five pot 2.3 high pressure turbo. Problem was I bought the car as a shed to tidy me over (it was an auto and I'd badly broken my left leg) then fell in love with the thing so wanted to keep it. As I was doing 20,000 miles a year I couldn't stomach the poor mpg though.
I decided to try LPG as I was aware of the benefits in terms of lower fuel costs.
I had a good and bad experience tbh.
Good in that it did cost me a lot less, getting 50mpg equivalent when LPG was cheaper. Plus when it was working, it was superb, completely seemless transition and perfect running on gas.
The main bad bit was how long it took the converters to get it working properly, eventually traced to a sensor that was causing no problems with petrol. That was probably over 20,000 miles and 20 visits to the bloody garage and it manifested as a stutter at full throttle. Then I had to get rid of it after 75,000 miles (the car had done 220,000 miles) when what turned out to be another sensor issue caused problems that I gave up trying to trace.
Compared to a diesel I'm not sure it really pays unless you buy a thirsty petrol engined car that you fall in love with. Maybe if you are that fixated with petrol over diesel. I now have a diesel Octavia VRS which is fast, spacious and averages 45mpg without any of the hassles of short range, extra servicing and no Chunnel use.
Edited by JezF on Tuesday 1st March 14:12
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