LPG Chimaera (Follow My Conversion)
Discussion
CHIMV8 said:
Will she sound the same??
In it's current normally aspirated state, it will sound 100% exactly the same.Combustion on LPG produces the same tone & volume as combustion on petrol.
I have the no cats (pre-cats removed & ACT Flowed Y-piece) & standard silencer set up, which for me is as far as I want to go given I like to tour Europe in the car.
With this exhaust set up, it sounds like a TVR should on petrol, & will sound like one on LPG.
So absolutely no change at all in the sound department, or the performance department either.
There will be no external evidence the car is running on LPG & no loss of range or luggage capacity (roof on or off).
All the TVR thrills, practicality & unique character remain completely unaltered, this was an essential part of the design brief.
The only difference the LPG conversion delivers is the car will now return the cost equivalent of 40 - 45mpg depending on how you dive it.
Cake & eat it
Edited by ChimpOnGas on Saturday 2nd March 20:00
rburnham11 said:
Great project and certainly well thought out, nice. One thing.... by law do you have to display those bright stickers on the back of the car saying that there is compressed gas on board? I hope not as if I was going all out to make it so you couldn't tell it was lpg from the outside having to put a cruddy sticker on it would drive me mad.
Just thinking out loud
Thanks rburnham11.Just thinking out loud
Honestly folks you could take this one to a TVR show & even the TVR nerds won't be able to spot it's been converted.
Even with the bonnet open it'll be easy to miss, and with the tanks trimmed in the same grey boot carpet it's the exactly same story if I display the car with the boot open too.
With no external filler which is the normal givaway a car is running on LPG, & no nasty "gas on board" safety sticker required, it will be impossible to tell its on gas.
For some reason there still seems to be a stigma surrounding LPG, but I just don't get this.
If it sounds the same & performs the same, if it looks the same & holds the roof & luggage the same, then I can't see why there should be any stigma whatsoever?
This one isn't a taxi & it isn't a cheap old worn out 4x4 either.
It's 100% TVR, just one that will do the cost equivalent of 40-45mpg.
I hope people can see in this case the LPG stigma needs to be forgotten?
Dr Mike Oxgreen said:
The elephant in the room is government taxation policy, which is something nobody can control (not even as voters, if we're honest). It wasn't so very long ago that diesel was cheaper than petrol; I hope you reach payback before the chancellor scuppers your plans.
That argument has been touted as a reason not to convert for years & years.If people converting hadn't chosen to ignore it back then, the facts are they would have missed out thousands of ponds in fuel savings.
I don't want to miss my future savings either.
I choose to let history be our best guide, & the fact is the percentage price difference between petrol & LPG has remained the same for well over 10 years.
The truth is the Uk are in a domestic energy crisis right now & it's not getting any better, the gas we use to heat our houses comes from Russia & the Russians know we can't live with out it.
So while they continue to have huge reserves of natural gas they keep pushing the price up because they've got us firmly over a barrel.
So how does all this affect the price of liquid petroleum gas?
Well the government is responding to being held to ransome by Russia by looking for new ways to harvest our own natural gas reserves.
Fracking licences have just been granted & the first attempts at this controversial gas extraction process have already sucessfully taken place just outside Liverpool.
The technology comes from the USA where they have a clear target to become 100% energy self sufficient in just a few years.
This is a replacement to their traditional policy of walking into oil rich countries to steal oil, which has just become too costly to sustain.
Since the fracking started the US natural gas production has rocketed, soon the Yanks will have more natural gas than they know what to do with.
We've been watching all this and copying it because all the geology reports suggest the UK has huge gas reserves just waiting to be tapped, just like our American cousins we will be a wash with our own domestic supply of cheap natural gas in 10 years time or less.
Converting my LPG TVR to compressed natural gas is no more complicated than a 10 minute tweak of the vaporiser.
So you see, history tells us LPG stays at the same price differential to petrol, & the future tells us cheap CNG is on the way.
Consequently even though I still don't have a crystal ball, I remain quietly confident we'll actually be seeing a lot more gas powered vehicles on the UK roads in the next few years.
Elephant in the room, EVICTED!!!
Edited by ChimpOnGas on Sunday 3rd March 09:34
Podie said:
I seem to recall LPG has benefits - quieter engine noise, increase octane, no acids or carbon deposits and improved combustion.
Correct 
On the engine noise point, people typically are referring to the smoother idle you get with LPG.
Engine noise actually remains the same it's just you get a smoother idle so it sounds sweeter on LPG.
Open the taps & on LPG it's still traditional full fat TVR sound effects all the way
Edited by ChimpOnGas on Sunday 3rd March 10:46
Podie said:
ChimpOnGas said:
Podie said:
I seem to recall LPG has benefits - quieter engine noise, increase octane, no acids or carbon deposits and improved combustion.
Correct Graphs will be posted, so until then I encourage you to place your bets folks.
To help, I'll try to give you an idea of the spec.
Firstly its important to stress the car is a 4.0 litre, with no head work whatsoever.
Both fuel types are independently controlled with the Canems system, ignition on both fuels is also independently & fully mapped 3D wasted spark.
The cam is a fresh Stealth profile from V8 Developments, this is accompanied by new followers and JP timing gear set & a lightened flywheel all from Rob Robertson.
All cats have been removed & an ACT flowed Y-Piece is in place, 250cc twin port pintel injectors replace the Lucas disc type originals.
An SC-Power plenum spacer helps lift the plenum just high enough to tuck the LPG injectors under the throttle body, it also keeps the mouths of the velocity stacks clear of the plenum roof and increases it's volume slightly too.
A full ACT induction kit is used including a K&N filter.
The Canems also allows for the deletion of the Air Flow Meter in favour of a free flowing large bore pipe, but remember its still on the standard throttle body & the wheezy restrictive 4.0 HC cylinder heads.
I'll start the bidding at:
Petrol: 245hp
LPG: 243hp
Place you predictions here, or tune in early next week for the true confirmed results.
SILICONEKID350HP said:
No problems MOT time with LPG ,the car will go through the emissions no problem .
For any tree huggers that may be out there (& I very much doubt there are many):Overall LPG produces 33% less CO2 emissions than petrol and 45% less CO2 than diesel.
- 63% less Carbon Monoxide
- 40% less Hydrocarbons than petrol and 70% less than diesel
- 50% less particulates than petrol and 98% less than diesel
- 40% less oxides of nitrogen than petrol & 50% less than diesel
- 87% less ozone than petrol
But it's nice to know I'll be ready to counter the challenges from any dolphin lovers I may be unlucky enough to meet when I'm out there ripping up the streets in "Ol Gasbag"
It takes over 120 LPG cars to equal the fine particles produced by one equivalent diesel car!!
It's a pocket friendly
dippy gas bag TVR with no loss in performance, character or sound.What's not to like
SILICONEKID350HP said:
We don`t have any or very little natural gas left because the Yanks who built the oil rigs and supplied the technology sold it has part of the deal while Norway kept on to there`s .
The Government at the time promised the UK we would have cheap oil /gas but they were full of bull
t. ,it did not stop them useing Tax payers money to part fund the project .
Not true Daz, that was back in the day when we were extracting from under the sea bed.The Government at the time promised the UK we would have cheap oil /gas but they were full of bull
t. ,it did not stop them useing Tax payers money to part fund the project .Gas extraction technology has moved on immeasurably, fracking has allowed us to look at huge reserves of natural gas trapped in bed rock hitherto thought to be completely inaccessible.
And this time were in charge of it.
Soon we'll be saying..
"Those thieving Rusky gas man can go do one"
pk500 said:
I dont do enough miles in my 500 to make a gas conversion pay! but on the plus side it does have benefits if you have it as a daily driver ! petrol super is £1.45 a litre and gas is 70p ish a ltr ! so 20 mpg is worth 40mpg ! I use an mot bay in sudbury and they do good quality lpg conversions not the rubish what the polish slap on !they do from ka`s to V8 audi`s supercharged range rovers ect ect done properly it is great ! no power loss ! i guess there are some people say it shouldn`t be done to a tvr ! same as changing wheels !suspension !light conversions !its all up to the indivdual prefrence i guess cant please every one ! i did mention the flash lube system but hey looks like you have researched and got every thing covered ! so good luck hope all goes to plan !
Thanks Paul, you're right you'll need to do the miles to make financial sense of any LPG conversion.So if all the downsides can be eliminated the only real argument against it that holds water is the one that says:
"I do too few miles for an LPG conversion to make financial sense"
Horses for courses and all that....
But I wouldn't mind betting there are quite a few TVR owners following this who are now at least considering something similar.
At the end of the day if the thing that most makes you smile about owning a TVR is driving it, then an LPG conversion can definitely help make driving it less financially painful.
You could in fact boil all this down to one simple equation:
More TVR miles
= More TVR smiles Well that's the way I see it
Hi Hugo,
The advance curve will be very different on LPG.
In the simplest terms LPG requires a lot more advance early on, but as engine speed rises the curve will flatten significantly when compared with petrol.
It is of course more complicated than this, as we know the picture is a three dimensional one, strategies will differ between the fuel types under the same RPM, air temperature & load conditions.
Fuel & ignition requirements work hand in hand, alter one & the other will be affected, but it's the different ignition requirements of LPG that are most often the downfall of a lesser conversion.
This is the reason why the ignorant continue to insist LPG will lose you power.
The truth is LPG shouldn't lose you any power whatsoever, this has been proven time & time again & in the real world, modern systems have banished the LPG power loss theory to the history books, FACT!
It's almost always the crude ignition control systems that conversions are often burdened with that are the culprit.
Sadly some people are still reading the old history books and really should update their knowledge on LPG engine management systems before making the outdated assumption LPG will lose you power.
Like all things engine management things have moved on immeasurably in the last few years, & LPG systems have finally caught up delivering very very impressive results.
It's well accepted that (until very recently) you really needed to replace the distributor to get the best performance from LPG.
I say "until very recently" because those still burdened by the distributor can now resolve many of the distributor's disadvantages for less than £200 by fitting something like this:
http://www.aldonamethyst.co.uk/
The Aldon Amethyst gives you back a lot of the control you need to make a half decent job of an LPG conversion for a relatively small outlay, of course to get the best from it you will still need the ignition mapping by someone that properly understands the unique requirements of LPG.
http://questmotorsport.co.uk/
Fuelling is a whole different subject, but essentially the same, by that I mean each fuel type has very different characteristics so will require very different strategies.
The LPG conversion industry get around these ignition & fuelling differences by fitting a second ECU, essentially this second ECU looks at the petrol injector durations & ignition timing and completes a little calculation to correct things for LPG.
This is known as a piggyback system & is what you will always find on every single modern LPG conversion out there, however not all piggyback systems are created equal.
Piggybacks range from the very crude to the extremely sophisticated, the difference typically being the amount of correction that's available to the installer.
I was given a demo of the Prins system, & you would be amazed how clever it is, yet also how simple the software & set up is too.
Select number of cylinders, lambda feedback ect ect & click OK.
Turn the key & it runs, a few very minor tweaks of the vaporiser ect and the mapping is complete, the ECU does the rest.
While this is extremely impressive and makes life incredibly easy for the installer, a piggyback system like this is only as good as the algorithms within & the correction inputs available.
At the end of the day all piggyback ECUs are trying to work with second hand petrol signals that are fundamentally wrong for LPG, it then makes assumptions that if it's "X" on petrol it should be "Y" on LPG.
It's a dumb system if you like, the LPG piggyback isn't looking directly at engine sensor inputs but trying instead to work out what's best for LPG from what essentially is only best for petrol.
As you can see, this is far from ideal.
In the ideal world what you actually need is an ECU that lets you build a unique LPG map based on first hand direct engine sensor inputs, just like you would on petrol.
Of course this does indeed exist in the form of the excellent Emerald system,.... MegaSquirt and many many others.
However, here's the problem....
You can easily get these systems delivering fantastic results on LPG, or petrol....
BUT NOT BOTH....
When you set up one of these stand alone systems you start by telling it the impedance of your injectors, & your petrol injectors will always have a very different impedance to your LPG injectors.
Surprisingly, these stand alone ECU systems do not have the ability to readily fire the petrol injectors on map one & the LPG injectors on map two.
It's a one or the other type deal, which is no good for a dual fuel vehicle, so even if you have an Emerald or similar you are still forced to fit a piggyback ECU
Consequently you are back to twisting second hand petrol signals to try and get the best from LPG.
Enter the Canems Dual Fuel ECU
Canems took the fundamentally flawed operation of the piggyback LPG system, & designed it out.
The Canems DF system for the first time not only allows you to build the perfect fuel & ignition map for petrol, but also allows you to build the perfect map for LPG based on first hand engine sensor inputs, not the second hand petrol information that's completely wrong in the first place.
For the driver it's simple, just flick the changeover switch on the move and you seamlessly switch from your perfected petrol map firing the petrol injectors, to your perfected LPG map firing the LPG injectors.
This sounds like quite a simple thing to design into an ECU, but I'm reliably informed it most certainly isn't.
I'm sure if you approached Phil Ringwood he could do it on a MegaSquirt or Dave Walker for the Emerald.
But as it stands & to my knowledge, the only people that have achieved the dual fuel ECU holly grail in an off the shelf proven package is Canems.
Canems also took the opportunity when designing the dual fuel system to add in other essential LPG specific requirements like LPG solenoid control, this contributes to making the system a much neater & integrated package for anyone looking to move to dual fuel.
The reality is all this is great in theory, but to really explore the potential advantages of the Canems DF ECU will require some extremely skilful mapping, however in practice these skills are no different to those used when mapping on petrol.
But you do need someone who truly understands the different requirements of the two fuels, and more importantly the specific & unique requirements of LPG.
The bottom line is, it doesn't matter how good the Canems DF system is, it doesn't matter how many advantages it seems to offer in theory, if the LPG mapping isn't done well it stands to be no better or worse even than a good piggyback.
As with all these things, the devil is most definitely in the detail
The advance curve will be very different on LPG.
In the simplest terms LPG requires a lot more advance early on, but as engine speed rises the curve will flatten significantly when compared with petrol.
It is of course more complicated than this, as we know the picture is a three dimensional one, strategies will differ between the fuel types under the same RPM, air temperature & load conditions.
Fuel & ignition requirements work hand in hand, alter one & the other will be affected, but it's the different ignition requirements of LPG that are most often the downfall of a lesser conversion.
This is the reason why the ignorant continue to insist LPG will lose you power.
The truth is LPG shouldn't lose you any power whatsoever, this has been proven time & time again & in the real world, modern systems have banished the LPG power loss theory to the history books, FACT!
It's almost always the crude ignition control systems that conversions are often burdened with that are the culprit.
Sadly some people are still reading the old history books and really should update their knowledge on LPG engine management systems before making the outdated assumption LPG will lose you power.
Like all things engine management things have moved on immeasurably in the last few years, & LPG systems have finally caught up delivering very very impressive results.
It's well accepted that (until very recently) you really needed to replace the distributor to get the best performance from LPG.
I say "until very recently" because those still burdened by the distributor can now resolve many of the distributor's disadvantages for less than £200 by fitting something like this:
http://www.aldonamethyst.co.uk/
The Aldon Amethyst gives you back a lot of the control you need to make a half decent job of an LPG conversion for a relatively small outlay, of course to get the best from it you will still need the ignition mapping by someone that properly understands the unique requirements of LPG.
http://questmotorsport.co.uk/
Fuelling is a whole different subject, but essentially the same, by that I mean each fuel type has very different characteristics so will require very different strategies.
The LPG conversion industry get around these ignition & fuelling differences by fitting a second ECU, essentially this second ECU looks at the petrol injector durations & ignition timing and completes a little calculation to correct things for LPG.
This is known as a piggyback system & is what you will always find on every single modern LPG conversion out there, however not all piggyback systems are created equal.
Piggybacks range from the very crude to the extremely sophisticated, the difference typically being the amount of correction that's available to the installer.
I was given a demo of the Prins system, & you would be amazed how clever it is, yet also how simple the software & set up is too.
Select number of cylinders, lambda feedback ect ect & click OK.
Turn the key & it runs, a few very minor tweaks of the vaporiser ect and the mapping is complete, the ECU does the rest.
While this is extremely impressive and makes life incredibly easy for the installer, a piggyback system like this is only as good as the algorithms within & the correction inputs available.
At the end of the day all piggyback ECUs are trying to work with second hand petrol signals that are fundamentally wrong for LPG, it then makes assumptions that if it's "X" on petrol it should be "Y" on LPG.
It's a dumb system if you like, the LPG piggyback isn't looking directly at engine sensor inputs but trying instead to work out what's best for LPG from what essentially is only best for petrol.
As you can see, this is far from ideal.
In the ideal world what you actually need is an ECU that lets you build a unique LPG map based on first hand direct engine sensor inputs, just like you would on petrol.
Of course this does indeed exist in the form of the excellent Emerald system,.... MegaSquirt and many many others.
However, here's the problem....
You can easily get these systems delivering fantastic results on LPG, or petrol....
BUT NOT BOTH....
When you set up one of these stand alone systems you start by telling it the impedance of your injectors, & your petrol injectors will always have a very different impedance to your LPG injectors.
Surprisingly, these stand alone ECU systems do not have the ability to readily fire the petrol injectors on map one & the LPG injectors on map two.
It's a one or the other type deal, which is no good for a dual fuel vehicle, so even if you have an Emerald or similar you are still forced to fit a piggyback ECU
Consequently you are back to twisting second hand petrol signals to try and get the best from LPG.
Enter the Canems Dual Fuel ECU
Canems took the fundamentally flawed operation of the piggyback LPG system, & designed it out.
The Canems DF system for the first time not only allows you to build the perfect fuel & ignition map for petrol, but also allows you to build the perfect map for LPG based on first hand engine sensor inputs, not the second hand petrol information that's completely wrong in the first place.
For the driver it's simple, just flick the changeover switch on the move and you seamlessly switch from your perfected petrol map firing the petrol injectors, to your perfected LPG map firing the LPG injectors.
This sounds like quite a simple thing to design into an ECU, but I'm reliably informed it most certainly isn't.
I'm sure if you approached Phil Ringwood he could do it on a MegaSquirt or Dave Walker for the Emerald.
But as it stands & to my knowledge, the only people that have achieved the dual fuel ECU holly grail in an off the shelf proven package is Canems.
Canems also took the opportunity when designing the dual fuel system to add in other essential LPG specific requirements like LPG solenoid control, this contributes to making the system a much neater & integrated package for anyone looking to move to dual fuel.
The reality is all this is great in theory, but to really explore the potential advantages of the Canems DF ECU will require some extremely skilful mapping, however in practice these skills are no different to those used when mapping on petrol.
But you do need someone who truly understands the different requirements of the two fuels, and more importantly the specific & unique requirements of LPG.
The bottom line is, it doesn't matter how good the Canems DF system is, it doesn't matter how many advantages it seems to offer in theory, if the LPG mapping isn't done well it stands to be no better or worse even than a good piggyback.
As with all these things, the devil is most definitely in the detail
Edited by ChimpOnGas on Monday 4th March 10:54
Dr Mike Oxgreen said:
Do you seriously think that chancellors are going to sit back and watch hordes of people migrate from petrol to LPG without doing something about it?
And that's just it, hordes of people aren't migrating from petrol to LPG.The truth is since the abolishment of Congestion Charge dispensation for LPG vehicles by the London Mayor Borris Johnson, the picture is quite the opposite.
My own company has now replaced our central London LPG delivery fleet (at the end of their natural life) with diesel Merc Sprinters because of this.
While we were saving £10 a day on every vehicle, LPG made perfect sense, now the LPG dispensation rule has been abolished it's back to giving London kids asthma with our carbon particular rich diesels
The truth is I'm actually more concerned that the recent fall in converted vehicles in the south will alter the economic viability of LPG being offered at a decent enough number of petrol stations.
However, what we do know now for sure is how the Tax Man works, & how he focusses his revenue harvesting energies.
He will look at easy quick wins that deliver high yield gains.
As such I personally very much doubt he will be focussing his efforts on a small niche market like LPG.
You may argue why not, isn't it's easy for him to raise the duty on LPG, and isn't it a case of every little helps?
Well not if that revenue stream dispersals the moment it's been created.
How so?
Here's how so - the typical man on the street who converts his car to LPG does so to save money.
This chap will soon stop filling up with LPG if he sees the price approach petrol, you must remember these conversions are dual fuel, they still run on petrol just like they always did.
So as fast as the Tax Man can stick up the price of LPG, the cost conscious duel fuel user will be hitting the petrol switch and passing the LPG pumps by.
No LPG sales = no additional tax & the whole revenue stream disappears as quickly as it was created.
But the biggest driver is my first point, LPG is still very much a niche market, so the Tax Man isn't really going to be investing his time looking closely at it.
I may be wrong of course, but I prefer to work with this type of evidence that pessimistic speculation, so here's some more evidence.
Historically LPG has always followed the same price differential to petrol, & for years & years, even when there was a small Congestion Charge discount bubble in LPG and conversions became quite popular in and around London, the Tax Man still wasn't interested.
I doubt he'll be interested in it now either as it represents an even smaller prize.
Fast forward five years when we start producing lots of shale gas, this may change, (for the better or worse) but my conversion will have easily paid for itself by then so again I'm not unduly worried.
Finally we need to look at the LPG taxation policies of other countries that have a lot more LPG vehicles on the road than us.
I have recently returned from Brazil, where you have three choices: Alcohol (Ethanol), Petrol or LPG.
Even with the abundance of cheap Ethanol literally millions of taxis still take the the LPG option because it's cheaper, for years each fare they take consistently delivers more profit on LPG than any other fuel.
The price difference remains the same between LPG & Petrol in Brazil as it is in the UK, and that's in a country where a gallon of petrol will cost you less than £4.00 BTW.
The Brazilian Tax Man isn't interested in LPG any more than UK Tax Man is.
It's the same story in France, Germany, Holland, Italy, Denmark ect ect, all countries where LPG is way more popular, and all countries where the price difference has remained static for years & years & years.
Finally, what are we going to do with all this LPG if we don't use a bit of it in our cars?
It's only a by-product of the petrochemical industry anyway.
Perhaps we should go back to 20 years ago when it was simply burnt off at the refinery releasing wasted energy into the atmosphere?
For a multitude of well considered reasons I doubt very much if LPG is going to rocket in price any time soon.
Like I say people have been pedalling this old chestnut in the UK for well over 10 years now as a reason why not to convert, and in all those years it simply never ever happened, here or anywhere else in the world for that matter.
If those considering an LPG conversion had listened to the LPG tax hike doomsayers back then, they'd have missed out on literally thousands of pounds of savings, FACT!
Ok it's always going to be a gamble, I'll give you that, but I believe history and a bit of reasoned logic places the odds in my favour.
Only time will tell.
Edited by ChimpOnGas on Tuesday 5th March 07:39
pjac67 said:
^^^ Well said Dave - I am more than impressed by your research, factually knowledge and measured, unbiased, informative responses posts throuhgout this thread.
Was given this link over on the Wedge forum - is this LPG commentary now out of date do you think?
http://www.mez.co.uk/TuningTheRoverV8-pt7.html
I did a 200 mile round trip at the week-end in the Griff and used £25 worth of fuel with still 1/3 of a tank left.. as you say "what's not to like"...
Keep up the good work and look forward to comparing notes when you are up and running.
Paul.
Hi Paul, thanks for giving us those figures, its great to hear some real world results from an existing TVR LPG user.Was given this link over on the Wedge forum - is this LPG commentary now out of date do you think?
http://www.mez.co.uk/TuningTheRoverV8-pt7.html
I did a 200 mile round trip at the week-end in the Griff and used £25 worth of fuel with still 1/3 of a tank left.. as you say "what's not to like"...
Keep up the good work and look forward to comparing notes when you are up and running.
Paul.
If you did 200 miles on £25 & I've got my maths right, you're seeing a real world 27mpg.
That's a good figure for these cars on petrol, never mind LPG that should by rights reduce direct fuel economy by 15%.
I believe you are running an Emerald ECU which is still one of the best & easiest to work with engine management systems available.
It's also giving you proper mapped ignition, which is essential if you want decent LPG economy & no loss of performance.
Clearly it's set up extremely well & the piggyback ECU is a good one doing an excellent job.
Lets look at that 27mpg figure again for a minute.
I use the 0.55 multiplier, you can check it works like this:
Petrol @ £1.35 litre x 0.55 = LPG at £0.75 per litre
So at a real world LPG consumption of 27mpg it looks like this:
27mpg x 0.55 = 14.85
14.85 + 27 = 41.85
Please feel free to correct my maths if its wrong, but from what I can see thats a truly excellent cost equivalent of 41.85mpg
I dont know what fuel economy you were getting on petrol in your Griff but knowing these cars typical fuel economy figures, it looks unlikely your losing much if any economy on LPG, let alone the much touted 15%.
If that's correct I speculate you would have spent £45.00 on petrol to cover those same 200 miles, so you've just saved £20.00 in only 200 miles, or put another way, £0.10p saved for every mile you drive the car.
Lets say your conversion cost you £1500, at £0.10p a mile saved it will have paid for itself in just 15,000 miles.
Assuming the tax man doesn't stick the duty up, even if you're only do 5,000 miles a year the conversion has paid for itself within only 3 years.
Or just 18 months if you do 10,000 miles a year
After that you are laughing all the way to the bank & driving an epic TVR Griffith that returns Ford Focus fuel economy.
Congratulations Paul, I call that a truly amazing result.
On the other hand if you take a litre price of petrol at £1.35 then times it by 1.80 you get the true LPG price of £0.75p a litre.
And having been following pump prices for a while now, these seem to be the correct average real world pump prices of both fuels.
If we use the 1.80 multiplier with Paul's figures it actually looks like this:
27mpg x 1.80 = 48.6
So Paul is actually seeing a mind bending cost equivalent of...
48.6 mpg
That conversion will pay for itself in no time mate
Edited by ChimpOnGas on Monday 4th March 16:20
pjac67 said:
Not sure of the maths there Dave - I fill up at 69p (soon to be 64p when I get my ountrywide a/c) so my 200/£25 is 25mpg (was a boring motorway/A road procession - I normally average closer to 20 when 'hooning' 
)
This is equivalent to 49 mpg assuming no equivalent MPG (or knock 10% off if you wish to assume some MPG loss = 45 mpg equiv.
The saving of 66p/litre means my £1400 system payback is within 2121 litres /466 gallons x 20 mpg av. = 9323miles which will be 18m for my 6k+ pa...
Does this look right or is there a flaw in my maths..?
Nice one Paul, your maths are indeed better than mine. )This is equivalent to 49 mpg assuming no equivalent MPG (or knock 10% off if you wish to assume some MPG loss = 45 mpg equiv.
The saving of 66p/litre means my £1400 system payback is within 2121 litres /466 gallons x 20 mpg av. = 9323miles which will be 18m for my 6k+ pa...
Does this look right or is there a flaw in my maths..?
I assumed an LPG price of £0.75p a litre, but I do live inside the M25 and we get ripped off on everything here.
Your price of £0.69p a litre is excellent, and £0.64 is amazing.
Your cost equivalent of 45mpg is what I'm aiming for with my baby 4.0 litre on the expensive stuff I will be buying.
Mind you, I do find it mildly amusing I'm referring to £0.75p a litre as expensive
I looked at getting a Countrywide acc but they mostly seem to be in the more rural areas, which I guess makes sense for the type of business they are.
My nearest Countrywide fill point is 30 miles away in Surrey, I'd really need one closer to home that that to make an account worthwhile
I do however have three LPG stations on my doorstep, BP that robs you at £0.78p a litre, while Sainsburys serves up the gas at £0.75 a litre.
So you are doing very well indeed with those prices mate, or more likely I'm just getting mugged again
The third option is as yet un-tested, it's a boat yard at the bottom of my street that advertise as selling Auto Gas.
I may just walk down there now & see what price they sell at.
Sardonicus said:
Dave not quite sure what's happened on this post or if some of the posts have been deleted? I didn't get the impression that Dr Oxgreen was sending you up so I am slightly 
has I have said already I have no intention of ever going LPG but I still find this post interesting same as the others & look forward to seeing the old girl running on the stuff Dr Oxgreen was actually just opening the debate wider, it wasn't the direct challenge I first thought it was at all.
I guess it's the way I read things sometimes, God knows Ribol & I have had some similar banter in the past
Apologies to Dr Oxgreen, I will try and read your responses better in future.
Actually from what I can see you are enjoying the debate & are interested in the project, if you really unpick it there are actually elements we agree on too.
I'll try & wind my arrogant neck in
Best regards, Dave.
gas wedge said:
chimpongas
just got the heads up from zig, good to see someone else taking this route, my wedge has only got a 55ltr tank ( as not designed for golf clubs and hairdressers bags )and the auto stop works at 80% that gives me about 46ltrs i get around 210-220 miles and that is usually spirited,that gives me around 21-22 mpg if on a long run i can get up to 25-26mpg. Its a bog standard 350i with flapper system, the gas is a sequential injection set up. The filler is hidden behind the number plate it hinges down for access neat as can`t be seen and can fill up from either side of the dispenser. The routing of the feed pipe from the tanks can be a pain too route to get the req 250mm from the exhaust otherwise heat shields all over the place. I like your idea of the 2 tanks 1 on top of the other, the fill line should have built in back check valves in the tee to prevent flow of gas from 1 tank too the other, but if you use a standard tee without back checks and doctor the auto stop on the bottom tank so the gas can flow between the tanks and leave the top autostop as standard you will retain some ullage space on the top tank that would give 54ltrs gas capacity almost 12 gallons @25mpg =300miles. Lpg prices dont worry me too much as i have used it for over 25 years and it has always been around half bat, currently the duty rate is about 18p per ltr so there is along way to go before it catches up with petrol and diesel.
Excellent John, in some ways you were my early inspiration for an LPG TVR.just got the heads up from zig, good to see someone else taking this route, my wedge has only got a 55ltr tank ( as not designed for golf clubs and hairdressers bags )and the auto stop works at 80% that gives me about 46ltrs i get around 210-220 miles and that is usually spirited,that gives me around 21-22 mpg if on a long run i can get up to 25-26mpg. Its a bog standard 350i with flapper system, the gas is a sequential injection set up. The filler is hidden behind the number plate it hinges down for access neat as can`t be seen and can fill up from either side of the dispenser. The routing of the feed pipe from the tanks can be a pain too route to get the req 250mm from the exhaust otherwise heat shields all over the place. I like your idea of the 2 tanks 1 on top of the other, the fill line should have built in back check valves in the tee to prevent flow of gas from 1 tank too the other, but if you use a standard tee without back checks and doctor the auto stop on the bottom tank so the gas can flow between the tanks and leave the top autostop as standard you will retain some ullage space on the top tank that would give 54ltrs gas capacity almost 12 gallons @25mpg =300miles. Lpg prices dont worry me too much as i have used it for over 25 years and it has always been around half bat, currently the duty rate is about 18p per ltr so there is along way to go before it catches up with petrol and diesel.
It seems you've been enjoying the benefits of gas for many years now, so I really value your input.
Hopefully I'll see you at the BBWF this year?
My boot still has plenty of space left even with the LPG, so I'll make sure I bring my golf bats
And yes.... even with the roof off
SILICONEKID350HP said:
Chipmongas can you recommend a good Piggy back system ? I know there is alot of Polsih cp on the market .
Read through one of your posts above ,you mentioned low and high impedance injectors !there must be LPG injectors to match petrol on`s on the market .Would that do the trick on the "stand alone" ECU.
Will your TVR be excempt from the congestion charge ?
The Prins system from the Netherlands is widely regarded as the best.p on the market .Read through one of your posts above ,you mentioned low and high impedance injectors !there must be LPG injectors to match petrol on`s on the market .Would that do the trick on the "stand alone" ECU.
Will your TVR be excempt from the congestion charge ?
But what you really need Daz, is someone that understands MegaSquirt who's also an LPG expert.
How about having a chat with the LPG chap that fitted your MegaSquirt?
OleVix said:
Very interresting read... what do you think the total cost of the project will be?
pjac67 paid £1400 for his conversion but mine will be more.I went with Keihin injectors which aren't cheap believe me, and a high end Prins vaporiser which again adds to the cost.
I wanted two tanks not one, my design also necessitated the fabrication of a bespoke aluminium 7 gallon auxiliary petrol tank.
Add in some other little wants like replacing the clock with a second TVR fuel gauge to show the LPG level, and you can see where the extra cost is coming from.
Of course both pjac67 & I started with a decent stand alone engine management system in the first place, advanced man maths permits us to remove this from the cost equation
You could convert a standard car with the 14CUX & distributor, in fact it's been done thousands of times on Range Rovers.
But I would strongly recommend fitting the Aldon Amethyst to give you a second ignition map you can alter for LPG, which will add another £200.00.
There are other mappable ignition systems from the likes of Omex, or you could fit the 123 Tune distributor, but these are both in the region of £600 & do nothing differently or better than the £200 Aldon Amethyst.
Perhaps MegaJolt is another cost effective option.
On the fuelling side your piggback ECU will be working with the 14CUX fuel map, and we all know how hard it is to alter that.
But that doesn't mean a standard converted Chim or Griff won't work well, it just needs to be done properly by someone that knows what they're doing.
If you're smart and choose your parts carefully, I see no reason why even a standard Lucas equipped TVR couldn't be converted for £1500.
At the end of the day each conversion is a tailor made exercise, different starting points, different parts, different budgets.
The most important thing is, whatever way you choose to do it, you absolutely must choose a respected & trusted LPG expert to help you unless you've done this type of thing before.
I've learnt loads from the guy I've been working with on mine, & it's proving to be a real pleasure.
Hope this helps, Dave.
UPDATE
Especially for GasMunkey here's some more pictures
The tank frame nears completion.
A great deal of effort has gone into fabricating the frame to ensure it fits perfectly flat against & follows the contours of the rear bulkhead, this ensures minimum tank intrusion into the boot space.
Pleasingly the LPG tanks (even with the valve boxes) now look like they will take up no more space than the original petrol tank, which in turn means no "roof in boot" issues, and no loss of luggage capacity whatsoever
We've decided it needs two more fixing points on the upper horizontal bar.
I wasn't keen on anything being visible from inside the car, even if we use nice polished dome headed bolts, but I had a little think & here's what I've come up with.
The parcel shelf on a Chimaera is a potentially very practical storage area for a medium sized sports bag.
However, I don't like using it on the grounds of safety.
In the event of an accident (as it stands) there is nothing really to stop said sports bag from hurling itself at great force into the cabin.
So for a long time I have been pondering adding some tasteful restraining straps, there are two ideal & very strong mounting points under the parcel shelf floor where you would fix a roll bar.
But to do the job properly you really need four anchor points for the straps, not two.
That issue has now been resolved, two "B" pillar seat belt loops will replace the polished dome headed bolts that were first proposed.
You couldn't do this easily without the tank frame, as the rear bulkhead is just a sheet of very weak paper thin fibreglass, so totally unsuitable.
These loops will be directly tied to the very strong LPG tank frame, which is in turn fixed securely to the rear of the chassis with four strong bolts (the body mount bolts in the boot).
The luggage straps themselves will be made up from red seatbelt webbing to match my carpets, so wont be immediately obvious when not in use.
The belts will be made up by:
http://www.quickfitsbs.com/
I've used these guys before, they offer many colours of webbing and nice classic chrome buckles, conveniently they are just up the road from me too.
In summary I took the negative of needing the upper tank frame mounting bolts, and used it to solve another little idea I've been musing.
Genuine safe stowage of a bag (or Le Mans Beers) is now a reality, and I think it should look very neat & factory too.
Especially for GasMunkey here's some more pictures
The tank frame nears completion.
A great deal of effort has gone into fabricating the frame to ensure it fits perfectly flat against & follows the contours of the rear bulkhead, this ensures minimum tank intrusion into the boot space.
Pleasingly the LPG tanks (even with the valve boxes) now look like they will take up no more space than the original petrol tank, which in turn means no "roof in boot" issues, and no loss of luggage capacity whatsoever
We've decided it needs two more fixing points on the upper horizontal bar.
I wasn't keen on anything being visible from inside the car, even if we use nice polished dome headed bolts, but I had a little think & here's what I've come up with.
The parcel shelf on a Chimaera is a potentially very practical storage area for a medium sized sports bag.
However, I don't like using it on the grounds of safety.
In the event of an accident (as it stands) there is nothing really to stop said sports bag from hurling itself at great force into the cabin.
So for a long time I have been pondering adding some tasteful restraining straps, there are two ideal & very strong mounting points under the parcel shelf floor where you would fix a roll bar.
But to do the job properly you really need four anchor points for the straps, not two.
That issue has now been resolved, two "B" pillar seat belt loops will replace the polished dome headed bolts that were first proposed.
You couldn't do this easily without the tank frame, as the rear bulkhead is just a sheet of very weak paper thin fibreglass, so totally unsuitable.
These loops will be directly tied to the very strong LPG tank frame, which is in turn fixed securely to the rear of the chassis with four strong bolts (the body mount bolts in the boot).
The luggage straps themselves will be made up from red seatbelt webbing to match my carpets, so wont be immediately obvious when not in use.
The belts will be made up by:
http://www.quickfitsbs.com/
I've used these guys before, they offer many colours of webbing and nice classic chrome buckles, conveniently they are just up the road from me too.
In summary I took the negative of needing the upper tank frame mounting bolts, and used it to solve another little idea I've been musing.
Genuine safe stowage of a bag (or Le Mans Beers
) is now a reality, and I think it should look very neat & factory too.Ribol said:
Nice idea - is the weight of the bottom tank taken by the boot floor and the other tank sat on top of it? In other words is the frame only there to stop fore/aft movement but not take any weight?
Or are both tanks suspended by their straps fixed to this frame with the frame taking the weight of them?
The frame takes the weight, which in turn is securely bolted to the chassis.Or are both tanks suspended by their straps fixed to this frame with the frame taking the weight of them?
So in effect the frame becomes an extension of the chassis (all be a bolt on), the frame is designed to ensure the chassis is taking the load.
Not the boot floor
This was always the critical element of it's design.
Neither tank supports the other, in load terms they do not touch.
However, neoprene pads are used on the boot floor & between the tanks simply to reduce vibration.
The LPG tank brief dictates priority was given to:
1) Safety
2) Best weight distribution
3) Range
In that order.
The vehicle gains 40kg just behind the rear axle line when all three tanks are brimmed, in practice this absolute maximum addition weight does not exist for long when the car is driven.
The additional weight can be easily reduced if required by half filling the auxiliary petrol tank, reducing the LPG fill, or both.
However I believe some addition weight over the rear wheels is actually an advantage, it could very easily be argued these cars are a little too light at the rear.
I'm confident the design will be extremely safe & well balanced, I anticipate one click of the Gaz Gold Pros is all that will be needed to restore sufficient damping to the rear suspension.
I will check & adjust the ride height if required but is unlikely to be affected given the springs used are already 25% stiffer than standard.
All my heavily loaded big Euro tours and trips to Le Mans showed the car is more stable at speed & handles better with some addition weight in the boot.
Edited by ChimpOnGas on Tuesday 5th March 17:59
Ribol said:
This is not nitpicking in any way but looking at what I see in the photo and remembering how much these things actually weigh when full that doesn't look strong enough to hang them from.
Forget all the theory for a minute, pick a full tank like that up and then envisage your car going over a pothole .................. and that is before we get into running into the back of another car (God forbid etc)!!.
The bottom tank, partly supported on the floor and properly located, no problem - the top one needs more thinking IMO.
As practical a solution as it seems to be, because of what you have to play with, it simply doesn't look strong enough, again IMO.
Truth is it's all in there tighter than a Nun's Chuff Ribol, I think you'll agree photos are one thing, but you'd need to see it first hand to be able to pass reliable judgement.Forget all the theory for a minute, pick a full tank like that up and then envisage your car going over a pothole .................. and that is before we get into running into the back of another car (God forbid etc)!!.
The bottom tank, partly supported on the floor and properly located, no problem - the top one needs more thinking IMO.
As practical a solution as it seems to be, because of what you have to play with, it simply doesn't look strong enough, again IMO.
The fact I've not posted a snap with the tanks on the frame yet doesn't help either.
The frame is designed to take the load, but the bottom tank only requires a thin neoprene pad to pack it tightly at the floor.
The floor doesn't take any load as such but in the event of hitting a pot hole there will be a cushioning effect to fall back on at the moment of severe shock.
If there's any doubt we'll add feet at either end of the bottom tank secured to the floor, but again they wont be taking any meaning full load as such, more as a steadying support function.
But at this stage, having seen it in the real world, I'm confident it'll be fine as is.
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