LPG Chimaera (Follow My Conversion)
Discussion
You probably don't need canems to do you something special for the extra ign advance.
Say your current least timing is a sensible 12-15deg around idle, you can move your crank reference trigger setting these (say) 12 degrees so your new idle timing number in the map is 0, but is actually 12deg static offset of advance. Then every other number in the ign map becomes offset by that 12 deg. hey presto your previous max of 49 deg is now 61.
Say your current least timing is a sensible 12-15deg around idle, you can move your crank reference trigger setting these (say) 12 degrees so your new idle timing number in the map is 0, but is actually 12deg static offset of advance. Then every other number in the ign map becomes offset by that 12 deg. hey presto your previous max of 49 deg is now 61.
spitfire4v8 said:
You probably don't need canems to do you something special for the extra ign advance.
Say your current least timing is a sensible 12-15deg around idle, you can move your crank reference trigger setting these (say) 12 degrees so your new idle timing number in the map is 0, but is actually 12deg static offset of advance. Then every other number in the ign map becomes offset by that 12 deg. hey presto your previous max of 49 deg is now 61.
Thanks, that makes sense Say your current least timing is a sensible 12-15deg around idle, you can move your crank reference trigger setting these (say) 12 degrees so your new idle timing number in the map is 0, but is actually 12deg static offset of advance. Then every other number in the ign map becomes offset by that 12 deg. hey presto your previous max of 49 deg is now 61.
However I think I'd feel more comfortable seeing the true figures and having a wider table showing the full range of advance from true zero to a true sixty degrees. If I over type a cell with the figure 55, I want to know its 100% genuinely firing the spark at 55 degrees BTDC.
Interestingly it seems LPG needs lots more advance early on and in the low load cruise sites than on petrol, however as you get up towards the opposite corner of the table you may actually need less timing.
The good old bum dyno and the extensive experience of my mapping team has got us this far, but I'd like to see how close we've really got to the best maps? For that the car needs to go on the dyno so we can find where power rises then falls away again at each key load/RPM site, the truth is as it stands we have no conclusive proof where peak torque genuinely lives, only the dyno can tell us that for sure.
Perhaps the first step is to get it on the dyno before we ask David Hampshire for any more advance, if we see the torque is still rising in areas where we currently have 49 degrees then it could be worth while to approach Canems for more. On the other hand if we find peak torque actually lives at say 47 degrees, we'd know it would be pretty pointless to have a table that went any further than it does now (49 degrees).
What we've learned so far is being able to map LPG independently from the petrol is as big an advantage as we predicted it would be, this is especially true of the ignition side. Unsurprisingly given the completely different burn speed characteristics of LPG and it's huge ability to resist detonation you end up with a very different ignition curve/map.
The idea of fudging the timing up the scale is an option, but I think I'd be much happier seeing the true figures rather than needing to do the little sum in my head.
I'm sure David Hampshire will give me what I need, it may even be as simple as a software tweak he can email over?
But thanks for the idea anyway
Ok gas sniffers, I've just realised I started "Project Gas Bag" exactly three years ago almost to the day, so I thought you'd like an update on the latest developments and the results arising from them.
Recently we've been testing my theory that there may be some more hidden LPG fuel economy beyond the 49 degrees of advance my Canems dual fuel system currently offers.
'Ol Gasbag' was bolted to Lloyd Specialist Developments hub dyno and the team tested my ignition timing theory on LPG at 50-60kPa load sites at 2000rpm, 2500rpm, 3000rpm and 4000rpm. They experimented with timing values between 40 and 49 degrees for each of these rpm sites.
During the session AFRs were also closely monitored to see how they were affected by changes in timing, and to ensure they remained inside ideal AFR tolerances for the 50-60kPa engine load window we were working in and looking to develop.
Here are the results:
The above figures clearly debunks my theory there could be benefit in extending the ignition table beyond 49 degrees of advance on light load cruise.
Am I disappointed?
Well no not at all, and here's why!
Firstly the dyno session allowed us to scientifically prove without any dispute where peak torque truly lives, this allowed the LSD team to effectively fine polish what was already an excellent set of maps (petrol & LPG). The team also discovered some more torque under full load at 4000-4500rpm on LPG by actually reducing the ignition timing slightly.
After the hub dyno runs 'Ol Gasbag's' power & torque graphs were compared against a very healthy but completely standard 4.0 litre petrol only Chimaera that had recently enjoyed a session on the same equipment. This back to back comparison using the same hub dynonometer proved conclusively that my Chimaera burning LPG is delivering 7% more power to the road than the fit standard petrol only Chimaera running Lucas 14CUX injection and distributor ignition.
I'm absolutely delighted with that, especially when many doubters tried to convince me I would be sacrificing a big chunk of performance and my TVR would be spoilt by converting it to consume LPG.
Now we've proved the car is actually more rather than less powerful on gas and that I haven't spoilt my TVR at all, we can start to look at how running a TVR Chimera on LPG genuinely improves fuel economy.....
Yesterday on the way back from Lloyds I filled up with LPG at the Murco fuel station Stonehenge. Their 95ron petrol was £1.00 per litre and their LPG was £0.45p a litre, that makes LPG just £2.04p per UK gallon!!!!
The last time petrol prices were £2.04p per gallon was 1983, I was 13 years old so was still 4 years off having a driving licence and many who read these pages were probably still in nappies
But what does all this really mean when compared with running my TVR on petrol which I freely admit has become quite cheap to buy of late?
Well if you take the £1.00 per litre for petrol and divide it by the £0.45p per litre I paid for LPG you get 2.222, now if you take my true LPG fuel economy and times it by 2.222 you get the petrol cost equivalent miles per gallon. IE the fuel economy any petrol car would need to deliver to match the pence per mile my LPG TVR is achieving.
Stay with me boys, here's the simple calculation...
My true LPG fuel consumption = 24mpg X 2.222 = 53.33mpg!!!
Yes that's right folks, while petrol is cheap these days... LPG is cheaper still, in fact if you purchase your LPG wisely its actually less than half the price of petrol.
In conclusion I've achieved a TVR that's both faster than when it was new, and one that now delivers the fuel economy equivalent of 53.33mpg!
All of this would be irrelevant if I'd lost drivability or refinement on gas, fortunately the truth is the Canems duel fuel system actually delivers big improvements in drivability over the standard car's old Lucas injection system & distributor ignition.
I'd say we've nailed it chaps
Now prepare yourselves for the next exciting development where we'll be taking 'Ol Gasbag' into a new stratosphere of 5.0 litre destroying performance while still retaining it's 50mpg plus fuel economy on cruise
Recently we've been testing my theory that there may be some more hidden LPG fuel economy beyond the 49 degrees of advance my Canems dual fuel system currently offers.
'Ol Gasbag' was bolted to Lloyd Specialist Developments hub dyno and the team tested my ignition timing theory on LPG at 50-60kPa load sites at 2000rpm, 2500rpm, 3000rpm and 4000rpm. They experimented with timing values between 40 and 49 degrees for each of these rpm sites.
During the session AFRs were also closely monitored to see how they were affected by changes in timing, and to ensure they remained inside ideal AFR tolerances for the 50-60kPa engine load window we were working in and looking to develop.
Here are the results:
- At 2000rpm torque was not improved beyond 45 degrees ignition timing
- At 2500rpm torque was not improved beyond 47 degrees ignition timing
- At 3000rpm torque was not improved beyond 44 degrees ignition timing
- At 4000rpm torque was not improved beyond 45 degrees ignition timing
The above figures clearly debunks my theory there could be benefit in extending the ignition table beyond 49 degrees of advance on light load cruise.
Am I disappointed?
Well no not at all, and here's why!
Firstly the dyno session allowed us to scientifically prove without any dispute where peak torque truly lives, this allowed the LSD team to effectively fine polish what was already an excellent set of maps (petrol & LPG). The team also discovered some more torque under full load at 4000-4500rpm on LPG by actually reducing the ignition timing slightly.
After the hub dyno runs 'Ol Gasbag's' power & torque graphs were compared against a very healthy but completely standard 4.0 litre petrol only Chimaera that had recently enjoyed a session on the same equipment. This back to back comparison using the same hub dynonometer proved conclusively that my Chimaera burning LPG is delivering 7% more power to the road than the fit standard petrol only Chimaera running Lucas 14CUX injection and distributor ignition.
I'm absolutely delighted with that, especially when many doubters tried to convince me I would be sacrificing a big chunk of performance and my TVR would be spoilt by converting it to consume LPG.
Now we've proved the car is actually more rather than less powerful on gas and that I haven't spoilt my TVR at all, we can start to look at how running a TVR Chimera on LPG genuinely improves fuel economy.....
Yesterday on the way back from Lloyds I filled up with LPG at the Murco fuel station Stonehenge. Their 95ron petrol was £1.00 per litre and their LPG was £0.45p a litre, that makes LPG just £2.04p per UK gallon!!!!
The last time petrol prices were £2.04p per gallon was 1983, I was 13 years old so was still 4 years off having a driving licence and many who read these pages were probably still in nappies
But what does all this really mean when compared with running my TVR on petrol which I freely admit has become quite cheap to buy of late?
Well if you take the £1.00 per litre for petrol and divide it by the £0.45p per litre I paid for LPG you get 2.222, now if you take my true LPG fuel economy and times it by 2.222 you get the petrol cost equivalent miles per gallon. IE the fuel economy any petrol car would need to deliver to match the pence per mile my LPG TVR is achieving.
Stay with me boys, here's the simple calculation...
My true LPG fuel consumption = 24mpg X 2.222 = 53.33mpg!!!
Yes that's right folks, while petrol is cheap these days... LPG is cheaper still, in fact if you purchase your LPG wisely its actually less than half the price of petrol.
In conclusion I've achieved a TVR that's both faster than when it was new, and one that now delivers the fuel economy equivalent of 53.33mpg!
All of this would be irrelevant if I'd lost drivability or refinement on gas, fortunately the truth is the Canems duel fuel system actually delivers big improvements in drivability over the standard car's old Lucas injection system & distributor ignition.
I'd say we've nailed it chaps
Now prepare yourselves for the next exciting development where we'll be taking 'Ol Gasbag' into a new stratosphere of 5.0 litre destroying performance while still retaining it's 50mpg plus fuel economy on cruise
Edited by ChimpOnGas on Sunday 28th February 11:17
'Ol Gasbag' keeps delivering the goods and it's getting even cheaper to run
I've just worked out my latest cost equivalent economy from the last gas-up.
Last weekend the petrol at the Murco in Stonehenge was being sold at £1.13 a litre, but their LPG was just £0.46p.
So that's £1.13 / £0.46 = 2.456
Take my true LPG economy of 23mpg and times it by the 2.456 and I get a petrol cost equivalent figure of 56.5 mpg.
That is... I would need to be driving a petrol car that did 56.5 mpg to match me old gas powered 4.0 litre V8 engined TVR Chimaera.
Happy with that
I've just worked out my latest cost equivalent economy from the last gas-up.
Last weekend the petrol at the Murco in Stonehenge was being sold at £1.13 a litre, but their LPG was just £0.46p.
So that's £1.13 / £0.46 = 2.456
Take my true LPG economy of 23mpg and times it by the 2.456 and I get a petrol cost equivalent figure of 56.5 mpg.
That is... I would need to be driving a petrol car that did 56.5 mpg to match me old gas powered 4.0 litre V8 engined TVR Chimaera.
Happy with that
Four years on since I pulled the trigger on this alternative fuel madness I'm pleased to present Gas Sniffer update no 764.
'Ol Gasbag' continues to deliver the goods, and I'm happy to report the cost of the conversion has long since been covered by the considerable fuel savings I've enjoyed by running my Chimaera on LPG, I therefore declare the project a resounding success.
Admittedly I took a rather expensive approach to my conversion, but I make no excuses for this, I did so because I sought perfect reliability, drivability and best in class LPG economy. Some basic facts.... a full 14 gallon LPG fill costs £35 and easily takes me 290 miles, a full 12.3 gallon fill of petrol in a standard petrol only 4.0 litre Chimaera may take you the same distance if you're easy with the loud pedal, but will typically cost you a whopping £67.
So that's a clear £32 saved on every 290 mile fill and with the conversion cost all completely covered by past savings, that's £32 I'm enjoying spending on something more interesting than fuel. It's not quite half price TVR motoring but its as near as damn it, essentially the conversion has made the car as cheap and cost effective to use as my wife's little 75 horsepower 1.4 litre Nissan Micra yet it loses nothing in the way of performance or TVR magic.
I'll probably do about 6,000 miles in 'Ol Gasbag' this year, so that's more than 20 fill ups and a clear saving of £662, money I'll be spending on a nice return flight to Brazil
I'm still surprised more of you haven't converted to gas
'Ol Gasbag' continues to deliver the goods, and I'm happy to report the cost of the conversion has long since been covered by the considerable fuel savings I've enjoyed by running my Chimaera on LPG, I therefore declare the project a resounding success.
Admittedly I took a rather expensive approach to my conversion, but I make no excuses for this, I did so because I sought perfect reliability, drivability and best in class LPG economy. Some basic facts.... a full 14 gallon LPG fill costs £35 and easily takes me 290 miles, a full 12.3 gallon fill of petrol in a standard petrol only 4.0 litre Chimaera may take you the same distance if you're easy with the loud pedal, but will typically cost you a whopping £67.
So that's a clear £32 saved on every 290 mile fill and with the conversion cost all completely covered by past savings, that's £32 I'm enjoying spending on something more interesting than fuel. It's not quite half price TVR motoring but its as near as damn it, essentially the conversion has made the car as cheap and cost effective to use as my wife's little 75 horsepower 1.4 litre Nissan Micra yet it loses nothing in the way of performance or TVR magic.
I'll probably do about 6,000 miles in 'Ol Gasbag' this year, so that's more than 20 fill ups and a clear saving of £662, money I'll be spending on a nice return flight to Brazil
I'm still surprised more of you haven't converted to gas
Have read this with interest and had been wondering about LPG .................... well was doing so until we got the 75 CDT for towing and sold the 75 V6 petrol auto. However after reading this through am wondering if when I do get a TVR this might not be worthwhile for us to consider. Thank you for all the information you have included in the thread.
but for most folk annual milage doesn't justify doing it in their own opinion. You say that, but if mine were cheaper to run I'd probably do a lot more miles in it. I'm considering going Burghley at the weekend depending on the weather, but it's a 4 hour motorway slog so will take the missus diesel nissan squashi thing at 50mpg. I'd take the scenic route in the chim if it was half the standard price and sunny though.
Well I shall pop over to Burghley at the weekend and will running on petrol too unless something happens to the MGF between now and then. Not got a TVR yet but am still learning more about them so this seems to be an obvious chance to do just that! The Mulberry Red (Maroon) MGF should be easy to spot I am thinking.
If the worse comes to the worse will be in the dark red (Copperleaf Red) Rover 75 CDT (Diesel) Auto but should be there in one of them.
If the worse comes to the worse will be in the dark red (Copperleaf Red) Rover 75 CDT (Diesel) Auto but should be there in one of them.
Ahhh well as there were only 372 MGF's painted in this Red the thought was that is was very unlikely for there to be more than mine there on the day. Burghley has of course seen more than one of them there at the same time as they also hold several MG and MG-Rover meets there during the year. Now we would not want there to be any more cross contamination than there is already now would we!
Hi,
Congratulations for the dedication, the hard work and of course the results!
You must really love your car.
Do you think it is possible to obtain good results with a piggy backing LPG ecu, a timing advance processor (with a RPM and MAP 3d map?) the car's knock sensor and narrow band oxygen sensors? (I don't have access to a dyno so i will use some convervative timing advance found from similar experiments as yours)
I've ran around 4000 miles on lpg already so i can make some comparisons to see if is there any mileage improvement.
Car's ecu knock prevention system should save me from any knock related problem.
I have converted my mercedes w211 2.6L N/A v6 engine a year ago with a stag fully seq system.
I've seen that the engine stays in closed loop with target lambda=1 (the only measurable lambda with narrow band sensors) through the whole rpm range except WOT.
Car goes back on petrol around 4500rpm or WOT, so i don't care about WOT performance anyway.
Switching is seamless.
Currently the trims are max +-15%, typically revolve around +-5-10% on LPG and +- 5% on petrol.
So i guess need to adjust fueling, just adjust the piggy backing i will get the trims as similar as possible with the ones on petrol and temperature corection so i will minimize the oxygen sensor based corection as much as possible.
Will try the temperature and gas pressure correction as well, as the gas system has them available.
AS you pointed out in your LPG saga, it's probably due to lack of pressure/temperature compensation, which are currently on zero.
Regarding your MAP measuring after the throttle plate, where do you exactly place the MAP sensor?
Is it near the injector/close to the intake port?
I run a similar setup and i noticed that there is a discrepancy between the car's MAP (right after the throttle plate) and the LPG map which is near the intake port.
The latter measures low pressure, except when WOT and high rpm.
Is this normal?
No intention of diverting the thread, i will probably open a new one as soon as i will really start working on this.
There are quite people here mounting these piggy back units, but very few of them go beyond autocalibration and remapping, so experience sharing on these aspecte is scarce.
Please share your thoughts on this, i am interested if working on this with only the basic tools is a viable aproach.
I am not targeting optimum performance, but at least an improvement.
Best regards from Romania,
Serban
Congratulations for the dedication, the hard work and of course the results!
You must really love your car.
Do you think it is possible to obtain good results with a piggy backing LPG ecu, a timing advance processor (with a RPM and MAP 3d map?) the car's knock sensor and narrow band oxygen sensors? (I don't have access to a dyno so i will use some convervative timing advance found from similar experiments as yours)
I've ran around 4000 miles on lpg already so i can make some comparisons to see if is there any mileage improvement.
Car's ecu knock prevention system should save me from any knock related problem.
I have converted my mercedes w211 2.6L N/A v6 engine a year ago with a stag fully seq system.
I've seen that the engine stays in closed loop with target lambda=1 (the only measurable lambda with narrow band sensors) through the whole rpm range except WOT.
Car goes back on petrol around 4500rpm or WOT, so i don't care about WOT performance anyway.
Switching is seamless.
Currently the trims are max +-15%, typically revolve around +-5-10% on LPG and +- 5% on petrol.
So i guess need to adjust fueling, just adjust the piggy backing i will get the trims as similar as possible with the ones on petrol and temperature corection so i will minimize the oxygen sensor based corection as much as possible.
Will try the temperature and gas pressure correction as well, as the gas system has them available.
AS you pointed out in your LPG saga, it's probably due to lack of pressure/temperature compensation, which are currently on zero.
Regarding your MAP measuring after the throttle plate, where do you exactly place the MAP sensor?
Is it near the injector/close to the intake port?
I run a similar setup and i noticed that there is a discrepancy between the car's MAP (right after the throttle plate) and the LPG map which is near the intake port.
The latter measures low pressure, except when WOT and high rpm.
Is this normal?
No intention of diverting the thread, i will probably open a new one as soon as i will really start working on this.
There are quite people here mounting these piggy back units, but very few of them go beyond autocalibration and remapping, so experience sharing on these aspecte is scarce.
Please share your thoughts on this, i am interested if working on this with only the basic tools is a viable aproach.
I am not targeting optimum performance, but at least an improvement.
Best regards from Romania,
Serban
Hi Serban,
In the UK we have a saying.......
"There's more than one way to bake a cake"
You don't need to follow my Canems ECU, Hana Injectors & Prins vaporizer recipe... but I can confirm it works extremely well on my car.
I can't really comment on other recipes or the one you're proposing other than to say "untested is unproven", good luck with it though.
The one thing you'll immediately discover when you have the option of driving on either fuel.... is you'll never select petrol.
Dave
In the UK we have a saying.......
"There's more than one way to bake a cake"
You don't need to follow my Canems ECU, Hana Injectors & Prins vaporizer recipe... but I can confirm it works extremely well on my car.
I can't really comment on other recipes or the one you're proposing other than to say "untested is unproven", good luck with it though.
The one thing you'll immediately discover when you have the option of driving on either fuel.... is you'll never select petrol.
Dave
Dedicated ECU is out of the question for my car. Besides fueling and ignition it also coupled with ABS/ESP and other important functions.
The timing is the one that would be tricky to setup as i don't have any feedback besides knock sensor. A dyno would be nice.
Can you please share the timming diff between gas and petrol maps?
I don't need the exact maps, as you probably don't want them public, just some guidelines on the timing increase compared to petrol at part and full load.
From your writtings i can conclude that for LPG the knock limited ignition timing is not necessarily in the same place as max torque is.
At least i will have some gross guidelines, an then adjust by feel/feedback from OBD and injection times.
You are right on the driving on lpg.
Done the conversion in October for 750 GBP, 6500km/4000miles since then I already covered a quarter of the convertion price.
The current lpg/petrol time is 90:10.
Keeping the petrol for starting and 4500rpm+ for overtaking as currently car is slower on gas now. Made a comparison against a 150hp audi a4, there is a small but observable difference, no doubt about it.
SILICONEKID 345HP 12.03, those days are long gone.
1.9 TDI with lots of black smoke are all over the place now.
Modern horses, modern farts.
The timing is the one that would be tricky to setup as i don't have any feedback besides knock sensor. A dyno would be nice.
Can you please share the timming diff between gas and petrol maps?
I don't need the exact maps, as you probably don't want them public, just some guidelines on the timing increase compared to petrol at part and full load.
From your writtings i can conclude that for LPG the knock limited ignition timing is not necessarily in the same place as max torque is.
At least i will have some gross guidelines, an then adjust by feel/feedback from OBD and injection times.
You are right on the driving on lpg.
Done the conversion in October for 750 GBP, 6500km/4000miles since then I already covered a quarter of the convertion price.
The current lpg/petrol time is 90:10.
Keeping the petrol for starting and 4500rpm+ for overtaking as currently car is slower on gas now. Made a comparison against a 150hp audi a4, there is a small but observable difference, no doubt about it.
SILICONEKID 345HP 12.03, those days are long gone.
1.9 TDI with lots of black smoke are all over the place now.
Modern horses, modern farts.
Hi Serban,
The timing differences will be different for every engine, this is a forum specifically dedicated to the rather rare low production TVR Chimaera, do you own a TVR Chimaera?
If not your questions will be much better answered on a general LPG forum.
http://www.lpgforum.co.uk/
Just be aware the above forum is mostly full of LPG fitters looking for work.
Thanks for your interest in my car and LPG project, Dave.
The timing differences will be different for every engine, this is a forum specifically dedicated to the rather rare low production TVR Chimaera, do you own a TVR Chimaera?
If not your questions will be much better answered on a general LPG forum.
http://www.lpgforum.co.uk/
Just be aware the above forum is mostly full of LPG fitters looking for work.
Thanks for your interest in my car and LPG project, Dave.
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