Chimpongas I need advice please

Chimpongas I need advice please

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Classic Chim

Original Poster:

8,722 posts

87 months

Saturday 12th January
quotequote all
Is it possible to convert a twin carb XJ6 series 2 to LPG or does it need to be fuel injection?
I know this isn’t really the place to ask but you know lpg like few others. Thanks in advance
If anyone else can add to this your most welcome.

Edited by Classic Chim on Saturday 12th January 20:59

phillpot

14,633 posts

121 months

Saturday 12th January
quotequote all


Cars were running on LPG long before EFI came along smile

Classic Chim

Original Poster:

8,722 posts

87 months

Saturday 12th January
quotequote all
phillpot said:
Cars were running on LPG long before EFI came along smile
Yeah,,, divvy biggrin ,,,,, but how ?
I should do some googling thumbup

The second world war comes to mind but I don’t fancy a big bag on the roof hehe

phillpot

14,633 posts

121 months

Saturday 12th January
quotequote all
Classic Chim said:
I should do some googling
yes

Classic Chim

Original Poster:

8,722 posts

87 months

Saturday 12th January
quotequote all
Open loop single/ double point, that’s about as far as my googling skills go.

As this is a 70’s engine will it need harder valves and guides similar to when unleaded came in to cope with the lack of lubrication and extra heat.
Cooling system might need upgrading
I had an XJ8 converted with multi point injection but can’t quite work out how it would work with twin carbs.
There’s info on the gubbins required but I can’t quite picture how it actually works, is it as simple as two lpg injectors plumbed in on the inlet manifold directly ahead of the carbs,, as there’s no Ecu how does it know how much fuel to inject?

Fascinating subject. I’ll probably change my mind by tomorrow morning but I’d love another proper XJ6 one day.
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ChimpOnGas

8,405 posts

117 months

Sunday 13th January
quotequote all
Without injection you are stuck with going back in time to the bad old days of the mixer system which is really more or less just the very crudest carburetor ever, a mixer is nothing more sophisticated than a tapered ring with holes drilled all around the inside which is why they are sometimes reffered to as a gas ring, they look like something you use to heat your beans up with when you go camping.



Working on the venturi principle LPG is draw through the holes in the ring into the engine based on air flow passing through the tapered ring (the venturi), in terms of fuel metering accuracy mixers are absolutely shockingly poor performers and get ready for backfires powerful enough to blow your air cleaner to smytherines because along with pish poor fuel economy and rubbish drivability backfires are one of the mixer's more alarming party tricks eek

Mixers were really all there was when I got into gaseous fuels almost 30 years ago, I myself ran a Chevrolet Caprice in New Zealand that's small block V8 was fed with gas using a mixer system. To be honest the car was given to me as joke on the Pommy by the other mechanics at the forestry commission as none of them could make it run properly, I got it working reasonable well so the joke was actually on them in the end laugh.

Mixer systems are very much what gave LPG a bad name, basically back in the late 80's and even the early mid 90's you took the latest fuel injected petrol car that ran great and fed it LPG through a metering device that in petrol terms was less sophisticated and performed worse than the most basic pre-war era carb!

Unsurprisingly these mixer systems gave truly terrible results so as ignorant people tend to do they put 2 and 2 together and made five slating LPG as the devils fuel. The thing is if you ripped the petrol injection system of the same car and made it run on petrol using a pre-war carburetor it would have run like dogst too. This is what people who slagged off LPG weren't smart enough to understand and is why even to this day there are still loads of idiots who will tell you never to go anywhere near LPG.

Its also why I promised myself I would return to LPG when the technology had caught up with petrol injection systems which it has now, although the advent of ever more sophisticate petrol engine management systems and direct injection are causing the LPG industry some real headaches these days for sure.

Mixer systems did however get better over the years and these days they resemble, operate and perform much the same as a 1970's tech carburetor with the added benefit of a kind of closed loop lambda metering control system available to cobble on to it.



You could put the Jag on one of these better mixer/LPG carb systems but how you would integrate it with the twin SU carb inlet manifold will present a bit of a challenge and it'll still be plagued by the occasional dreaded backfire.

This again forces you back in time to running two LPG SU Carb mixers (one on each carb) like this LPG powered XJ6...



Personally I wouldn't bother, buy an injection car and convert that to gas, or better still buy one that's been concerted already as this will work out cheaper. I'm not saying you cant convert a twin SU fed Jag XJ6 to LPG, I'm just saying the results will not be great so you're better off leaving the car to drink petrol as nature and Sir William Lyons intended wink

Penelope Stopit

3,732 posts

47 months

Sunday 13th January
quotequote all
In the past I used to watch a friend doing these conversions on carbs with what I think the Chimp calls a gas ring, he said the job was easy and it did look uncomplicated apart from running the pipes and all the drilling on the roof
Never any problems with them and they ran well

Classic Chim

Original Poster:

8,722 posts

87 months

Sunday 13th January
quotequote all
ChimpOnGas said:
Without injection you are stuck with going back in time to the bad old days of the mixer system which is really more or less just the very crudest carburetor ever, a mixer is nothing more sophisticated than a tapered ring with holes drilled all around the inside which is why they are sometimes reffered to as a gas ring, they look like something you use to heat your beans up with when you go camping.



Working on the venturi principle LPG is draw through the holes in the ring into the engine based on air flow passing through the tapered ring (the venturi), in terms of fuel metering accuracy mixers are absolutely shockingly poor performers and get ready for backfires powerful enough to blow your air cleaner to smytherines because along with pish poor fuel economy and rubbish drivability backfires are one of the mixer's more alarming party tricks eek

Mixers were really all there was when I got into gaseous fuels almost 30 years ago, I myself ran a Chevrolet Caprice in New Zealand that's small block V8 was fed with gas using a mixer system. To be honest the car was given to me as joke on the Pommy by the other mechanics at the forestry commission as none of them could make it run properly, I got it working reasonable well so the joke was actually on them in the end laugh.

Mixer systems are very much what gave LPG a bad name, basically back in the late 80's and even the early mid 90's you took the latest fuel injected petrol car that ran great and fed it LPG through a metering device that in petrol terms was less sophisticated and performed worse than the most basic pre-war era carb!

Unsurprisingly these mixer systems gave truly terrible results so as ignorant people tend to do they put 2 and 2 together and made five slating LPG as the devils fuel. The thing is if you ripped the petrol injection system of the same car and made it run on petrol using a pre-war carburetor it would have run like dogst too. This is what people who slagged off LPG weren't smart enough to understand and is why even to this day there are still loads of idiots who will tell you never to go anywhere near LPG.

Its also why I promised myself I would return to LPG when the technology had caught up with petrol injection systems which it has now, although the advent of ever more sophisticate petrol engine management systems and direct injection are causing the LPG industry some real headaches these days for sure.

Mixer systems did however get better over the years and these days they resemble, operate and perform much the same as a 1970's tech carburetor with the added benefit of a kind of closed loop lambda metering control system available to cobble on to it.



You could put the Jag on one of these better mixer/LPG carb systems but how you would integrate it with the twin SU carb inlet manifold will present a bit of a challenge and it'll still be plagued by the occasional dreaded backfire.

This again forces you back in time to running two LPG SU Carb mixers (one on each carb) like this LPG powered XJ6...



Personally I wouldn't bother, buy an injection car and convert that to gas, or better still buy one that's been concerted already as this will work out cheaper. I'm not saying you cant convert a twin SU fed Jag XJ6 to LPG, I'm just saying the results will not be great so you're better off leaving the car to drink petrol as nature and Sir William Lyons intended wink
I’ve read about the valve that’s incorporated to help with the backfire issue on these systems which does leave one feeling slightly un nerved about the whole idea.

I had a 1980 V reg ( in old money ) series 3 XJ6 which was the first year of fuel injection for these cars which I think was the same system that’s used on wedge cars the Cu system and the car ran very smooth as you’d expect with a Jaaaag so that’s probably a better bet as you say Dave.
I can see getting any system to run as proficient as petrol would be quite some challenge and probably cost more than I’d ever re coupe as I’m hardly going to be doing big miles in such a vehicle, it’s a classic after all

As Penelope stopit says people do seem to have got the carb system running ok but it does seem rather risky and most reports I’ve read shy away from it on the XJ.
A pity really as they are fantastic machines that could do with a new lease of life but fuel is never going to ge getting cheaper so resign them to bit part players for most people owning them.
A bit of a pipe dream really as most series 2 and 3 cars were built when BL were falling apart and reliability of components and build quality suffered as a consequence. 40 years on they are not going to be any more reliable but the tech is simple in modern terms.
As an old mechanic who helped me learn a few things about these cars years ago said
“ they are not that hard to work on but you usually have to remove half the car to get at the bit you want to fix which is what takes the time”

I’ve looked at an example of a series 2 that’s like a show room car for not a lot of money for what you get, maybe it’s best to leave it as a show room example as they rust like hell if not constantly looked after and kept dry.

Finally regards LPG on these dizzy controlled cars and after reading your posts on the dizzy restrictions which include the series 3 fuel injected cars would this also be quite a hinderence and make the risks of engine damage more likely as you obviously can’t contol spark timing like you can with multi point trigger wheel driven Ecu.





Classic Chim

Original Poster:

8,722 posts

87 months

Sunday 13th January
quotequote all
Would it be a far fetched idea to replace the series 2 inlet manifold for the series 3 fuel injected manifold then buy a modern Ecu system to run it on both petrol/ LPG similar to what you have on the Chimaera Dave?
This would remove all the Cu components and allow a new playing field entirely if it was possible.
If we could get a Jag of this vintage to run on a modern system and in view of the fact these cars are very cheap to buy compared to say an 80’s Ford it could work out as not such an expensive car for the huge pleasure that can be derived from such machines.





QBee

16,290 posts

82 months

Sunday 13th January
quotequote all
Classic Chim said:
...........but I don’t fancy a big bag on the roof hehe
Mind actively boggling here.......often wondered how to fit three in a Chimaera.

Classic Chim

Original Poster:

8,722 posts

87 months

Sunday 13th January
quotequote all
QBee said:
Mind actively boggling here.......often wondered how to fit three in a Chimaera.
Trust you to do some lateral thinking hehe

Happy new year Anthony thumbup

We can mess with the atom, bugger about with genes but can’t run an old Jag on LPG very successfully. Now if the yanks had expensive fuel this problem would have been fixed yonks ago biggrin

spitfire4v8

2,726 posts

119 months

Monday 14th January
quotequote all
Classic Chim said:
Would it be a far fetched idea to replace the series 2 inlet manifold for the series 3 fuel injected manifold then buy a modern Ecu system to run it on both petrol/ LPG similar to what you have on the Chimaera Dave?
This would remove all the Cu components and allow a new playing field entirely if it was possible.
If we could get a Jag of this vintage to run on a modern system and in view of the fact these cars are very cheap to buy compared to say an 80’s Ford it could work out as not such an expensive car for the huge pleasure that can be derived from such machines.
For low mileage it makes no financial sense, but if you plan on using a classic more and more because (let's face it) most modern stuff is boring, then crack on! smile
I was one of the lpg sceptics that Dave talks about, but the technical excercise of his lpg journey has been interesting reading and certainly changed my viewpoint.
It's of no benefit to me to change because I spread my driving between 6 separate cars at the moment so never spend enough time in one car to make it financially worthwhile .. but if I was a classic car lover and had one classic as a daily then it would be much higher on the priority list.

Classic Chim

Original Poster:

8,722 posts

87 months

Monday 14th January
quotequote all
Having owned one before Tvr are less maintenance and probably more reliable and easier to work on for sure.
What’s nagging me is I drive the Tvr with a lot of mechanical sympathy and rarely use the cars potential, I really enjoy smooth driving and the rewards that brings so an old Jag would be perfect for my old man technique

I’m not one for garage queens though but a metal car does rust before your eyes if your not on top of it so the Tvr still keeps its appeal as something that can be owned and enjoyed without that worry.
We replaced the floor in both foot wells ( twin skinned) on my series 3 Daimler which was a task and a half, I don’t fancy doing that again in a hurry wink

We never bought panels from Robey we made them as the master who actually did it repaired vintage cars so had all the tools to shrink/ stretch and corrugate the tin. It was a lot of fun back then but he’s long since left this mortal coil and I’m nit skilled enough to consider it alone.
Beautiful cars though.

ChimpOnGas

8,405 posts

117 months

Monday 14th January
quotequote all
spitfire4v8 said:
For low mileage it makes no financial sense, but if you plan on using a classic more and more because (let's face it) most modern stuff is boring, then crack on! smile
I was one of the lpg sceptics that Dave talks about, but the technical excercise of his lpg journey has been interesting reading and certainly changed my viewpoint.
It's of no benefit to me to change because I spread my driving between 6 separate cars at the moment so never spend enough time in one car to make it financially worthwhile .. but if I was a classic car lover and had one classic as a daily then it would be much higher on the priority list.
spitfire4v8 is right, modern stuff is boring, very boring!

I have a modern German company car and to be honest I can't wait to get out of the thing and jump in my TVR.

The bottom line is LPG is just another hydrocarbon, burn it and it creates heat and a rise in pressure just like any other hydrocarbon fuel, if you trap these expanding gasses in a confined space you can slowly release that stored energy to do work like turning a crankshaft.

LPG is a byproduct of the crude oil refining process that gives us everything from petrol to paraffin to diesel and everything in between



As we can see liquefied petroleum gas (LPG) is a 4% inevitable consequence of getting to all the other stuff we pull out of crude oil, my point is for as long as we're pulling oil out of the ground to make petrol, diesel and all the other stuff we will need to do something with that 4% of LPG because its coming if you like it or not.

Many years ago believe it or not we used burn a lot of it off destroying the ozone layer for zero benefit to the human race, these days LPG or propane as it's otherwise known represents the third most used fuel in internal combustion engines around the world. Go to Brazil, Poland, Turkey, Australia and a host of other countries and LPG vehicles are so common no one gives them a second thought so it always amuses me when people on our tiny little island claim you can't make a car run well on the stuff laugh

People looking to convert an 8 cylinder car need to budget paying a well researched and endorsed professional roughly £2,000 to do the job properly, do keep in mind there are a lot of jokers in the LPG world that don't have a clue what they're doing which is another reason the fuel gets a bad rap.

My conversion was a little different, I was always going to replace the 14CUX and distributor setup even if I stayed on petrol so as I would have done this LPG or no LPG I choose to exclude this element of the cost. The Canems Dual Fuel ECU is after all a petrol aftermarket ECU with a few extra bells and whistles so for example even if I'd never activated the LPG element for the same money as an MBE I still had myself an aftermarket petrol ECU that functioned just like an MBE or any other stand alone petrol ECU.

If I now look at the LPG conversion itself it was basically the £2,000 quoted above plus £500 for the bespoke aluminum petrol tank I had fabricated. The car makes good power, still sounds like a TVR should, retained 95% of it's already generous boot space and will do the same 300 miles on LPG as a standard petrol Chimaera will on the expensive stuff.

Best of all the car actually drives better on gas that it did on petrol when it was running the 14CUX and distributor, it makes more power too.

So almost six years on since I started all this was it all worth it? Hell yes it was worth it, I'm not saying I haven't had my challenges along the way but I learned a lot from the project which has been a very rewarding process. So I spent £2,500 to get my Canems equipped Chimaera to run on LPG which may sound a big investment to some but you never hear people being challenged on spending the same sum on a set of decent heads or say a cam and ACT twin plenum package, and neither of those upgrades are going to pay for themselves.

With that out of the way it's now super easy to use some very basic maths to work out how many miles it took me to drive on LPG before I recovered my initial £2,500 investment in fuel savings. In simple terms if I buy my gas wisely my Dual Fuel Chimaera costs £0.11p a mile to fuel on LPG and £0.22p a mile to fuel on petrol so for every mile I drive I save £0.11p.

All we now need to do is take £2,500 and divide by £0.11p which gives us 22,727 miles, that's 22,727 miles to drive to get my £2,500 investment back in fuel savings. I appreciate that may sound like a lot of miles to many Chimaera owners who really just use their TVR as a hobby/weekend toy and may only do a few thousand miles in it every year. For these people I say maybe LPG is not for you, but as I started out saying just like spitfire4v8 I consider modern cars very boring, and I simply can't wait to get out of my two year old Audi and jump in my TVR so I guess I do enjoy my TVR more than most.

This is the point really, my TVR gives me pleasure every time I dive it so the more I drive it the more I get to access that pleasure, and quite simply with half price fuel costs using the car more suddenly becomes feasible proposition. Of course after six years running on LPG I passed that 23,000 mile break even point a long while back, even if you only do 6,000 miles a year in your TVR which given these are such excellent GT cars is super easy to do, you will have achieved a full return on your investment in under 4 years.

The thing is once it's all paid for itself what you're left with is that super cheap £0.11p a mile classic British sports car that sounds like a Cobra and goes just as well but has very real GT capabilities too, to bring this to life for everyone that's a far more practical but just as fast AC Cobra that offers the same pence per mile as a petrol car that delivers an average of 50mpg which is basically what you genuinely get from a Toyota Prius wink

So if you do 6,000 miles a year in your Chimaera and you plan on keeping your TVR more than four years, far from it being a mad idea to convert your TVR to LPG it's actually financially a very shewed move indeed. Now consider you are also massively reducing your tail pipe emissions and extending your engine life too because LPG burns so cleanly, and you can start to appreciate the benefits go way beyond just the cost savings on fuel.

TBH I'm genuinely surprised more people haven't done it, the Rover V8 is a totally proven gas friendly engine, the tens of thousands of Discoveries and Range Rovers that have been converted to LPG over the last 30 years or more proves that without question. The Chimaera scores again because of it's capacious boot so there's plenty of room to house the gas and in my case a very practical 150 miles of petrol too, finally LPG just makes sense on cars that consume a lot of fuel so the Chimaera really couldn't be a better candidate for an LPG conversion.

My switch to LPG was really just part of my extensive development of a great British sports car to make it the best improved classic, I see my Chimaera is my very own Eagle E-Type on a budget. In the 10 years I've owned it and with everything I've done to improve the brakes, suspension, reliability, drivability ect ect ect it still only stands at way less than £20k. Compare this with the £500k to £1m you need to buy that Eagle and you can soon see the Chimaera makes the best value back to basics but improved classic you can genuinely use on a daily basis by a country mile.

The LPG part of my development program simply just made the car cleaner, greener and massively cheaper to run without compromising the aesthetics, boot space, touring range, V8 sound track or performance one bit, what's not to like confused

Dave thumbup