Chimpongas I need advice please
Discussion
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.
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
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.
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.
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
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
.
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 dogs
t 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
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. 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
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
.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 dogs
t 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
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.
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.
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 said:
Mind actively boggling here.......often wondered how to fit three in a Chimaera.
Trust you to do some lateral thinking 
Happy new year Anthony
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
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
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.
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
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.
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