Maybe ask if all V12 engines are problematic on LPG and also if their fixes apply

http://www.go-lpg.co.uk/BMWV12.html

You could also ask here

http://www.lpgforum.co.uk/

 

I have seen a late 80s XJ-S V12 Convertible running on LPG some years ago and the owner seemed fairly pleased with the results. However, with most XJ-S now retired from high mileage commutes to and from work, you have to ask if the project cost and potential disruption teasing out any set-up issues is really going to be worth it? Personally, I would go with the respray (and waxoyling) and use Shell V-Max premium fuel instead.

Cheers, Rich

 

If you want to save a bob or two on fuel then you've bought the wrong car. The LPG system is great for a daily driver but I wouldn't hang it on such a complex machine as the V12 is. All that wiring is already filling the engine bay and if you then fit an LPG injector system (no venturi... They are biggest crap going for a modern'ish car), you might as well take the V12 out and fit a diesel 4 cylinder from VW...

I would only fit LPG to a 6 cylinder as it makes a bit more sense, as they are more economical. Ever heard of someone fitting an LPG system to a Ferrari, Lambo or Aston?

 

If you can afford to buy and run a Ferrari, Lambo or Aston, fuel is probably the least of your costs!

 

And if you drive a Jaguar V12? Again, a V12... If someone wanted to LPG their Fiat Panda 0.8l TwinAir, I'd understand... But saving on fuel costs on a super greedy engine is kind of in the wrong world. My opinion though

 

Being a 89 it should have the Marelli engine management system. That means replacing the lot if you go lpg. You could of course add throttle body lpg but then the gain would be negligible anyway, full multiport is the only sensible option. So you would need a system like Zytec (expensive) etc etc. So my conclusion would be that this is really a non starter.

 

I only use my V12 in the summer and work on it in my garage over the winter . I was using a 1999 ford Ka for 6 years as a every day car but now upgraded to a 13 reg 1.0T 3 cylinder ecoboost 125 ford fiesta. Fiesta is very fast 122mph, 0-62 9.4 sec and free road tax so I can now save some money to run the V12 in the summer. The XJS is my No 1 car but these are no longer a every day car even if the fuel is not a problem .

I would recommend a cheap ford to run every day and keep the XJS for best !

 

just google and you will find loads

https://www.facebook.com/permalink.php?id=127372910723864&story_fbid=555122501282234

 

I had my 1994 XJ40 Sovereign 4.0 litre converted in 2003 when I first bought it. To be honest I wouldn't have bothered as my situation changed (company car) and the Jag is lucky if it covers 1000 miles a year (It's only got 63,000 on it from new to date). The system works great though and was the best on the market at the time (Romano IV with separate injectors) which cost around £1,650 fitted. The specialist that fitted mine did mention that the worst cars to set up were most V12's and BMW V8 engines in particular. The straight six however is an ideal platform to convert.

Some points to consider if you or anyone does decide to go for a conversion:

Positives:

1. The modern systems are great and talk to the car ECU so you get no annoying engine management lights on when running on gas (on the older ring systems this used to happen as the ECU couldn't understand why the engine was running when the fuel pump wasn't)
2. As above - do you do the mileage to warrant the outlay?
3. Same MPG however LPG half the price of petrol (or at least it was) Last went on a fishing trip from Solihull to Fort William and it only cost £50 in LPG to get there
4. Far less oil and filter changes - LPG burns far more efficiently than petrol so very little carbon in the oil - I did a full oil change back in 2006 on mine and the full synthetic oil is still clean as a whistle to date
5. Modern system uses plug and play - I paid £35 to have mine checked for calibration last year and I drove the car round on a series of different roads and speeds etc whilst the technician was in the passenger seat with a laptop plugged into the system ECU - he then re calibrated each injector accordingly.

Negatives:

1. You lose boot space - I have a 90 litre torpedo tank in the boot . You can get ones that are the same shape as a spare wheel and go in the space, however smaller tank = far less range and what do you do if you have a flat tyre?
2. If ever you sell your car and want to get the most money for it the purist will not want to see an LPG system, so you will incur a cost to remove any evidence it has been there.
3. Check you can buy LPG locally to where you live. I'm lucky as I have two garages within 2 miles of my house that sell LPG. A few years ago a guy I know who bought a Jeep Cherokee and had it converted only to find that the nearest LPG stockist resulted in a 10 mile round trip to fill up. For longer journeys you can download an app onto your sat nav / I phone that will tell you all the places that sell LPG along your route. I always usually keep 1/3 tank of petrol in anyway just in case.

Hope this has been of some help