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Thread: X350 3.0 V6 LPG conversion

  1. #1
    Junior Member
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    Feb 2020
    Germany, Stahnsdorf close to Berlin
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    X350 3.0 V6 LPG conversion

    Dear all,

    since I'm driving really a lot for professional reasons I use for many years LPG converted cars.

    I've bought in this year a 2006 X350 3.0 V6 petrol and plan again to make a conversion. There are 2 questions.

    1. I need the space in the boot, therefore a cylindrical tank is out of question. A
    toroidal tank in the spare wheel well is needed. The question is the placemaent of the air reservoir and the valve block. I've seen some fotos of such conversions with a relocated air reservoirs and blocks to the side wall of the wheel well. Has somebody here done that work? How about the length of cables and hoses? Here is what I mean:
    Click image for larger version. 

Name:	juguar-XJ6 LPG Kofferraum.jpg 
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    2. My last Jag was an S type 2001 with the same engine. At the end 1 - 2 engine valves were burnt, seemingly because of the LPG. The LPG specialised garage has told me that the engine was running to lean on LPG. That has never happened to any of my cars before after driving several 100 000s of Km. I've googled a lot but coudn't find a serious information whether that engine needs an extra lubrificant for LPG. Does somebody know it?

    Thanks in advance for your answers,

  2. #2
    Junior Member
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    Feb 2020
    Germany, Stahnsdorf close to Berlin
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    Anyone who has some knowledge?

  3. #3
    Senior Member
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    Sep 2008
    NW London
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    There may be some info here,
    Jagary, 09 XJ Sovereign 2.7 LWB Liquid Silver/Warm Charcoal & 98 4.0 X308 Aquamarine/Warm Charcoal

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  5. #4
    Senior Member Alec Escolme's Avatar
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    Dec 2012
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    My old Super V8 was LPG converted by the previous owner at great expense- a very thorough installation apparently. The boot looked identical to your photo.
    I tried it briefy and found it was lacking power and never felt right, the engine sounded diesel like at idle. Combined with the stories about valve wear, I decided to have it removed and run on petrol only. It did have flashlube too.
    Mercedes CL 4.7 V8 Biturbo, Magnetite black on Anthracite Exclusive Leather - 84,000 miles
    BMW M6 Coupe V10, Saphire Black on Black Merino Leather, Alcantara Headliner- 29,000 miles

    Super V8, X358 Facelift + Portfolio Vents + Wald Spoiler, Black Cherry with Ivory/Charcoal leather

    XJ X350 3.0 Silver/Dove

  6. #5
    Senior Member FlatCap's Avatar
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    Feb 2019
    West Yorkshire
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    Rhubarb, 2003 Super V8 Radiance Red,Sepangs, Iron Fist Velvet Glove. I am not a car guy.

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  7. #6
    Junior Member Aix's Avatar
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    Jul 2018
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    All I can contribute is some experience with my 2003 XJ8 running on a Vialle LPG system.

    First of all my boot looks quite similar to the picture, fitting an 80 liter LPG tank next to the relocated air reservoir. That seems to be common, probably because it's the only way the parts fit properly and can be hidden away.
    My car was converted by a previous owner at Henk Bortien in the Netherlands, at least that's what the stickers on the LPG tank say. The conversion is done quite well and absolutely no lack of power can be felt when driving on LPG. Tracking AFR signals by OBD connection while driving showed that lambda is perfect, also when switching between fuels there is only a slight twitch, then lambda is 1 again. So the setup is really done well. The car has the LPG system since at least 200.000kms.

    Some observations that may or may not be caused by LPG operation.
    The car is just short of 330.000km and had the clearance of all intake valves down to almost zero. One intake valve was even just about not closing fully when the cam was supposed to free it, all the others were still sealing tight. The smooth V8 stumbled in idle. I re-shimmed them all (intake and exhaust) and the pressure test of all cylinders was perfect again.
    LPG generally has the reputation to wear valves faster due to changed combustion behavior and therefor thermal load on the exhaust valves. That's also well known from many old Mercedes that were regularly converted to LPG. Now in my case exhaust valves were tight but still ok, intake valve clearance was off. Vialle, injecting the LPG in liquid form in front of the intake valves like any regular petrol does, should actually cool the intake valves by the evaporation in front of them, so that shouldn't have happened.

    Conclusions whether the valve wear is due to LPG or just due to the quite senior mileage and which of the 2 contributed how much are in the eye of the beholder. I haven't got to a final conclusion on the behavior of my engine yet. LPG is certainly wearing the cylinder sealing elements more when you drive a large share under high-load high-speed conditions, just because of the different combustion characteristic and temperature and the lacking valve cooling effect on systems that introduce the LPG in gaseous form to the intake.
    But given that my 4.2L V8 is almost never driven close to its potential (the car has a very comforting influence on my driving style) this thermal effect should be not relevant, as load levels should most of the time still be far beneath what they are on a full-throttle petrol operation.

    Generally I would not use LPG on a car that I wanted to whip all the time, but a comfortable cruiser with a huge engine, that is operated far below its potential anyway most of the time, should theoretically be running long term with LPG.

    If it hadn't been for these 16 intake valves ...
    2003 Jaguar XJ8, extremely cheap to drive due to Vialle LPG system, quite expensive to maintain due to 325.000km mileage, and a beauty in the truest of all Jaguar colors

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