Porsche Cayenne LPG Conversion

The Big Pig (Cayenne S) continues to rack up the miles. Except now it’s doing it fuelled by Liquid Petroleum Gas/LPG, which is proving rather cheaper than petrol. I also just put a new battery on it: made no difference to anything, but it’s another maintenance item off the list for winter. Seen here with good old Northants dirt, winter tyres on 18s and 11 year-old Ciara in the front seat.

Porsche Cayenne with dirt at SVP Droitwich 1 (2)

I’ve run LPG cars for a few years and been really pleased with the ownership experience. Cayenne creates a few problems when run on LPG, but it’s nothing to do with the fuel. My current issues are all to do with the design of the chassis – specifically the shallow rear floor – and the amount of power the V8 shoves out.

Porsche World might run a story on the conversion, so I’ll save some details until that’s been in print. The basic plot is I was intimately familiar with the kit I’ve been running for the last few years, so had my own views on what might work best for the Cayenne. I emailed a bunch of LPG places to get what the experts felt, had a few crazy quotes back to convert it and did some more research.

Porsche Cayenne with dirt at SVP Droitwich 1

In the end, I went for a 59-litre tank in the wheel well and the same OMVL system as used in my Subaru Outback up front. It runs a treat at speed – had 120 out of it thus far and no problems – but it doesn’t much like screaming out of roundabouts or really quick throttle openings in M3/M4 to overtake, so flicks seamlessly straight back to petrol when I do that. Which is fine apart from the LPG alarm beeping.

It’s either a pickup issue (which I doubt, as it happens on an almost-full tank) or just the evaporator can’t handle the sudden demand for all gaseous horses to report to the intake manifold. The installer said the system would handle this motor at full tilt so it is probably just an adjustment issue. I’ll give him some time to sort it out.

Porsche Cayenne sofa mover big pig

The only other issue is a max fill of 43 litres at the minute. I’m getting 18 mpg with air con on and not driving flat-out everywhere, but that’s still only 160 miles. I would love another 160 per tank so the only solution to maintain the boot space would be to cut the boot floor about and squeeze in a 100-litre tank.

Luckily, I know a man – Mr Rob Campbell at Racing Restorations – who can do that fabrication stuff. He loves a challenge and has already promised to make the Big Pig louder, so what’s a little boot floor between friends when the exhaust is being chopped?!

That bottom pic is a six-foot sofa in the back of it last Sunday. Yes, the tailgate closed – who said Cayennes were too small?

7 Comments

  • Darren says:

    Hello. I too have just had my cayenne converted to LPG. Can I ask if you had the enlarged tank you mentioned fitted? I too have just the tank in the spare wheel area and feel it’s going to be to small.
    Thank you.

    • John Glynn says:

      Hi Darren. I get along OK with the 55 litre tank. Max fill is theoretically 44 litres but most I usually squeeze into it from E is about 41 litres. I can do about 140 miles on that if I go steady, 120 if I am hammering it. Would be more useful with a bigger tank but it is not a huge deal.

  • Rory says:

    I have a 100 litre cylindrical tank in the boot of my cayenne turbo. It does take up 35% of the boot space but would rather that and get the extended range.
    John did u get a larger tank yet and if so what arrangement did you go-for/achieve? I wouldn’t say no to getting some boot space back if possible. 2 kids and 2 dogs require a lot of space 🙂

    • John Glynn says:

      Hi Rory, I have stuck with the smaller tank as I use the Cayenne less frequently nowadays – mostly running around in the Polo I bought for the kids to do lessons in. Cutting the boot floor would be a lot of work and I keep having thoughts about selling the Cayenne. Have made a false floor and the boot gets a lot of use when I do take the Cayenne out so I wouldn’t be able to live with a big cylindrical tank. Now done 35k miles on LPG and still going well – it is an excellent fuel for these cars.

  • Pod Gora says:

    Any experiences with more miles driven on LPG, maybe more than 150-200k? They say that it burnes injectors…

  • Antoni says:

    Hiya John.
    I’m about to put an LPG on my 2006 Cayenne and was just wondering what system you have on yours? Did you put bigger injectors on it? And is everything still running fine?
    Cheers

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