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.

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.

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.

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?

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