computingcode

Hello,
I own a n Audi A8 D2 with a 2.8 AAH engine (no quattro). For the past few years I thought of putting LPG (Liquid propane gas) on the car. My main reasoning is the fuel economy. Did anyone do this on this engine (or similar)? I wish to know if there are any disadvantages of doing this. My main concern is doing damage to the engine and the car as an extension.
If it's a bad idea all around I can give up on the idea. No issue
If I go through with this, anything to keep in mind for a longer life of the car?
Regards,
Soare Alex

jfrahm

Hey that sounds kinda cool. You might look for info on conversions based on much more common AAH engined cars though, there are loads of 90, 100, A4 and A6 cars with that engine and relatively few A8s.

-Joel.

Chrisindominican

I live in the Caribbean and many people here use lpg and some suffer the problems you mention. In my experience there are two things you can do to solve that; 1. Switch to gasoline once in a while to inject some lubricant, and 2. Buy a newest generation system possible, preferably italian as they seem to be the best and I believe the quality of the system is the greater part of where problems are born.
I have a friend who runs a lincoln town car limo on it and I can’t believe how ridiculously inexpensive it is to run.

twentysevenlitres

LPG has been very popular in Australia for around 4 decades, mostly for large engined cars to attempt to bring their running costs down.
I've owned a dual fuel car in the past and have so far decided against doing so again.
in the UK though, where your fuel is stupendously expensive (twice Aussie price, three times US price) I might consider it on an otherwise unattainable car.

The biggest advantage of LPG is obviously the cost per mile, and this will remain an advantage for as long as LPG is around half the cost of petrol.
It has numerous other advantages too: cleaner emissions (less CO and NOx), cleaner soot deposits (this becomes apparent with how clean your oil stays between changes), higher octane (good for high compression engines and custom tunes), cooler denser charge (cooler engine, potentially better burn).

Although LPG has a reputation for reducing power, the latest Liquid Injection systems can actually increase power over the equivalent petrol tune on a PFI engine (not sure how they fare against direct injection engines).
Earlier vapour injection systems are still very good (and cheaper), but will drop power slightly.
Don't bother with vapour rings or gas carburettors, horribly inefficient and a complete waste of time.

There are plenty of disadvantages too!
Tanks - you'll have two choices in the A8. A conventional cylindrical tank holding about 75 usable litres mounted in the boot/trunk behind the back seats, or a donut tank holding about 45 usable litres mounted in the spare wheel well.
The cylindrical tank will block access to the fuel pump and sender of the fuel tank and take up a lot of boot space.
The donut tank is much neater, but you will lose your spare wheel and suffer from reduced range, and depending on the fit is how well the boot floor fits and sits flush or not...
Then there's lots of holes - holes to mount stuff, holes to feed pipes and wires through, holes in the inlet manifold mount pipes or injectors, and a big hole in the body for the filler cap.
The switch and fuel gauge have to mount somewhere in the interior too.
Then there's wiring - they'll have to cut and mess with fuel wires, injector wires and any number of other things to get the power and signals they need and cut the petrol.
So from that perspective only use a quality installer and don't buy a cheap system. Back on the day Impco (Italian) used to be the best, these days I don't know who's on top.

Drying out seals isn't really a thing - petrol doesn't lubricate, it's a solvent. I suppose it does "wet" things, but not for long!
You should always start and warm up a dual fuel car on petrol anyway, as LPG can freeze things when cold, so that generally takes care of wetting seals.
Similarly valve seat recession used to be a thing with LPG way back when, but it simply doesn't happen on unleaded engines as they all have hardened valve seats.

Anyway... My 2c!