G500 mods

I don't know if you have seen this thread from our friend in Greece, but it's quite a neat setup (admittedly for different purposes) but could get some ideas...
http://gwoa.co.uk/index.php?name=Forums&file=viewtopic&t=6966

Hi Tarrick,

If you are LPG-converting your car then, as far as I'm aware, you don't actually need cats. This in itself should up your mpg AND performance by about 10-12%: I've done this on both my V8 Range Rover and petrol Land Cruiser and never had any problems with the MOT. The official verbage goes something like, the car has to be tested on the fuel that it will be used on, which would have to be LPG since only any idiot will want to pay twice as much for the same thing! The calorific value of LPG is less than petrol and therefore this is a slight (and it is very slight as you've got no cats to kill your engines exhalations) reduction in the performance of the car. I've never really found this to be very noticable unless you floor it. Even then, you can cure this if you go down the dual evaporator route (most gas conversions only fit one evaporator) with which you can effectively force more LPG into the combustion chamber...a bit like a turbo charger type effect. However, these systems are expensive and quite honestly I've never felt the need for them (I've had 3 cars now running on LPG and never had a problem with lack of performance.....admittedly they weren't G500s, but one in particular had the same BHP rating albeit in a different package). Hope this goes some way to answering your queries with regard to the conversion.

Phileas

I think the 55 only has one silencer on each pipe, the large one in the middle on the 500 is omitted.

I would go for something like that, it will then sound like a 55.