Propane

It does. So even though it gives slightly less power, you can raise the compression ratio of the engine to compensate, without fear of pinking.

Hoever, your average LPG install isn't going to do this, for obvious reasons (ie, a new set of fitted pistons will cost *PLENTY*), so you'll be a smidgeon down on power.

That is correct.

As I understand it, it has a higher octane, but a lower calorific value for the same ammount of propane as petrol.

Higher octane means it will resist knock/pinking/pre-ignition better than petrol, so on a purpose built LPG gas only engine you could raise the compression to get more bang, and run more ignition advance.

But the lower calorific value means that it will take more fuel to convert the same ammount of energy when burnt compared to petrol.

Also gas conversions need some kind of upper cylinder lubrication (especially on older vehicles) because propane/LPG/CNG are a "dry" fuel, and don't have their own built in lubricants like petrol does.

Cars that are duel fuel and spend a lot of time on petrol usually get away with it, but LPG only, and cars that spend most of their duel fuel time on gas benefit.

I think its pretty similar...????

Or run more boost!!! Or Nitrous... or both...

In article , snipped-for-privacy@ntlworld.com spouted forth into uk.rec.cars.modifications...

Not very scientific but "LPG has only 80 per cent of the calorific value of petrol and so you get only eight miles of motoring for every ten using petrol. In other words, the quoted combined mpg of the Streetwise (as tested) of 37.8 mpg in petrol mode becomes around 30 mpg when cooking on gas. "

From

Odd, I thought all petroleum based fuels were pretty similar. Diesel is around 15,000 to 15,500 calories per pound... Petrol goes from

14,400 to 14,700, Paraffin 15,000 ish etc. But maybe its the case. 80 percent sounds a bit extreme though...