Propane has a higher Octane rating so can use a higher compression ration and mire timing. Doing so will win back some of the lost power due to the lower BTUs. What is it you want to convert?
Newer vehicles with the right kit run very well on propane or gas, newer vehicles typically run higher compression ratios than what was found in the the '80s when propane conversions were at their peak. Also computer controlled vehicles can easily have their timing and fuel maps changed to accommodate propane fuel by the use of a module that plugs into the stock computer.
Downside is these kits are expensive, hard to find and expensive to install. The tank and lines have to be certified so you can not install it yourself. Also the tank and lines have to be re-certified on a regular basis. Used to be 10years but I think its 5 now.
The tank can only be filled to 80% capacity, is "pill" shaped and since you don't have as good efficiency as on propane you won't go as far. So range is always and issue with a propane vehicle. Couple that with the fact that there are also way fewer fill stations than there used to be and the pumps have to be operated by trained personnel(no self serve) that are rarely around after 10pm, makes owning/operating a propane only vehicle difficult, thus a dual fuel setup is a must.
Dual fuel setups on older vehicles(carbs) were always problematic as it was a comprise in tuning to get the vehicle to run decent on both fuels. As said with todays electronics that issue has been resolved. However you still have the issue on where to put the tank. On a Jeep, for example, if you want dual fuel, you will need to retain the gas tank so the propane tank will have to be mounted inside which limits its size(and your range). Also it compromises your interior cargo room. As well when mounting the tank inside special care must be made to box it in and vent to the outside. More cost.
Cold weather operation; propane turns to a liquid state at -40C, in my experience even the best setup propane vehicle won't start below -30c on propane. I had a 1980 Grand Wagoneer on propane that wouldn't start below -20c. A dual fuel vehicle could be started on gas and then switched over.
Basically the cost of the kit for a modern vehicle is so expensive that only commercial use fleet vehicles would ever see the pack back. When I last looked at a propane sytem 15yrs ago it was $3000+ installed, I'm guessing its $5000-$8000 now. For that kind of money go buy a used subaru,honda,toyota,etc and leave the Jeep at home. A small car will still be cheaper to operate(including gas, maintenance, insurance,etc) than a propane powered Jeep will ever be. Even fleets aren't bothering with Propane, the new trend is CNG, compressed natural gas.
Topic: Propane Mileage (Read 1382 times)