Has anyone done a propane conversion on a 95 F250 or similar truck? My 95 with a 460 does pretty good as far as gas mileage goes, but since propane is so much cheaper most places I was wondering if anyone has tried this or if there are even any kits for doing so. What I would probably do is add an auxillary propane tank somewhere so that if I'm roadtripping and can't find a propane fueling station I could still use gas, and maybe have a switch in the cab to change wheter I'm running on propane or gas. Any ideas/tips/suggestions (besides buy a new/smaller truck) would be appreciated.

 

I am thinking of doing the same thing, I know running dual gas and propane is a breeze of carbed motors, I want to find more info on what is needed for EFI.

 

hmm so I guess Carb engines are almost as simple as tapping a propane line from a regulator into the carb. I would assume there is something needed to deliver the propane to the fuel rail on our EFI motor.

 

The principles behind running propane on an EFI motor is the same as on a carb motor - you inject the propane into the intake manifold using an injector (or two) that is capable of handling gaseous or liquid propane.

Here is a very brief outline on LPPFI.
Fuel injectors must pulse width modulate to properly meter the fuel. Nitrous injectors have too much internal mass to modulate in the order of millisecond response time.

LPG vapor pressure is high, on the order of 8.5 BAR at 70 Deg F, and 17 BAR at 125 F. To keep LPG in liquid form at these temperatures on an engine, you must keep at least 3.5 BAR above vapor saturation pressure, or you will have a mixture of liquid and vapor propane. Now, add in underhood temperatures of around 225 F, and you can reach propane vapor pressures in excess of 400 psig (27 BAR). This is out of range for even the most advanced over the counter fuel injector (or stock) and even if they don't explode, the seals will die very quickly.

If you just want to use propane as an octane enhancer, remember that the liquid expands 270 times from vapor. Even the tiniest amount will quickly exceed the air fuel handling capabilities of many engines.

Here is an excellent web resource: http://www.gotpropane.com/

MSD also sells stuff and kits for propane: http://www.msdignition.com/dpi_kits.htm though the kits are for diesel engines. The concept is the same actually.

Here is another link, that provides many other links:
http://cars.rasoenterprises.com/Links-Propane.htm