One big problem with using propane as a fuel is that none of the propane industries have kept pace with the fuel management systems on the newer cars. The propane industry’s idea of a converstion was to disconnect the fuel injectors, add another computer that tells the OEM ECM that everything’s fine with the injectors even though it isn’t. They hung a antique propane mixer, ( not really a carburetor) in front of the throttle body and let the engine inhale propane vapor and air thru this contraption into the plenum and finally into the engine. Problems with this arose from the fact that due to intake backfires into the plenums would cause the entire plenum, manifold and some hose length to the mixture to explode. After this fiasco someone decided to remove the ECM and reflash it for a propane fuel curve. This seemed to help but at the same time voided any warrant work on the engine period.

Propane operaters at a higher combustion temperature that gasoline. Because of this it seems to remove some of the ductility from the compressions rings. This of course causes huge amount of blow by into the crankcase. I’ve personally done leak down tests on propane fueled International Harvester 392 school bus engines that showed a 55% leakage factor into the crankcase. Because propane is a dry gas, exhause valve seat especially, take a beating. I have seen exhaust valve recession on GMC 366 propane school bus motors to the point of sticking the valve in the head and the rockers are either broke on the valve end or the push rod bent so badly it fell down into the lifter galley, or both.
The idea that just bolting on some propane carburetion equipment, and a fuel lock off valve and a converter is all that’s needed to convert a gasoline engine to run on propane is nonsense, I know I’ve seen the results of that.
In my opinion if a gasoline engine is to be converted to any sort of dry gas usages such as propane or natural gas, it needs a lot more preparation than just the induction modifications. I would run a bit more clearance on the piston skirt to cylinder wall dimensions, a set of compression rings that can withstand higher cylinder temperatures, and a modifed ignition curve. this is just for starters. Most of the natural gas engine conversions I’ve driven are even more sluggish than the propane versions. Most of the compressed natual gas vehicles I’ve seen here in the States require 8-12 hours for refueling. Gee that sounds conveient.
A few years back a company decided to modify an existing fuel system on a new vehicle and acutally pipe liquid propane to the injectors thru the factory harness. There were some problems but they were initially overcome and this was the best propane conversion of a new vehicle I’ve ever seen. There was absolutely no intake backfiring at all. The throttle response was great too. I think the company went out of business, but not because their product was a bad idea.