Usually the guys running propane do not do it to increase the revs of the engine and that is a MYTH about diesel burning too slowly to achieve 4500rpm my friendhell my old isuzu Imark would run 5 grand all dayand also in experiments with motorcycle engines converted to diesel by an engineer friend of mine in CT revs of over 10000 rpm were normal. Epi the reason the engine grenade..think of this..I have a diesel with a static compression ratio of 17.5:1 and add 22 psi of manifold pressure from the turbo and then add some propane...too much burn to early is detonation in a diesel and with propane acting as a catalyst the propensity to bearn early is there..now with that compression ratio PLUS alreadyhaveing forced induction froma turbo...little room for error..a few guys int he club have chunked rods through the block the main reason they use propane is because it extends the mileage by a very decent amount enough so to justify the purchase of the propane.