i wanna learn how to madify a cummins and other diesels

Actually diesels are simplier than gas engines cuss there's no spark or spark timing to worry about but there is diesel injection timing, how much and when, hence the rechipping of the ECM on newer diesels. Most first gen. diesels (like the Jimmy's and the Cummings 350 and 400) used fully mechanical injectors that were operated from the camshaft through lifters, push rods and rocker arms (one per cylinder) or other engines like the Mack used a timed high pressure fuel pump delivering precise amounts of fuel to injector nozzles (one per cylinder) which were basically a spray nozzle with a check valve just upstream of it. The go peddle operated a rack affair, on the cam shaft operated engines that would increase or decrease the actual fuel pumped by each injector whereas the high pressure pump design had a single pump plunger that also pumped a precise amout of diesel to each injector and was also controlled by the go peddle. I suspect in your instructors case he's using a big assed turbo or even 2 and opening up the flow orifices on the injectors eg. more fuel and more air. There was an old trick that truckers would use in the old days to help pull the mountain passes before the really big diesel engines took over and that was propane injection (you didn't hear that from me:toothy10:). Just a little bit mind you and they'd watch the EGT (exhaust gas temperature) guage to make sure they didn't melt down the engine. Maybe that's also what he's using. He may even be injecting water to increase the charge density therefore horsepower.

Terry