Take a look at my mod to see how it's done exactly. Basically the car power depends both on the engine RPM and the torque, if you increase just the torque you will get a similar effect to a diesel engine so you need the RPM too. The RPM and torque values are in a big table/array in the engine Jbeam file. But you also need to change the physical RPM limit and torque and overtorque limits so the engine doesn't explode instantly. You can also reduce friction and dynamic friction. There's also inertia, reducing that will make your engine gain RPM faster, but reducing it too much will break the engine. Apart from engines there are also intakes you can change. Normal intakes add extra torque at set RPM so increase that if you want, it's another big table. With superchargers you can edit pressure and ratio which will directly affect the power added to the engine. And turbochargers are too complex for me to explain here, again take look at my mod to see how it's done. Also after increasing the power you may want to edit the gear ratios to use it to its full potential so put on race final drive and race transmission and customize them as you wish.
