I've heard that reducing an engine's weight is a good way to increase power and mileage. But what parts are they talking about? aluminum parts? I want to know what lightweight engine parts I can buy for my 4 banger. Or is there anything else lightweight that's not engine related that I could get?
not sure in which context you heard that but if i were to guess is referring to rotating parts inside the engine and also the rods and pistons - going lighter increases response and revs and since there is less force required to overcome inertia of the moving parts there is less loss while those parts are accelerating. to gain more power there are other mods required so just by itself (lighter parts) the gain is not that much. Lightweight flywheel is also a factor. Now, with the Jeeps a lot of guys actually add rotating weight by the means of an inertia ring on the flywheel - that is to keep the engine running smoothly at low rpm and as a stall prevention in low rpm situations like when crawling.
reducing overall weight of the vehicle also improves mileage and acceleration, same concept of less inertia that needs to be overcome and therefore less parasitic loss - and same for drivetrain (larger tires, bigger driveshafts and axles are detrimental to fuel mileage), but here many of us are going bigger and not helping the mpg cause.
