If you lightened every available component of an engine and used?
Yes, No, Maybe Making the engine lighter might help to improve the ratio HP/Weight of the car. If the reduction in weight of the engine is significant, you may see a difference. For example, replacing a cast iron big block V8 normally aspirated by a smaller Aluminium 4 Cyl Turbo compressed might reduce the weight significantly for the same HP output. A lighter car for the same HP always seem to have more power. Lighter piston, connecting rod and flywheel might help to make the engine more Responsive. Especially without load, the inertia of the engine is reduce so it climb faster in RPM. With a suitable camshaft and spring setup it might also permit a red line at a slightly higher RPM.Again, if the flywheel is lighter, the engine might be unpleasant at idle in traffic.Furthermore, some engine are already equip with lightweight component similar to what you found in a race car. The normal production part are somewhat heavier but mostly to ensure the longevity of the part. Often, lightweight camshaft and pushrod are a bad idea. Your camshaft and pushrod need to be very rigid to make sure the engine is properly feed and exhaust is perform properly.Otherwise, changing the profile of the camshaft might help to deliver noticeably more performance. However, all is a question of compromises. The engine might have a rougher idle Might have all it torque at the high end of the RPM range or whatever Compromises Underdrive pulley. It depend on the car model. Many ECU disable several accessories when the car is under significant acceleration. For example, on many car, when you floor the accelerator, the ECU Disable the Alternator Charging Function (Switch most of the load to the battery). The cooling fan are electric and reduce their load under the same condition (unless the engine is critically hot). Some car even disable the AC compressor. So, the accessory driven by the pulley that remain operational are the Power Steering (Unless it is electric) and the water pump (unless driven otherwise). Therefor, on many cars, an Underdrive pulley does not free a lot of power under hard acceleration.