High compression high revs, good flow characteristics from the head/ports/valves and manifolds are all the fundamentals of a good N/A engine.
lightweight and balanced engine components also really help by reducing rotational mass and allowing the engine to run much higher revs due to the crank, pistons,rods,flywheel all being balanced together.
camshafts are then used to shift the power band into the higher rev range
Individual throttle bodies give each cylinder its own throttle body to try and ensure each cylinder is getting maximum possible air and all cylinders get equal airflow for maximum power and efficiency with a less turbulent inlet route
that's the key to N/A engines, ensuring that the maximum amount of COLD air and fuel get into the cylinders as efficiently as possible, meaning things need to be as smooth as is practically possible, and once in the cylinder, the spent gasses need to get out as smoothly and quickly as possible for the cycle to start over again,
(since there's no charger to force air, an N/A engine needs to be able to breathe really well)
If the Air/fuel mixture or spent gasses cannot get in/out fast enough it creates a huge restriction, there's no point having an engine capable of revving to over 8500RPM if it cant flow enough gasses @ 7000RPM and is strangling itself because it cant breathe well enough.
exhaust manifolds need to be well designed to ensure that there is maximum flow, but also sustained mid range torque ( the let down of most N/A engines).
A well designed manifold will be of equal length and of a 4-2-1 or 4-2 design, each having its own pros and cons.
or something along those lines I think lol
I cant be assed to write any more ATM so will pick up and carry on later about valves,induction kits, uprating parts to take extra stresses from increased revs ect if no one else puts better posts up ( more than likely they will lol lol)