[cruisingdownthestreet]

what engine mods can i do on a 4 cylinder without you saying, "if you're gonna do that why didn't you just buy the 6 cylinder?!"

[The Wind Breezes]

Your question makes no sense, but assuming the 6 cyl starts off with more power and has as much relative headroom as the 4 cyl does, you would do better to start with the 6 cyl cuz the engine that started off with more power will usually end up with more power for a given level of mod / $ spent. Of course, these days there are plenty of 4 cyl that make more power from the factory than a 6 cyl. Number of cylinders doesn't really have much to do with anything until you're trying to absolutely MAXIMIZE power from a given displacement. For engines like you'd find in a modern BMW this would be over 1000 HP depending on what you consider reliable. Reason more cylinders is good in THAT case is you get a higher surface area to volume ratio so the cylinders can fill / exhaust more easily.

[Vigilante375]

No matter the cylinder size. They both will deliver a lot of power, when they are modded correctly. Every engine (except rotary) will be and can be modded the exact same. Cam(s), header(s), intake manifold, head(s), pistons, crank, turbo/supercharger/nitrous oxide (forced induction), etc.

Its just finding the right platform to mount it on to maximize the output of whatever engine.

What is your question more in reference to? Decisions on buying and modded a certain car? If so, which?

[ShocknAwe]

If its a question about BMW turbocharged 4 or 6 engines, the N20 is pretty weak and will need to be built before handling remotely even moderate power levels.