As most of you may or may not know, I bent a valve in my ZHP a few weeks ago. Ever since, I've been on a philosophical journey to see how the stock head can be improved. I've devoured several forum threads and even bought a book on cylinder head porting, which led me down an even larger rabbit hole of fluid dynamics type education. It has been interesting...
I guess we can start with this guy named Adam or "PEI330Ci" who's done a lot of footwork for the M54 engine. I really appreciate that he's openly sharing what he has learned about the platform. He has spent, who knows how much, time and money on obtaining hard data for this engine.
With that being said, the exhaust port is the weakest link in the chain. It appears that some work here produces tremendous gains in flow across the board from low lift (2.5mm) to high lift (9.5mm). Almost 40 CFM difference in some spots! What that means for power in an N/A application, with stock ZHP cams is what I want to find out. I also need to figure out how to get those gains. Sure I could hog out the exhaust port, but that doesn't learn me anything about what I did and also increases the likelihood of me getting a new cylinder head.
Next, improvements in intake flow vary from around 20-40 CFM and start at around 6mm of lift and end at the peak lift of 10mm for stock cams. Not bad gains there either!
BMW has made some compromises (not their fault, simply part of the engineering process) in the cylinder head as it is a mass produced head, that fits multiple engine displacements, that has to meet a general populations' idea of a strong engine, and also emission requirements, yada. The goal here is to attempt to optimize cylinder head breathing (note that I did not use the word 'flow' here) for our more aggressively cammed, 3 liter engine.
I'm starting from zero...no tools, little knowledge of how air works, not much time either as I want to be up and running by summer...This is going to be a long journey and I'm here to document it. Let's go...