900 HP Club - N54
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Offtopic, resume here: https://bmw.spoolstreet.com/threads/nizpro-6hp21-billet-transmission-internals.1885/
First thing I thought when I saw 38psi. I just don't think this is commonly thought of on this platform. Strange as people have been porting heads since the 50's. The hotrod guys did it a lot more before the world of cheap V8 CNC heads came to be. And they are still doing it. How many ported heads in the N54 world, total? I bet it is countable. But I agree 110%.
Filippo
According to the guys at Nizpro I met with, I am. Unless of course they lied to me.
I did with the help of a local shop. I didnt do the machining though took that to a local spot. The car originally had the 9mm head studs but I lifted the head. So I put in the 11mm outer head studs and havent had a problem
Would porting head help or hurt spool and response? I know the reason it's so restrictive is for na feel on stock twins but I would think at some point the increase in flow would make enough more power with less boost that it could actually feel more responsive in the mid and lower end. Iirc part of design was to promote tumbling and velocity to increase efficiency for emissions purposes, once again I would think at a certain power level their is plenty of velocity and turbulence .
To get the real benefit you need a cam that keeps the valves open longer. Otherwise the gains are minimal.
My point was that the stock head flow results show no benefit to higher lift from a cam. But a ported head does show results by itself. Obviously a ported head with cam is the best option.
Cams on a stock head yields more power than a ported head with stock cams.
Ported N54 head flow gains are mostly above .300" lift which the stock cam cant take advantage of.
Bigger cams in a stock obviously have valve lift beyond where the port flow has plateaued, but its time at max flow is longer; earlier and later. This increase in duration also increases spool and midrange by adding overlap without sacrificing the optimal angle for cylinder filling.
What specifically do you need to tune or change to run high lift cams? I've heard people say the high lift Shrick cams wont fit the stock N54 pistons, is this true?
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