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Datsun_240z Datsun_240z is offline
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Car: BMW
Default N54 head flow / intake cam - 10-06-2020, 01:22 AM

My first post and still considering car (or engine) like this, but of course before doing anything, I would like to know how to make most of an engine like this.
Of course all the external mods I have read about, but there is a thing that puzzles me with this motor and comparing it to anything else I've worked before.

My analysis so far indicate that the N54 is massively intake limited engine. The intake flow is poor, intake cam is small (compared to exhaust) and this means that you need massive boost levels to fill the cylinders. High boost means hot air and high exhaust back pressure, both bad for the engine and turbos.
My analysis is based on this info:
1. Head flow: BimmerBoost - Doc Race before and after N54 CNC head porting data
2. Stock cams: ENGINE SELECTION | *** CAMS performance camshafts
(select N54 engine from the list if link doesn't take you to right page)

Based on the data above, exhaust flow is about 85% of intake but still the exhaust cam has 24-degrees more and also a bit more lift. With exhaust flow 85% of intake flow, I would expect symmetry on cam profiles on a turbo engine.

Now considering the first actions with an engine like this, everything helping the motor to breath needs to be done, so FMIC, better air filters and intake tubes, etc.
However my question is that wouldn't just dropping in another intake cam be quite straight forward and that would address the massive imbalance between intake and exhaust in these engines. I would expect that to give quite nice bang for the buck since cam costs around 700USD and would use stock equipment and you only need to open the valve cover to change the cam (or am I missing something here), not the whole head. This would also to allow the stock turbos also to reach higher power levels since they would not need to deliver so much pressure, only extra flow. Air in the cylinder creates power, not the boost pressure, but with N54 you need massive pressure to get the air in to the cylinder due all the restrictions on the inlet side. So shouldn't this be a thing you do before you upgrade your turbos?
Of course ideally you would port the intake (and simultaneously exhaust) channels as well since the flow is low for engine/cylinders this size, but that is much bigger thing....

FYI, I come from Volvo B234F background and this engine, made in early 90s, comes with flows in stock head 50% bigger (230cfm @34,5mm valve) on 600cc cylinder and best heads flowing up to 350cfm with 39mm intakes on high lifts.
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