Quote:
Originally Posted by 0l0dom0l0
I wouldn't worry about the airbox, it isn't the restrictive element of the system. From what I've read I think you'd see better gains trying to stop the disa valves shutting and increasing the rev limit. Should be good to 7500rpm.
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Be good if you could qualify some of that, esp on the airbox. As you can see above, I'm basing my thoughts on the intake manifold pressure I'm seeing, the shape and size of the long and thing entries to the snorkel, the flow path in general and the comparatively small entry to the airbox etc. I don't really know for certain whether it will make much odds, but note that Dinan take the same approach on the n52 and that the m3 has a different system etc. Be interested to know what makes you think differently.
On the disa valves, my understanding is that both are open at high rpm, and the valves are shut to give different inlet lengths at low and mid rpm to optimise port length/velocity? I'm not sure why I'd want to prevent them from shutting? If I wanted to not have disa, I understand I could just fit an n54 manifold, but I wouldn't want to as it's a road car.
As for running to 7,5k rpm, I'm surprised that's safe on a standard engine and would wonder whether you'd make much power up there. I wonder at what rpm the hydraulic lifters are over-pressured and what rpm the valve springs are good for etc. I've left the rev limit alone, tbh I wasn't even running it quite to the redline when mapping, I don't actually think I've ever run it to the limiter!