Quote:
Originally Posted by Nezil
A lot of talk on this topic which is great... I'm happy it's getting attention because I too agree with these statements:
It actually shocks me that no other 6MT N55 or S55 owners have picked up on this issue.
Anyway... I'm pretty sure that a tuner doesn't want their 'secret sauce' spread about, and I have no intention of doing that with the tuner I'm working with, even if they were to tell me... which they're not.
What I will say though, is that the N55 in the M2 (and probably other vehicles) has two ways to control boost pressure... one somewhat crude way, because of latency etc. is with the waste gate and the diverter valve. The other, which is the way BMW does it typically, is with the throttle plate. If you take a look at logs of the manifold MAP sensor vs the pre-throttle MAP sensor there are times with the stock map that the throttle plate closes to control the pressure in the manifold, causing the pre-throttle pressure to increase. With a stock charge pipe you may not want this to happen because any spike in pressure here could cause it to fail, but with the aftermarket charge pipes most of us are using, a boost spike can be tolerated by the engine (by using the throttle plate) and by the charge pipe (because it's uprated).
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I think it's a little more complicated than that. There's more map data tables in the boost group for BMW than I've seen in any other car. There's a reason no one has really figured this out yet....no one 100% knows how this logic all ties together.