Quote:
Originally Posted by Nezil
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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Hmm. I would think that closing the throttle plate would also potentially be bad for the turbo, as it might cause a reverse shockwave back up the system as pressurized air "bounces off" the throttle plate. But there's a big intercooler in the way that I suppose would absorb most of that shock before it could reach the turbo itself. So maybe not as bad as I thought originally.
When I first started reading your research into all of this, what popped into my head was, "Is this part of the auto-revmatching?" Per BMW's documentation & statements, the ECU on 6MT cars does "magic" to help smooth performance during upshifts. My first thought was that this could be the root cause of this behavior.
Since we know that revmatching is disabled (on an OG car like Nezil's) when you disable traction control entirely, I was wondering if your tests were being performed with ESP entirely off, or whether that has any change in behavior? It seems like some people have tested with it off and say they are still feeling the lag though...
Also, have you tweaked anything else, like "Euro MDM" or other traction or DME-related stuff?