Quote:
Originally Posted by clivem2
I'm still trying to totally comprehend how the turbos are managed, or at least what BMW are saying:
1) MSD80 cars originally had the wastegates closed at low revs
2) MSD80 cars from 29.2 have the wastegates held open for 150ms
3) MSD81 cars do not have the wastegates held open
So the 0.5 sec delay at low revs (when hot) that I have on my 07/08 is genuine turbo lag?
I'm not convinced we know anywhere near enough yet about how the turbos are managed.
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Yup, that is what BMW is saying. My opinion is:
Point 1) is most surely correct. That is what has been measured by Shiv@Vishnu, in contrary to v29.2.
Point 2) is "almost" correct in that most people believe that initially, with advent of v29.2, the delay was more like 500ms (felt), and they only changed it in v31.1.1 to the 150ms they now claim. They play it down, in other words.
Point 3) Here is the translation from Autobild: "After all these improvements current 335i accelerate again nearly without turbo lag. Autobild has convinced itself of that fact with measuring trips and on the dyno. The Reason: Because of the improved wastegate hardware, the software of the engine control unit can regulate less restrictive.". In the U.S. statement, BMW says that "X6, 135i, and 3 Series/5 Series vehicles from March 2008 production onward are not affected."
Note the word "nearly" in the Autobild article. I understand your doubts about MSD81 cars. Never having driven one of these myself, from what I've read here, my feeling is that those are like MSD80 cars with v31.1.1., namely "
less restrictive". Or as
Shiv put it: "Maybe not as responsive but very close.".