Quote:
Originally Posted by scheherazade
BMW designed the DME to induce knock, back off, learn, and adapt.
BMW condones it.
You can't make advertised power with timing relaxed too much.
If you want an engine to be equal power on lower effective octane, you're gonna have to have a larger engine with less effective compression.
-scheherazade
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Gee....that's strange.
I run quite a few datalogs including some that are at near-stock boost levels (like around 10 psi on pump gas) and the only knock I ever see is that vanos-shift.
I think Shiv is right on this one.
My datalogs confirm that the DME always targets advance of around 7.5 degrees mid-rpm up to 12 degrees near red-line. This never seems to adapt itself out.
I never saw any knock in between those values running near stock boost values.
So what I conclude is that maybe BMW designed a timing curve that in most cases will be close enough to the threshold as to not induce knock on stock boost levels and normal operating conditions.
That seems to leave the knock sensors as a backup/safety system should something get out of norm.
Like, say....you pour in 87 octane.
Seems to me that you are stating that BMW designed their engine to knock and that this is safe?
If that is so......how much knock is considered safe (ie number of instances and number of degrees of timing pulled).