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      03-10-2013, 06:57 AM   #16
Bönz
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Drives: 2018 M5
Join Date: Jan 2012
Location: Michigan

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Quote:
Originally Posted by mlai View Post
Not only in first gear. In 1st, 2nd, 3rd at least. And not even at WOT, just when rpm hit above 4.5k rpm with the tune at pos 6, rear end becomes unstable, even in a straight-line.
Are you sure it's the rear end? What you are describing sounds like it could be an engine induced vibration, perhaps felt as a rear end instability, which is why I asked the question. Whatever it is, it's not good. Keep the setting on the lower numbers. My fear is the factory fuel map cannot keep up with the over boost condition from the "tune" and you are forcing the engine into a lean condition. This is sensed by the O2 feedback loop and the ECM is doing what it can to compensate by adjusting spark, boost, fuel, etc. This could be the cause of the shake you feel.

These engines (without tune) produce nearly 100% of peak torque at WOT from as low as 1800 RPM. If your problem were torque induced rear end instability, you would feel it from much lower on the power band.

Personally, I would be wary of these low cost aftermarket systems. You spend over $100k (a lot more in Hong Kong) on a premium automobile and then want more cheap HP.

Quote:
Originally Posted by roadsta View Post
Bonz, always good to read your posts. I can tell you know what you are talking about.

Roadsta.
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