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Old 04-22-2014, 02:27 PM   #7
wparsons
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Garage
Quote:
Originally Posted by Luckrider View Post
This is something I have wondered about myself. The only compensation I have seen is for the calculated gear based on Engine RPM compared to revolutions per mile. I don't believe it effects how the speedometer reads.

Edit: This interests me more for higher HP builds that can benefit from a larger diameter tire.
It will definitely affect the speedo.

Quote:
Originally Posted by Ranatsu View Post
The ecu doesn't do the calculation. Its done within the transmission.
No, it's 100% the ECU. There's actually no sensor in the transmission or rear end at all, the ECU uses the wheel speed sensors (ABS/TC/VSC) to calculate the vehicle speed. This is why changing the final drive doesn't affect the speedo at all, only a change in tire diameter will affect it.
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