I have a manual transmission and was under the impression that a certain RPM on a particular gear will always generate the same MPH. The other day I noticed I sit at 2,800 RPM in 6th gear @ 80 MPH, and other times it’ll be at 3,200 RPM – Could some explain?
In: Engineering
Your original assumption would be correct. Assuming the drivetrain is rigidly coupled and not slipping, achieving the same speed in the same gear will result in the same engine speed. It’s a fixed relationship between the engine and wheel.
Either there’s something that’s variable (the clutch slipping for example) or your measurements are incorrect. It definitely wouldn’t change by 400 RPM. The tachometer or speedometer could be faulty too.
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