Home Dyno (was) Datalogging RPM signal

[Bernd Felsche]

Glen Beard tapped away at the keyboard with:

> I don't know what the formulas are, but I know I have seen
> them scattered on the web.  The only ones that ever really
> gave me trouble were drag coefficient, frontal area,
> drivetrain loss, and tire diameter (because it grows from 15
> mph to 70 mph and is not accounted for).  It only takes
> being off by a little to really throw your curves off. 

Drag (Cd * A) can be measured by a high-speed coast-down and rolling
resistance by low-speed coast-down tests. Procedure is described in
the Bosch Automotive Handbook.

Not just useful for engine tuning, but also selection of tyres and
body mods.

> Other than that...  If you don't look at the output numbers
> themselves, but instead keep everything constant and look at
> the trends, it's a fairly repeatable tool for tuning.

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