Wheel Dynos - What are they good for

Wheel dynos are great for tuning but not for comparison to other engines, dynos, or even other days running. There is not enough accuracy involved.

You MUST have a correction factor for the day involved. That means: barometer, vapor pressure,and accurate temperature at the carburetor inlet. Without these you are just comparing the last run with the one just made but not a reference to anything done that morning or even later in the day. As the engine becomes more heat sinked the power will change.....so...consecutive runs may be actually better in power but give a lower or the same reading.

On an engine dyno the temperatures are controlled and thus you can do a lot more work, and consecutive runs, with excellent accuracy. Clutch and rear wheel slippage, gear frictional loss all count to reduce the accuracy along with the temperature of the oil in all those little moving and rotating items.

Wheel dynos are a good tuning tool, I used one a lot in the far past, but as a scientific instrument for making comparisons there is just too much lacking in information & accuracy.

Kas Kastner

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