My friend Henry has a shop called Revolutions in Eau Claire, WI. You all might know him as "the" Rota wheel guy

He has a very nice Dynapak 3000. When I go back in June we are going to do a series of Fixed RPM/Variable Load runs. This is really what sets the Dynapak apart from roller dynos. Basically you tell the dyno what RPM you want to hold at, and once you get to that RPM you hold the pedal at full throttle. The dyno adds enough resistance to hold the engine at that rpm +/- a few revs. It shows you the real time power production on a graph.

We are going to use this method to precisely tune the A/F curve. An example....

The dyno is told to hold the engine at 5000 rpm. We get to 5000 rpm and hold the throttle wide open. Then we get on the VAFC and start triming the fuel... you can see on the dyno screen what impact that change in fuel has on power production. You repeat this process at various RPM points and the end result is an optimized fuel curve.

The problem with a roller dyno is that it is based on interia where you have to accelerate a drum with a known weight. You can't hold at a certian RPM... The other problems are with tire slippage, alignment, etc.... There are many external variables that a hub dyno, like the Dynapak, eliminates providing more accurate and repeatable results.

Anyway....



[Modified by Ausmith, 5:54 PM 5/17/2002]