according to the calculater my HP would be 588. I made 635 on a Dynapack so 588 to the wheels would kind of make sense?

 

Doesn't the Dynapack already measure HP at the wheels?

 

At the hubs, dyno dynamics does it at the wheels

 

If you have something to datalog with, it's basic physics:
http://www.motoiq.com/magazine_artic...-datalogs.aspx

 

At the hubs, dyno dynamics does it at the wheels
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Do you think there would be about a 47 horsepower different if you used a conventional chassis dyno from rolling resistance of two tires? That seems a bit on the high side to me, but maybe I'm wrong.

At 2800 lbs and 100 mph, a 0.012 rolling resistance coefficient, I get 9 HP for all four tires.
http://ecomodder.com/forum/tool-aero...resistance.php

So, I'd buy a 10-15 HP difference, not 47 HP. Stock S2000s see less than a 47 HP loss between the SAE 240 HP tested at the crank.

 

That's more difference than I would expect. Not sure what tire slippage factor would be, but it does seem high. Did you get the weight right, including driver, etc?