Anyone have a formula for prop shaft HP on an international dyno?

[outboardnut]

Hi Everyone.
I'm trying to see if anyone can lend me a hand figuring out prop shaft HP.
I have an international DYNO, which will measure pressure generated from the prop shaft and engine RPMS.
I can figure out prop shaft RPMS, and the "pressure" this machine generates, but have no forumula to covert it to HP.
I tried contacting the MFG with no response.
They have a chart that goes into pressure units but I would rather have a conversion for prop shaft HP.

http://www.internationaldyno.com/Intl_Dyno_Performance_Guidelines.PDF

 

[Dhadley]

Re: Anyone have a formula for prop shaft HP on an international dyno?

It doesn't really work that way. You need to factor in all sorts of weather conditions and other variables, commonly called the correction factor. You can have two motors the same and get two different hp ratings from two different dyno runs.

It's not uncommon to have two motors rated at the same hp and one will be much stronger than the other. IE - a 200 crossflow vs a 200 looper.

Torque is what you really need to know.