Miata Mailing List: February 1996, Message #86
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   From: pturin@sunspot.ssl.berkeley.edu (Paul Turin)
Subject: Dyno HP conversions
   Date: Fri, 2 Feb 1996 13:38:22 -0500

	All you Miata-meisters seem to be a well informed bunch, so you probably 
know this; but I'll post it anyway in case somebody was wondering (I was).

	In the recent flurry of turbo/SC discussions, HP numbers are being quoted
both from factory specs and dyno results. The factory specs are brake horsepower
measured at the crankshaft, and dyno results are measured at the wheels. The 
difference is due to losses in the transmission, differental, and tires.
The accepted conversion between brake and wheel HP is

		DIN (brake) HP = 1.28 x HP at wheels 

	Thus, Brian Goodwin's Autorotor conversion, which measured 150 HP on the 
dyno, is putting out 192 HP at the crankshaft. I'm jealous!

	Now, you might think that this factor would vary a lot depending on make, 
construction of the tranny & diff,  tire pressure & size, etc., but supposedly 
its very consistent between cars, regardless of these things.

	OK, I got this from an engineering book and from a dyno guy I know, and 
I'm interested in hearing opinions to the contrary.

Paul Turin
'96 montego blue mica PopOp