The Richards wrote:
>
> Is there a forumula for comparing one standard to the other? I would think
> some plus/minus would definately be in order since the differences in
> 'where' they are measured would make a formula problematic. This is just
> layman's logic, but would SAE, measured at wheels include more variables
> than BHP?
>
> Michael, New Bern, NC
> >
THere is no conversion. Brake Horsepower (BHP) is a loosely defined
term that comes from the old water brake, and earlier prony brake
dynos. When we refer to it, we are really talking about the old
practice of car manufacturers whereby the H.P. developed by an
engine(without a drive train attached - measured at the flywheel) on a
test stand was reported. This is where the old claims of 500 H.P. from
stock Detroit iron of the 60's came from.
In an effort to simplify, and quantify the claimed power from a car, the
Society of Automotive Engineers (SAE) developed a standardized method of
measuring H.P. in cars. This is now done on a rolling road dynamometer,
and the horsepower measured is measured at the drive wheels, and takes
into affect all of the inefficiencies of the transmission, and
differential, as well as windage losses, and bearing drag. This method
was adopted in the early/mid 70's. Hence the reason that early texts
made referenece to 95 H.P. from a stock B mill, while experts today
widely report that figure as inaccurate, with a more reasonable figure
being around 80 H.P. Since every car's drivetrain is going to be
slightly different, trying to convert old factory numbers is not really
feasible.
REegards,
Chris Delling
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