<< > > > > Which liar/incompetent ran the dyno?

 > > > > YES! One thing to watch for is the "correction factor." Corrections
are applied to raw dynamometer data to compensate for different conditions at
different test facilities. Basically, an engine will make less power as the
inlet temperature increases, the humidity increases, and the barometric
pressure decreases. There are various ways to "normalize" these effects to
some standard condition. There are different correction factors, some of
which give grossly overstated power ratings that are rarely seen in the real
world (corrections to 60 deg F, zero (!) humidity, 30 inches Hg baro, etc.)
The power rating thus achieved is not very useful for calculating any kind of
BSFC. BSFC must be calculated based on OBSERVED hp, not corrected hp. Another
trick is getting the hp on a snap acceleration. The engine may produce a few
extra hp for a few moments before things heat up, and the dyno may also
record an overshoot due to inertia effects. All this is pretty commonplace
among the high
 > performance engine promoters
 > .
 > > >
 > > > Jon

 > I think most people use SAE tables published years ago to correct to sea
level, inlet air temp and humidity.
 > Otherwise its all garbled. Same with the flow bench. I should be able to
call Drummond on the left coast and say "do this and that on the flow bench"
and he should be able to recover the same sized data element.
 > Lynn E Hanover >>

OK, I think I need to clarify my position here. I fully agree that correction
factors are necessary to have a reasonably equivalent basis for comparison.
HOWEVER: There is more than one correction factor in use, and they can give
very different results. The more recent SAE corrections are reasonable, the
older ones are not. The older ones are often used to this day because they
give higer numbers. A disreputable person can also fudge the corrections by
using the wrong temps, humidity, pressures, etc. My original point, poorly
made, was that one needs to be certain which correction is applied, and one
needs to be confident in the accuracy of the data used.

Jon

 
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