Miata Mailing List: May 1999, Message #228

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Skip Cannon wrote:
> 
> >The whole topic began with the idea that turbocharged engines don't suffer
> >from the same
> >altitude-induced power loss that NA and sc engines do.  A few feel this to be
> >the case.  Your
> >numbers (please correct me if I'm wrong) were 257rwhp with a 1.18 correction
> >factor (most of
> >which is arguably over-correcting for the 4300' altitude).
> 
> I don't know where this 18% comes from.  Your own figures were 3% per
> thousand for NA and 1% per thousand for turbo.  Taking off 18% then adding
> back 1% doesn't make sense to me.  Take the corrected 257 hp and deduct
> 4.3% for the altitude leaving 246hp.

The 18% came from Bill C.'s earlier.  Assuming I understood him correctly, 1.18 was the 
dynojet correction factor.  That means that the actual *measured* (uncorrected) hp was 
257/1.18= 217rwhp.

> >That means that your uncorrected
> >numbers (what you actually spun the rollers at) is 257/1.18 = 217rwhp.  Right?
> >Check your
> >sheets.  If you got a print out, there should be two columns, one with
> >corrected numbers and one
> >with uncorrected numbers.  Usually, we disregard the uncorrected numbers and
> >go with the
> >corrected ones.
> 
> The graph only shows the corrected hp and torque, no figures for raw hp.
[SNIP]

There's another print out which lists corrected and uncorrected hp & torque output at every 
50,100,250, or 1000 rpm.  If you didn't get it, you didn't get it.  I usually ask for the 
raw data so I can plug it into an Excel file and graph it.  It needed when we display hp 
graphs in the mag.

Shiv