[s-cars] Re: From the Horses Mouth at DynoJet (SAE)

[QSHIPQ at aol.com]

Now confirmed from both sides of kicked dead horse?

If some engineering type has access to J1349 or J1995 (bundled together and very expensive to buy) it would be quite obvious turbo cars "SAE correction" on a chassis dyno (that's twice removed from intended)is bogus. Uncorrected with roughly the same conditions on the same dyno is a better measure.  

I believe Dan to infer that a measuring tool that spits a number, only correlates that tool with that number (good unto itself = a good tuning tool, not a good tool to compare other tuning tools).  We could explore how accurate any dyno is within the realm of turbo spool up with awd and a torsen, but I'd just rather ditch correction factors first.  

Scott "covering the backside" J

In a message dated 11/16/2004 12:27:44 PM Eastern Standard Time, "Cody Payne" <cpayne at bconnected.com> writes:

>"The correction factors that we use in our dynamometer software are not
>valid with forced induction applications. The most popular correction
>factor, SAE CFJ1349 JUN90 and J1995 JUN95, does not account for the
>conditions present in boosted applications. Atmospheric pressure is the
>major component of this calculation, and anything that varies from the
>standard (29.235 inHg) can easily be corrected for NA applications. When
>you are forcing an "artificial atmosphere" into your motor, these
>standards go out the window.
>
>Technically any boosted car should be viewed as uncorrected if you want
>to compare apples to apples. If we had a correction factor that just
>took into account temperature and humidity, that may make things easier
>to compare in boosted applications. If you are forcing 1 atmosphere
>(14.7 psi) in your motor at 6,000 feet, or 1 atmosphere at 100 feet,
>that's really the same difference.................IF you are measuring
>manifold ABSOLUTE pressure, it's absolute, don't rely on a standard
>boost gauge to give you an absolute value. Regards,
>----------------
>Dan Hourigan"
>
>
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