Topic: Going to try the new Dyno in Manassas

[Imaj]

Hi Rich...It has been said that if one has a Wester's tune on a Turbo GXP...going with a .028 to .030 gap is ideal.

[Treeman]

I know very little about this dyno stuff except to understand the concepts of torque, power, and RPM.  But I have to wonder about 238's 3k dip.  I realize that this was done at the wheels and not the engine, but the published chart for the engine does not show this dip (see attached) and I can't think of why the drivetrain would introduce one.  I wonder if there is something specific with 238's car or - going by his butt dyno - if there was some issue with the dyno run?

[Sol Asylum]

Treeman

Your graph is for crank horsepower which means that the engine was dynoed on its own (under ideal conditions).  They literally attached the engine directly to the dyno and those were the numbers that it yielded.  238's numbers are RWHP so it includes all the quirks of the drive line, its possible that there is something in the transmission or rear axle that can effect the numbers.  Another factor is GM doesn't say what tune they used to get the numbers used for marketing but there could be some differences between stock tunes too.  The point is the marketing dyno would only be useful in comparing different engines but once you put them into something they may behave entirely different.  So as LG has pointed out crank hp don't mean shit.

[Critterman]

That graph was drawn with a ruler.  You will never see straight lines like that.  Can you say marketing?

[Treeman]

Ah.  Like I said, I don't know much about this dyno stuff.

[Uranium-238]

Could also be they used a slightly different tune. I could easily see them running tune X while the engine was in development, then putting tune Y in a production kappa. IIRC, variable valve lift was designed for fuel economy, so it would make sense to cut it back in development, then back on for a regular tune.

But yeah, that dyno doesn't look too real. Looks like something an engineer calculated more than a real-world chart.