I can see 2 approaches that make sense.

One would be to deduce a drivetrain loss from a baseline dyno of the unmodified car, and stick with that loss consistently. One could argue that the % drivetrain loss should go down as the power goes up, but we'll set that aside until better data is available. This approach neglects the fact that each engine with produce a different power than its nominal rating - but the amount of this difference is unknowable.

In your case, I seem to recall you had something like 265 RWHP in your baseline dynos. That would imply a drivetrain loss of about 10%. On that basis you could reasonably claim that your engine now makes 370 FWHP, which is pretty damn impressive!

The other approach would be to talk about increased RWHP from a baseline, and not try to speculate about what FWHP might be present. As I recall, you've added something like 65 RWHP above your baseline, which is also fantastic! In this approach, since the drivetrain loss is unknowable, we just avoid talking about FWHP altogether.

According to Rototest Research Institute, the drive train loss for a manual Cayman is 8%, for a Tiptronic Cayman S is 12%.

Powertrain Performance Graphs - Rototest Research Institute

I frequently edit long-winded posts after they're posted. I have a hard time with the tiny posting editor window. Sorry for any confusion...

My concern is that the dyno might be reading high across the board. For example, if the data were acquired on a Dynapack dyno, where the dyno is connected directly to the wheel hubs, then the "driveline loss" would be expected to be much lower. Thus, an unmodified car might dyno at 280 HP on a Dynapack, implying a drivetrain loss of about 5%. In that case they have a GT334 (317/0.95 = 334). Without seeing a baseline we don't really know how much power has been added.

I'm not asking them to do anything... especially not for me. I'm just pointing out that there is some uncertainty in their results since no baseline has been posted.

That's a fantastic link Titanic! Thanks! Note that their data was for a base Cayman. Also, their dyno was a wheel-hub type dyno. Thus, their 8% loss is less than what one usually sees on a rolling-drum type dyno, where 10-11% is more typical.

You are welcomed.

Fort,

In this thread just a few post back (see #43) you were sugesting these type dynos had a 5% loss.

This seems to be the same type dyno and is reporting 8% loss is your quess just off by 160% on the amount of loss or is the wheel-hub type dyno you mentioned that much different.

As I have stated several times, I believe that a rolling start comparison is the only thing that matters. Take a video of a GT350 versus stock. From 25mph tp 125mph. Or pick your favorite speeds.

Isn't that what you are looking for? An increase in acceleration? More torque?

If a "GT350" is quicker than a "GT390", but each comes with a certified Dyno sheet...which would you want?

I say we standardize on GTxxx, where xxx = 1/4 mile time expressed as xx.x seconds.

__________________

2007 Speed Yellow Cayman GT 2.7 (retired)
2008 Guards Red Cayman GT 3.4
"Carpe Cayman"

I just made up the 280 RWHP number (and the resulting 5% loss) as an example of what might happen. I did use the word "might" in the earlier post. I didn't mean to suggest that 5% was the right number. Jeez... For the record: I don't know what the differences are between the dyno used in the link and a Dynapack. They do seem superficially similar. I don't know what the driveline loss would be on a Dynapack, but it should be lower than on a rolling-drum type dyno.

Fort,

Sorry my bad, I thought that you had first hand knowlege of the Dynapack machine and I can see in the above post you do not so thanks for making that clear and forgive me for being mistaken and hope there is no hard feelings.

No worries, it's all good. Thanks for the note.