Dock

Can dyno pulls be started from a complete stop, or at least from a very low rpm start? The times I've done dynos the runs have started from ~2000 rpm. Is traction on the drums the issue?

robertp

And hopping under heavy torque and low wheel speed.

Kevin

Dock many good dyno's can edit the software so that the run can start earlier. With my Dynapack I can start applying load at lets say 1500 RPM and start the data at 1550 or any RPM that I set. You have to have enough torque to start the hubs turning.. And also enough to hold it.. With the hubs bolted to the dyno, we hop isn't a issue.. Insist on disconnecting your drive-shaft on every dyno except a Mustang..

tkerrmd

Are these "dyno runs" hard on the car or bad for it in any way??

Dock

Thanks Kevin -

Until we get a chassis dyno on the 997 Turbo, we have to evaluate it's power curves based on the data released by Porsche. As I understand it, this data is from an engine dyno and shows the great low-end torque the new turbos make. All of the 996 Turbo dynos I have, many from EVO, are from a chassis dyno. These dynos don't start as low in the rpm range as the Porsche graph, so I can't evaluate the difference in low-end torque between the two cars. From what I have been able to extract from the available data, the 996 Turbo with GIAC Stage 2 is generating the same power as the 997 Turbo from ~3500-4000 rpm. Above 4000 rpm the Stage 2 makes better power.

The current data shows the 997 Turbo making better power below 3500 rpm, but that's because the 996 dynos I have don't start until ~2200 rpm, so it's "behind" in terms of building boost.

Here's the data I have (based on a dyno from EVO)...rounded to the nearest 10, and obviously not entirely scientific. Just a point of discussion. The data for the 997 Turbo is from an engine dyno started at ~1200 rpm. The 996 Turbo Stage 2 data is from a chassis dyno starting at ~2200 rpm. I converted the 996 Turbo numbers to flywheel numbers by using a correction factor of .875 (a 12.5% drive train loss). At each listed rpm the value listed is the +/- power of the 996 Turbo versus the 997 Turbo...

Torque

2500...-170
3000...-115
3500... -35
4000...even
4500... +25
5000... +30
5500... +50
6000... +20

Horsepower

3000... -70
3500... -40
4000... +10
4500... +25
5000... +35
5500... +35
6000... +30

Obviously, if a correction factor of 15% is used, the numbers would be more favorable for the 996 Turbo...but I decided to go conservative.

Dock

They sure can be...if not done correctly.