So i remember when i was modifying my mustang in University the rule was 1 hp = .8 whp and also i have heard 1 hp = .85 whp

Which if the two is more accurate for the 991 GT3?

 

Most assume 15% loss. So 1 hp=.85 whp

 

A 15% loss is what I typically see stated for drivetrain loss on a 911.

 

WHP x 1.2 = CRANK HP
APPROX

 

For our dyno it's right at 15% drivetrain loss. Each dyno and tire combination is different. The Dynapak hub dyno is about 8% loss as no tires to turn, it connects to the hubs. On a dynojet (the one most use) 15% is pretty standard...

All of our dyno's we've posted you can divide by 0.85 and you're right on it.

 

I am making several dyno charts from stock GT3's showing wheel HP and then divide their total by .85 and get Flywheel HP. The dyno I use is about the most accurate one I know of and is consistent 15% loss. It is a dyno jet 248c with the large rollers.

Most places don't pay to get their dyno calibrated because they don't care
Most poreches are dead on but I have only ever seen 2 under rated.

1) 996.2 GT3
2) 997.2 3.8RS

Those both seem to make 15-20hp more than rated and this is well documented

 

without getting too cluttered on here, this is 5 GT3's stock dyno's. I have dyno'd dozens of GT3's and other Porsche's over the years and everything always seems to dyno the same give or take a few HP.

RED- 996 GT3. I have had about 12 996 GT3's on this dyno over the years, all are 354-357whp bone stock other than all had the 997 RS LWFW clutch setup.

356whp = 418hp means well under rated but everyone would agree to that i'm sure (rated at 375 SAE HP)

BLUE- 997.1 GT3RS. I have had 7 3.6RS on the dyno, all 359-363whp.

359whp = 422hp (rated 415 SAE HP)

GREEN- 997.2 3.8 RS. I have had only 3 of these on the dyno now but they all run 397-399whp stock. well under rated but again many others out there would agree especially those on the track.

398whp = 468hp (rated 450 SAE HP)

DARK BLUE- 991.1 GT3 I have had 3 of these on the dyno and all are 397-401whp stock. These are actually varrying a lot on run to run for whatever reason but the peak numbers are always consistent. I am sure I will have more and more of these on the dyno as time goes on.

402whp = 473hp (rated 468 SAE HP)


BROWN- 991.1 RS. Only have one of these so far but will have more as they are delivered. seems exactly on par as it should be.

425whp = 500hp (rated 492 SAE HP)


Other Porsche's I have had on the dyno
996 C2 273whp = 320 hp (315 rated)
997 C2S 308whp = 362hp (355rated)
986 3.2 S 217whp = 255hp (252 rated)

 

Tagged.

Molotov. Moose. Dyno - like that wont turn up 1000 threads.

Dan (searches sometimes)