dbryant61

I had my engine dynoed last May. This is a little over a year since a top-end rebuild. This is a stock SC with -74 heat exchangers and Monty 2-in, 2-out muffler. 168 hp, 178 torque. I was happy with these numbers considering the default 15% driveline loss resulting in 198 hp, 209 torque at the flywheel.

However, I have heard and read recently that 15% is high for a 911. So, I am asking for your dyno numbers and any hard data you may have on actual driveline losses for a similar 911.

Thanks in advance.

hebrewhomeboy

I would definitely think our transaxles would be lower than 15%. Nice numbers though, and I'll bet it sounds great. You should post a sound clip!

Steve Weiner-Rennsport Systems

Don,

Driveline loss figures do vary so attempting to extrapolate accurate crankshaft HP numbers from RWHP results is "Kentucky Windage" at its best. We have both an engine dyno and chassis dyno and they are both very useful tools for their respective jobs. I don't make comparisons about the results from each,......

Variables include transmission gear lube viscosity, transmission condition, CV joint condition and angles, rear tires (type, diameter, and pressures) so you can see that its simply an exercise in conjecture.

Chassis dynos are extremely useful for a quick confirmation that a given engine's output is close to expectations, but its real purpose is both fine-tuning and making quick comparisons about certain bolt-on components.

dbryant61

hebrew, I'll have to ask some buddies for a recorder. I do not think the one on my camera would be good enough.

Steve,

Thanks for the data. I think I'll just "shut up and drive".

Thanks,

Don

Kika

I had my 80 SC dyno'd at 162hp/172ft-lbs. I also assumed 15% drivetrain loss. I have heard that 12% is more realistic for rear engine cars though.

My SC was completely stock at the time.

Chris M.

Higher torque than horsepower? You don't usually see that on a normally aspirated motor.

dbryant61

Chris,

"Higher torque than horsepower? You don't usually see that on a normally aspirated motor."

I posted the same post in the racing forum. All of the numbers I got back had higher torque than hp. I believe it has to do with the stock SC cams. You can change it by going to the 964 cams, which open up the top end and allow it to pull to red-line. Mine still feels like it pulls to redline (and on up to 7000), but the graphs say that it is not pulling as hard.

Don

Tippy

I was hoping to get some relative #'s.

Steve, can you at least give a range you have witnessed?

Oh, pretty please!

KeithC2Turto

Where one's motor has its TQ peak is where it is running its most effecent and making the most power for each power stroke.

TQ will start to fall off after the TQ peak. However, increases in RPMs make up for this untill the point where HP peaks.

After the HP peak the losses in effecency of each power stroke can not be made up for with increasses in RPMs.

There is nothing wrong with having higher TQ numbers than HP. However, this is usally indicitive of a truck or RV motor.

Porsche's TQ & HP numbers are very close to begin with. Put a SSI on it that is very effecent at low rpms and this is very possable.

It may be that there are opertunities for more hp if effecencies can be found at higher RPMs. We look first to cams and restrictions in the intake and exaust to do this.

With an 80SC that already has SSI's and sport muffler it might be the cam timming or small port heads that keeps the HP peak from being higher than the TQ number.

I am not an expert, just my thoughts.

GothingNC

The peak Tourque on my SC was a little higher at the wheels

SSI's
JE pistons 9.7
Intake Ports and Runners Ported and Blended to 36mm
Elgin SC330 Cams
Dansk Sport Muffler

How does the dyno below compare to stock?

John

dbryant61

Keith,

Thanks for the thorough analysis.

John,

It looks like you are up 16 hp and 10 ft-lbs in comparison to my stock motor with -74 heat exchangers and Monty Muffler.