What is the general consensus on drive train efficiency for 7 GT3/RS? 10%, 12.5% or 15% loss? Does light weight flywheel play any role in this calculation? The reason why I ask this question is because my RS dyno at 368 hp and 282 lb-ft 100% stock with 91 octane gas and if you use the conventional 15% drive train loss at the wheel, my RS makes as much hp/torque as the 2010 GT3?

Here is the published figure for 7 GT3/RS

Power bhp (kW) at RPM: 415(305) / 7600
Torque lb-ft (Nm) at RPM: 300(407) / 5500

Here is a break down of the power generated at the crack with various hypothetical drive train efficiency:

10% loss:
408 hp
313 lb-ft

12.5% loss:
420 hp
322 lb-ft

15% loss:
433.6 hp
331 lb-ft

Dyno was done today comparing 100% stock exhaust vs Sharkwerks' center muffler bypass. It was done by Driving Ambition using Dynapack system. All paramaeters were measured and keep consistant between runs including air intake temperature. Rear decklid was closed. Shad at Driving Ambition is one of the best in the business and produce consistent numbers time and time again. My dyno numbers from a year ago with same set up was only off by 0.3 hp!

By looking at the above numbers my drive train loss has to be around 10% - 12.5% which is unheard of per Shad. He thinks my RS make alot more power than 415 hp and 300 lb-ft. What are your thoughts?

2010 GT3 power chart



07 GT3 RS dyno chart. Blue = 100% stock. Red = Sharkwerks center muffler bypass. Green box numbers are for 100% stock and yellow box numbers are for Sharkwerks center muffler bypass



Dynapack does not artificially produce more hp than dynojet

http://www.youtube.com/watch?v=UZXbk3o-xHg

 

subscribed -- nice post

I am guessing but I think the DT loss is less that 10%

 

Being rear-engined I would have guessed 10-12% anyway. Taking into account dyno variances, hp at various operating temps, it seems like a safe number.

 

According to Shad at Driving Ambition, anything less than 12% is very hard to come by even for a rear engine car. 10% or less drive train mechanical loss is unheard of. He serious thinks my (our) GT3/RS are packed with much more hp than publicized. Imagine how much more power you get with 93 or higher octane gas

 

I've heard the weakest Porsche make at least the published HP rating. This is one of the reason I love Porsches.

 

Good stuff as always man... It's pretty known that the dynapack is at 12-15% drive train loss. Depends upon the set up of course. Most of the rs' and
gt3s dyno'd show at least the published crank hp
or more. Not like ferarris that show less

 

Yes! Shad and I love how your center muffler bypass sound and it deliver couple extra hp up top as expected. I forgot how horrible the stock center muffler sound. It sounded like some donkey got kicked in the *****! lol The damn thing drone like mad at sport mode and weight a ton.

Dynapack is a pretty unique system and Shad thinks the drive train loss is between 12-15% as you mentioned. This means Mr. Porsche may have packed a 3.72L under my RS rear decklid

 

I would think a Porsche engine tuner that has dyno'd engines by themselves could say either way.

Also, I wouldn't think an N/A motor would not "take advantage" of a higher octane beyond the factory programmed parameters vs. a boosted engine. Comments on that?

As far as factory tolerances, SRT Engineers stated there is an allowable 2% horsepower variance in the production 6.1 engine. I would expect Porsche to be even tighter than that.

Another consideration is that at a coolant temp of 170-180 degrees vs. normal operating temperatures (and full emission compliance) in the 6.1, the horsepower difference is suspected to be 20-30hp. I wouldn't be surprised if other engines have this variance running cool, normal and hot.

 

My observations are that Porsche 911s on a Dynojet are about 11 to 12% drivetrain loss. So take the SAE Dynojet number and divide by 0.89 or 0.88 to get your corrected hp number at the engine.

Numbers from all other dynos, such as DynaPacks, Mustangs, DynoDynamics, etc can be anywhere from 20% low to same as a Dynojet, depending on how the operator sets up the dyno operating factors, loading, corrections, and if there's a built in weather station to compute and correct for atmospheric conditions. The good thing about Dynojets is there's no variables for the operator to mess with, so a car dyno'd on one in New York will measure within 2 hp if it was tested on another in Los Angeles.

 

I believe that Porsche states that the GT3s have an 8%-10% drivetrain loss. When my 2010 GT3 was stock, it put down 400-404 whp SAE on 2 different Dynojets. Using the 8%-10% Porsche claims, would out it slightly over their claimed HP. I've always heard from tuners and other long time Porsche owners, its really 11%-13% though... at the end of the day, the only thing that matters is WHP

Mikemu, I think these results you posted in OP, would be right around 415 crank HP (10% loss), if 93 gas were used:
All the advertised HP outputs are obtained with 93/94 gas, I believe.

As a reference, here are my same day, before/after dynos, when I installed the Akrapovic race exhaust system. ECU and intake filters were stock on both runs:

 

I thought it was less an issue of very low drivetrain loss and more an issue of Porsche understating reported crankshaft HP.

 

Thanks for posting this, Mikymu. I spoke to and placed an order from Alex last week. Was about to PM you to ask how much you liked the Sharkwerks bypass AND was going to look into dyno'ing before and after as well! It's nice to have something to compare... and your data has me excited... yeah, boyyy!
-E.

 

^^

I think 12% is a safe general number to go by for most dyno applying to GT3.

Very good choice in selecting Sharky's center muffler. You will love the sound and ask yourself how you live with stock exhaust all this time. No need to before/after dyno your GT3 since I done the work already but it's a good idea to baseline dyno your 3 so you can use it to compare with future mods.

Oh, Sharkwerks' customer service is next to none! He will back up his product 100%

 

Mike,

Did you happen to dyno with and without the sport button activated?

 

Nope. It was dyno with sport ON. Sport off will produce less hp for sure