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Re: X51 Dynoed close to 400 HP
Quote:
Dilinger said:
i m sure if the X51 was 400 Porsche would not hide it
Porsche is notorious for understating performance. There's only about a 5% difference between 381 and 400. I've heard reports that the C2S is actually closer to 370 HP. So 400 for the X51 doesn't seem too far fetched.
Re: X51 Dynoed close to 400 HP
Quote:
AeroSmith said:Quote:
Dilinger said:
i m sure if the X51 was 400 Porsche would not hide it
Porsche is notorious for understating performance. There's only about a 5% difference between 381 and 400. I've heard reports that the C2S is actually closer to 370 HP. So 400 for the X51 doesn't seem too far fetched.
Yes, and the GT3 (which is supposed to have 1 horsepower less than X51) has dyno'd well over 400hp. I think dyno's (particularly chassis dynos) are terribly unreliable for any purpose other than to compare various cars on the same machine on the same day. They are most useful for tuning a particular car while on the dyno and maximizing its performance.
Sep 15, 2005 3:24:19 PM
- 69bossnine
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Re: X51 Dynoed close to 400 HP
I haven't dyno'd mine, but I know that when magazines test a 3,300 lb 400 h.p. Corvette, and a 3,300 lb 355 h.p. Carrera, and they both are doing 112-114 mph through the 1/4 mile traps, that SOMEBODY is understating, or overstating, their power. I believe that Porsche is understating, as 355 h.p. cars that weight 3,300 lbs + + (depending on options) simply don't run mid-twelve second quarter miles at 112+ mph. The performance stats for the 997S overachieve for the data-sheet stats. Of course I'm shooting from the hip on this, but I believe it to be valid theory, or close enough...
Re: X51 Dynoed close to 400 HP
Quote:
mumbasic said:Quote:
AeroSmith said:
I just read a post over on Rennlist that the C2S with the X51 is showing close to 400 HP on the dyno. Incredible!
I know for sure,that three test cars from Porsche AG has not less than 390 hp.
AM
Well, there you have it folks, straight from our man on the ground in the Black Forrest.
Sep 15, 2005 3:53:15 PM
- Grant
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Re: X51 Dynoed close to 400 HP
Quote:
69bossnine said:
I haven't dyno'd mine, but I know that when magazines test a 3,300 lb 400 h.p. Corvette, and a 3,300 lb 355 h.p. Carrera, and they both are doing 112-114 mph through the 1/4 mile traps, that SOMEBODY is understating, or overstating, their power. I believe that Porsche is understating, as 355 h.p. cars that weight 3,300 lbs + + (depending on options) simply don't run mid-twelve second quarter miles at 112+ mph. The performance stats for the 997S overachieve for the data-sheet stats. Of course I'm shooting from the hip on this, but I believe it to be valid theory, or close enough...
69- Couldn't part of this equation be the superior traction of the rear-engined 997 and the less lossy drivetrain (no torque tube/driveshaft) as well as less rolling resistance (narrower rubber) and smaller frontal area for less air resistance?
Sep 15, 2005 4:10:17 PM
- 69bossnine
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Re: X51 Dynoed close to 400 HP
Superior traction explains slightly quicker E.T. than Vette, but does not explain the matching terminal speed at the end of the 1/4.
Less parasitic loss? Maybe a bit, and when I say a "bit", I mean there's likely not enough difference to measure in 100ths.
Less rolling resistance? The Corvette is the one with the skinnier tires, so that makes up for any potential driveline efficiency disadvantage. Call it a draw.
I also do not believe there's any difference in drag coefficient between the two cars. Somebody with more time than I could research that...
Less parasitic loss? Maybe a bit, and when I say a "bit", I mean there's likely not enough difference to measure in 100ths.
Less rolling resistance? The Corvette is the one with the skinnier tires, so that makes up for any potential driveline efficiency disadvantage. Call it a draw.
I also do not believe there's any difference in drag coefficient between the two cars. Somebody with more time than I could research that...
Sep 15, 2005 4:21:38 PM
- Grant
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Sep 15, 2005 4:24:24 PM
- Ferdie
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Re: X51 Dynoed close to 400 HP
Reg. drag SportAuto tested both cars independently in a windtunnel. Cw for the 997S is .27 (if I recall correctly) and .29 for the Vette (its predecessor had and value of .30). Since the latter has a bigger front fascia as well the drag index is higher.
But not only drag was better for the Porsche, what seemed remarkable to me is that aerodynamic lift was significantly better as well.
http://www.track-challenge.com/main_e.asp
(Single test, Miscellaneous tag)
Regarding trap speed, the Porsche has three significant advantages:
1. traction
2. lower drag (tyres and aerodynamics)
3. better gearing
But not only drag was better for the Porsche, what seemed remarkable to me is that aerodynamic lift was significantly better as well.
http://www.track-challenge.com/main_e.asp
(Single test, Miscellaneous tag)
Regarding trap speed, the Porsche has three significant advantages:
1. traction
2. lower drag (tyres and aerodynamics)
3. better gearing
Sep 15, 2005 4:26:24 PM
- LowPolarMoment
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Re: X51 Dynoed close to 400 HP
Quote:Right on Bossman. There are a lot of factors in 1/4 E.T., such as gearing and traction, but weight and horsepower are basically the only factors in terminal speed in the 1/4 mile.
69bossnine said:
Superior traction explains slightly quicker E.T. than Vette, but does not explain the matching terminal speed at the end of the 1/4.
Sep 15, 2005 6:41:07 PM
- 69bossnine
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Re: X51 Dynoed close to 400 HP
Chevrolet claims 0.28 cd for the new C6
The tires on the C6 are 245/40-18 up front, 285/35-19 in the rear
The tires on the 997S are 235/35-19 up front, 295/35-19 on the rear
So, in the rolling resistance argument, you can basically call the tires a "draw", with neither car gaining a real advantage.
We're picking the fly-$hit out of the pepper here, which is my analogy for nit-picking.
Think of it another way. Look at the 1/4 mile performance leap from the non-turbo 996, to the 997S. Then consider that Porsche only rates the 997S as having 35 more h.p., and it's a bit chubbier to boot. Something doesn't add up....
The tires on the C6 are 245/40-18 up front, 285/35-19 in the rear
The tires on the 997S are 235/35-19 up front, 295/35-19 on the rear
So, in the rolling resistance argument, you can basically call the tires a "draw", with neither car gaining a real advantage.
We're picking the fly-$hit out of the pepper here, which is my analogy for nit-picking.
Think of it another way. Look at the 1/4 mile performance leap from the non-turbo 996, to the 997S. Then consider that Porsche only rates the 997S as having 35 more h.p., and it's a bit chubbier to boot. Something doesn't add up....
Re: X51 Dynoed close to 400 HP
Quote:
alexis said:
Aerosmith,
please do you can help me to find the message? where on rennlist?
I have ordered my 997 4s + x51 today...
Thank you !!!!
Post #24 in this thread.
Re: X51 Dynoed close to 400 HP
A place called TPS Superchargers in Jessup Maryland, who race in the Rolex series have dynoed GT3's and they claim just over 400 hp with 370 to the rear wheel. An 8 to 10 percent loss. For 200 dollars they will put your car on the dyno. Haven't done mine yet, no reason to, they were nice enough to tell me and save me the cash.
Sep 15, 2005 8:56:11 PM
- GA997S
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Re: X51 Dynoed close to 400 HP
Quote:
69bossnine said:
Superior traction explains slightly quicker E.T. than Vette, but does not explain the matching terminal speed at the end of the 1/4.
Less parasitic loss? Maybe a bit, and when I say a "bit", I mean there's likely not enough difference to measure in 100ths.
Less rolling resistance? The Corvette is the one with the skinnier tires, so that makes up for any potential driveline efficiency disadvantage. Call it a draw.
I also do not believe there's any difference in drag coefficient between the two cars. Somebody with more time than I could research that...
Terminal velocity does not occur at 1/4 mile for either car. Weight/gearing/power then traction/Cd influence E.T. & speed. (Assuming the Vette didn't sit there and spin) I'm sure rolling resistance delta is negligible.
"Less parasitic loss?" What?
Re: X51 Dynoed close to 400 HP
Quote:
GA5656 said:"Less parasitic loss?" What?
Refers to the power lost through the drivetrain (between the engine's crank and the tires) - driveshaft/torque tube is required to transmit Vettes front engine power to rear transaxle - not necessary in the 997.
Re: X51 Dynoed close to 400 HP
Quote:
Grant said:Quote:
GA5656 said:"Less parasitic loss?" What?
Refers to the power lost through the drivetrain (between the engine's crank and the tires) - driveshaft/torque tube is required to transmit Vettes front engine power to rear transaxle - not necessary in the 997.
Yeah... should have figured that one out myself.
Loss due to ring/pinion (direction change) in diff... other than that aren't the driveline components the same?
different fetzer valves? 40 weight ball-bearings? 
Sep 16, 2005 6:25:09 AM
- andreas_mue
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Re: X51 Dynoed close to 400 HP
Quote:
AeroSmith said:
Porsche is notorious for understating performance. There's only about a 5% difference between 381 and 400. I've heard reports that the C2S is actually closer to 370 HP. So 400 for the X51 doesn't seem too far fetched.
I wouldn`t be too sure about that: I complaint lack of power by my former 993 4S. The car was therefore dynoed at PAG in Stuttgart and it showed 272 PS instead of 285 PS ! PAG was so merciful to overwork the exhaust. The result was 276 PS ! I'm still so much grateful, thank you very much PAG (grrr...) !
OK, my present 996 4S is fine.
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