997 GT3 vs. ?
#46
Originally Posted by tdf360
From talking with several drivers who have done back-to-back tests at the track, it appears R tires are approximately 3 to 4 sec/lap faster than the best street tires on a 90 sec lap, and full race slicks are about 2 to 3 sec faster than the R's. Tests were done on the same day, with the only variable being the tires. I think there was a write-up in one of the smaller enthusiast magazines a while back about it - maybe Grassroots Motorsports.
Gary
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Originally Posted by tdf360
From talking with several drivers who have done back-to-back tests at the track, it appears R tires are approximately 3 to 4 sec/lap faster than the best street tires on a 90 sec lap, and full race slicks are about 2 to 3 sec faster than the R's. Tests were done on the same day, with the only variable being the tires. I think there was a write-up in one of the smaller enthusiast magazines a while back about it - maybe Grassroots Motorsports.
Gary
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#48
Originally Posted by MetalSolid
I had the Pirelli P-Zero Corsa System - same tire as Stradale - on my GT3, while they have more grip than most regular street performance tires, I wouldn't call them R-compound. The difference between a true R-comp tire, the MPSC that I have now and the Corsa System is night and day.
#49
I take delivery of a new 430 in May/June. Our local Porsche club should have a PDE at Barber Motorsports Park shortly afterwards. I intend to take my GT3 and the new 430 to the track for testing. You know what would be really cool; I wonder if any of the magazines would be interested in coming here to do a comparison of the GT3 and the 430, using my cars. I don't know why they wouldn't; BMSP is a premier race track. Both cars will be availble at the track. Hurley Haywood could be the driver (it could be scheduled for a day after he teaches class at the track for Porsche Driving Experience). Anyone know who I could call?
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The 300lbs penalty on the F430 is offset by the amount of torque available on the new engine. That car will be faster than the 360CS at any racetrack. It will be faster than the GT3 as well. It just need the right tires.
The problem is that there are not r-comps available on 19", but they will come. Viper, Z06, 997S, and plenty of other high performance cars are coming with 19".
On my Boxster S I was turning Pocono North at 65 secs average on GForce KD. These are one of the fastest street tires (no r-comps) out there. Same car on MPSC was running 63 secs.
On a 45 seconds lap autocross, the Hoosier A3S04 is 0.7 secs faster than the Kumho V700. The V700 is 0.4 faster than the MPSC. The MPSC is almost one second faster than the MPS2.
At Pocono Full course with the two infields, the R3S04 Hoosier is almost 2 seconds faster than the MPSC.
There are plenty of threads on the Racing forum that compare tires.
I'm planning to attend the 2005 Porsche Parade at Hershey, PA. The new class S13 is for the GT3, GT2 and Carrera GT. You will see Boxsters and 911 on r-comps turning faster laps than the CGT on street tires at that event.
The problem is that there are not r-comps available on 19", but they will come. Viper, Z06, 997S, and plenty of other high performance cars are coming with 19".
On my Boxster S I was turning Pocono North at 65 secs average on GForce KD. These are one of the fastest street tires (no r-comps) out there. Same car on MPSC was running 63 secs.
On a 45 seconds lap autocross, the Hoosier A3S04 is 0.7 secs faster than the Kumho V700. The V700 is 0.4 faster than the MPSC. The MPSC is almost one second faster than the MPS2.
At Pocono Full course with the two infields, the R3S04 Hoosier is almost 2 seconds faster than the MPSC.
There are plenty of threads on the Racing forum that compare tires.
I'm planning to attend the 2005 Porsche Parade at Hershey, PA. The new class S13 is for the GT3, GT2 and Carrera GT. You will see Boxsters and 911 on r-comps turning faster laps than the CGT on street tires at that event.
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Originally Posted by ben in lj
so the 430 with R compound tires is faster than the enzo (and CGT which has pretty near R equivalent on the outter 1/3 of the tire - where you'd need it)? mark me down as skeptical.
Gary
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Originally Posted by MetalSolid
I had the Pirelli P-Zero Corsa System - same tire as Stradale - on my GT3, while they have more grip than most regular street performance tires, I wouldn't call them R-compound. The difference between a true R-comp tire, the MPSC that I have now and the Corsa System is night and day.
Gary
#53
Originally Posted by Greg Fishman
Did you ever think it might not have to do with drivetrain loss but gearing differences? Show me proof that rear engine cars have less drivetrain loss, I don't believe it.
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Long, heavy driveshaft has nothing to do with drivetrain loss. It affects acceleration (inertia) but the weight and size of components is not a factor in loss. Drivetrain loss is a function of friction. The transmission gears, bearings, etc add to the loss. The U-Joints in a driveshaft create friction. Gears, bearings, etc in the diff do the same. Wheel bearings too. With independent suspension, the CV joints add drag as well.
So all told, the FWD or Rear engine package has a very slight advantage as it has eliminated 2 U-Joints for the driveshaft and any additional bearings. It is no where near the 5% loss you have claimed.
So all told, the FWD or Rear engine package has a very slight advantage as it has eliminated 2 U-Joints for the driveshaft and any additional bearings. It is no where near the 5% loss you have claimed.
#56
Originally Posted by Greg Fishman
So all told, the FWD or Rear engine package has a very slight advantage as it has eliminated 2 U-Joints for the driveshaft and any additional bearings. It is no where near the 5% loss you have claimed.
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Fishman, your examples don't seem to help your argument.
To simply illustrate: the 2001 Z06 was rated at 385 bhp, and put down 342 bhp, an 11% "loss." The 2003 Z06, rated at 405 bhp put down 335 bhp, a 17% "loss."
If there is such a variance between two cars on the same dyno, how can you honestly compare a different car on an entirely different dyno?
By the way, Evo MS has another dyno plot on their site of a 320 bhp 996 putting down 283 bhp, an 11.5% loss.
The point is that comparing dyno runs is pretty much useless, unless you are comparing the averages of several runs on each car, on the same day, on the same dyno. Even then, it is virtually impossible to determine the actual drivetrain loss without putting the engine on an engine dyno, then measuring the power at the wheels.
People much more technically minded than I have debated this subject to no end, and about the only thing everyone can agree on is that parasitic losses in automatics account for 15-20%, while manual gearboxes are in the range of 10-15%.
As Greg said, the driveshaft affects inertia and thus acceleration, there is no way the two additional U joints can account for 1/4 to 1/3 of the parasitic losses.
To simply illustrate: the 2001 Z06 was rated at 385 bhp, and put down 342 bhp, an 11% "loss." The 2003 Z06, rated at 405 bhp put down 335 bhp, a 17% "loss."
If there is such a variance between two cars on the same dyno, how can you honestly compare a different car on an entirely different dyno?
By the way, Evo MS has another dyno plot on their site of a 320 bhp 996 putting down 283 bhp, an 11.5% loss.
The point is that comparing dyno runs is pretty much useless, unless you are comparing the averages of several runs on each car, on the same day, on the same dyno. Even then, it is virtually impossible to determine the actual drivetrain loss without putting the engine on an engine dyno, then measuring the power at the wheels.
People much more technically minded than I have debated this subject to no end, and about the only thing everyone can agree on is that parasitic losses in automatics account for 15-20%, while manual gearboxes are in the range of 10-15%.
As Greg said, the driveshaft affects inertia and thus acceleration, there is no way the two additional U joints can account for 1/4 to 1/3 of the parasitic losses.
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Do you think it is possible (likely?) that the cars in your example may not make the hp they claim? Were both these tests done on the same dyno?
Only way I can imagine to compare driveline loss between cars would be to engine dyno both cars and then compare it to a chassis dyno (same dynos for both) and then do the caluculations. Without it there are too many variables to give a meaningful comparison and and any results are purely speculation.
Only way I can imagine to compare driveline loss between cars would be to engine dyno both cars and then compare it to a chassis dyno (same dynos for both) and then do the caluculations. Without it there are too many variables to give a meaningful comparison and and any results are purely speculation.
Last edited by Greg Fishman; 01-24-2005 at 09:42 AM.
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Originally Posted by Fishman
The dynos appear to show otherwise. They are 5% or more. Here is a chart which shows a 320 bhp 911 with 295 hp at the wheels which is approx. a 7% loss. (This dyno is taken from the Evo website evoms.com, a highly respected tuner of Porsches that have an interest in downplaying the factory hp reading if anything since their job is to improve it). The Corvette Dynos are from a website which has the stock dyno results from a series of Z06 Corvettes: http://www.dynoperformance.com/ The drivetrain losses for the Corvettes were more like 15%. There is a big difference in drivetrain loss between the two cars.
No offense dude, but this is wacky. Can you get any more unscientific? There is no way to scientifically prove what you are trying to say. There is no dyno that is both a motor dyno and a wheel dyno. WIthout that, your assumptions are nothing more than unscientific guesses.
In order to make it work, you would have to take a car, run it on the wheel dyno, remove the motor, and run just the motor on the same wheel dyno. Oh, and the conditions would have to be the exact same too.
And BTW - a wheel dyno has driveline loss too from the big wheel spinning. Sure, they account for that in their software, but how do we know that is accurate?
Are you starting to understand?
Oh, and its pretty funny that you took stock HP claims from a manufacturer for your baseline numbers. Boy, those are never inflated. Can anyone say Mustang Cobra?
#60
Originally Posted by e6tme
Fishman, your examples don't seem to help your argument.
Originally Posted by e6tme
If there is such a variance between two cars on the same dyno, how can you honestly compare a different car on an entirely different dyno?
Originally Posted by e6tme
By the way, Evo MS has another dyno plot on their site of a 320 bhp 996 putting down 283 bhp, an 11.5% loss.
Originally Posted by Greg Fishman
Do you think it is possible (likely?) that the cars in your example may not make the hp they claim? Were both these tests done on the same dyno?
Only way I can imagine to compare driveline loss between cars would be to engine dyno both cars and then compare it to a chassis dyno (same dynos for both) and then do the caluculations. Without it there are too many variables to give a meaningful comparison and and any results are purely speculation.
Only way I can imagine to compare driveline loss between cars would be to engine dyno both cars and then compare it to a chassis dyno (same dynos for both) and then do the caluculations. Without it there are too many variables to give a meaningful comparison and and any results are purely speculation.
I already got Greg to admit that I was right and there was less drivetrain loss
Originally Posted by Greg Fishman
....So all told, the FWD or Rear engine package has a very slight advantage as it has eliminated 2 U-Joints for the driveshaft and any additional bearings. It is no where near the 5% loss you have claimed.
"On the other hand, a Mustang dyno will correct with a 21% loss figure. Actual over-the-road loss is probably in the 17-20% range. A lot of front-wheel-drive cars do not have any 90-degree gear changes. All gearing is straight transfer. Losses are less; I'm going to guess at 11 to 12%."
http://www.europeancarweb.com/tech/t...02d/index.html.
Here's another article from a different magazine which, although the numbers are different, makes my point:
"A lot of people also don't realise that a FWD has significant benefits over a rear wheel set-up. For a start, a front wheel drive delivers a greater portion of engine power to the wheels. It's widely generalised that there's a 30% power loss through a RWD's drivetrain, while a FWD loses only 20%. Needless to say, 10% is a big difference. That's the kind of power gain you get when you go out and install a high flow exhaust. And, with reduced drivetrain loss, you're also talking improved fuel economy as well."
http://www.autospeed.com/cms/A_697/article.html
Ok, two articles from reputable magazines. I forget, what evidence did you guys have?
My point is proved correct in real world tests as well considering that 911s with less bhp are faster than Corvettes.
Road and Track found that despite having 55 hp less, the new Carerra S was faster than the new Corvette. Click here:
http://roadandtrack.com/article.asp?...&page_number=1
According to Car & Driver which tested both cars, the newest Corvette with 80 hp more than the Carrera 2 only beats it by 0.2 of a second in the quarter mile. Click here:
http://caranddriver.com/article.asp?...&page_number=5
I know that there is more to this than drivetrain losses as 911s also have much better traction than a Corvette, but my original point
Originally Posted by Z06
What do you think Porsche can or will do to step up to the new high HP competion?
Originally Posted by Fishman
Yeah, but it is not as big of a deal as one might expect.
Right or wrong?