Road America in GT2 RS & GT3 RS
04-30-2019, 04:21 PM
#151
It was in September and from what I can remember, the weather was decent, but not too hot. I ran that same Cup car there for a few seasons and raced at RA a few times each year and could consistently run in the 2:15's-2:16's.
04-30-2019, 04:30 PM
#152
Rennlist Member
Thread Starter
Someone mentioned GT2 RS CS. Yep...now that's a car built for Road America. Times on that will be mega should one show up with the right driver, and yet somehow less magical than a car with license plates. One of those odd laws of nature.
04-30-2019, 04:35 PM
#153
Rennlist Member
04-30-2019, 04:41 PM
#154
Downforce is proportional to the square of the speed, so you can calculate the downforce at any speed using this equation -
Downforce@v2 = Downforce@v1* (v2/v1)^2
*This won't work if the car has movable aero, or at very low speeds/high angle of attacks causing aero surfaces to stall below certain speeds, but not the case here.
Downforce@v2 = Downforce@v1* (v2/v1)^2
*This won't work if the car has movable aero, or at very low speeds/high angle of attacks causing aero surfaces to stall below certain speeds, but not the case here.
04-30-2019, 04:42 PM
#155
Rennlist Member
^ Another interesting data point. What time of year? What temps, etc?
It would be very, very interesting to see what a 991.2 GT2 RS MR might pull at Road America (and other tracks) with a full factory effort including tire engineers, factory race techs, and current factory driver. The data points from the Sellers lap and Donohue laps are extremely positive.
Something to note with last week's test: It rained on Monday, washing the track, and then was windy/sunny on Tuesday. Temperatures were lovely on Wednesday...
It would be very, very interesting to see what a 991.2 GT2 RS MR might pull at Road America (and other tracks) with a full factory effort including tire engineers, factory race techs, and current factory driver. The data points from the Sellers lap and Donohue laps are extremely positive.
Something to note with last week's test: It rained on Monday, washing the track, and then was windy/sunny on Tuesday. Temperatures were lovely on Wednesday...
So appears it was a little warmer during the runoffs than last week. For another reference when Sellers did his run it was at a David Murry Track Day the week of the PCA Club Race at Road America. I believe he did it on Wednesday or Thursday of that week, August 29th/30th. Highs were 70 and lows were 52 temperature wise with sunny conditions.
04-30-2019, 04:57 PM
#156
Sellers' run was on August 29 (I was there), and looking at the pictures and videos from that day on my phone it was almost 100% cloudy. What blue sky you could see was only the occasional sliver here and there.
04-30-2019, 05:03 PM
#157
Three Wheelin'
Lots of DEs as always this year at RA. I was hoping to get people to come to the PCA one over Memorial Day holiday (made a thread about it) but didn't get any takers.
But this formula doesn't take into account certain elements like wing surface area or angle, correct? Can you provide a sample calculation?
But this formula doesn't take into account certain elements like wing surface area or angle, correct? Can you provide a sample calculation?
04-30-2019, 05:08 PM
#158
Burning Brakes
Here is a sample of Sebring Driver of Excellence "Trakcar" and how downforce plays into lap times.
He's pedaling a 997.2 GT3 RS 4.0 (the days are gone for these cars to be fully seen on track days), and his 991.1 GT3 RS. Both cars rated at 500Hp, the 997.2 GT3RS 4.0 was lighter.
At 120mph, entering Bishop's bend, the 997.2 GT3RS produces around 156# of downforce. At the same speed, the 991.1 GT3RS in max-aero produces around 321#. Fast forward to the 1:15 mark on both videos, and look at how relaxed and composed is the 991.1GT3RS taking that turn at more than 130mph.
On my low aero (compared to a 991 GT3 RS) 991 Turbo S and C7 Z06, I'm well under 120mph entering Bishop's bend, I hit the brakes hard on the Vette before committing to the turn, and I brake lightly in the 991 Turbo S. The Turbo S produces around 120# of downforce at 120mph (the new .2 GT3 only another 20# at this speed), and I can't carry anything over 120mph through Bishop's in the TurboS, and 116-117mph in the Z06. All cars on the same tires (Hoosier). The heavy Aero cars build this gap on the medium and high speed turns, and they can also brake later (which is the most shocking feature on modern F1 cars, not their power, but their braking thanks to big Aero).
...and big Aero is what makes the latest Viper ACR-E such a gem for DE Cup.
Big power is good, Big aero is better.
He's pedaling a 997.2 GT3 RS 4.0 (the days are gone for these cars to be fully seen on track days), and his 991.1 GT3 RS. Both cars rated at 500Hp, the 997.2 GT3RS 4.0 was lighter.
At 120mph, entering Bishop's bend, the 997.2 GT3RS produces around 156# of downforce. At the same speed, the 991.1 GT3RS in max-aero produces around 321#. Fast forward to the 1:15 mark on both videos, and look at how relaxed and composed is the 991.1GT3RS taking that turn at more than 130mph.
On my low aero (compared to a 991 GT3 RS) 991 Turbo S and C7 Z06, I'm well under 120mph entering Bishop's bend, I hit the brakes hard on the Vette before committing to the turn, and I brake lightly in the 991 Turbo S. The Turbo S produces around 120# of downforce at 120mph (the new .2 GT3 only another 20# at this speed), and I can't carry anything over 120mph through Bishop's in the TurboS, and 116-117mph in the Z06. All cars on the same tires (Hoosier). The heavy Aero cars build this gap on the medium and high speed turns, and they can also brake later (which is the most shocking feature on modern F1 cars, not their power, but their braking thanks to big Aero).
...and big Aero is what makes the latest Viper ACR-E such a gem for DE Cup.
Big power is good, Big aero is better.
04-30-2019, 05:16 PM
#159
Rennlist Member
Thread Starter
SCCA Runoffs are always at the end of September and the Runoffs were the week of Sept. 19th in 2013. Here is the data for the weather that week for comparison: https://www.timeanddate.com/weather/...th=9&year=2013
So appears it was a little warmer during the runoffs than last week. For another reference when Sellers did his run it was at a David Murry Track Day the week of the PCA Club Race at Road America. I believe he did it on Wednesday or Thursday of that week, August 29th/30th. Highs were 70 and lows were 52 temperature wise with sunny conditions.
So appears it was a little warmer during the runoffs than last week. For another reference when Sellers did his run it was at a David Murry Track Day the week of the PCA Club Race at Road America. I believe he did it on Wednesday or Thursday of that week, August 29th/30th. Highs were 70 and lows were 52 temperature wise with sunny conditions.
04-30-2019, 05:30 PM
#161
04-30-2019, 05:38 PM
#162
The 991 GT2 RS is a time-distance warper much like the 918, and on a distinctly different level than the 997 GT2 RS. I think this is part of what I found mesmerizing about the car. One more of its challenges. Something new, in a 911. And more fun and less clinical to me than a 918.
Two cars that are similarly quick and yet the "better" one isn't as fun. It's a question that always fascinates because I suspect I'll never fully figure it out.
04-30-2019, 05:56 PM
#163
Race Director
Chris Hall went flat full throttle through Bishops in my 2012 Carrera GTS... I have video somewhere of that....insane. I could never do it. I think he was entering around 115 exit 123ish....nuts in that car. I haven't done it either in my GT3 but i enter and breath off throttle 1/2 way and slowly back to full throttle by mid turn. Car can definitely go through full throttle.
TrakCar must be doing Bishops full throttle....he better be!!! lol
TrakCar must be doing Bishops full throttle....he better be!!! lol
Here is a sample of Sebring Driver of Excellence "Trakcar" and how downforce plays into lap times.
He's pedaling a 997.2 GT3 RS 4.0 (the days are gone for these cars to be fully seen on track days), and his 991.1 GT3 RS. Both cars rated at 500Hp, the 997.2 GT3RS 4.0 was lighter.
At 120mph, entering Bishop's bend, the 997.2 GT3RS produces around 156# of downforce. At the same speed, the 991.1 GT3RS in max-aero produces around 321#. Fast forward to the 1:15 mark on both videos, and look at how relaxed and composed is the 991.1GT3RS taking that turn at more than 130mph.
On my low aero (compared to a 991 GT3 RS) 991 Turbo S and C7 Z06, I'm well under 120mph entering Bishop's bend, I hit the brakes hard on the Vette before committing to the turn, and I brake lightly in the 991 Turbo S. The Turbo S produces around 120# of downforce at 120mph (the new .2 GT3 only another 20# at this speed), and I can't carry anything over 120mph through Bishop's in the TurboS, and 116-117mph in the Z06. All cars on the same tires (Hoosier). The heavy Aero cars build this gap on the medium and high speed turns, and they can also brake later (which is the most shocking feature on modern F1 cars, not their power, but their braking thanks to big Aero).
...and big Aero is what makes the latest Viper ACR-E such a gem for DE Cup.
Big power is good, Big aero is better.
https://youtu.be/XWzam4dPUDo
https://youtu.be/HiEA-9ugrWk
He's pedaling a 997.2 GT3 RS 4.0 (the days are gone for these cars to be fully seen on track days), and his 991.1 GT3 RS. Both cars rated at 500Hp, the 997.2 GT3RS 4.0 was lighter.
At 120mph, entering Bishop's bend, the 997.2 GT3RS produces around 156# of downforce. At the same speed, the 991.1 GT3RS in max-aero produces around 321#. Fast forward to the 1:15 mark on both videos, and look at how relaxed and composed is the 991.1GT3RS taking that turn at more than 130mph.
On my low aero (compared to a 991 GT3 RS) 991 Turbo S and C7 Z06, I'm well under 120mph entering Bishop's bend, I hit the brakes hard on the Vette before committing to the turn, and I brake lightly in the 991 Turbo S. The Turbo S produces around 120# of downforce at 120mph (the new .2 GT3 only another 20# at this speed), and I can't carry anything over 120mph through Bishop's in the TurboS, and 116-117mph in the Z06. All cars on the same tires (Hoosier). The heavy Aero cars build this gap on the medium and high speed turns, and they can also brake later (which is the most shocking feature on modern F1 cars, not their power, but their braking thanks to big Aero).
...and big Aero is what makes the latest Viper ACR-E such a gem for DE Cup.
Big power is good, Big aero is better.
https://youtu.be/XWzam4dPUDo
https://youtu.be/HiEA-9ugrWk
04-30-2019, 07:56 PM
#164
Rennlist Member
Thread Starter
Bingo, that's what I hoped to hear. But it begs the ever elusive question: why is that? Chassis adjust-ability and rear wheel drive? An actual torque curve and the way the power rolls in? The chassis actually moving around due to a higher CG or polar moment?
Two cars that are similarly quick and yet the "better" one isn't as fun. It's a question that always fascinates because I suspect I'll never fully figure it out.
Two cars that are similarly quick and yet the "better" one isn't as fun. It's a question that always fascinates because I suspect I'll never fully figure it out.
Not sure, entirely, and don't get me wrong: I had a lot of fun with the 918 on track. Leipzig was mind-bending but full of fear with the stakes (it was raining, and the brake pedal was noted as "funny feeling") and Valencia in the dry was truly mind-warping (a whole new mental challenge due to the power and traction, which effectively eliminated straights by comparison to anything I'd driven to that point, not to mention the insane stability of the thing at all speeds). Then came Laguna, which provided a measuring stick I knew for the 918, and I really didn't want to get out. The turn-in was eerily genius on the way into T2, and I found myself wishing for more laps. A lot more.
But…
But, I think the GT2 RS was more fun. "Challenge" is the word that comes to mind. In the GT2 RS, you feel like you are driving, even if the car is doing things for you. In the 918, you know you're in a spaceship that's interpreting everything. It might be as stupid as this: One has one drivetrain, with no interpretation or "power share" shifts at work. And then there's the chassis. Even as a "mid-engined guy" (who came up on 914s and loves Boxsters/Caymans, CGTs, etc), there's something magical about the light, free-wheeling nose of a 911...along with all that rear end traction under braking and out of a bend. It's the challenge-rhythm of the 911, and the GT2 RS has it...and goes faster than any 911 with a plate ever has. Sure, there are tuner cars, but I suspect even the best I've driven would be obliterated by the GT2 RS in a track environment…particularly as the laps accumulated. Just add fuel and distilled water.
Anyway, there's a first attempt at an answer. Feel free to poke holes in it. ;-)
