Corvette Racing (GT1 and GT2) Downforce
12-29-2011, 12:26 PM
#1
Melting Slicks
Thread Starter
Corvette Racing (GT1 and GT2) Downforce
With the recent discussion around downforce I would like to know the max. downforce (at 150) that the GT1 and GT2 cars are capable of within the rules they were/are bound by. I know - this is TOP SECRET data, and the only thing I could find comparing the two cars were a few statments about the GT2 making 25% less downforce than the GT1, but it was not clear from the context if that was for the rear wing only (since it is narrower on the GT2 car) or if that was for the total downforce. I also found a few statements saying that while total downforce is less for the GT2 car, the lift/drag ratio is better.
Last edited by Everett Ogilvie; 12-30-2011 at 12:59 PM.
12-29-2011, 01:12 PM
#2
Former Vendor
Im not sure youll find that data.
The splitter is smaller, the rear wing is smaller, as is not as much rear diffuser. There are no fender vents. I would also say that its not a fair comparison because the bodies are not the same, and the development over the last 2 years is an apples to oranges comparison.
I see the aero thread, but there is way too much mis-information.
The splitter is smaller, the rear wing is smaller, as is not as much rear diffuser. There are no fender vents. I would also say that its not a fair comparison because the bodies are not the same, and the development over the last 2 years is an apples to oranges comparison.
I see the aero thread, but there is way too much mis-information.
12-29-2011, 05:24 PM
#4
Le Mans Master
Everett, you are not going to find out! Downforce is changed from track to track on race cars for maximum performance. I have done a lot of wind tunnel testing. Wind tunnel testing tells you a lot but it does not always translate directly to the track. You take various readings at various set ups at the wind tunnel to help you make positive track adjustments.
To give you and idea, here are some of the readings you get with each wind tunnel test:
Crm, Qpsf,Q(InH20), Drag HP, Drag lb, Lift lb, front lift, rear lift, Lift/Drag, Side force lb, Rad Top Vc, Rad Top Ctr, Rad Btm, Tube 1, Tube 2, Tube 3, Nine (9) Relative Coefficient Deltas, Seven (7) Relative Force Deltas, and this is done over and over at 50 MPH, 100 MPH, 150 MPH, etc. And then you have to know what all the above crap means and how it relates at different tracks and speeds.
One of the interesting things is when you change say a wing or splitter you change side force because no matter how hard you try car bodies are never ever exactly square and straight. Then the air going over the car is never the same because the car is turning, the wind changes, there are or are not cars cars around your car, etc. Also, wheel weights are very important so the car is never square on all four corners with the track resulting in different conditions on all four corners and surfaces.
I have been involved in races where I have had contact with other cars and the damage actually made my car better and faster but most of the time any contact slows you down a bit or adds down force on one particular tire so it works more and goes away faster.
How about the fact that the stock Z06 as I tested it has over 250# of lift at 100 MPH!
Whew, I am tired of typing. Have a GREAT New Year my friend. I hope to see you in 2012.
Jim
To give you and idea, here are some of the readings you get with each wind tunnel test:
Crm, Qpsf,Q(InH20), Drag HP, Drag lb, Lift lb, front lift, rear lift, Lift/Drag, Side force lb, Rad Top Vc, Rad Top Ctr, Rad Btm, Tube 1, Tube 2, Tube 3, Nine (9) Relative Coefficient Deltas, Seven (7) Relative Force Deltas, and this is done over and over at 50 MPH, 100 MPH, 150 MPH, etc. And then you have to know what all the above crap means and how it relates at different tracks and speeds.
One of the interesting things is when you change say a wing or splitter you change side force because no matter how hard you try car bodies are never ever exactly square and straight. Then the air going over the car is never the same because the car is turning, the wind changes, there are or are not cars cars around your car, etc. Also, wheel weights are very important so the car is never square on all four corners with the track resulting in different conditions on all four corners and surfaces.
I have been involved in races where I have had contact with other cars and the damage actually made my car better and faster but most of the time any contact slows you down a bit or adds down force on one particular tire so it works more and goes away faster.
How about the fact that the stock Z06 as I tested it has over 250# of lift at 100 MPH!
Whew, I am tired of typing. Have a GREAT New Year my friend. I hope to see you in 2012.
Jim
Last edited by Painrace; 12-29-2011 at 07:20 PM.
12-29-2011, 05:57 PM
#5
Race Director
Member Since: Sep 2004
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St. Jude Donor '07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18
Everett, you are not going to find out! Downforce is changed from track to track on race cars for maximum performance. I have done a lot of wind tunnel testing. Wind tunnel testing tells you a lot but it does not always translate directly to the track. You take various readings at various set ups at the wind tunnel to help you make positive track adjustments.
To give you and idea, here are some of the readings you get with each wind tunnel test:
Crm, Qpsf,Q(InH20), Drag HP, Drag lb, Lift lb, front lift, rear lift, Lift/Drag, Side force lb, Rad Top Vc, Rad Top Ctr, Rad Btm, Tube 1, Tube 2, Tube 3, Nine (9) Relative Coefficient Deltas, Seven (7) Relative Force Deltas, and this is done over and ovet at 50 MPH, 100 MPH, 150 MPH, etc. And then you have to know what all the above crap means and how it relates at different tracks and speeds.
One of the interesting things is when you change say a wing or splitter you change side force because no matter how hard you try car bodies are never ever exactly square and straight. Then the air going over the car is never the same because the car is turning, the wind changes, there are or are not cars cars around your car, etc. Also, wheel weights are very important so the car is never square on all four corners with the track resulting in different conditions on all four corners and surfaces.
I have been involved in races where I have had contact with other cars and the damage actually made my car better and faster but most of the time any contact slows you down a bit or adds down force on one particular tire so it works more and goes away faster.
How about the fact that the stock Z06 as I tested it has over 250# of lift at 100 MPH!
Whew, I am tired of typing. Have a GREAT New Year my friend. I hope to see you in 2012.
Jim
To give you and idea, here are some of the readings you get with each wind tunnel test:
Crm, Qpsf,Q(InH20), Drag HP, Drag lb, Lift lb, front lift, rear lift, Lift/Drag, Side force lb, Rad Top Vc, Rad Top Ctr, Rad Btm, Tube 1, Tube 2, Tube 3, Nine (9) Relative Coefficient Deltas, Seven (7) Relative Force Deltas, and this is done over and ovet at 50 MPH, 100 MPH, 150 MPH, etc. And then you have to know what all the above crap means and how it relates at different tracks and speeds.
One of the interesting things is when you change say a wing or splitter you change side force because no matter how hard you try car bodies are never ever exactly square and straight. Then the air going over the car is never the same because the car is turning, the wind changes, there are or are not cars cars around your car, etc. Also, wheel weights are very important so the car is never square on all four corners with the track resulting in different conditions on all four corners and surfaces.
I have been involved in races where I have had contact with other cars and the damage actually made my car better and faster but most of the time any contact slows you down a bit or adds down force on one particular tire so it works more and goes away faster.
How about the fact that the stock Z06 as I tested it has over 250# of lift at 100 MPH!
Whew, I am tired of typing. Have a GREAT New Year my friend. I hope to see you in 2012.
Jim
12-29-2011, 07:17 PM
#7
Le Mans Master
12-29-2011, 07:19 PM
#8
Le Mans Master
12-29-2011, 10:24 PM
#9
Melting Slicks
Thread Starter
I am waiting. 
All kidding aside, the reason for my question was simply to get a crude idea of a downforce "ranking" if you will of some current race classes relative to each other. For example as a first guess I would rank them in this order;
Grand Am GT
ALMS GT2
(Prior) ALMS GT1
Grand Am Daytona Prototype
ALMS P2
ALMS P1
I think the only debatable pair in the list above would be the GT1 car and the DP. I say the DP is capable of making more downforce than the GT1 car, but I believe they would be pretty close to each other. Note, I am referring to the potential total maximum downforce that each car is capable of.
Happy New Year to you Jim, and indeed I hope we get to see each other this coming year at a track event.
All kidding aside, the reason for my question was simply to get a crude idea of a downforce "ranking" if you will of some current race classes relative to each other. For example as a first guess I would rank them in this order;
Grand Am GT
ALMS GT2
(Prior) ALMS GT1
Grand Am Daytona Prototype
ALMS P2
ALMS P1
I think the only debatable pair in the list above would be the GT1 car and the DP. I say the DP is capable of making more downforce than the GT1 car, but I believe they would be pretty close to each other. Note, I am referring to the potential total maximum downforce that each car is capable of.
Happy New Year to you Jim, and indeed I hope we get to see each other this coming year at a track event.
12-30-2011, 10:38 AM
#10
Le Mans Master
I am waiting.
All kidding aside, the reason for my question was simply to get a crude idea of a downforce "ranking" if you will of some current race classes relative to each other. For example as a first guess I would rank them in this order;
Grand Am GT
ALMS GT2
(Prior) ALMS GT1
Grand Am Daytona Prototype
ALMS P2
ALMS P1
I think the only debatable pair in the list above would be the GT1 car and the DP. I say the DP is capable of making more downforce than the GT1 car, but I believe they would be pretty close to each other. Note, I am referring to the potential total maximum downforce that each car is capable of.
Happy New Year to you Jim, and indeed I hope we get to see each other this coming year at a track event.
All kidding aside, the reason for my question was simply to get a crude idea of a downforce "ranking" if you will of some current race classes relative to each other. For example as a first guess I would rank them in this order;
Grand Am GT
ALMS GT2
(Prior) ALMS GT1
Grand Am Daytona Prototype
ALMS P2
ALMS P1
I think the only debatable pair in the list above would be the GT1 car and the DP. I say the DP is capable of making more downforce than the GT1 car, but I believe they would be pretty close to each other. Note, I am referring to the potential total maximum downforce that each car is capable of.
Happy New Year to you Jim, and indeed I hope we get to see each other this coming year at a track event.
If you are just looking for MAXIMUM down force I would say you could get to the 1,500#+ range with a GT-1 car. The splitter would have to be way out in the front and the spoiler has to take a big bite and there needs to be a full flat undertray with some good side skirts. The car will go around 80 MPH corners fast as hell but will get killed on all straight aways because of the drag. It takes about 175 HP for a stock Z06 to overcome the 450+# of drag at 150 MPH. A car with 1,500# of down force would need tons of HP to get to 150 MPH and it would take a while.
A DP car can develop a lot more down force because of the side pods but again, too much is not a good thing at a place like Daytona. You have to hit the right mix of speed (as little drag as possible) and cornering ( as much down force as posible) to make all drivers happy. The key here is ALL DRIVERS HAPPY!. Drivers are a weird bunch as you know.
Your car at Autobahn I would suggest a ton of down force with the ability to take some out and try it.
HAPPY NEW YEAR and remember, the above is about 100 years old!
Jim
12-30-2011, 11:17 AM
#11
Melting Slicks
Thread Starter
Hey Jim, thank you for the reply - I think you are very close with your estimate of the max. possible downforce for the GT1 car, and it was pretty much dead on with my estimate as well.
Last season at Road America my car was definitely top end limited on the straights (and that's with no shortage of HP) - by that I mean it was still accelerating but at a much slower rate after "hitting the wall at 150-155" (not the actual wall thank goodness!). When I get back to RA I will probably dial out some downforce, but as you suggest I think it would be nice to have at Autobahn (also because it won't hurt the top end as much there).
With all the aero discussion lately and especially the posts about aero vs. top speed at Road America, it reminds me of a video I found some time ago regarding qualifying a ALMS P1 car at Road America. This particular team found that their fastest lap time and highest top speed were actually with near-maximum downforce dialed in; with enough downforce they were able to turn the Kettle Bottoms (the exit of the Carousel, through the Kink, and all the way to Canada Corner) into a "straight" and they actually made their highest top speed here rather than either true straightaway. Obviously that kind of downforce and grip would only be possible on the P1 type of car - I believe they were going through the Kink at 150 or 160, and near 190 just before Canada Corner!
Edit - I can't find the video mentioned above but found several interviews with David Brabam and Simon Pagenaud for thier P1 car and they were going with the minimum downforce that would let them go through the Kink flat out..... this is a very interesting interview;
Last season at Road America my car was definitely top end limited on the straights (and that's with no shortage of HP) - by that I mean it was still accelerating but at a much slower rate after "hitting the wall at 150-155" (not the actual wall thank goodness!). When I get back to RA I will probably dial out some downforce, but as you suggest I think it would be nice to have at Autobahn (also because it won't hurt the top end as much there).
With all the aero discussion lately and especially the posts about aero vs. top speed at Road America, it reminds me of a video I found some time ago regarding qualifying a ALMS P1 car at Road America. This particular team found that their fastest lap time and highest top speed were actually with near-maximum downforce dialed in; with enough downforce they were able to turn the Kettle Bottoms (the exit of the Carousel, through the Kink, and all the way to Canada Corner) into a "straight" and they actually made their highest top speed here rather than either true straightaway. Obviously that kind of downforce and grip would only be possible on the P1 type of car - I believe they were going through the Kink at 150 or 160, and near 190 just before Canada Corner!
Edit - I can't find the video mentioned above but found several interviews with David Brabam and Simon Pagenaud for thier P1 car and they were going with the minimum downforce that would let them go through the Kink flat out..... this is a very interesting interview;
Last edited by Everett Ogilvie; 12-30-2011 at 12:32 PM.
12-30-2011, 01:34 PM
#13
Melting Slicks
Thread Starter
12-30-2011, 02:38 PM
#16
Melting Slicks
One clue to GT1, remember the Saleen had enough DF at what was it, 160mph to run upside down? That could give you a baseline as race versions ramped up from there...
12-30-2011, 03:11 PM
#18
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There is always the wind tunnel guys. Come on down to North Carolina we have at least THREE race car wind tunnels
http://www.aerodynwindtunnel.com/index.html
http://www.a2wt.com/
Penske's is Private
http://www.aerodynwindtunnel.com/index.html
http://www.a2wt.com/
Penske's is Private