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I can't find a thread on this that still seems to be active, so here goes. I posted my fastest lap at Road Atlanta in my new (2k miles) GT 4. Factory Aero settings. My top speed on the lap was 140, average speed 90.1. Like many others, though, I was hell bent on adjusting the Aero, and did so per the manual. This weekend, I posted a lap within a 10th of a second of the first one, but my top speed was only 131.6 while my average speed was 97.7. In fact, pedal to the metal numerous times the best I could get was 134 on that long back stretch. I also noticed high-speed passing seemed a bit more difficult. Does that seem consistent with your experiences with the supposed drag effect of the Aero? I had already vowed to be more aggressive in the corners, but I assume the Aero adjustment helped me some in that respect. Interestingly, the distance traveled in the more recent lap was .2 miles longer, suggesting that I was faster through the corners, but not as sharp. I realize there are other possible factors at play. I still don't have a clue about tire pressures on my !!$$!!&! Dunlop Sport Maxx Racers, and was fiddling with that all weekend. If I am missing something, please don't hesitate to ridicule me in pointing it out. Thanks for any and all feedback.
 

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What were the ambient temps for each day? In my experience with several cars and several different tracks vmax correlates strongly with temp. (cooler temps = more hp). I did the aero adjustment last time out at COTA but to be honest I couldn't feel any difference and too many other factors to isolate the aero effect if any. I ran 20in RE-71R for the first time. Great tire btw. Previously ran MPSC2. I did get a new best lap, but mainly due to having a rabbit and almost no traffic in the last session.
 
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Well I'm no expert but simple minded explanation might be that your adjustment to the Aero increased you downforce, which helped corner speeds, but also increased your drag which lowered you top speed. As I said "simple minded explanation" but it makes sense to me. Good luck!
 

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Discussion Starter #4
Well I'm no expert but simple minded explanation might be that your adjustment to the Aero increased you downforce, which helped corner speeds, but also increased your drag which lowered you top speed. As I said "simple minded explanation" but it makes sense to me. Good luck!
Well, it must be "simple-minded" for sure, because that's my best explanation as well. Thanks!


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Discussion Starter #5
What were the ambient temps for each day? In my experience with several cars and several different tracks vmax correlates strongly with temp. (cooler temps = more hp). I did the aero adjustment last time out at COTA but to be honest I couldn't feel any difference and too many other factors to isolate the aero effect if any. I ran 20in RE-71R for the first time. Great tire btw. Previously ran MPSC2. I did get a new best lap, but mainly due to having a rabbit and almost no traffic in the last session.
This is quite possibly a factor, and my pilot friend suggested the same. The ambient temp was about 25 degrees higher this weekend. The thing is though, I have run much higher speeds than this weekend in a CGTS in much higher temps on the same track. I have to think drag from the Aero is also in play. I keep hearing great things about the RE-71R's. I am thinking about a set of those before my next track outing. Thanks for weighing in.


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I can't find a thread on this that still seems to be active, so here goes. I posted my fastest lap at Road Atlanta in my new (2k miles) GT 4. Factory Aero settings. My top speed on the lap was 140, average speed 90.1. Like many others, though, I was hell bent on adjusting the Aero, and did so per the manual. This weekend, I posted a lap within a 10th of a second of the first one, but my top speed was only 131.6 while my average speed was 97.7. In fact, pedal to the metal numerous times the best I could get was 134 on that long back stretch. I also noticed high-speed passing seemed a bit more difficult. Does that seem consistent with your experiences with the supposed drag effect of the Aero? I had already vowed to be more aggressive in the corners, but I assume the Aero adjustment helped me some in that respect. Interestingly, the distance traveled in the more recent lap was .2 miles longer, suggesting that I was faster through the corners, but not as sharp. I realize there are other possible factors at play. I still don't have a clue about tire pressures on my !!$$!!&! Dunlop Sport Maxx Racers, and was fiddling with that all weekend. If I am missing something, please don't hesitate to ridicule me in pointing it out. Thanks for any and all feedback.
What was the factory angle of attack and the post adjusted angle of attack? There is a $20 digital angle level tool on Amazon if unsure.

I'm guessing 7 degrees stock and 12.5 adjusted? In theory that would change downforce from like 200 pounds to 300 pounds at 135 MPH.

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I have run max aero since I started tracking my GT4. I don't have the exact angle but believe it added about 4 degrees. There is no way that this can change your top speed and average speed by the amounts stated. When I went from the factory spoiler on my 987S to a Getty Wing my top speed dropped about 3 mph and lap times improved by about .5 seconds. Top speed is highly dependent on when you brake at the end of the straight.
 

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Discussion Starter #8
I have run max aero since I started tracking my GT4. I don't have the exact angle but believe it added about 4 degrees. There is no way that this can change your top speed and average speed by the amounts stated. When I went from the factory spoiler on my 987S to a Getty Wing my top speed dropped about 3 mph and lap times improved by about .5 seconds. Top speed is highly dependent on when you brake at the end of the straight.
This was my gut feeling as well, although the adjustment clearly facilitated aggressive braking and I definitely took advantage of that. As I said, the tires could have been a factor--or maybe it was just the driver. Thanks.


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Discussion Starter #9
What was the factory angle of attack and the post adjusted angle of attack? There is a $20 digital angle level tool on Amazon if unsure.

I'm guessing 7 degrees stock and 12.5 adjusted? In theory that would change downforce from like 200 pounds to 300 pounds at 135 MPH.

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Thanks for the response. I keep hearing 2-3 degrees change only, but you could be correct.


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Thanks for the response. I keep hearing 2-3 degrees change only, but you could be correct.


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I was close. The media quoted number was 220 pounds of downforce. I'd guess that's at 250 km/h, or 155 MPH. Rear wings don't start working until 90 MPH, and don't really produce meaningful results until 130 MPH.

At my tracks out in California, the front straight speeds don't really get over 130 MPH (140 in a GT3).
 
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Discussion Starter #11
I was close. The media quoted number was 220 pounds of downforce. I'd guess that's at 250 km/h, or 155 MPH. Rear wings don't start working until 90 MPH, and don't really produce meaningful results until 130 MPH.

At my tracks out in California, the front straight speeds don't really get over 130 MPH (140 in a GT3).
I appreciate your checking that out and the additional info as well. I simply haven't measured the angle. Don't think the max angle is quite as steep as 12 degrees


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I appreciate your checking that out and the additional info as well. I simply haven't measured the angle. Don't think the max angle is quite as steep as 12 degrees


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Someone smarter than me could figure out the stall angle - I'd hazard a guess at 15 degrees. The way Porsche sets it up is for low drag, for fuel economy. I like the kits that raise the height on the wing by 4". Those would provide cleaner air to the foil.


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Discussion Starter #13
Someone smarter than me could figure out the stall angle - I'd hazard a guess at 15 degrees. The way Porsche sets it up is for low drag, for fuel economy. I like the kits that raise the height on the wing by 4". Those would provide cleaner air to the foil.


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Well, I know I need to learn more about this and I will. Thanks for your help. If there is reason to think that the settings did not hold down my top speed that much, there is reason to think they helped me through the corners. Car felt planted as heck in the faster ones.


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Well, I know I need to learn more about this and I will. Thanks for your help. If there is reason to think that the settings did not hold down my top speed that much, there is reason to think they helped me through the corners. Car felt planted as heck in the faster ones.


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I did a bunch of the arithmetic to get my 59% nose heavy track Audi to behave more like a balanced car at speed. It took 4 seconds off at Thunderhill, more than any other mod I'd done including horsepower. Wouldn't have believed it unless I tried it. The downside is the car is -7 MPG. So I get like 19 going to the track instead of 26. But man can I get on the throttle early.

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Read some posts on rennlist from one of the Clubsport race series drivers and he said max aero makes 3-4 mph diff on long straight at Daytona. I've had mine on max for quite a while...


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Discussion Starter #16
Read some posts on rennlist from one of the Clubsport race series drivers and he said max aero makes 3-4 mph diff on long straight at Daytona. I've had mine on max for quite a while...


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Thanks. I know the adjustment probably slowed me some on the straights, but for now, the cornering and braking advantages outweigh that. Over the winter though, I expect to go back to the factory setting.


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Discussion Starter #17
I did a bunch of the arithmetic to get my 59% nose heavy track Audi to behave more like a balanced car at speed. It took 4 seconds off at Thunderhill, more than any other mod I'd done including horsepower. Wouldn't have believed it unless I tried it. The downside is the car is -7 MPG. So I get like 19 going to the track instead of 26. But man can I get on the throttle early.

View attachment 157042
Tell me about the MPG. I am sure mine is off at least that much, if not more.


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