Aero - Make a difference at speed? You bet - CODE BROWN.
04-10-2010, 10:16 PM
#61
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04-11-2010, 12:18 PM
#63
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04-11-2010, 05:01 PM
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04-11-2010, 07:37 PM
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Where did you get that drag coefficient figure? 
probably more than double that! a sleek street car has a Cd of about .32, a race car with wings, has a bunch of drag associated with downforce.
I was racing one of those subies this weekend at thunderhill (Ron Pippen's wrapped subie. looked cool! ). Not, 6 or 800hp, but probably 450rwhp+) Front straight speed, with a 40knot tail wind was about 140mph. (normally 130-135mph) I had NO wing and no splitter, and it was a little scary, but my lap times were only 1 second off my best from a replica car that had better tires, wider tires, wings, 100lbs less weight, and the track temp where tire temps were 50 degrees higher. I could have certainly been faster with aero, especially with the 100mph turn 8. So, I was backing off a notch. maybe the new car is a lot faster. we will soon see when we go back with all the Aero mods and bigger , better tires.
Mk
probably more than double that! a sleek street car has a Cd of about .32, a race car with wings, has a bunch of drag associated with downforce.
I was racing one of those subies this weekend at thunderhill (Ron Pippen's wrapped subie. looked cool! ). Not, 6 or 800hp, but probably 450rwhp+) Front straight speed, with a 40knot tail wind was about 140mph. (normally 130-135mph) I had NO wing and no splitter, and it was a little scary, but my lap times were only 1 second off my best from a replica car that had better tires, wider tires, wings, 100lbs less weight, and the track temp where tire temps were 50 degrees higher. I could have certainly been faster with aero, especially with the 100mph turn 8. So, I was backing off a notch. maybe the new car is a lot faster. we will soon see when we go back with all the Aero mods and bigger , better tires.
Mk
A DP is 2275 pounds and 500 HP. 4.7 or so pounds per HP and the Riley has a top speed of 200 mph so it can't be too much of a brick. 200 mph with 500 hp is something like .32 Cd. The DP has better power to weight, better handling yet is slower than the subie the end of a short straight?
The same straight that was fed into by a set of turns that the DP should have made a heck of a run out of?
I have watched them come out of that section and they look like slot cars tearing up the hill. Still does not add up for me but it is not important to this thread so I will give it a rest.
The same straight that was fed into by a set of turns that the DP should have made a heck of a run out of?
I have watched them come out of that section and they look like slot cars tearing up the hill. Still does not add up for me but it is not important to this thread so I will give it a rest.
04-11-2010, 07:44 PM
#67
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I totally agree, having run my car (new) this weekend on a track that Ive run for 15 years! It was a little dicy running without aero, but no OMG moments!
maybe, if the wing fell off just before a 100mph turn, it might be an issue, as it was in the video. In my math, all these things are a few tenths, not seconds. again, if we took all the stuff where people attach 2 seconds and added all them all up, we could be 15 seconds a lap faster, and thats just not reality. I think most estimations are off by a factor of 4. IMHO 
mk
maybe, if the wing fell off just before a 100mph turn, it might be an issue, as it was in the video.
In my math, all these things are a few tenths, not seconds. again, if we took all the stuff where people attach 2 seconds and added all them all up, we could be 15 seconds a lap faster, and thats just not reality. I think most estimations are off by a factor of 4. IMHO mk
*warning - this is strictly my opinion - no facts were harmed in it's making*
From what I have found, most of the aero on our cars has a minor but tangeable benefit. We are not generating many hundreds of lbs of downforce that will keep the car stuck if we can keep our speed up. Mostly we are eliminating lift and producing downforce generated stabilty. When I had my GT3, the change to the RS wing allowed me greater stability in the high speed esses at VIR. When I pulled the element from the 3.8 wing on my RSA at Daytona, I had a few mph greater top speed, paid for by noticeably greater instability in the braking zones for turns 1 and the bus stop. This is incremental gains, not OMG transformations.
From what I have found, most of the aero on our cars has a minor but tangeable benefit. We are not generating many hundreds of lbs of downforce that will keep the car stuck if we can keep our speed up. Mostly we are eliminating lift and producing downforce generated stabilty. When I had my GT3, the change to the RS wing allowed me greater stability in the high speed esses at VIR. When I pulled the element from the 3.8 wing on my RSA at Daytona, I had a few mph greater top speed, paid for by noticeably greater instability in the braking zones for turns 1 and the bus stop. This is incremental gains, not OMG transformations.
04-12-2010, 11:01 AM
#68
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If it is double how do you cover the published 200 mph top speed from 500 hp and 2300 lb?
I can find lots of # on weight HP and speed but little on the Cd of the DPs. TheCd is also not a fixed # based on wing angles and the like. Given the speeds and HP numbers you could make a rough guess of the Cd based on the HP and Cd of other 200 mph top speed cars.
You are trying to make a 600 hp street based sedan with less HP per pound faster than a 500 HP DP in a short straight that was fed into by a set of turns. The DPs rip through the lower esses before the straight. Something is not right., it could be me, thats for sure but my spidey sense is tingling
I can find lots of # on weight HP and speed but little on the Cd of the DPs. TheCd is also not a fixed # based on wing angles and the like. Given the speeds and HP numbers you could make a rough guess of the Cd based on the HP and Cd of other 200 mph top speed cars.
You are trying to make a 600 hp street based sedan with less HP per pound faster than a 500 HP DP in a short straight that was fed into by a set of turns. The DPs rip through the lower esses before the straight. Something is not right., it could be me, thats for sure but my spidey sense is tingling
04-12-2010, 08:39 PM
#69
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Total drag is not equal to drag coefficient. If you have half the frontal area and the same drag, you would have double the drag coefficient.
yes, total drag would be easy to guess. F=Pv, so if a car has 500rwhp, and its top speed is 200mph you can find the drag force, minus the rolling friction and determine its drag coefficient, if you know the frontal area.
There is a 928 with a 210mph top speed that had 500rwhp and a drag coeffient of .32. If you know the frontal area of the DP cars, you can determine the coefficient of drag if the top speed is 200mph and HP available is 500.
mk
yes, total drag would be easy to guess. F=Pv, so if a car has 500rwhp, and its top speed is 200mph you can find the drag force, minus the rolling friction and determine its drag coefficient, if you know the frontal area.
There is a 928 with a 210mph top speed that had 500rwhp and a drag coeffient of .32. If you know the frontal area of the DP cars, you can determine the coefficient of drag if the top speed is 200mph and HP available is 500.
mk
If it is double how do you cover the published 200 mph top speed from 500 hp and 2300 lb?
I can find lots of # on weight HP and speed but little on the Cd of the DPs. TheCd is also not a fixed # based on wing angles and the like. Given the speeds and HP numbers you could make a rough guess of the Cd based on the HP and Cd of other 200 mph top speed cars.
You are trying to make a 600 hp street based sedan with less HP per pound faster than a 500 HP DP in a short straight that was fed into by a set of turns. The DPs rip through the lower esses before the straight. Something is not right., it could be me, thats for sure but my spidey sense is tingling
I can find lots of # on weight HP and speed but little on the Cd of the DPs. TheCd is also not a fixed # based on wing angles and the like. Given the speeds and HP numbers you could make a rough guess of the Cd based on the HP and Cd of other 200 mph top speed cars.
You are trying to make a 600 hp street based sedan with less HP per pound faster than a 500 HP DP in a short straight that was fed into by a set of turns. The DPs rip through the lower esses before the straight. Something is not right., it could be me, thats for sure but my spidey sense is tingling
04-12-2010, 09:16 PM
#70
Mr. Excitement
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OK then the DP has a higher Cd but lower total drag because it knee high to a buried grasshopper.... Tell me again how it is slower in the short straight?
04-13-2010, 02:22 PM
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04-13-2010, 03:04 PM
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04-13-2010, 04:02 PM
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04-13-2010, 04:24 PM
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