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JBL930 JBL930 is offline
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Join Date: May 2006
Location: UK
Posts: 1,172
They say that the Ruf "A" piller fillers are worth 5mph above 185mph... That is a lot of free speed for very little change. That car of Bello's is slippy as hell compared to Gabe's, i don't have figures for either car obviously, but it doesn't take a clever guy to see that with the same power in each car, Bello's car is going to a lot further down the road once you get anywhere near 200mph.
I can't wait to see Gabe's car run, it's an epic project! And i don't doubt it'll lap the ring quicker than Bello's could.... But in a straight line, with that body, it's going to need a monumental amount of spoot to keep up!!

Jean, who some of you are familiar with over on Rennlist, did a test with his 993's some time ago, here's a copy of one of his posts

"I went out with each of my stock 993TT and my GT2 bodied 993TT, and tried to measure the aerodynamic drag difference between both cars. This is a very difficult exercice as there are many factors impacting the readings so one needs to eliminate as many as possible..

So the runs were done a few minutes apart, and tried to get at the same exact point before letting go the throttle and putting it in neutral.

The measurements need to be taken at high speed as friction losses are lesser relative to aerodynamic drag. As speeds drop, tire friction and other losses become more significant.

Car 1: 100% stock 993TT with P zeros, stock sizes.
Car 2: Running weight close to 1500kgs, Michelin race full slick tires, -.2.7 camber up front, toe out 8', Gt2 wing at full downforce setting.

Method, speed up to 130 mph and then put the car in neutral. One run each way back and forth with each car, the impact of slope and wind turned out to be minimal as the slope was insignificant and there was no wind.

Car 1: 125mph - 85mph in 26 seconds and 1193 meters (around 3900 ft)
Car 2: 125mph-85mph in 18.5 seconds and 845 meters (2772 ft)

So the GT2 bodied car reached 85 mph 7.5 seconds and 1200 feet earlier than the stock 993TT !!



The big question mark is how much does that represent in terms of HP robbed?? Tough one! I did A LOT of calculations, and my findings are that at 125 mph, my 993gt2 needs around 60hp more than my stock 993TT to beat aerodynamic drag!

In terms of CDxA, based on published aerodynamic figures (circa 0.66), the drag should have robbed around 100 hp at 125 mph from my stock 993TT, wheras my datalog measurements and calculations showed me 90 hp, so I am not too far from theory. Based on the same measurements and calculations, the GT2 bodied car needed about 150 hp at 125 mph, meaning it is an equivalent CDxA of 0.9! this is adjusted for weight difference as well. Part of this is rolling resistence (alignment settings) , part is downforce rather than drag, and largest part is drag obviously. This gives an idea of how big an ennemy drag is to performance.

Next, will measure with and without GT2 wing alone, and will also measure at low speed to determine rolling resistence rather than drag.

I hope you find this useful. "
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Jonathan.
87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
Old 540 BMW, XB12S Modified, for being a total hooligan
Old 10-02-2010, 09:32 AM
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