Andy Brown of Galmer Racing gave Race Car Engineering the following figures for the Galmer G-92. This is the car (driven by Al Unser Jr.), that won the 1992 Indianapolis 500 mile race.

 

	Downforcerce	Drag	L/D	Cd	Speed For Measurements
Short Oval	3460 lbs.	1310 lbs.	2.64	1.397	165 mph.
Street Circuit	3040 lbs.	1070 lbs.	2.84	1.141	165 mph.
Speedway	2835 lbs.	972 lbs.	2.92	0.669	220 mph.

In the days before roof fairings a Cd (drag coefficient) figure of 1.0 was typical for a high drag truck. Trucks are now down to a Cd of 0.6. This shows a 40% drag reduction using a fairing. This is importatnt in fuel economy. The figures quoted for the 1991 Indy 500 winning Penske PC20 in speedway trim were 3010 lbs. of downforce at 220 mph. with 1075 lbs. of drag. (Load/Downforce, L/D=2.80). Brown stated, "I'm always a little cautious of comparing figures from different wind tunnels. Experience has shown them all to vary slightly. The L/D figure, however, is usually close." The L/D or downforce to drag ratio is important data because it reflects the necessary car modifications determined by the racing circuit (in this case the short oval compared to the speedway). Drag reduction is particularly important in the speedway setup of the car. Note the drag and downforce difference in comparing a short oval setup to the speedway setup.

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Author: Bryan Yager, Ralston Middle School, Belmont, CA (12/94)