Description
This article is from the Motorsport
FAQ, by A H Henry bspahh@midge.bath.ac.uk with numerous
contributions by others.
31 Aerodynamics (1994 IndyCar Specifications)
Andy Brown from Galmer gave Racecar Engineering the following figures
for the Galmer G92, the car which won the 1992 Indy 500.
Downforce 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
Fuel consumption is higher on a street circuit such as Long Beach
than on a short oval such as Phoenix: consequently the car has to be
set up so that it pulls less drag.
By way of comparison, in the days before cab roof fairings, a Cd
figure of 1.0 was typical for a high-drag truck. These days trucks
are down to the region of Cd = 0.6 The figures quoted for the 1991
Indy 500 winning Penske PC20 in speedway trim were 3010 lbs downforce
at 220 mph with 1075 lbs drag (Load/Downforce, L/D, = 2.80)
Brown commented: `I'm always a little cautious of comparing figures
from different wind tunnels because experience has shown them all to
vary slightly. The L/D figure is usually close though, and I'm
pleased to see that ours is better than that quoted for the PC20.
Provided we're both telling the truth, that is !'
Note: The downforce is approximately double the weight of the car,
so the car could drive upside-down with a suitable bit of road.
 
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