docmirror

It's buried in the middle of the article as an aside. Interesting read anyway

http://www.telegraph.co.uk/motoring/...icroscope.html

UncleMaz

For the linky challenged:

In a recent issue of Evo magazine, writer Harry Metcalfe interviewed legendary Lamborghini test driver, Valentino Balboni, who admitted that he used every trick in the book to get the best top speed for the first Lamborghini Countach. “We did the performance testing at Nardo,” Balboni said, “and we removed the mirrors and wiper blades, increased tyre pressures and even taped up every joint on the car. Everyone did this sort of thing at the time.”
That doesn’t always work. At Auto Express magazine, road test editor Angus Frazer and I employed the same techniques to crack the magic 170mph in a Porsche 928 that had refused to lap at more than 168mph. Thus modified, it did 165mph. In those days of turbocharged engines, a quick twist on the wastegate was often enough to flatter the performance, but the strain of four laps around the formidable high-speed bowl at GM’s Millbrook test track near Bedford would often lead to souped-up road-test cars coming to a smoky halt.

Charley B

Open Road Racers take note:


...............................we removed the mirrors and wiper blades, increased tyre pressures and even taped up every joint on the car. Everyone did this sort of thing at the time.”

That doesn’t always work. At Auto Express magazine, road test editor Angus Frazer and I employed the same techniques to crack the magic 170mph in a Porsche 928 that had refused to lap at more than 168mph. Thus modified, it did 165mph.

123quattro

Removing mirrors and taping up seems in body panels always helps.

docmirror

Aerodynamics is a funny beast. Sometimes it doesn't act like we want it to act. There's something called the 'boundary layer' of air that resides on the surface of a body in flight. Just as dimples on a golf ball make it travel further, so changing the surface of the 928 may affect the boundary layer of air across the car, and make it more 'sticky' as it passes through the air.

We(928s) don't have a real good history with flat plate drag cooef, so this doesn't surprise me all that much.

dr bob

Several long years ago, a friend with a red F car and I decided to test the car's top speed. he flt he had a particularly strong example. Tires aired up a little hard, less than half a tank of fuel, and a new stretch of freeway opening nearby. Early in the morning, a two-way banshee run revealed that we were more than 15 MPH below the published top-speed numbers. Some quiet inquiry with other owners shwed that our results were typical. Years later, consulting on some emission control issues for cars from that same company, the situation had not changed much. Ringers were being presented for model certification, with numbers tailpipe that were way less than what we'd see later from a 'typical' consumer's example. Horsepower and performance numbers were never from the same cars. In fact the test cars were returned to the factory, thanks to some US laws about what could be sold here after testing. This included press cars, by the way, so the Jadz press car is quite unusual.