11-09-2006, 07:40 PM
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#1
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Pro Street Racer
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Horsepower difference with the fan on and off on a dyno
Came across this, and thought it was interesting...
Full article here: http://www.caranddriver.com/article....age_numb er=1
Quote:
Now Dinan opens the hood and turns on a small Home Depot shop fan blowing about 10 mph worth of air. The M5 is allowed to shed some excess heat and then run again. This time the computer finds another 37 horsepower, or 371. Things are looking up, but the M5's output is still nowhere near Dinan's expected number of 415.
"I can't claim something I can't measure," says Dinan, so the crew then wheels out the big gun: a $7000 electric fan that looks like it should be hanging on the wing of a Boeing 737. It blasts 38,000 cubic feet per minute of air at 75 mph down a narrow duct, right into the M5's radiator. The fan roars, the M5 howls, the computer twinkles, and the graph paper ticka-ticks out of the printer. It says 411.4 horsepower, the best run of the day.
"I'd pick up four or five more horsepower if I came back tomorrow morning and ran it at 70-degree room temperature," says Dinan. The room is currently 81 degrees.
"Basically, what horsepower would you like? I can give you anything from 330 to 420 with the same car," Dinan says. "Blowing air with a fan isn't the same as creating a bow-pressure effect over the whole front of the car. BMW can simulate that because it has billions to spend on wind tunnels. We don't, but we can come close by spending $250,000 to $300,000 on a climate-controlled room."
That's Dinan's next step. It's a huge expense for a boutique parts-maker, but BMWs aren't getting any stupider. The trend says the cars rolling into a tuner's shop will have more and smarter sensors with each passing model year. BMW may be at the leading edge of electronic engine controls right now, but the rest of the industry is sure to follow.
When it does, the "brag-ability" of dyno numbers will get even more dubious as dyno printouts become merely a reflection of what a particular car does on a particular dyno under a particular set of conditions. What happens on the street could be another matter altogether. As in Vegas, sure bets are in short supply when you measure horsepower.
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96 EK Hatch 343whp, and 245ft/lb torque at 11psi - Stock GSR Motor
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