In Detail: Drag Racing's Smokey Tires And Exhaust Fires
TRANSLOGIC 75 shines a light on the techy side of drag racing, from the advanced materials used in the body and framework of these purpose-built vehicles, to the fuel mixtures that power them. But, perhaps all of the smokey burnouts and fire-breathing exhaust systems leave you unconvinced. These yee-haw! displays aren't simply for thrills, though. Both burnouts and flaming tailpipes play a vital function in the driver's ability to clock a decent time. You've probably noticed that the rear tires of a Top Fuel dragster are pretty wide. In fact, tread width of a drag tire is around 17", or about 8" wider than a typical street tire. Also, drag tires are only filled to about 7 psi, much less than the 30+ psi of the tires on your daily driver. The overall width and low tire pressure add up to a greater area of tread contact with the pavement. More contact area means more traction and a better launch. So, are those burnouts that precede every run really necessary?
Spinning the tires in a smokey burnout may look like fun (or wasted energy, depending on your perspective), but they actually serve a purpose. First, the friction generated heats up the tires, making the rubber more tacky with an aim to improve traction. Second, the force of the spinning wheel expels debris from the tire and track to ensure a more stable launch. Third, a burnout will lay down patches of rubber on the concrete surface, aiding in tire grip and providing guides to help the driver keep the vehicle moving straight off the line.
So, that explains all the smoke, but what about the fire? While dragsters are underway, flames can be seen bursting from the vehicles' tailpipes. It may look macho, but that's not why they're there. The explanation can actually be traced back to the nitromethane fuel mixture we discussed during the episode.
Nitromethane requires much less oxygen to burn than gasoline, meaning that it can produce more power per engine stroke, despite actually having a lower overall energy density than standard gas. What does that mean? Nitromethane is the perfect fuel for going really fast in short bursts. The tradeoff is that nitromethane burns slower than gasoline, meaning that combustion lasts longer--all the way into the exhaust cycle, producing the flames you see bursting from the tailpipes.
Top Fuel dragsters are in no way green, nor efficient. These racers apply technology as a means to a different end: speed and safety.
Click the image below to watch TRANSLOGIC 75: NHRA Drag Racing:
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