MAX Update No. 35: Nose Job for Better Aerodynamics

http://www.motherearthnews.com/green-transportation/100-mpg-nose-air-resistance.aspx

The new MAX body is getting a new nose. Cardboard and computers are working hand in hand on this aspect of the design. Don’t worry, the finished nose won't look like this, we’re just seeing how small an air inlet we can get away with.

For drag reduction, the less air that goes through the car, the better. Properly guided, air that goes around, over and even below the car can have relatively low air resistance, but air that goes through will always be a big drag, to coin a phrase. If you assume that all the air MAX nosethat goes through a radiator is converted to drag, you won't be far wrong. If you go back to Update No. 16, you can see that MAX’s radiator opening is substantial — a full square foot of MAX’s frontal area. Is that enough area to be worth messing with?

Dynamic pressure (shown by the letter ‘q’ in the aerodynamics biz, for reasons shrouded in mystery) is the pressure of air in motion. For horseback calculation of car performance you can use q = 1 pound at 20 mph. Dynamic pressure (q) increases at the square of airspeed (if you double your speed, you hit twice as many air molecules and you hit them each twice as hard, etc.) so q at 40 mph (20 mph x 2) is 4 pounds per square foot (2 squared). At 60 mph (20 mph x 3) q is 9 pounds per square foot (3 squared). I’ll spare you the math, but it takes 1.5 horsepower to exert 9 pounds of force at 60 mph. If we could reduce the size of the radiator opening to one-third of a square foot (as shown in the photo), MAX’s “cooling drag” would only be 3 pounds, would only take one-half horsepower to overcome, and would save us one full horsepower at 60 miles an hour.

Testing will show how little air MAX needs for cooling, but my guess is not very much. While Kinetic Vehicles encourages even our high performance customers to build their cars with four cylinder engines, we have a few who have put Chevy V-8s in cars that look just like MAX — same nose and everything — and they cool just fine. Still, one test is worth a thousand guesses, all it takes is some cardboard zip-tied to the grill and a keen eye on the temperature gauge, and when we’re done we can recycle the cardboard!

 


Photo by Jack McCornack 

 


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