Feeding the Beast -Sunday, November 02, 2003 -10:16 pm-
Although this entry is about cars, it's probably still amazing even to people who aren't gear heads. My car has started making a whooshing sound from the exhaust when I stand on the gas. It got me thinking about what volume of gas (in the chemistry sense) the car has to expel. The math on this is kind of amazing. Take a 3 litre, 6 cylinder engine (like in my car), rev it up to 4000 RPM (shift point on my car). Since it's a 4-stroke engine (suck, squish, bang, blow), each cylinder is filled and emptied at half the crankshaft RPM. So each cylinder is filling 2000 times a second. 3 litres x 2000cyc/min = 6000 litres/min, or 100 litres per second flow into the engine. Now, all that air and fuel have to get bigger when they burn, or else the car won't go forward. The combustion process makes the stuff entering the engine want to be about 10 times larger when it leaves. So somewhere around 1000 litres/second is trying to leave the engine. That's the rushing sound I hear from the tail pipe.