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Robert's correct ... (archive)

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Posted by Kessler on September 24, 1998 at 08:25:58:

In Reply to: Upcoming Free Performance Upgrade (Cold Air) posted by Robert on September 23, 1998 at 16:49:29:

For a given engine, power is roughly proportional to how much fuel you burn. The amount of fuel you can burn is proportional to the mass of air you get into the engine. If you keep pressure constant, the mass of the air in the cylinders is inversely proportional to the temperature. So lower temp = more power.

On a normally aspirated car, the difference isn't huge, but may be enough to notice if you pay attention. On a turbocharged or supercharged car w/ air to air intercooler, the difference is very noticable (not only does the intake charge start cooler, but the intercooler can cool it even more!).

Now, before you folks in the great white north get too excited, keep in mind that this only works down to a certain point. If the intake charge gets too cold, it becomes difficult to vaporize the fuel which means poor (incomplete) combustion and reduced power. I don't have any way to calculate where the break even point is (depends on the design of the engine), but I'd guess it's somewhere around 50 deg F.

-Dave Kessler

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