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Old 01-05-2008, 01:08 AM   #4 (permalink)
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Join Date: Jan 2008
Location: Corvallis, Oregon
Posts: 42

Base Metro - '96 Geo Metro
90 day: 54.24 mpg (US)

Neon ACR - '98 Dodge Neon ACR

Banana Slug - '64 Volkswagen Bug

Spirit - '92 Toyota Class C Motorhome Winnebago Itasca
90 day: 17.26 mpg (US)
Thanks: 8
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I understand that cold air is denser and contains more oxygen by volume than warm air, but the reason for depowering the motor I don't quite get. Maybe if you can explain what you mean by "pumping losses" I'll begin to get it. I was under the impression that under steady state circumstances the motor produced the amount of power required to maintain the steady state (say 55mph on a flat freeway with zero wind). Regardless of the amount of power the engine is capable of producing, it only actually produces the amount of power required of it at the time. I was also under the impression that the amount of power produced by an engine, all other things being equal, was proportional to the difference in the temperature of the air/fuel mixture entering the combustion chamber vs. the temperature of the combusted air/fuel mixture (exhaust) leaving the combustion chamber. The temperature difference would be greater if you start with a colder air/fuel mixture. Wouldn't this mean that with cold intake air the engine would not have to work so hard to power the car? This being the case, could you have a smaller engine or a smaller carburetor/throttle body and still get sufficient power for your needs? In the end, wouldn't this result in better economy?
I don't mean to be argumentative, but I'd like to understand. I come from a hotrodding background and it always seemed that a cold air intake was a cheap way to increase performance without suffering other ill effects, such as poor economy from a performance cam or a big carb. It seems that some of the performance tricks work okay for economy (free-flowing exhaust, aerodynamic mods, etc.) but others don't. Sometimes the differences are obvious (hot cams come to mind) but I don't get the cold air thing. Enlighten me please.

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