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post #1 of 5 (permalink) Old 10-11-04, 02:01 AM Thread Starter
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How much does air temp affect performance

How much of an effect does the temperature of air have on a vehicle's performance ? Can running a car at night vs during the day cause you to lose as much as a few tenths or more ?

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post #2 of 5 (permalink) Old 10-11-04, 02:08 AM
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Re: How much does air temp affect performance

Its not a matter of day or night, its a matter of height above sea level, humidity, air density, and temperature, but to best of my knowledge we are only talking 10ths of seconds, but a 14.2 can become a 13.9 so i guess its relevant.

I did put something here, but it vanshied, I think

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post #3 of 5 (permalink) Old 10-11-04, 03:05 AM
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Re: How much does air temp affect performance

Cold air instead of hot air can make a huge difference, more than a few 10th's maybe as much as 1/2 second.

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post #4 of 5 (permalink) Old 10-11-04, 05:17 AM
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Re: How much does air temp affect performance

taken from FORCED INDUCTION: Performance tuning by A. Graham Bell

"heat expands air, consequently at sea level 40 degree celsius air is less dense than air at 5 degree celsius. therefore, our 3 litre engine will make less power on hot air than cold air. another RULE OF THUMB: you LOSE 1% hp for EACH 7 degree celsius INCREASE in AIR TEMP"

"....... it should follow that a 3 litre engine will fill its cylinder with 3 litres of air at 10,000ft just as it does a sea level.
however, at altitude, because those 3 litres of air contain less oxygen (about 26% less), the engine will produce substantially less power. In fact a RULE OF THUMB is that hp will DECREASE 3% for EACH 1000ft"

high humidity will also decrease engine power in much the same way altitude does, but not as greatly unless combined with elevated temps. eg. 65% humidity and 35 degrees celsius at sea level reduces the oxgyen content similar to that at 100ft elevation.

so pretty much your car prefers air which is cold and dry, rather than high altitude, hot an humid air.

hope this explains it all to ya
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post #5 of 5 (permalink) Old 10-11-04, 06:23 PM
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Re: How much does air temp affect performance

My car lost 6kw going from a 10 degree day to a 20degree day on the same dyno with same engine setup

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