How much HP does the A/C "steal"? - Ford Mustang Forum
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post #1 of 4 (permalink) Old 06-04-2014 Thread Starter
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How much HP does the A/C "steal"?

I can feel a modest difference in pull when running the A/C. Many years ago when i had a first gen Integra, turning off the A/C was like a poor man's turbo. It's not nearly as bad in the 3.7 but it is noticeable.

Just wondering (for curiosity's sake) how much pulling power does running the A/C take from the driveline?

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post #2 of 4 (permalink) Old 06-04-2014
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Well it is another pulley going. Even in my prior car SRT-8 6.1l I could slightly tell the diff, it really depends on the motor size and if it is slightly bothered by it, you can tell if you turn it on and off. I have no clue of how to measure how many ponies it takes, but it is extra work-load on the motor. I know with a 6.1l it never effected my MPG just performance. Low speed fan kicked in @ 219f, high speed 226f, that even in a GT-500 5.4l or 5.8l is ridiculously high, and flat out robs power, the HEMI's run hot as hell. A\C on though triggered the hi-speed fans naturally so it actually ran "cooler" with the A\C on...

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post #3 of 4 (permalink) Old 06-04-2014
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Yes there is going to be some pumping loss when the AC clutch is engaged. When at idle you can hear and feel the load on the engine change as the clutch engages and disengages while it's running. There are also certain parameters in the ECM that disable the AC clutch when you go to wide open throttle. It's hard to say what you felt or you think you felt but I'd be willing to bet the difference, if any, is so small that you really wouldn't notice.

Originally Posted by rpaulg87 View Post
Well it is another pulley going.
The compressor pulley is always turning regardless of whether the AC is on or not.
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post #4 of 4 (permalink) Old 06-05-2014
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Other than the tiny amount of pully inertia and friction, it is drawing nothing from the engine at WOT because the clutch disengages. Under normal circumstances I would guess 2 to 3 hp, but that is purely a guess.

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