A/C vs. HP
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In the Staging Lanes
Joined: May 2011
Posts: 77
A/C vs. HP
How much power does the air conditioner rob from the engine? I can really tell when its on. The car wants to roll at around 83 or 84 with it off, and around 76 to 78 with it on. If Im just going a steady speed and switch it on, I notice it immediately.
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I've read figures anywhere between a 3-20 h.p. drag, depending on which style compressor it is. Also keep in mind that when the A/C kicks on, so does a second radiator fan on a lot of cars. That extra current draw puts more drag on the alternator, so you're getting it from both ends. Most of the cars I've had before (even my current d.d.) did have a very noticeable difference in engine performance between A/C on and off. And the smaller the engine (in h.p.), the more noticeable the drag will be.
Last edited by Camaro 69; Aug 9, 2011 at 08:07 PM.
I've been always told the ac when turned on does indeed rob power because of the resistance, but at highway speeds having your Windows down creates more resistance than your ac on and windows up.
Thread Starter
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In the Staging Lanes
Joined: May 2011
Posts: 77
Best way to find out is with a stopwatch.
Turn on A/C, find straightaway, start timer at steady speed, say, 60mph, and floor it. Stop timer at say, 100.
Turn off A/C, go to original start point at 60 mph, start timer, floor it, stop timer at 100 mph.
Leave A/C off, roll down windows, go to original start point, 60 mph, start timer, floor it, stop timer at 100 mph.
Compare results.
Who wants to try? I live alone, so I have no passenger to run the watch. Doing it alone, isnt going to be very accurate.
Turn on A/C, find straightaway, start timer at steady speed, say, 60mph, and floor it. Stop timer at say, 100.
Turn off A/C, go to original start point at 60 mph, start timer, floor it, stop timer at 100 mph.
Leave A/C off, roll down windows, go to original start point, 60 mph, start timer, floor it, stop timer at 100 mph.
Compare results.
Who wants to try? I live alone, so I have no passenger to run the watch. Doing it alone, isnt going to be very accurate.
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Best way to find out is with a stopwatch.
Turn on A/C, find straightaway, start timer at steady speed, say, 60mph, and floor it. Stop timer at say, 100.
Turn off A/C, go to original start point at 60 mph, start timer, floor it, stop timer at 100 mph.
Leave A/C off, roll down windows, go to original start point, 60 mph, start timer, floor it, stop timer at 100 mph.
Compare results.
Who wants to try? I live alone, so I have no passenger to run the watch. Doing it alone, isnt going to be very accurate.
Turn on A/C, find straightaway, start timer at steady speed, say, 60mph, and floor it. Stop timer at say, 100.
Turn off A/C, go to original start point at 60 mph, start timer, floor it, stop timer at 100 mph.
Leave A/C off, roll down windows, go to original start point, 60 mph, start timer, floor it, stop timer at 100 mph.
Compare results.
Who wants to try? I live alone, so I have no passenger to run the watch. Doing it alone, isnt going to be very accurate.
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