HELP - car's power different when AC is on

[dirtyred11]

First of all, you need to simmer down a bit. And second... 2-3 hp? Seriously?

The air conditioner takes mechanical power away from the engine. The blower takes electrical power from the alternator, then the alternator itself takes a bit more mechanical power. I think at highway speeds, the air conditioner takes approximately ten percent of the car's power to run. At idle, it would be significantly more... maybe a third? When the AC is on, the ECM compensates for the additional load by richening the mixture, adjusting idle control flow and injector firing. It's pretty common knowledge that running the AC robs away a significant amount of the car's power. Hence why Goldmember pointed out that we call it our "V6 Tune"

If you really think there's something wrong, a couple of things to check for:
- Alternator issues
- Worn out or faulty AC pump, maybe a bearing or seal going out
- Dirty IAC (which you've already ruled out)
- Loose belt

That's all that I can think of right now. But from the way you describe what's going on, it really sounds about typical.

Thanks for clearing that up for me, of the ones on your list I can rule out all but the a/c pump so I will go with that and see what happens. Thanks again for the help....

 

[mcglsr2]

Jesus Christ people, your cars performance has NOTHING to do with the AC being on or off. Only ricers complain of AC performance loss

Um...actually it does. The A/C compressor places a load on the engine. You are using the engine to turn the compressor. This equates to more load, more friction. The type of engine you have depends on how noticeable it is. If you have a big torquey engine, then yah maybe you won't notice. I have a 4 cyl turbo that made 175 hp from the factory (back in 1987), if you had the A/C on and then went to WOT, the "computer" would turn the compressor off to give full power until you went out of WOT. This from the factory. So, obviously, the car's performance is affected by the A/C. Now maybe ricers use that as an excuse or something. I don't know.

 

[96blak54]

Well said...thank you

 

[nightfire]

Um...actually it does. The A/C compressor places a load on the engine. You are using the engine to turn the compressor. This equates to more load, more friction. The type of engine you have depends on how noticeable it is. If you have a big torquey engine, then yah maybe you won't notice. I have a 4 cyl turbo that made 175 hp from the factory (back in 1987), if you had the A/C on and then went to WOT, the "computer" would turn the compressor off to give full power until you went out of WOT. This from the factory. So, obviously, the car's performance is affected by the A/C. Now maybe ricers use that as an excuse or something. I don't know.

Maybe I should have elaborated. Yes, a draw on the engine is a draw no matter what. My point is that no matter what the draw is, it is incredibly minute. Even with a 175hp 4-cyl, the draw of an AC is not going to be remotely noticeable.

For those continuing to argue otherwise, I want to see proof.

 

[PonyGlued]

the draw of an AC is not going to be remotely noticeable.

For those continuing to argue otherwise, I want to see proof.

I think what may sway you a bit is if you try to turn a compressor pulley by hand, not really so easy. Its not as free turning as lets say an alternator for example, there is considerable resistance there with a compressor, when tried being turned. actually I'm sure that somewhere the required hp to turn that compressor is listed in its spec's.

 

[mcglsr2]

Maybe I should have elaborated. Yes, a draw on the engine is a draw no matter what. My point is that no matter what the draw is, it is incredibly minute. Even with a 175hp 4-cyl, the draw of an AC is not going to be remotely noticeable.

For those continuing to argue otherwise, I want to see proof.

Lol I'm telling you, my proof is a 1987 Shelby CSX from the factory with a turbocharged 2.2L I4 running about 12 psi. With the A/C, there was a noticeable lag in the power delivery. Which is why the factory programmed the computer to turn off the compressor while the car was in wide open throttle, as the driver obviously wants all the power the car could give. Once the driver was done flooring it, the computer would turn the compressor back on. In other words, you don't get no A/C while flooring the car. If the reduction to power was trivial and not noticeable, the factory would not have spent time and money creating the above function. I'm willing to bet there a lot of cars that discretely turn off the A/C compressor when the driver goes past a certain throttle threshold, and I bet the driver never notices.

Edit: Trust me man, there is a noticeable drop in power. It is more prevalent in some cars and less so in others. Perhaps you have been lucky to always have driven cars that weren't as noticeable, or did have those cars and didn't realize the computer was turning the compressor off at certain times.

 

[mcglsr2]

I think what may sway you a bit is if you try to turn a compressor pulley by hand, not really so easy. Its not as free turning as lets say an alternator for example, there is considerable resistance there with a compressor, when tried being turned. actually I'm sure that somewhere the required hp to turn that compressor is listed in its spec's.

This. There absolutely MUST be resistance. The compressor is just that, a compressor. It takes energy to compress things, there is no free lunch in physics (though turbos get really, really close). Whereas an alternator is passing wires by a magnet, there isn't necessary any contact. No contact means you are dealing with just the weight of the rotating components, which is very small in comparison.

 

[DeepList]

My point is that no matter what the draw is, it is incredibly minute. Even with a 175hp 4-cyl, the draw of an AC is not going to be remotely noticeable.

For those continuing to argue otherwise, I want to see proof.

:snoopfacepalm:


Each and every vehicle I've ever owned or driven has had a noticeable decrease in power while the AC was running, for reasons already mentioned.