Does the A/C reduce power

[jtzako]

Originally Posted by Trevorw24

That's interesting, not sure if that's true for every car though.

It isnt true for city driving (stop and go) but the way the Mythbusters tested it was basically a 'highway'. Most things other than speed/wind dont have much affect on MPG when driving a constant speed.

Running the heater when your car is overheating is letting the heat have another way to escape the engine compartment. It has no bearing on whether running the A/C (in any mode) would cause an overheat condition.

[Steve Dallas]

Yes, turning off everything will maximize the engines horsepower AND gas milage.

A/C uses substantial horsepower to pull heat (refrigerate) from the air going into the cabin. Reduced horsepower does also mean you'll need more gas to go the same speed. This means slightly reduced gas milage as well, but we're talking a very small percentage here...so that's probably why mythbusters couldn't notice a difference.

Same goes for electrical system. Yes, you will be pulling a little horsepower to recharge the battery, but it's far less than what the A/C pulls out of the system in horsepower. Most home generators use 2-4 horsepower engines, and they can handle quite a few more electrical devices/systems than your car uses.

About overheating. Turning on the heat will help remove heat from the cooling system. Generally on older cars, turning on the A/C would add more heat, though that may have really been due to the added load on the engine.

[Cam#7]

It's been 30 years (80 Z28) since I've had a manual for a DD. I do notice how the AC compressor drops my RPMs quicker between shifts.

As far as MPG. This was a big debate 30 years ago when everyone didn't have or use their AC. I think it was proven (highway driving) to be a wash to run your AC with the windows closed versus not using your AC and having your windows open.

[East Coast Supercharging]

Originally Posted by Smart Line

under WOT the camaro (i was told) eletricly turns off the A/C. even when the a/c is on.

well guys is it true??????????????

That is actually NOT true regardless of what was posted here guys. I dont understand why the new Camaro or the C6 Corvette does not shut the AC off at WOT, but it does not until you reach 6000 RPM from the factory regardless of throttle position.

As part of our basic tuning, whether mail order or in person, we change the throttle percentages and RPM points that the AC will shut off. Leaving the AC on in a stock Camaro/Corvette will rob 8-10 rwhp consistently, I have done many back to back comparisons of this. We change it to 4000 rpm and 70% throttle to kick it off, it is not noticed by the driver at all, but keeps that extra little bit of power on tap for when you want it.


Doug @ ECS

[BenningJ]

Originally Posted by Shift

Not true, Mythbusters proved you get better MPG using the A/C rather than driving with the windows down but your MPG still goes down.

+1

Because driving with the windows down dramatically effects the aerodynamics of your car; it increases drag. This leads to the drop in mpg. Also, you do get more parasitic power loss when the A/C compressor is on because now you are actually spinning the compressor whereas when you aren't using the air, the engine is only spinning the pulley; the clutch is not engaged in the compressor.

[NYJets77]

Originally Posted by PnCRedJwl2SS

Can anyone answer this one finally for me? Can running the A/C in recirculate mode cause the engine to overheat, especially at idle? No one had ever been able to tell me (definitively) what the impact of using this mode is.

Little help?

At most, you'll create a micro singularity, but nothing big enough to be called a black hole or affect the space-time continuum.

[stand-al0ne]

Originally Posted by stieger

Mythbusters proved that running the A/C does not hurt mpg

What you said is sorta true. The comparo was between running with A/C on and running A/C off BUT windows down.

They proved that the increase drag of the windows down was worse than increase load on the engine from running the A/C.



if you were to not run a/c, just vent, and keep windows up, you would see best MPG...


But if you are like me and live in FL, that would be a deathwish. haha

[Chevrolet Customer Svc]

Originally Posted by smokingcamaro

So it just started to get really hot in NC like 90 degrees hot. So i turned on the A/C because I could not take it anymore and went to step on it and feels like the A/C reduced its power. Am I going crazy or is this normal?

Glad to see you were able to get your question answered. If you have any issues feel free to contact me.

Jeff Morris, Chevrolet Customer Service

[VTXrider]

Originally Posted by stieger

Mythbusters proved that running the A/C does not hurt mpg

Wrong, the Mythbusters test was flawed. The said they were testing whether or not running the A/C hurt MPGs. This is not what they tested, they tested whether running the A/C hurt MPGs more than opening the windows at a certain speed. If the wanted to test if running the A/C hurt MPGs they would have had to keep all other variables equal, meaning keep the windows closed.

This is a big difference, in most cars I've owned running the A/C at 80 MPH takes 10-15% of the MPGs, opening the windows at that speed is much worse because of the aerodynamics. However many times people can turn off the A/C, leaving the fan blowing outside air if it is cool enough and you'll see the MPGs go up. I park in a garage and usually leave my A/C off for parts of my drive and if it's cool outside. It helps a lot if you do not open the windows to do it.

[VTXrider]

Originally Posted by liquidsmoke

Cold air in the summer, hot air in the winter but never off.
Really don't care what any of the negative sides are.
Lower HP or perceived lower HP, more gas being used or whatever but I'm not gonna sweat or freeze my ass off to preserve either.
It's the American way.

Hell sometimes when it's a bit cold outside at night and I'm driving on a long stretch of highway going at a decent speed, I'll roll all the windows down and turn the heat on full blast to counter balance the 80mph+ cold wind.
I love it.

The heater does not cost you any load on the engine, it's just an electric fan taking heat of the engine

[VTXrider]

Originally Posted by CamaroFemme

Probably because constantly re-using the same air on long trips isn't good for you. Wouldn't wanna see you pass smooth out mid-drive from lack of O2.

Main reason I don't use it permanently is that it dries out the air to much for my liking. I do leave it permanently on around town, just not long drives.

I doubt you would ever run out of O2 since the car is just not that well sealed.

[Bonanza7]

Originally Posted by Trevorw24

That's interesting, not sure if that's true for every car though.

I know on my Honda, it cuts MPG by about 3/gal. 40 with A/C off....36-37 with it on. Computer shows immediate drop when the A/C is turned on.

[Devon]

Another good argument for a sunroof. I know it is no substitute for A/C, but it is good to vent the hot air out of the cabin so the A/C does not initially have to work as hard to cool it.

[coolman]

Running the A/C in a car that is already having overheating problems can cause the problem to get worse in two ways. It puts more load on the motor plus the condenser coil is most often mounted in front of the radiator which can cause warmer then ambient air to be pulled through the radiator from the cooling fans. The condenser coil is where the heat from the cabin is expelled outside thus causing warm air to be pulled across the radiator thus making it less effective.

As far as running the heat in a car that is having overheating problems, this can help because the heater core is nothing more then another (although smaller) radiator that will help to remove more heat from the antifreeze which will help cool the motor. It only helps though if you have enough antifreeze to allow flow through the core. If the level drops low enough to air lock the core, running the heater won't help anything.

Also, there is no possible way that running the A/C in the recir mode could ever cause the motor to over heat. If anything thing it would be more likely to happen in the standard mode because on a hot day in the standard mode your pulling outside air across the evaporator coil which causes more load on the A/C system and more heat to be expelled from the condenser coil thus more heat going across the radiator thus making the radiator less effective.