crashedout

I have an 05 GT 5-spd with 22k on it and I am curious if anyone else has noticed that the AC seems to suck the power out of the engine. I know it takes mechanical work to turn the compressor but on an engine this powerfull this seems extreme. Over last summer and this year I have noted that I loose 10% of my MPG when I use the AC. Also the lowend acceleration becomes horrible. The AC does blows cold and I don't hear the noises others have complained about, yet.

The reason I ask this is to find out if this is normal or if it is something I have to get the dealer to look into. So I ask, has anyone else noticed this? Did you get it fixed? An guidance greatly appreciated.

Louie

10% off is normal on most cars, when the A/C is on, I wouldn't worry too much about it.
For the sluggish acceleration (if it's a real problem, not just a sotp feeling), you might want to have your dealer check the car.

Boomer

Don't cars have the WOT/clutch that when it hits WOT, the A/C is turned off for that brief moment until you let off?

I know the AC sucks a lot of juice...
4 banger cars its WAY worse....

MusicMan66

I will never again own a 4-banger for that very reason... (last 4 cars have been/are V6s)

crashedout

So you are saying you guys have noticed the same thing in MPG and low-end power/acceleration? I have driven a fair amount cars and always notice this effect but it tended to decrease with the power of the engine. It just seems that with that much HP it should be minimal at best...I suppose I am just way too picky. Thanks for the info.

SixtySix

Completely normal, it's just the way it is. Don't forget why you have the A/C on...it's hot, that robs power as well.

Believe me, I KNOW hot

Paris MkVI

I found the solution to the power issue - I just apply more right foot.

As for mileage - well, I run my A/C even when the top is down. I decided when I bought this car I wasn't going to let MPG bother me. It just isn't what this car is about - to me anyway. But that's just me.

MY05GT

I do the same thing. I just wish the vents were better located as in the sn95s.

mrkabc

Ummmm... this may be an off the wall question, but why would you want to have the A/C running with your top down?

The SN95 vents were terrible... the vent at the lower left was utterly useless other than to cool off my turn signal stalk. I think the current dashboard vents are placed MUCH better than before.

Paris MkVI

When it is hot, I'll have a couple of the vents pointed at me, set the fan on 3, turn on the AC, and I'm comfy, even though the top is down! Not hot, not sweating. Is it wasteful? Sure it is. Everything about this terrific car doesn't make sense from a practicality point of view.

This is mostly for in-town, low speed driving. The AC is off on the highway. Don't need it then.

SixtySix

Well, those of us that live in extreme heat know why! It's called balance

MY05GT

Mainly .... because I can. A good time for this would be stop and go traffic, you bake in the sun without that 70/1 A/C going ( as opposed to 4/40 )

MY05GT

I feel like the SN95 vents are closer to me, so I get more of the air. My left vent cools the lap just fine.

mrkabc

Sixty Six: Here in the Los Angeles area, it gets pretty hot (it's 102 degrees as I write this), but I don't get DRY HEAT like you AZ folks do! Days like this I leave the top up and blast the air conditioner. The black leather is killer in this weather!

My05GT: I like vent air in my face, not my lap, guess that is why I hated that left-most vent in my SN95. It was pure bliss in my s197 when I could AT LAST have the left vent blowing in my face as it should!! <grin>

Different strokes for different folks I guess!

ford4v429

I dont think the power lost is actually due to the compressor running- I think the pcm is just programmed to limit things when the ac is on...Ive noticed the same in mine- no way a compressor should pull more than a couple hp, yet feels like your dragging an anchor...the tune likely limits to prevent overheating due to the expected heat loads added by the condensor ahead of the radiator- tunes can be funny that way.
my old 85 camaro was a v6- when warm it was a toad- but if engine was cold AND ac was switched on it would spin the tires pretty good for a 170 inch motor...ac richens it up to maintain idle(yet wot cutout seemed to still leave rich) and cold = rich(fuel injection dont have a choke- just pump hrder when cold)...while not good for the engine, to romp on it when cold, the lowend torque was probably near 50% better...Id guess the mustang went the other way- instead of richening up with ac on, it might just limit throttle/play with timing to reduce heat...sure does seem like a lot of wasted power...doubt if my central air pulls over 1~2 hp to cool an entire house...wonder if the car ac system BTU ratings are published somewhere?

SonicStanGirl

I'm with you guys! I was complaining to my significant other the other day that the car totally BOGS when the AC is on. You can totally feel the computer pulling power out when you try to gun it (or even take of normally) and the AC is on. Glad it is safe-guarding my engine from overheating and other things (if it is) but absolutely HATE the huge reduction in MPG! Also noticed that sometimes when I let out the clutch the engine doesn't react the same way when the AC is on. Probably the fact that there is greater load on the engine? It's just weird. Seems like I don't know how to drive a manual tranny or something...kind of jerky some times.

I also noticed that the throttle hesitation problem, that my car has had since I bought it, happens more frequently when the AC is on MAX (and it is super hot outside). I happen to have the car at the dealer today for the throttle hesitation TSB 06-09-09 so I am crossing my fingers that 1) they don't give me the run aournd and they actually replace the fuel pump and 2) it solves some of my problems.

karman

mikem solved the problem completely.
He removed the compressor and all the pipes under the hood.
No loss of power at all.

crashedout

I looked around the net, what I could find indicated that an A/C compressor in a car can take anywhere from 5-20hp. On our engine we should not notice this. I like the idea for the ECU retarding the engine but is there any proof? And would that effect MPG that much?

My theory is the fuel pump, after reading the TSB is seems possible that the fuel pump may be the problem. SonicStanGirl please report on your experience with that.

My gripe is that the HVAC air supply apears to be routed close to the engine, because on a cool day the vent air is very warm. This is not the first car I have driven that has this problem but it is an annoyance.

I am going to try to get that TSB done as soon as I get the time. Will report back if it fixes anything.

HolyPony!

There is also an issue with heat, with or without A/C ... Basically the ECU will retard ignition when hot to minimize pinging ... With a high-pressure turbo this is highly annoying ! Higher octane usually makes up for it though.

SonicStanGirl

Hey crashedout,
I got the fuel pump TSB done last Friday and I can report that not only does the car run like a scared rabbit now with more pickup than it had overall, but it also runs stronger with the AC on too!

Of course it doesn't run as strong as it would with out the AC on, but I do notice a significant improvement. I think my car was starved for gas most of the time and the computer was pulling out all the stops to keep it running.