A/C Tax on Engine Power

wondermalt

wondermalt

Well-Known Member
184
69
Toronto
Vehicle Model
Subaru WRX Sport
Driving an LX manual right now, this topic probably won't apply to the Si folks.
My question is that whenever the A/C is on, the engine feels very loaded.
Specifically, it feels like I'm engine braking on an upshift and the power band is all over the place.
It just doesn't feel smooth and I am frustrated when I drive it.

Will flashpro be able to forcefully fix this or am I stuck with this forever?
Can any of the R18 automatic drivers comment on this?
 
I have both an Si and a R18 and it is noticeable in both cars. The load feeling comes from the resistance the compressor places on the engine when the ac clutch is engaged. I don't have a specific draw number, but as a reference point it takes about 5hp to spin a hydronic power steering pump.
 
That's pretty much all cars with the
A/c on. It's more load on the engine and quite a bit more load I believe. That's why I don't use the a/c, and I live in Arizona (and also because of loss of power). Now that's dedication!
 
I never turn the A/C off...... So I haven't noticed any difference in power. The only thing I do to get more power is to take it out of economy setting.

Even with the air on I get great MPG(high of 48.9), just don't seem to have issues with power, but I've had mostly 4 bangers for most of my life, and this is the best of the lot.
 
I notice it a lot in my 08' LX. You are stuck with it unfortunately. The only fix is turning off the AC for things like onramps and merging. It definitely helps. IIRC people on the 8th forum were saying it eats something like 10-15hp, which is crazy high but not outlandish considering the way the engine feels with it on.

I will say that hitting the recirculate and making sure its only blowing from the upper vents lessens it a bit. Try that one day once the car is cooled down a bit.

My AC quirk: Whenever my wife and I go somewhere with the AC on and I have to get on the highway I reach over and turn it off and proclaim that I'm "turning on the turbo" or that "I need the turbo for a minute!" I act like the ac "off" button is a magic turbo boost. So yea, its definitely noticeable. hahaha.
 
Nix said:
My AC quirk: Whenever my wife and I go somewhere with the AC on and I have to get on the highway I reach over and turn it off and proclaim that I'm "turning on the turbo" or that "I need the turbo for a minute!" I act like the ac "off" button is a magic turbo boost. So yea, its definitely noticeable. hahaha.
Click to expand...

^ that's a good tip!

Thanks for chiming in guys! Good to know that I'm not the only one.
I do know that in fact the recirculated air mode uses your A/C more efficiently because you are not pulling the ambient hot air into the mix.
A/C off = "TURBO MODE" mind set from now on :P
 
Same thing with econ mode, I use that as much as my cruise control..... same with having to turn my traction control off when I start my car........ Anyway I use my gears, and Econ as one...... what ever it needs to be in at that time, I'm going to manually change it....... After all, since it's an automatic I've got nothing else to do anyway, so I play with all the things that will make her do her best.
I could get into a whole mind melt of what all I do while driving........ I pretty much run my air on recycle as well, only run fresh to keep the fogging down on some Winter days, but I still run the air in Winter as well(helps with dryness control).
 
Yea your A/C compressor is making upwards of 250-300psi so you can imagine it takes some power to make that happen. The faster your rpms the faster the compressor speed the higher psi the higher the load your motor needs to use its power to spin the compressor. Newer compressors have a "wobble plate" that can vary the amount of pumping power/psi levels when a lower threshold is needed like cruising for mpg after the cabin temps drop and the system doesn't need to work as hard or like WOT where you don't want a heavy load from the a/c but still have it on. Even v8's suffer from parasitic loss from a/c. With all that said I don't use my A/C unless it's raining or I'm getting over heated. MOE POWA!!
 
I have a question. Does the compressor/AC disengage immediately when you turn the fan to the off setting and / or when you hit the AC button off?

Also on fuel saving websites, the tip they give about AC is that it can sap your MPG at low speeds so waiting until at highway speed and switching it on and off can help.

A funny story I know is a friend of mine whom I go to the track with has a boxster D and he said he was running laps with the AC on full blast! Im not sure if his car maybe has electric AC?

Also another funny thing is in a lot of small aircraft the AC has to be turned off during take off to give you enough power. However some are all electric and can be kept on during takeoff and climb!
 
I like the "broom" the extra load from the a/c gives my Si. I try not to pay attention to the extra load or mpg decrease because when the A/C is off vtec comes on so it makes no difference
 
NoTorque said:
I have a question. Does the compressor/AC disengage immediately when you turn the fan to the off setting and / or when you hit the AC button off?

Also on fuel saving websites, the tip they give about AC is that it can sap your MPG at low speeds so waiting until at highway speed and switching it on and off can help.

A funny story I know is a friend of mine whom I go to the track with has a boxster D and he said he was running laps with the AC on full blast! Im not sure if his car maybe has electric AC?

Also another funny thing is in a lot of small aircraft the AC has to be turned off during take off to give you enough power. However some are all electric and can be kept on during takeoff and climb!
Click to expand...

When you hit the AC button, MAX AC button or the defogger buttons, you'll hear this distinctive click underneath the hood of your car.
That is the A/C unit kicking in.
When you turn the fan off, the A/C unit also turns off and you can verify with that clicking sound.
 
You can turn the ac off and still run the fan without running the ac.... I don't know that the fan alone will tax anything, just saying you can get some kind of air pumped into the cockpit.

Since this thread started, I went out and tried running without the ac running..... Sorry I don't see much difference, if any, that I can tell by the seat of my pants, but I can tell it is hotter in the cockpit with it off.

Not saying you guys are wrong, this is what I've noticed, I'll stick with running my ac, and still getting 32 to 49 mpg.
 
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