Air Conditioning Sucks Power
Thread Starter
Pro
Joined: Apr 2013
Posts: 505
Likes: 52
From: MN
Air Conditioning Sucks Power
Anyone else avoid using the AC because it sucks the power and make the shifting rougher ? It might not be noticeable to those who don't drive it daily, but I sure do.
Race Director
Joined: Sep 2006
Posts: 19,035
Likes: 269
From: Bentonville, AR
I think something else is going on.
Just a WAG, but have you done an E-Gas calibration recently? Procedure is in the owners manual.
(For my cars without touching the gas pedal turn the key on and leave on for 1 minute. Then turn the key off and leave off for 10 seconds. Done. The times don't have to be exact but they can't be less than the numbers given. IOWs, leaving the key on for 65 seconds is ok. Leaving it on for just 55 seconds is not ok.)
Also, if you haven't had it done in a while do a brake/clutch fluid flush bleed. I had this done -- it was overdue -- for my Boxster a few months back and the clutch action and shift action improvement was remarkable.
Rennlist Member
Joined: May 2013
Posts: 1,394
Likes: 28
From: Southern Arizona
After I get used to how my vehicles "feel", I can usually detect when the A/C clutch kicks in. Just barely.
But the few HP that the A/C consumes does not affect the performance in any real way.
I agree with Macster that there must be some other issue(s) with your particular car.
Typically an engine's ECU will compensate for the A/C load by increasing the throttle position very slightly when the A/C clutch engages and will then reduce the throttle position when the clutch disengages.
If this did not occur, a person would notice the reduced RPMs, and the engine may even bog down or die. Likewise when the A/C clutch disengages the engine would surge.
Perhaps there is a problem with the switch/sensor in your A/C system that the ECU relies upon for this info.
But the few HP that the A/C consumes does not affect the performance in any real way.
I agree with Macster that there must be some other issue(s) with your particular car.
Typically an engine's ECU will compensate for the A/C load by increasing the throttle position very slightly when the A/C clutch engages and will then reduce the throttle position when the clutch disengages.
If this did not occur, a person would notice the reduced RPMs, and the engine may even bog down or die. Likewise when the A/C clutch disengages the engine would surge.
Perhaps there is a problem with the switch/sensor in your A/C system that the ECU relies upon for this info.
Rennlist Member
Joined: Oct 2007
Posts: 21,788
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From: Seattle, Washington
just drove my C4S home from SF calif 2 weeks ago in 100-108 degree weather thru redding calif and noticed no difference in power pull at all - 2 days of extremely hot weather with A/C on - i think you have another issue going on
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Pro
Joined: May 2015
Posts: 606
Likes: 11
Yep mine too. Pulls way harder and smoother with the AC off. I have tried all the tricks I just think it robs noticeable power. Back in my eagle talon days AC on at the drag strip cost ya 3 tenths.
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Race Director
Joined: Nov 2006
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From: Clifton, NJ
oh come on. significant parasitic drag? Unless you have a completely botched compressor, it costs no more than say 10bhp to drive the compressor (and thats being generous). If 10bhp is turning a dog into a sideways tire roaster, I'd be shocked. I think you're exaggerating. Either that or you have a more serious problem.
Banned
Joined: Mar 2010
Posts: 7,697
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From: Chicago
oh come on. significant parasitic drag? Unless you have a completely botched compressor, it costs no more than say 10bhp to drive the compressor (and thats being generous). If 10bhp is turning a dog into a sideways tire roaster, I'd be shocked. I think you're exaggerating. Either that or you have a more serious problem.
For those of you that wanna be hardcore like me, just run the fan on high with the windows down and get some vent clip mounted cup holders with cups of ice on all the vents. Old school AC.
Or if you need the heavy duty version...
Race Director
Joined: Sep 2006
Posts: 19,035
Likes: 269
From: Bentonville, AR
While I don't have the numbers recorded my Boxster's A/C system in maintain cabin temperature mode -- that is not blasting arctic to cool down an overheated cabin -- requires less than 1hp at idle. This is based on monitoring engine load -- via the OBD2 port and using a hand held OBD2 code reader/data viewer -- in "real time".
Now occasionally my Boxster appears to get into a perfect storm with the A/C on and while not running full blast still working to bring down the cabin temperature and with the radiator fans on (naturally) (and maybe on high) the engine compartment fan kicks on.
The engine, at idle, begins to labor some. I have not had the OBD2 code reader handy to view engine load at this time. I do not believe this is a problem with the A/C system. I worry more it is either a sign of a battery wearing out -- though the battery does not give any of the typical signs of pending trouble -- or a sign the alternator is getting tired. The alternator is original equipment and the car now has just under 292K miles on it. Other owners have had alternators go out in fewer miles...
Thread Starter
Pro
Joined: Apr 2013
Posts: 505
Likes: 52
From: MN
All kidding aside, my car drives and feels significantly different when running the AC. The shifting is rougher, and the acceleration is noticeably slower. I agree with 300hp on a car this size you wouldn't think it would matter or be noticeable, but it is. I wonder how much hp the air compressor uses and is this something that could work its way out of whack over the years ? It is after all a '99.