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Old 06-26-2019, 08:32 AM   #1
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Less Power With A/C On

I know that running the A/C is a draw on engine power, but it seems the Boxster's loss of power is quite significant, much more than any other car I've driven.

Anyone else notice this? Is this just a characteristic of the car?

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Old 06-26-2019, 09:15 AM   #2
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I only notice a slight dip in idle when I first turn it on. I have never felt any power loss.
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Old 06-26-2019, 09:31 AM   #3
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I know that running the A/C is a draw on engine power, but it seems the Boxster's loss of power is quite significant, much more than any other car I've driven.

Anyone else notice this? Is this just a characteristic of the car?
I'll make a confession here:
I can't identify a difference in my laptimes when I forget and leave the A/C on for a session..... hahaha. (I like to turn it on while I'm waiting on the grid... 'cuz I'm overweight, and I sweat alot. You're welcome, for that image)
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Old 06-26-2019, 02:26 PM   #4
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I have never felt any kind of power loss in either my 2.7 base or my S.
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Old 06-26-2019, 05:31 PM   #5
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You’re not the only one. I felt what I thought was a significant power loss when I had the A/C on in my Boxster. It was why I mostly drove it without it on. I don’t notice it with my C2S.
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Old 06-26-2019, 09:37 PM   #6
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Keep the rev's up!

The M96 makes most of its power in the upper RPM's. At low RPM + the drag of the A/C, it can feel like its tapped out, but spin it up to 5K rpm and you'll never notice any difference.
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Old 06-27-2019, 06:34 AM   #7
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Quote:
Originally Posted by BoxMann View Post
I know that running the A/C is a draw on engine power, but it seems the Boxster's loss of power is quite significant, much more than any other car I've driven.

Anyone else notice this? Is this just a characteristic of the car?
The A/C compressor only consumes about 2-3hp which is not very much unless you have one that is failing. Then it will add significantly more load. Revs matter and keeping the car between 3k-6k will eliminate that lagging feeling.

In lap time comparisons I see very little difference with it on. Hot weather has a much greater effect on performance than running the A/C in my testing. Once the car becomes heat-soaked I may give up 2-3 seconds per lap due to both engine and tire grip losses. My personal best laps always happen with plenty of cold air at the intake when ambient temps are 50-60F here in SoCal.
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Old 06-27-2019, 04:54 PM   #8
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Yes I definitely feel less power with AC on, especially initial launch. Also during shift change with clutch in, rpm drops noticeably quicker. The AC effect lessened after installing underdrive pulley as expected, but still noticeable to me.

Also unlike other cars, my AC compressor clutch does not cycle on and off even the set temp is achieved, once I turn AC on it compressor is always on. I wish it cycles and also disengages at WOT so it does not drag the engine all the time less turned off. Or maybe something is not normal with my system? AC works great, takes little time to chill small cabin.
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Old 06-27-2019, 05:27 PM   #9
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Keep the rev's up!

The M96 makes most of its power in the upper RPM's. At low RPM + the drag of the A/C, it can feel like its tapped out, but spin it up to 5K rpm and you'll never notice any difference.
After thinking more about it, I think that's the right answer, it makes perfect sense. I generally shift between 4k - 5k rpm, but not always. Maybe it was when I didn't that I noticed it the most.
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Old 06-27-2019, 05:29 PM   #10
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The A/C compressor only consumes about 2-3hp which is not very much unless you have one that is failing. Then it will add significantly more load.
I sure hope that's not the problem. IIRC, a new a/c compressor is something like a $4,000 job.

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Hot weather has a much greater effect on performance than running the A/C in my testing. Once the car becomes heat-soaked I may give up 2-3 seconds per lap due to both engine and tire grip losses. My personal best laps always happen with plenty of cold air at the intake when ambient temps are 50-60F here in SoCal.
Interesting. Come to think of it, I started noticing it when the weather turned hot. OTOH, I started using the a/c when the weather turned hot.
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Old 06-27-2019, 05:34 PM   #11
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After thinking more about it, I think that's the right answer, it makes perfect sense. I generally shift between 4k - 5k rpm, but not always. Maybe it was when I didn't that I noticed it the most.
I do usually keep the rev up high on my 2.5, but you canít avoid AC drag at launch unless turn it off.

As mentioned earlier, UDP works for me to counter it and also reduce noise from belt noise and more pleasing engine/ exhaust noise to listen to!
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Old 06-27-2019, 06:28 PM   #12
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I sure hope that's not the problem. IIRC, a new a/c compressor is something like a $4,000 job.
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$150 for a compressor from a wrecker + $500 to replace and recharge if you donít do it yourself.
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Old 06-27-2019, 06:36 PM   #13
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$150 for a compressor from a wrecker + $500 to replace and recharge if you don’t do it yourself.
Well, I was talking about a new one. I was looking at a 987 before I bought my car, and the guy just replaced the a/c compressor, and the bill was about $4,000. I think they changed the drive belt too at the time, and maybe there was something else on the bill, but nothing significant. At least that's what I recall.
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Old 06-27-2019, 07:47 PM   #14
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Well, I was talking about a new one. I was looking at a 987 before I bought my car, and the guy just replaced the a/c compressor, and the bill was about $4,000. I think they changed the drive belt too at the time, and maybe there was something else on the bill, but nothing significant. At least that's what I recall.
Somebody paid the P-car surcharge if they spent $4k on AC....
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Old 06-28-2019, 12:08 AM   #15
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I do usually keep the rev up high on my 2.5, but you canít avoid AC drag at launch unless turn it off.
That's odd. In my 2.5, I have to look at the climate control unit to tell if the AC is on.
There is no noticeable difference throughout the rpm range, on or off. AC is ice cold, too.

Maybe your compressor is tired...
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Old 06-28-2019, 03:28 PM   #16
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That's odd. In my 2.5, I have to look at the climate control unit to tell if the AC is on.
There is no noticeable difference throughout the rpm range, on or off. AC is ice cold, too.

Maybe your compressor is tired...
That statement was by theory... because you canít take off from dead stop with keeping rev up 4-5K high that could be done once you get moving...

I felt more AC drag from dead start with factory pulley, not much now with UDP.

Anyway does your AC clutch cycle on and off? Mine never does and Iím unsure if it is by design or not... most other cars I owned/ owns does...

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