08-19-2011, 05:04 AM
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#1
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Registered User
Join Date: Jul 2011
Location: Upper Marlboro, Md.
Posts: 268
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A/C Drag
I bought my "99 Boxster base about 1.5 monts ago. It has 68,000. mi. Runs great, no major problems except the stupid gas gauge. (but I digress) Anyway I was was wondering if anyone else notices major strain on the engine when you turn on the the A/C. My '944's were pathetic once you turned on the A/C, and I see that the boxster, while not pathetic, has more strain than my BMW.
Anyone care to comment?
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08-19-2011, 05:19 AM
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#2
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,588
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Yes. All vehicles, regardless of the HP output, feel the strain of AC to varying degrees.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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08-19-2011, 05:26 AM
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#3
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Registered User
Join Date: Jul 2011
Location: Upper Marlboro, Md.
Posts: 268
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Yes I know this as well. To define the question a little further... does anyone find the drag on the boxster engine a liitle more dissapointing than it should be?
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08-19-2011, 05:34 AM
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#4
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Registered User
Join Date: Jul 2011
Location: Upper Marlboro, Md.
Posts: 268
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Yes I know this as well. To define the question a little further... does anyone find the drag on the boxster engine a liitle more dissapointing than it should be?
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08-19-2011, 06:04 AM
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#5
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,588
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Define “disappointing”………… Just exactly what were you expecting? The AC drag on any car is substantial, as a percentage of the total HP available; it is relatively large number on the Boxster. Try driving a 90 HP compact with air, when it switches on, you’d think you hit the brakes.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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08-19-2011, 06:04 AM
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#6
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Track rat
Join Date: Nov 2006
Location: Southern ID
Posts: 3,701
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The smaller and lighter the car, the more you tend to feel the A/C kick in. I used to have a 1.6L Datsun pickup with A/C and it practically stopped the truck when the compressor engaged.
__________________
2009 Cayman 2.9L PDK (with a few tweaks)
PCA-GPX Chief Driving Instructor-Ret.
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08-19-2011, 06:19 AM
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#7
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Registered User
Join Date: Jul 2011
Location: Upper Marlboro, Md.
Posts: 268
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lol. I know. I had a '79 VW Rabbit w/ a/c. Wasn't passing anybody on hot days. IDK, like I said earlier, you would think that 2.5 engine, 200hp, modern technology, it woldn't be so noticable. My '04 325i isn't bad at all. Maybe I'm just spoiled.
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08-19-2011, 08:31 AM
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#8
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Registered User
Join Date: Feb 2008
Location: Du Monde
Posts: 2,199
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The typical parasitic draw from a car AC compressor is 10-15 crank HP.
Add to this, an additional 1-2 HP is drawn from crank HP by the alternator (which basically 'free wheels' unless a load is put on it) to power the blower, and you're getting dangerously close to a 10% reduction in usuable output on the 2.5L motor.
If that 2.5L motor is well used, and no longer putting out the 218 ponies it originally came with (or you're not driving at peak HP on the rev curve), the total reduction of usable output could easily approach 15%.
Those are numbers you're likely to feel.
Cheers!
Last edited by Lil bastard; 08-19-2011 at 08:35 AM.
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08-19-2011, 08:43 AM
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#9
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Registered User
Join Date: Nov 2010
Location: Philly
Posts: 594
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I personally don't feel the difference.
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Lil Red
2009 Porsche Cayman 2.9L
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