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2009 2.5X EJ253 Manual
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Discussion Starter #1
There is no mistaking it. When I have the A/C on my Forester has fatter low end power, and over all the engine seems more responsive and more capable. Same thing if the defrost is on. The key has to be some parameter in the ECU programming that when the climate control is set such that the A/C compressor will cycle on and off (air cond or defrost), it does something with the spark advance or the drive-by-wire throttle acuation that increases power.

I filled on 89 octane today (12 US gallons into remaining 5 gallons of 87 octane), and was driving around with the A/C on in ambient temps of around 82 deg and the car just felt frisky.
 

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2006 Forester XT
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657 Posts
I've noticed the idle is higher, but no 'boost' effect.....


.
 

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2015 Forester premium
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63 Posts
Ac on

I know on my MY09 NA I don't feel any lag or lack of power power or lower gas mileage w/ AC on.

Back when I started driving, you could feel the AC eating power even with the 300+ HP the V8's I had then.
 

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2010 FXT Limited 4EAT Sport Shift
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1,461 Posts
LoneRanger-
Sounds pretty subjective to me...do a comparison test, where you time your car under full acceleration, but short shifting through gears (shift religiously at say 3000) until you hit 3000 rpm in 5th gear (may need to do this on a freeway?, otherwise do this through 4th gear at 3000rpm).
Do this once with AC on, once with AC AND defroster off. Then tell us the results...we'll believe you!
-Quick

There is no mistaking it. When I have the A/C on my Forester has fatter low end power, and over all the engine seems more responsive and more capable. Same thing if the defrost is on. The key has to be some parameter in the ECU programming that when the climate control is set such that the A/C compressor will cycle on and off (air cond or defrost), it does something with the spark advance or the drive-by-wire throttle acuation that increases power.

I filled on 89 octane today (12 US gallons into remaining 5 gallons of 87 octane), and was driving around with the A/C on in ambient temps of around 82 deg and the car just felt frisky.
 

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Forester X
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288 Posts
My AC in my 2003 not only saps power, but also makes the car downshift roughly...

Hasn't been a problem yet, but now that we're getting into the 90s it will be an issue.
 

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2002 Forester L
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329 Posts
If I put my AC on it seems to take what little power I have away.....
 

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2010 FXT Limited 4EAT Sport Shift
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1,461 Posts
So dude,
It looks like you really are the Lone Ranger...those responding are wondering if you've managed to come up with an objective way explaining increased performance under greater engine loading...
-Quick

There is no mistaking it. When I have the A/C on my Forester has fatter low end power, and over all the engine seems more responsive and more capable. Same thing if the defrost is on. The key has to be some parameter in the ECU programming that when the climate control is set such that the A/C compressor will cycle on and off (air cond or defrost), it does something with the spark advance or the drive-by-wire throttle acuation that increases power.

I filled on 89 octane today (12 US gallons into remaining 5 gallons of 87 octane), and was driving around with the A/C on in ambient temps of around 82 deg and the car just felt frisky.
 

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Registered
2009 2.5X EJ253 Manual
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2,802 Posts
Discussion Starter #8
Leave me alone, what's up with you posting the same intentions twice in a row? Your first post, okay. But throwing it out again and repeating yourself is pointless. Subjective? Casual observations usually are. I know how my car reponds, and it runs better with the A/C or defrost on.
 

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2017 Foz 2.5i CVT
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1,919 Posts
There is no mistaking it. When I have the A/C on my Forester has fatter low end power, and over all the engine seems more responsive and more capable. Same thing if the defrost is on. The key has to be some parameter in the ECU programming that when the climate control is set such that the A/C compressor will cycle on and off (air cond or defrost), it does something with the spark advance or the drive-by-wire throttle acuation that increases power.

I filled on 89 octane today (12 US gallons into remaining 5 gallons of 87 octane), and was driving around with the A/C on in ambient temps of around 82 deg and the car just felt frisky.
In the old days, cars had a solenoid that would increase idle speed when the A/C compressor came on. Now the same thing is done electronically, and there is possibly some compensation at lower throttle inputs to make the car feel punchier. Via a recalibration of the drive by wire system. They have to make some kind of guess on A/C drag at various rpm's and throttle settings, and may overcompensate slightly.

I'm guessing that there may be some part throttle compensation, but at full throttle, you just have more drag from the A/C (or maybe not, if the compressor shuts off at full throttle as I know at least some other cars do). In other words, more drag cannot produce more power, but the compensation system may be giving the *illusion* of more power.

Or maybe the additional noise from the compressor makes the engine sound louder and therefore, faster :)

George
 

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2003 Subaru Forester XS
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167 Posts
exactly, mine does the same,with the Air con on it feels stronger in picking up speed from the start(lower revs) but on full throttle it just switches the compressor off. I guess there is some over compensation somehow
 

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2010 FXT Limited 4EAT Sport Shift
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1,461 Posts
Lone Ranger-
I agree at least with one of your comments...'Subjective? Casual observations usually are."
Where I come from, unsubstantiated claims get challenged...sorry, didn't realize you were so sensitive...I'll keep that in mind in the future.
Had you said that your Forester gave you the illusion that it had 'fatter low end power', I'd have not said a thing and went on...I mean, what it feels like to you, is what it feels like to you.
-Quick

Leave me alone, what's up with you posting the same intentions twice in a row? Your first post, okay. But throwing it out again and repeating yourself is pointless. Subjective? Casual observations usually are. I know how my car reponds, and it runs better with the A/C or defrost on.
 

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2017 Foz 2.5i CVT
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1,919 Posts
Lone Ranger-
I agree at least with one of your comments...'Subjective? Casual observations usually are."
Where I come from, unsubstantiated claims get challenged...sorry, didn't realize you were so sensitive...I'll keep that in mind in the future.
Had you said that your Forester gave you the illusion that it had 'fatter low end power', I'd have not said a thing and went on...I mean, what it feels like to you, is what it feels like to you.
-Quick
Man, who put iron filings in your breakfast this morning?:icon_razz:

He said his Foz "has fatter low end power" and based on drive by wire programming, that statement may be completely true with the qualifier "at a given pedal position" or "with my normal driving style"...

George
 

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2010 FXT Limited 4EAT Sport Shift
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1,461 Posts
YoGeorge-
Okay, I'll accept Lone Ranger's conjecture and subjectivity...and your "may be" optimism...feel better? Iron filings? Naw, too much bran in my muffins!
-Quick

Man, who put iron filings in your breakfast this morning?:icon_razz:

He said his Foz "has fatter low end power" and based on drive by wire programming, that statement may be completely true with the qualifier "at a given pedal position" or "with my normal driving style"...

George
 

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2009 2.5X EJ253 Manual
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2,802 Posts
Discussion Starter #14
What you must keep in mind about me lately, Quicksilver, is I am going through marital problems, on top of now taking on Power of Attorney over my father's affairs after the recent passing of my mother. I'm not throwing that out in search of a pity party at all, I'm just I guess, trying to justify or at least rationalize my flying off the handle too easily lately. Stress level is up lately. Sorry I snapped back at you, it wasn't right. At work I have to be uber courtious and respectful, so in my off time I've caught myself lashing out when I should hold my tongue instead.
 

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Pleiads' biggest leghumper
04's 2 FXT's.
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9,263 Posts
I feel the same with my 04 XT. With AC on it has lower end power from take off but when WOT'd AC turns off.


joe r
 
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