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necessary to turn off the air conditioner?

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45
36
Exp. Type
HPDE
Exp. Level
Under 3 Years
Spain
Is it necessary to turn off the air conditioner on the track? I thought more serious people ran with the AC removed to reduce weight, and perhaps even a little bit of more horse power by not having to power the AC, but since neither of those are relevant at my level (non-competition trackdays) I'm much more happy with my AC on. ;-)

Now I've seen some older posts (10+ years old) elsewhere talking abut that having the AC on at high RPM's is bad for it (too much pressure?), and coolant may leak out too. Is this applicable to the current (2020+) Mustangs too? Some posts said the system automatically shuts off the AC at WOT. If so, does that avoid all problems?

I'm in a manual 2020 GT, and I try to mostly shift before 7,000 to hopefully prolong clutch/gearbox/engine life.

Thanks.
 

TMSBOSS

Spending my pension on car parts and track fees.
7,529
5,245
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
Most modern cars will turn the A/C compressor off under hard acceleration. So power loss is not a big issue. The problem I have had running the A/C is with cooling. When you lift off the gas, the compressor kicks in producing heat at the condense. This extra heat causes the coolant to over heat Triggering limp mode.
I agree, it’s much nicer having a cool passenger compartment during track events. The problem for me was over heating the coolant while chilling the driver. YMMV.
 

JDee

Ancient Racer
1,797
2,001
Exp. Type
W2W Racing
Exp. Level
20+ Years
5 miles from Mosport
I took the air out for weight, but when it was in place I did not use it until the cool down lap. I didn't use it partly because of potential power loss running the compressor but also because it adds heat load and there's already enough of that in there. Gets pretty warm in the cabin during a 20 minute session during the summer since I run windows up, but it's bearable for that short period of time.

I also shift at 6750 rpm max these days, having dumped a pile of money into trans and clutch issues I'm ready to minimize that bleed. When you're not even running for trophies it makes zero sense to beat the car to death chasing a tenth of a second.
 

xr7

TMO Addict?
706
821
Exp. Type
Autocross
Exp. Level
10-20 Years
Minnesota
I only use my A/C before and after my run. I don't run my A/C for the usual reasons during a run. I also figure the A/C compressor is happier not getting spun up to 7500 rpm and slammed off and on because throttle position changes. I did a lot of A/C work and cleaning up after a trashed compressor is a real pain in the butt and wallet. Even worse when you have to pay a shop to do it.
 

Bill Pemberton

0ld Ford Automotive Racing Terror
8,424
8,349
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
What is air conditioning , ha. TMS is quite correct, the car should kick out of A/C under full acceleration if you forget , but just turn it off and crank it back on after your session is done.
 

Ludachris

Chris
Staff member
Moderator
1,658
1,962
Exp. Type
HPDE
Exp. Level
5-10 Years
Newcastle, CA
Wonder how well one of these would work for those in street-driven cars who are planning to turn off the A/C while on track:

Or you could step up to this:
 
7
9
Exp. Type
HPDE
Exp. Level
5-10 Years
Phoenix, AZ
Like others have said, the problem is that high engine RPMs cause the A/C compressor clutch to essentially explode. I only use the air when I’m waiting in pre-grid to go out or once I’m back in the pits.
 

Dave_W

Cones - not just for ice cream
984
1,277
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
Pro tip for cooling off before or after a session - put your palms up to the A/C vents. Your palms contain a much higher density of small blood vessels than most of the body, so they act as radiators. Cooling your palms cools your blood, which is then carried to your core, cooling it more efficiently. Don't over-cool your hands, though, as the blood vessels start to constrict if they get too cold and they become less efficient radiators.

For those without A/C, tightly hold a cold beverage bottle/can in each hand for a few minutes.

 
98
143
Exp. Type
Autocross
Exp. Level
20+ Years
Olsburg, KS
My earliest days at the track were at a dragstrip. There it is a major no-no to use an air conditioner, as it drops moisture on the track. I've honestly never considered turning on the a/c before, during or after a session. As others have said, the mechanics of high rpm cutout and reengagement is pretty hard on things, anyway.
 

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