Top Gear turn off A/C

Chive Driver · 10-07-2013, 07:38 PM

What does turning off the A/C do in a car?

What is the benefit? and is it really noticeable?

I hear it on Top Gear when they do the Star in Reasonably Priced car sometimes.

Aequitas & Veritas · 10-07-2013, 07:54 PM

Less movement under the hood, supposedly frees up more ponies. Does it add power you can tell the difference? Not to me, though I hardly use my ac since I hate hearing it running

Au201 · 10-07-2013, 08:52 PM

Quote:

Originally Posted by Aequitas & Veritas

Less movement under the hood, supposedly frees up more ponies. Does it add power you can tell the difference? Not to me, though I hardly use my ac since I hate hearing it running

It makes a small difference with these more powerful engines but a huge difference in a small 4 cyl. In my cruze turbo there's an amazing difference with a/c on and off. In the Camaro I can't tell at all.

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Number 3 · 10-07-2013, 10:16 PM

In many newer performance cars, the A/C compressor will disengage the clutch. When engaged, it is HP the engine must use to turn. Alternator is the same way.

menendez1293 · 10-07-2013, 10:23 PM

Normally speaking the AC compressor is like a leach and is stealing some power from the motor. With that being said in a car with a larger motor the reduction is far less than a little 4 cylinder. I have heard people say if takes 20 Hp but to that I say

derklug · 10-07-2013, 11:30 PM

Old a/c compressors used about 7hp, new models use around 5. On a 400 horse engine, this draw is like leaving your golf clubs in the trunk. On a 150 horse car, it is like having a passenger. At wide open throttle, most cars shut down the a/c compressor to get better performance, so turning it off on the Reasonably Priced Car probably doesn't make a difference.

sspolo · 10-08-2013, 12:32 AM

I haven't noticed (or cared to feel) a difference when I have the A/C on or off on my 100hp Saturn

dcoates18481 · 10-08-2013, 07:26 AM

i believe at WOT the A/C clutch is disengaged until WOT is let off.

ClawSS · 10-08-2013, 06:46 PM

FYI ... Never run your A/C when at the track...especially the drag strip. The water that will drip can cause severe traction issues for those running behind you and may cause a terrible accident.

ChrisBlair · 10-08-2013, 09:17 PM

Simply put- accessories driven off the engine all produce parasitic loses in power of some kind, at some time.

As an aside, but related, before 1971, engines were rated in gross horsepower- the engine itself, not even installed in the vehicle, no alternator, a/c compressor, nothing. That's why you'll see old ads for the "450 hp" Chevelle SS LS6. That was 450 gross hp. The LS3 spanks it in terms of hp. The V6 Camaro makes more brake hp than a lot of V8s of the golden era of muscle.

Scalded Dog · 10-13-2013, 10:37 AM

Quote:

Originally Posted by derklug

Old a/c compressors used about 7hp, new models use around 5. On a 400 horse engine, this draw is like leaving your golf clubs in the trunk. On a 150 horse car, it is like having a passenger. At wide open throttle, most cars shut down the a/c compressor to get better performance, so turning it off on the Reasonably Priced Car probably doesn't make a difference.

My vote for best answer.

Having driven many vehicles over the years, very frequently on the long grades ascending the 5000 ft. mountain I live on, I will testify, brothers and sisters: On a four banger, there are times that it makes the difference between being able to drive in fourth gear, or being forced to leave it in second gear. In vehicles with greater power, the accel/ torque difference is far less noticeable.

In my 1LT, it is nearly imperceptible... however, just to be sure, I still cut the AC off if I happen to be engaged in a contest to see who has larger manparts vs. a Ford, a German car, or even the occasional Italian ride.

MikeSVX · 10-15-2013, 01:43 PM

When your making a couple hundred horses it isn't really noticable, but in low horsepower cars you can feel it. Long ago I rented a Geo Metro with a/c in it. I was in California and I would have to turn off the a/c to get the thing to go up some of the mountains. Also, It is a common warning in desert areas to turn off your a/c when going uphill to prevent your car from overheating. This reduces the load on the engine and, the a/c heat exchanger is usually mounted in front of the radiator and will raise the temperature of the air before it passes to the radiator if the a/c is on.

Au201 · 10-15-2013, 09:57 PM

Interestingly enough, I recently had my obd 2 port hooked up and I looked at load at idle with A/C on and off and on max. With A/C off, it was 23-25% load and with A/C on, it was 40-45% load (quite a difference!) and on max A/C, it went up to 50-55%. So I guess that means Max A/C actually does more than just put it on recycle. Lol. Also, just for S and Gs, when I dry steered the car (I know! Shame on me!) the load went up to 85% and there was a 200rpm drop for a split second. Lol. So even though it doesn't seem like much, it obviously makes a substantial load difference. As for power at full throttle, I do not know if the A/C makes as substantial a difference. Although, as mentioned, the Camaro shuts off A/C at full throttle.

Sent from my bragging iPhone using an app that encourages it.

km9v · 10-18-2013, 10:13 AM

Living on the gulf coast, I use the AC ~8-9 months out of the year. When it gets cool enough, I really enjoy not having the load of the compressor on the engine. I don't drive @ WOT very much. Does anybody have an accurate HP loss number for LS3/L99?

10-07-2013, 07:38 PM	#1
Chive Driver Keep Calm and Chive On Drives: 2013 Camaro 2SS/RS Join Date: Sep 2013 Location: Maryland Posts: 88	Top Gear turn off A/C What does turning off the A/C do in a car? What is the benefit? and is it really noticeable? I hear it on Top Gear when they do the Star in Reasonably Priced car sometimes.

10-07-2013, 07:54 PM	#2
Aequitas & Veritas Drives: 2010 Camaro 2LT RS, 2009 GTR Join Date: May 2009 Location: Kansas Posts: 2,559 View My Garage	Less movement under the hood, supposedly frees up more ponies. Does it add power you can tell the difference? Not to me, though I hardly use my ac since I hate hearing it running __________________ Build thread: http://www.camaro5.com/forums/showthread.php?t=152335 Photos: www.flickr.com/bradbeer GTR Instagram: @NoCrustGTR

10-07-2013, 10:16 PM	#4
Number 3 Hail to the King baby! Drives: '19 XT4 2.0T & '22 VW Atlas 2.0T Join Date: Dec 2008 Location: Illinois Posts: 12,310 View My Garage	In many newer performance cars, the A/C compressor will disengage the clutch. When engaged, it is HP the engine must use to turn. Alternator is the same way. __________________ "Speed, it seems to me, provides the one genuinely modern pleasure." - Aldous Huxley

10-07-2013, 11:30 PM	#6
derklug Drives: 12 Boss 302 Join Date: Sep 2009 Location: Grand Rapids, Mi Posts: 1,369	Old a/c compressors used about 7hp, new models use around 5. On a 400 horse engine, this draw is like leaving your golf clubs in the trunk. On a 150 horse car, it is like having a passenger. At wide open throttle, most cars shut down the a/c compressor to get better performance, so turning it off on the Reasonably Priced Car probably doesn't make a difference. __________________ The biggest mistakes in life come when you know exactly what you are doing.

10-08-2013, 07:26 AM	#8
dcoates18481 Drives: 2010 CAMARO RALLY YELLOW SS/RS/M6 Join Date: Aug 2012 Location: Aransas Pass Texas Posts: 565 View My Garage	i believe at WOT the A/C clutch is disengaged until WOT is let off. __________________ I LIKE TO GO FAST! Lethal Racing Night Fury Cam Kit, Melling oil pump, C5R Timing Chain, Dyno Tuned by Shawn@Lethal Racing, Vararam Tuned intake, Vararam Power Wedge, LSR Tri Ax Short throw Shifter, VMAX Ported T/B, TSP 2" L/T Headers, TSP Cat delete, Borla axle back exhaust, Innovate A/F monitor, 471.7 HP/438.8 TQ

10-07-2013, 10:23 PM	#5
menendez1293 Emerald Coast Camaros Drives: 2010 Camaro 2LT/RS M6 Join Date: Nov 2009 Location: Tallahassee FL Posts: 9,686 View My Garage	Normally speaking the AC compressor is like a leach and is stealing some power from the motor. With that being said in a car with a larger motor the reduction is far less than a little 4 cylinder. I have heard people say if takes 20 Hp but to that I say

10-08-2013, 12:32 AM	#7
sspolo Drives: 2014 Camaro SS 1LE Join Date: Sep 2012 Location: Vancouver, WA Posts: 562	I haven't noticed (or cared to feel) a difference when I have the A/C on or off on my 100hp Saturn

10-08-2013, 06:46 PM	#9
ClawSS High-tech Redneck Drives: '10 CGM SS, '02 2500HD, '09 300SRT8 Join Date: Nov 2010 Location: Lexington, KY Posts: 757	FYI ... Never run your A/C when at the track...especially the drag strip. The water that will drip can cause severe traction issues for those running behind you and may cause a terrible accident. __________________ "My friends call me Chris. Are you my friend?" 2010 CGM L99 2SS/RS - GPI SS3 VVT, BTR DoD Delete, Circle D 4c, BTR springs, Katech C5R Timing Chain, MRR-228 315/275, CAI, Elite catch-can, TSP 1 7/8" Headers + offroad pipes, Magnaflow 3", Pfadt springs, BMR LCAs, toelinks, trailing arms, cradle bushings, & sway bars w/ endlinks, Vitesse paddles, heritage grille, and an eBay splitter. Power upgrades by Race Proven Perf.; Tuning by ShorTuning.

10-08-2013, 09:17 PM	#10
ChrisBlair Buick 455 Fan Drives: 1970 Buick, 2012 1SS LS3 Join Date: Jun 2010 Location: Boston MA Posts: 5,957	Simply put- accessories driven off the engine all produce parasitic loses in power of some kind, at some time. As an aside, but related, before 1971, engines were rated in gross horsepower- the engine itself, not even installed in the vehicle, no alternator, a/c compressor, nothing. That's why you'll see old ads for the "450 hp" Chevelle SS LS6. That was 450 gross hp. The LS3 spanks it in terms of hp. The V6 Camaro makes more brake hp than a lot of V8s of the golden era of muscle. __________________

10-15-2013, 01:43 PM	#12
MikeSVX The magic smoke genie.... Drives: Jewels (2010 RJT 1SS) Join Date: Dec 2009 Location: Escondido, CA Posts: 2,294	When your making a couple hundred horses it isn't really noticable, but in low horsepower cars you can feel it. Long ago I rented a Geo Metro with a/c in it. I was in California and I would have to turn off the a/c to get the thing to go up some of the mountains. Also, It is a common warning in desert areas to turn off your a/c when going uphill to prevent your car from overheating. This reduces the load on the engine and, the a/c heat exchanger is usually mounted in front of the radiator and will raise the temperature of the air before it passes to the radiator if the a/c is on. __________________ Support Search & Rescue. Get Lost.

10-15-2013, 09:57 PM	#13
Au201 Drives: Black V6 auto 2LT RS Join Date: Oct 2012 Location: Hampton Roads, Virginia Posts: 100	Interestingly enough, I recently had my obd 2 port hooked up and I looked at load at idle with A/C on and off and on max. With A/C off, it was 23-25% load and with A/C on, it was 40-45% load (quite a difference!) and on max A/C, it went up to 50-55%. So I guess that means Max A/C actually does more than just put it on recycle. Lol. Also, just for S and Gs, when I dry steered the car (I know! Shame on me!) the load went up to 85% and there was a 200rpm drop for a split second. Lol. So even though it doesn't seem like much, it obviously makes a substantial load difference. As for power at full throttle, I do not know if the A/C makes as substantial a difference. Although, as mentioned, the Camaro shuts off A/C at full throttle. Sent from my bragging iPhone using an app that encourages it.

10-18-2013, 10:13 AM	#14
km9v Drives: 2011 Camaro SS/RS M6 Join Date: Oct 2010 Location: Beaumont, TX Posts: 421	Living on the gulf coast, I use the AC ~8-9 months out of the year. When it gets cool enough, I really enjoy not having the load of the compressor on the engine. I don't drive @ WOT very much. Does anybody have an accurate HP loss number for LS3/L99?