twopointfivebar

I have an '04 TSX, and I still notice a dramatic power loss when my A/C is on when compared to my old Corolla.

Has anyone done a dyno test of any car with A/C on and A/C off?

carguyrob

I have never done a dyno test, but the A/C is a much larger drain on 4 cylinder cars than 6 cylinder cars. When I turn the A/C on in my TL-S, I can barely (almost not at all) feel a difference. When It turn it on in my S2K, it feels like the car is towing a trailer!

fsttyms1

When WOT the AC should cycle off so it would be hard to dyno it accurately

SuperTrooper169

iTrader: (2)

PortlandRL

The Santa Fe hates A/C, especially up hills. That 2.7-liter V6 is overworked as it is (3700 pounds to pull around) and you can feel it bog down when you switch the air on. Not as bad as my old '93 Toyota Previa. That thing could barely go 40 mph up Burnside with the A/C off. Never tried going up it with it on...

CG2PROJECT

A lot for me..

Since the SC is run on the pulleys.. I can feel a HUGEEEEEEEEEEEEEEE difference.

I'll try to get a before / after dyno when I go back for a check up tune.

Street Spirit

Not enough for me not to use it, so I've never really thought about it.

nokiaman

OT question: The general rule is to lift up all windows to allow proper circulation when A/C is on, but does that concern the sunroof as well? Some friends usually object and tell me to close it all but I feel like it's somehow different.

Trackruner228

iTrader: (1)

On my car you cant tell a difference AC on or off. Dont some cars switch the AC off automatically when WOT?

ChrisQ1980

I can hardly tell it's on in my TL-S, but I still follow the windows down for city driving, and A/C on for highway driving for fuel consumption. If I have to pass, or want to accelerate briskly I hit the "AC OFF" button. I'm sure it's a few HP difference.

Ken1997TL

Doesn't feel any different on any of my cars

Costco

I can crank up my A/C full blast and when cruising or giving half throttle and I won't feel ANY difference at all! It is very evident in 4-cyls though, in the Civic it felt like I downshifted, and in the Integra it was like I had another person in the car as soon as I turned on the A/C. In the TL it was a very slight SOTP feel, nothing major though.

and I wanted to make that my avatar!! Too bad I don't know how to compress/downsize gif files

RaviNJCLs

iTrader: (4)

Felt a bit of a difference with the CL and the Maxima. I have not really noticed a lot of power loss with the I35 or the Pathfinder. This is actually one of the reasons I will not likely own a 4 cylinder car.

Sly Raskal

iTrader: (1)

Some cars do. I wish my CL did or maybe it did but I never noticed. When I rented a grand prix I was surprised that it did. I wish more cars had this feature.

Sly Raskal

iTrader: (1)

Surprisingly, even for 4 cylinders and with the AC running, my avant has some decent pick up.

Dem1K

iTrader: (1)

How about gas consumption? How much extra gas is burned if you use your A/C constantly, which I am doing right now since it's so damn hot out? Is it a considerable amount, or negligible?

FiveLiterCheater

I just leave it on auto @ 74* all the time...unless the windows are down. Car doesn't feel any different if its on or off

Costco

If you use it all the time, probably 1-3 mpg. I would think it probably has a bigger effect on 4-cyls also with regards to mileage.

I'd also like to take this opportunity to say that contrary to popular belief, using your A/C with your windows up does not save gas compared to windows down.... even at freeway speeds

FiveLiterCheater

Why would you use A/C with the windows down? Theres no real point IMO...If its nice outside, roll the windows down. If its hot and humid...windows up, AC cranked. Maybe those in between days, but around here its one or the other. I hate MD

Costco

I meant windows down, no A/C need to be more specific. Nobody would someone turn on the A/C with the windows down, aside from when the car is still warming up and the air coming out of the vents isn't cold yet

In the DMV booklet or something it tells you to turn off your A/C and roll down the windows at slower speeds, and roll the windows up and turn on the A/C at highway speeds. That doesn't always work.

ThermonMermon

wow, really? OCD much??

ChrisQ1980

How is that OCD? I'm manually turning the A/C off when I want to "punch it" or give moderate acceleration. No need to put extra strain on the motor.

phile

^ I turn the A/C off too when accelerating. Cause in those cases I definitely feel the loss of power. But once I'm moving, I dont' feel the loss anymore once i turn the A/C back on.

charliemike

Everything should be closed. The sunroof creates drag because of the wind coming into the opening. That wind coming in has to displace whatever air is inside the car or you'd be crushed by the compression.

So, using my deductive powers and TruLogic® reasoning prowess I'm assuming that the outside air is forcing the cooler inside air out through all the seams and holes inside. The recirculating feature of modern HVAC systems in autos is probably far more efficient than blowing A/C into a car with open windows/sunroofs (is it roofs or rooves? LOL)

Or something.

charliemike

Mythbusters tried to determine that and failed miserably by screwing around with their test conditions so much that their results were pointless.

Windows up or down is every bit as contested as Mac v. PC and with just as many anecdotal references and as few un-scientific results.

To categorically state one way or the other without someone like NIST doing a test or a published scientific analysis deducing one is better than the other is intellectually dishonest.

Mokos23

yes i feel a loss of power, but i'd rather feel comfortable driving the TSX instead of sweating like a dog. the same can be said when i drove my folks MDX, i felt a loss of power too. i guess honda engines and a/c don't mix well together??

but, when drove my dads G35 with the a/c on and the fan speed was at maximum it didn't effect performance at all. i guess nissan knows how to keep the engine performance there while the a/c is on.

DAYTA

I wonder if upgrading the alternator will prevent the A/C from robbing any power ...

CLpower

I don't know of any vehicles that really don't

CLpower

no

fsttyms1

And when you floor it in the TL it turns off automatically so there is no need to turn it off.

is300eater

I don't feel any difference with the FX45... can't speak for the guys with the FX35's tho... BUT, with that said... I hate using A/C because psychologically I think there's power being lost... so I don't use it unless it's scorching hot or if I have people in the car

phee

iTrader: (5)

does my 99 do this? ive been at WOT and still felt cold air coming in

FiveLiterCheater

I think that 4.5L V8 can handle a little A/C

dallison

out of the 20 or so cars that i have owned, all of them showed some form of lag with the ac on.
Obviously the 4 cylinders have a decent amount of power taken away.

a way to tell if it does make the motor work a little harder is to drive at a normal speed or when accelerating with the ac on and turn it off. for those who know, it is obvious.

you really don't lose much in the way of mpg with a 6 or 8, but i am unsure of the 4 cylinders

myron

iTrader: (4)

mine too, mine doesnt do this cuz I can feel cold air coming in just the same and my car feels slower when accelerating. But I use AC, maybe 3-4 days a year so I dont really care

twopointfivebar

not to be a noob, but what does WOT mean? And OCD?

Back to original question, has anyone seen or test a car on a dyno while having the A/C put on lowest temp?

Will Y.

WOT = Wide Open Throttle

OCD = Obsessive Compulsive Disorder

I haven't done any dyno runs so no help with that.

mrmako

I live in a pretty hot place year round and use the A/C a lot, so let me share my

The reason for the power robbing has nothing to do with electricity. The compressor that is taking the hot gas (R134a in most cars) and compressing it is the culprit. The compressor is driven by one of the belts used to do various things in a car, and that takes work.This is generic, as most cars have one belt, some more than one.

The crankshaft provides the motion (via a pulley), and this turns a belt that connects to the fan, power steering pump, and the alternator. Where you are losing the power is the compressor turning on, and creating more of a drag on the belt. It just takes more effort by the engine to overcome the extra work. There is a clutch on the compressor that engages and disengages as you temperature in the car gets to where it needs to be. With a 300 plus HP engine you may not notice this, but a 4 cylinder making about 140 HP will be overworked.

The OP asked about a dyno with and without A/C. I've never done that, but if you are in need of every ounce of HP your engine is creating, then shut off the A/C.

fsttyms1

yes your car does this. In short acceleration runs where it does get shut off there is still enough cold in the system for it to blow cold. Turn it to max setting and floor it all the way up a on ramp. It will turn off, you will feel it get warmer.

zguy95135

I can definitely feel it the loss in power in the TSX if I try to accelerate hard with the AC going.