Motor_Mouth

Can you guys help me settle a bet?

My wife recently declined to purchase a brand new Mazda CX-3 because the AC compressor disengages at full throttle. This means every time you hit the detent on the floor - which is a lot in a 155hp car that weighs 3000lbs - the ac blows warm.

I posted on a Mazda page asking if this could be disabled since my wife really wanted the CX-3.

Everyone on that page assures me that all cars do it. Well, I know for a fact that my F-150 doesn't. I'm also certain my 997 doesn't do it.

They were equally as certain that the 997 does.

What's the consensus? Any idea if the 997 does?

I would bet the 997 has a high rpm cutoff because most compressor manufacturers don't want you spinning their compressors 7000 rpm, but that's not the same thing. I use full throttle a lot but I hardly ever get to redline. Like, almost never.

jhbrennan

Check your owner's manual (about page 140) -

General instructions for air-conditioning
compressor
– Can switch off briefly if engine is under an extreme
load to ensure sufficient engine cooling.

Philster

It's pretty common, with WOT being the easy off trigger. Some cars might monitor other conditions, such as coolant temp/load/whatever, but WOT cut off is getting to be the norm.

https://rennlist.com/forums/997-foru...elerating.html

Mazda note: Cars have more realistic powerbands now, and give them 7 or 8 speed trannies and they do less full throttle work than you think.

.

the_buch

I doubt a CX-3 would be driven at full throttle for more than 30 seconds at a time in which case there should be enough residual cool in the AC system that you probably wouldn't notice it??

Motor_Mouth

On the one we drove, the air got hot immediately. It was 105 out. The poor salesguy in the back seat was dripping sweat after a 15 minute drive. My wife is at that age where temperature matters a lot. If you know what I mean.

Bruce In Philly

My 2009 manual denotes: "air-conditioning compressor....... Can switch off briefly if engine is under extreme load to ensure sufficient engine cooling"

I read somewhere that it does shut off during hard throttle but I can't confirm this. Most of these on/off switches including fans are now computer solenoid controlled now and not by dumb on/off switches.

Peace
Bruce in Philly

the_buch

Surprising but obviously true. At that o/s temp I guess there's no residual capacity in a system like that.

Quadcammer

My understanding is that these are variable load compressors, I.e. there are always running, there is no compressor clutch. They may however use electronic wizardry to modify load depending on driving conditions.

gpjli2

Your wife must have some heavy foot

gpjli2

I can confirm this.

nwGTS

Think about how fast you would be going after 30 seconds at WOT even from a stand still. LUDICROUS SPEED. I would guess 10 seconds in a fast freeway merge would be the MOST. Just funny to think about a CX-3 at WOT for 30 seconds. Danger to manifold

Louis de Funes

I never noticed this before but since moving to Florida my Suburban does this. On the Porsche I have not noticed it yet.

Rikky001

My opinion; the ambient temperature and humidity you are currently facing is just too much for the ac system to handle. Part of the environmental BS all systems and equipment installed gets cheaper, lighter, etc... It might be possible that the safety system just shut dowm the compressor as the pressures in the system get too high due to the very high ambient temperature. The new(er) more environmental refrigerants used result in much higher pressures in the system as before.


Here is South Korea we are currently in the middle of the rain season, temperatures 38 degrees C and 95% relative humidity. The tiny cars suffer as the engines are just too small to turn around the compressor. My 997 4s keeps it cool but I am not racing these days, it is just too hot. My Ram 1500's ac is working fine too but you feel that the RAM has more difficulty to keep a constant temperature under these hot and humid conditions.


I would rebook the test ride if you like the car and see if the ac can cope when running the system not in auto mode. Yes, the system should work in auto too but if it is that hot and humid, it might just not work as it is not designed for these conditions. The cutting out of the compressor at hard acceleration is just to provide the extra power to propel the car. It was not an issue with the 6 liter V8 engine, but needed for the tiny engines we see today. On average a AC compressor can take between 5 and 8HP, with the newer refrigerants it is even higher!

Misdirection

I forgot my 997.2's AC was on once before going onto track on a hot day. I didn't even realize the AC was on until I came off track because it was not blowing cold air until the cool-down lap.

Motor_Mouth

This is an expected answer from someone living in Vancouver. I'm sure it follows the same logic trail used by the manufacturer when they decided on this idiotic plan. In fact, in Houston, it's at or near 100 degrees F throughout most of summer and traffic on the freeway routinely hits 80mph. Add to that the fact that all the businesses are on frontage roads and you'll find yourself constantly under full throttle in a CX3 and, if that's not enough, the residual cooling effect does nothing to help the car cool down when it's been sitting in a parking lot all day and is 140 degrees F inside.