I only turn off the radio because I don't want to hear it when I start the car and with the 997.2 it comes on anyway.

I do have a question though ... the track guys might know this .. do you race with the A/C on or off ? The old school mentality was that the A/C off gives a better edge.

 

I turn the compressor off (ECO button). No reason to be using power to spin the compressor instead of the wheels

 

never crossed my mind. I turn my radio down so that it wont be loud next time I get in the car, and this habit came from driving my parents cars when I was younger. I leave everything on

 

Ha - I was just thinking about this. On my wife's Acura MDX, the AC Compressor just went out. Cost $1600 to replace. The service guy said that it does reduce the stress on it, if you turn it off before you turn off the car and only start it back up when the car is on.

On my C2S i just leave the climate control where it was - dont run it off. Maybe I should.

 

interesting..guess i should turn it off...

 

No, for Heaven's sake, you should not. Not unless you really enjoy that feeling of running down a start-up and shut-down checklist like an aircraft. Since three quarters of the world just turns the key to shut down, do you really think an engineer would allow the start-up process to damage the car systems?

And I can't believe some shade tree mechanic kept a job at Acura long enough to dispense such silly advice about the compressor. Did he have any thoughts on why turning over the engine with the starter motor would somehow stress the compressor? No, never mind.

Gary

 

I do turn off the AC compressor and do it 2 to 3 miles before stopping for the day. I do that to dry the vent plumbing and prevent fungus buildup.

 

I turn off my Air Conditioning before turning off the car. I can't tell you why, I just do it. I remember someone sometime a long time ago back in the day telling me it was bad to leave your A/C on.

In my Audi, for example, if you leave the A/C on when you turn off the car, the next time you start it, the climate control doesn't actually turn on for about 2 seconds after the car starts. That led me to believe that Audi engineers intentionally made sure it wasn't running when the car started. So....maybe there's something to it.

 

I am not answering about racing in this post - only about having an edge or not in normal driving. On 996s and 997s with drive-by-wire throttle, the engine has a torque oriented function that will provide you with the torque needed according to how much the throttle pedal is depressed, independent of power robbing accessories like A/C, for example. The ECU memorizes the power requirements of the accessories throughout the rev range and compensates for that so that the driver gets always the torque asked for at the specified throttle input. I don't see how turning things off will give you an edge on cars with this kind of throttle setup. By the way, my source is Paul Frère on "The Porsche 911 Story" of which the edition I own includes the 997 and 997 S.

Now, on older cars I can feel a difference when the A/C is turned off, specially in my previous 944s and 951 and on my current '87 Carrera for sure. On my Carrera S, I've run full throttle accelerations both with the A/C off (in Winter and Spring in FL) and with it on and haven't felt the slightest difference.

 

That does make sense - I do recall that I have owned several cars that cut out the compressor at WOT. I have not noticed it on the Porsche, but it sure sound like it should be doing it. I will still hit the ECO button while tracking, but now more for a matter of principal.

 

The only reason is the one ADias provided. If you live in a moist climate, you may benefit from drying the filters before shutting down. I can't remember having a problem with that in Alabama or Ohio, but I freely admit I probably wouldn't have noticed unless it rose to the level of a noticeable stink. We were in the service with two kids and driving nothing but a beater in those days. It would have been hard to smell much over the stale french fries and old taco wrappers that kids generate spontaneously in such cars.

That precaution is akin to dropping below turbo speed in some cars for five minutes before shutdown so the turbine can cool and avoid seizing. But neither means anything when you start the car. We have been designing devices with staged wake-up for almost as long as Ferdinand Porsche designed cars. Any reputable modern car has relays on separate power buses that group devices by their sensitivity to such things as the start sequence. Notice that you can put the key in and your PCM will boot. (Though mine doesn't have the Porsche logo some people describe. Pity.) As soon as you move the key toward the start position, the bus the PCM is on will shut down and it will stay that way until you release the key. I can't imagine a way to damage the compressor because its clutch will be disengaged as well, just like the PCM.

These aren't hobby cars. You will rarely find something in an old drive's tale that Porsche engineers haven't considered and included in the design. I'm tempted to say 'never' since Porsche are actually consultants to auto manufacturers worldwide, most on a non-disclosure basis. Their staff at Zuffenhausen probably have the widest experience of all types of cars and all operating conditions of any single engineering organization in the world. That's part of the reason I kept looking forward to buying one of their named productions when the rest of my life settled down and I could.

You know those little "horror box" warnings in the manual? e.g. "DEATH AND DISMEMBERMENT AWAIT! Never stick your arm through the steering wheel to scratch your toes while driving!!!" Well, if they don't have a warning box that says "Shut this off before shutting down the engine" then you have nothing to worry about. And I've read my manual from cover to cover without seeing anything of the sort.

Don't worry. Except maybe about moss on your toes, as ADias says. Is it that humid in the Bay Area, ADias? I don't remember noticing forty years ago at school, but of course we were driving an MG at the time and lesser sensations tend to disappear in the background. Our 'conditioning' for the air was wing vents.

Gary

 

Yes, even in low-humidity climates like the Bay Area it is very easy to grow smelly bio stuff in air cooled vent pipes. Many people notice that.

 

yeah same here i always turn it off. Heard something about a long time ago and just did it ever since. I think it makes sense but i guess i dont really know.

 

I'll be darned. That's a useful tidbit. Had anyone asked I'd have expected the following day's usage to raise temps enough to burn off any wildlife. Or... are we talking about the cold side plumbing? Isn't there a dryer in the system for that side?

Gary

 

Like some others on here I turn off heat or a/c depending before turning off the car. The radio however does not get turned off. Not sure why I do that but that's the way it is!