I notice that the A/C is constantly on if you leave the climate control on Auto. Does that make any sense for a performance car? Doesn't the compressor draw power from the engine, slowing it down? Isn't it also bad for the compressor to be on all the time, even in the winter?

Makes no sense to me to have to turn the A/C off and live in "manuelle" mode all the time?

 

Not really your compressor likes to turn to keep the fluids flowing. I have not noticed a performance drain but if you turn it off. Punch it and let me know if you feel it.

 

I agree with you. Yes the compressor will draw power from the engine as many American cars have a cut out switch under the gas pedal for when the car is on full throttle. The down side is just like my Lexus, the over all system is designed for the compressor to run so when you switch to manuel to turn it off the car gets foggy, hot or generally uncomfortable. At least this is my experience.

 

Not only do I notice more engine noise with the A/C on, but you get worse fuel economy too. Compressor slows my 944 down, I have to think it has an effect on 996 performance too.

 

compressor shuts off on wot
and its only on on auto until it reaches your set temperature

 

The A/C compressor has a clutch to cycle it on and off. Like Firehawk stated it turns off at the set tempurature. While it affect performance to a degree, I haven't noticed it much in the 996 when compared to my Hondas. I actually left it on during the last rainy AX event to help defog the interior.