KahnBB6

iTrader: (5)

I'm genuinely clueless about this one and I started thinking today:

Some modern car A/C systems automatically and temporarily shut off the A/C compressor at high rpm both to increase available engine power and stop any excessive pressure buildup in the system.

Do our SC300's do this as well or is the compressor clutch on constantly throughout the entire rev range, even at 5,000-6,000+. I have honestly never noticed one way or the other.

Most of the time I have shut off my A/C when I know I will wind up the engine but not always.

No issues, I'm just genuinely curious about this if anyone knows. Thanks!

Ali SC3

iTrader: (10)

I wondered the same thing, the jury is out but I think it turns off when it goes to open loop more or less (maybe based off tps) because normally the A/c will affect the afr's without 02 correction. there was debate that it started on the mk3 but haven't seen proof either way. will check the manual for actual info.

ISFFUN

iTrader: (4)

I'm fairly certain it's always running, you would hear the clutch clicking on and off, right?

Ali SC3

iTrader: (10)

it is possible our cars don't even have that feature stock, but when I had an aem v1 in my car I had it set to turn off the a/c at 1 psi of boost and I don't recall being able to hear it clicking on and off. Definitely a neat feature but its not hard to turn off the a/c yourself if you will be pushing the car, it will get into boost faster without the a/c even though the standalone will turn it off in boost if you forget to.
I looked through the manual and did not find anything like that in the a/c section. there is a a/c lock/unlock based off rpm of engine and rpm of a/c unit and any more than a 30% difference it turns it off but doesn't say if that happens often or is just a failsafe if the compressor locks up and fails, so yeah still back at square one not really sure.

grumpi300

iTrader: (1)

It turns off. I looked at the wiring schematic when my a/c wasn't working and the ecu powers on a relay that powers the clutch. When going full throttle, or above a certain rpm, the ecu dezengages the relay until the rpms drop back down. I read it somewhere on all data to.

KahnBB6

iTrader: (5)

^^ Ali and Grumpi, thank you! That's enough confirmation for me. It's hard to tell if the compressor is automatically disengaging over the sound of the engine but it seems it does. And we got this feature on early 90's cars

Thanks, guys!

Ali SC3

iTrader: (10)

best way to tell would be to get a passenger on a really hot day to hold their hands in front of the vent and get on it. when the a/c kicks off you can usually feel the difference for a couple seconds.

KahnBB6

iTrader: (5)

^^ That's an excellent idea. I think I'll try that soon.