Cobb AP Fan tuning
 

Okay, so I know how to adjust the fan on/off, hysteresis, etc. in ATR but after searching I can't seem to find what controls how long the fans stay on after the car is off? I have realized over the years that some RX-8's fans stay running for quite some time after shutdown while mine even through different fan setups always stay on for a few seconds and then shut off.

For example, I have paid attention to temps on my RX-8 and Hoss-05's and there doesn't seem to be any rhyme or reason to it. Sometimes his will stay running for a minute or two while mine will shut off right away after shutdown even when our temps are similar and our settings on the tune are the same for teh fans..

It's not a big deal, I just wonder if anyone knows if this can be tweaked or if it is not possible to tweak.

Not adjustable directly. Might want to play with the A/c on or off to see if that makes a difference as to how long it runs.

Do you have a stand alone coolant temp sensor?

Hmm, didn't think about that. No I don't have a stand alone coolant sensor but I think I am going to get one.

I thought you were going to buy the aftermarket fan controller?

I did, I went with the FAL unit, I'm waiting on it now. That is what made me wonder even more since it will allow you to adjust how long it runs after shutdown. I was just wondering if it is possible in ATR.

Not directly

If you want to experiment, swap the coolant temp sensors between the two cars and see if the behavior moves as well. I suspect such a thing is caused by relatively minor variance in the main sensor. Also, it could relate to differences in the coolants used.

Interesting question, the manual says the conditions are:

I've found the following from the rom. Each condition has a hysteresis, and I think the switch off points will force the fan off once reached even if another switch on value is exceeded. Most have a hysteresis value as well.

IAT switch on temp: 40c, 3c hyst
IAT switch off temp: 32c, 3c
ECT switch on: 105c, 6c
ECT switch off temp: 85c, 6c
Catalyst temp switch on temp: 950c, 50c

I think these are the conditions that it looks for to determine if "engine compartment temperature is high."

There is also another subroutine that seem to look for 110c and a voltage range from some unidentified sensor, but I don't understand it yet.

Anyhow, cat temp is approximated from the rear o2 heater, it seems to be set to 1000c during startup. I'm not sure if it stays set like that if the sensor is missing, but it might be worth plugging it in and leaving it dangling to see if that has any effect (assuming it is gone.)

Good info oltman, thanks.

tripped across this while searching for something else

https://www.rx8club.com/series-i-do-yourself-forum-73/diy-flex-lite-variable-fan-speed-controller-123326/

I am not sure which one of the three fans, seen in the Cobb software, controls the parked/off fan....

Fan – ECT Hysteresis

The amount of coolant temperature reduction the ECU must see before it turns off a fan, after it has been turned on by the ECU.