Idle RPM settings - how do they work?

[Vlad Soare]

Hello,

I'm looking at the Engine/Idle/RPM tab for my 2020 Euro-spec Mustang GT, manual gearbox, and here's what I see:

Idle.png

I don't have any issue, nor do I plan to change anything, but I'd like to understand what all this means, how the actual idle speed is determined based on all these various values. Because it seems to me that what I'm seeing here isn't exactly a perfect match for what the car actually does. I mean it is, kind of, but not 100%.

Immediately after a cold start the idle speed is 1250 rpm, exactly as specified in the Startup box in the Cold section. Perfect.
Immediately after a warm start the idle speed is 1000 rpm, as specified in the Startup box in the Warm section. Perfect.
However, once the engine has warmed up, the idle speed goes down to 625 rpm. The only place where I see this value is in the "Transmission Based Setpoint" section. So the "Temperature Based" section seems to be ignored from this point on.
Then there's another section, "Climate Control Setpoint", which doesn't seem to be used at all. I have never seen an idle speed as high as 1400 rpm, be it with the engine warm or cold. What's the "heater performance cold" or "heater performance warm" supposed to mean? When are these tables used? When exactly is the idle speed supposed to be 1400 rpm?

I'd like to understand what the general idea is. What's the algorithm that the ECU applies in order to decide which table to use and when?

Thank you.

[Vlad Soare]

Also, the "Cold" tables of the temperature-based setpoint are supposed to be used as long as the ECT is below 48.9 degrees Centigrade. And the "Warm" tables are supposed to be used when the ETC is higher than 71.1 degrees Centigrade. But what happens in between? Which table will be used if I start the engine while the ECT is, say, 56 degrees?