D-Jet: CHT and the ECU, How the ECU reacts to the CHT resistance Options

[pbanders]

As you may know, the ECU uses the CHT resistance to determine how much to increase the injection pulse width (i.e. mixture enrichment) when the motor is cold. I have some charts on this on my ECU web page, and I simulated the action of the circuit, which showed that once resistance of the CHT dropped below about 300 ohms, the ECU no longer keeps leaning out the mixture - this is the "stead state" or "fully warmed up" mixture.

I never actually verified this behavior with an ECU, so I experiemented with three ECU's this morning (037, 043, and 052), and verified that what was simulated is how it actually acts. Independent of engine speed or load, once the CHT drops below about 330 to 375 ohms, the injection pulse width stays the same.

[pbanders]

OK, to complete my comments on this - The next step I need to do is to get a CHT gauge on my car to observe the head temp through warm-up and various drive cycles. From characterization I did on some CHT's, I have a decent correlation of resistance to temperature. My goal is to see if during normal running, and after the engine is fully warmed up, to see if the head ever cools off enough so that the CHT starts richening the mixture. I have a suspicion that it does, and it may explain certain driveability issues.

I also plan to get an oil temp gauge, and to see if it helps support my theory that the "warm start" problem with the 2.0L is due to the head cooling off more than the core engine temperature, leading to rich running and poor starting until the head warms back up.