 D-Jet: CHT and the ECU, How the ECU reacts to the CHT resistance |
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| pbanders |
 Apr 10 2010, 02:13 PM
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Senior Member  Group: Members Posts: 939 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805  |
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. |
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| pbanders |
Apr 11 2010, 01:32 PM
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Senior Member Group: Members Posts: 939 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
Re: realred914's comments - What I'm learning is that determining the combustion chamber temperature of an air cooled motor isn't a simple thing. Add in that the cylinder is cast iron and the head is aluminum, with different thermal properties, and it makes it worse. I agree oil temperature is a poor indicator, too. And for various reasons, I don't think placing a sensor on the outside of the cylinder is any better.
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Posts in this topic
pbanders D-Jet: CHT and the ECU Apr 10 2010, 02:13 PM
pbanders OK, to complete my comments on this - The next ste... Apr 10 2010, 03:34 PM
realred914
OK, to complete my comments on this - The next st... Apr 10 2010, 08:41 PM McMark Cool stuff! Thanks for sharing your experimen... Apr 10 2010, 08:04 PM Tom Thanks Brad for all of your research, you are doin... Apr 10 2010, 08:45 PM sean_v8_914 funny/interesting that you would be observing this... Apr 11 2010, 01:41 PM 914_teener This is really interesting stuff. I am a real beli... Apr 11 2010, 04:27 PM |
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