Quote:
Originally Posted by jmcc
It will depend on the vehicle and technology available, but EGR is generally switched off at cold ambient conditions because of the increased likelihood of misfire. So, my thought (not tested I should add) would be to trick the ECU into thinking its operating at low ambient temperature. Since the IATS generally works on a resistance basis, it should be possible to adjust this feedback.
I don't have more info than that at the moment, but if you have a scan tool and can see both EGR and IAT, you should be able to find out at what temperature this happens and using a multimeter measure the sensor response to temperature as a resistance. If you can then supply an adjustment to this resistance, making the engine think it's at cold ambient, then it will turn off EGR and I expect, advance the timing.
As I say, not tried it but think this may be easier than sending dummy MAF signals.
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I haven't looked into the cold ambient temp deal and EGR shutoff bit, so I'm not sure either way on that. I can say however that when you simulate lower coolant temperatures and lower intake air temperatures the engine will generally go more advanced and add more fuel to reduce cold startup issues. If the fuel quantity remains high during normal operation due to the reported lower temperatures, there goes any FE benefits.
We need to find a way to change the right couple of parameters that won't domino other things and send us in the wrong direction FE wise. I still like the idea of retaining EGR functionality during cold startup(to reduce warm up times). I have received some temperature switches and a couple 12 volt relays that I plan on using to modify my EGR simulator circuit to create "dynamic" EGR functionality.