In the 7747 and 8746, what are all the values that are effected by EGR?
For guys that used to disable EGR the "old way," what had to be modified?
How does one disable the EGR vacuum drop check? I have a check valve but I would just like to just disable the test.
The reason I need this information is to use the EGR on/off temp and speed to control my single fan. I don't see why it wouldn't work. Gives me more control over the fan since I can choose the range of temp and have it turn off when I get above ~50mph.

 

The code would have to be completely rewritten, not just the tables or constants. The EGR will not turn on at X temp just because it is being allowed to do so. It has to be at X rpm and map, etc. Also, and it may not matter, the egr is actually pulsed vacuum. The ecm pulses the egr solenoid. Maybe that's why it's called a solenoid and not a switch, or not. I'm sure it could be done but only with some work other than normal prom burning. Now a simple temp switch from say a GN and a relay does wonders. It doesn't matter that it's on at 50 mph because at that speed there is much more air coming through the radiator than the fan can pull. Basically, the fan is being pushed faster than it can spin.

 

Jon, here's a thought - hook up an LED to the EGR output and watch what it does. Change some of your parameters and see if you can get it to react the way you want.

Ken

 

Probably be easier to use the Charcoal Canister Purge. Trouble is there is not on and off values so the fan will be constantly cycling on and off as the temp changes 1d. Bad thing with that is the alternator loading a fluctuating battery voltage, and injector corrrections. Probably have a choppy idle as it cycled. Most folks run at least a 3d difference from on to off temps..
GN rad fan switch is a good cure. One less thing to thermally load the ecm.

 

Why not just install a fan switch into the passenger head (like SD & MAF cars use for the second fan)? If there is no spot in the passenger head, then you could look at installing the fan switch somewhere else in the "coolant flow".

I admit I prefer ECM control, but trying to make another driver (EGR, CCP, TCC etc) involves a lot of work to rewrite the code - basically you have to eliminate ALL of the old code and then graph new code.

Conversely, if you REALLY want to get into creating a disassembly and developing Source Code, it would be an interesting project and you'll gain great insights into how the 747 or 746 ECMs work.