I have a couple questions regarding the EGR valve.

I'm curious to know if the EGR valve shuts off above a certain rpm. It seems that if I highway cruise below 3000rpm I can get between 27-30mpg but if I go past that threshold the fuel economy drops down to around 23-25mpg.

Does the EGR valve shut off above a certain rpm?

Thanks in advance!

Jon

 

The service manual shows that the input the ECU uses to control the EGR solenoid are:

coolant temp
maf
TPS
crankshaft postion sensor

I'll see if I can find anything regarding limits.


Eric

 

Thank Eric.

I assume that some of those conditions could be altered to keep the EGR valve open at higher cruise speeds and increase our fuel economy.

Jon

 

Curious... At 3250PRM, which is 75MPH, I can get around 29MPG... if I'm "behaving" myself.

 

MAF and TPS would seem to denote load as well as TPS, both or which configurable in the Open loop tables. You could delay the drop in to open loop and keep the EGR open theoretically if you wanted to.

 

Just as said above, but to be more general the valve is almost always opened at light load.

For more detailed operation you need the diagram of the system and the solenoid input conditions (above)

 

It can also be that the power required to maintain the speed over 3000rpm(drag) is cause of increased fuel consumption.

 

Yep, I understand that but the difference in mpg is huge for just a couple hundred rpm increase. I mean the rapid reduction in fuel economy that seems to happen at some threshold has me thinking that the EGR valve is shutting at this point and that is why the mpg drops severely, about a 15% reduction in fuel economy.

This also would correlate with the percentage of EGR that is normally recycled back to the intake charge. Now there are many factors that come into play with the limits of EGR but typically 15% is the most EGR that can be back into an engine running on gasoline. Above that number you start seeing your hydrocarbon emissions going through the roof because of incomplete combustion & random misfires.

What I'd like to do is explore the limits of EGR by either going to a stepper motor driven EGR valve, like those on other Mitsubishi vehicles and having the factory ECU modified to control it. There are some worthwhile dividends to be paid by getting better control of EGR.

I know it's not a Prius but we could all stand to get a few more miles out of a tank of gas.

On a side note, those who run E85 could really boost their fuel economy being that you can run upwards of 40% EGR without pissing off combustion.

Jon

 

Interesting concept, it looks like our cars have a simple EGR system. I don't know if the open loop tables have anything to do with EGR, but maybe raising the load threshold to stay in closed loop at a higer load may keep the egr on over 3k rpm.

toyota manuals always seem more educational than others http://www.autoshop101.com/forms/h61.pdf

 

This should provide the info to allow you to figure out the drop in mileage:

https://www.evolutionm.net/forums/sh....php?p=5474289

You might have to do a little logging to figure out exactly what's happening.

 

Oh damn that is a good thread that I haven't read until now, you guys are brilliant . I can't wait to see how this clears up my friends EVO.

NOTE TO SELF: READ ALL ECUFLASH THREADS!