One thing about the EGR system that has always bugged me, is how does it know when to operate and for how long.


I know it is only an emissions control device to keep the formation of nox gas by intoduceing spent exhaust gas into the intake to lower combustion temps. Under normal conditions you never even know when it operates. Only when it malfunctions does it affect driveability.


With no sensors of any kind in the exhaust stream how does it know when to open and close?
Nox forms at a specific temperature range, with no sensors to measure exhaust temps or composition.
The only thing I can think of is time run. So many seconds of run time combustion temps would reach the level of nox formation and it opens the valve.


Anybody got a better idea speak up.

 

Ebp, iat2, vgt dc#, map, load calc, app%, rpm icp. Im sure there are others but off the top of my head these would all effect it.

 

I can buy that except how do those values relate to the temp that nox gas forms at?
I am fully willing to accept my thinking may be flawed on this.

 

Its an engineering mathematical mess.

 

Now that I can most definately buy. Proprietary info strikes again.

 

The PCM is a very busy device. Software determines operating charastics and output to drive the EGR valve can be very complicated, for a simple example in English, a single command may read like:
If the throttle position is greater than "x" and load is greater than "y" or rpm is less than "z" and EBP is less than "q" then EGR position = 123, it may have any number of variables and there can be a virtually unlimited number of these commands, recalculated and implemented many times per second.

There is room in The PCM for most any possible combination of operating conditions the engine may see. Once the engineering department maps the conditions under which they want the valve to open its not a big deal to write as much code as necessary to keep NOx below a certain threshold on the test mule engine. These test results shape the software we end up with in our trucks.

It's pretty amazing to think of all that's going on in the PCM and other logic devices on a modern vehicle.

 

I agree on the complexity but unless something has majoly changed the EGR sole purpose is pollution control. The prevention of undesireable green house gases from reaching the atmosphere by not allowing it to be produced in the first place.
That has been it's only real job since EGR was first developed. The cat converter takes care of the rest. Also an emmissons device.

 

And Thank Cali4nia for that Danny, re-burn the Exhaust , I would like to sit in the same room as these guys and let them smell my burned Gas

 

You would want to be in the same room as the likes of Jerry Brown???
You are crazy.

I wouls not want to bee in the same room with the guy. I might catch
something from his hair-brained ideas. Like… Revolt.

Sean

 

I have a scan tool that allows you to see when the EGR valve opens and closes. I used this before I had my EGR delete...I found that the EGR valve was really only open when the truck was at idle or when you were on the highway under light load. In any driving situation when you started to "hammer down" the valve would immediately shut.

 

Thats interesting, that makes sense to me, i would think the engine pollutes the most when idling and not working hard, lack of heat. I'm in the middle of an engine rebuild (injector tip broke off), i took the intake to a friend of mine thats a senior master tech at a ford garage to run it through the heated parts cleaner they have and he said my manifold was quite clean compared to most he has seen, its my wifes truck in sig and the truck gets very little idle time but does get a significant amount of light load hwy miles. i'm not disputing what you said, just stating my findings. I have often wondered how much and when the EGR is open and recirculating exhaust gases.
Thanks for the info!

 

In another post where I'm trying to determine what the parameters are for the egr valve, I monitor mine with my Dashboss and it doesn't "activate" after cold start up when idling until I start to drive it with some load. If I just sit in park, even with feathering the throttle, nothing happens.
Once moving, it only takes a few seconds to activate.
I'm not sure there's logic here, it seems to have a mind of its own!

 

I've been monitoring my EGR lately on my SGII, due to some black smoke issues. One thing I noticed was, the EGR doesn't start to move until the engine temp has reached 150°F. Ironically, that's when my truck starts blowing black smoke.....

 

About how long does it take to do an EGR delete? Something your average guy could handle alone?

 

Both the egr valve and egr cooler delete can be done with average mechanical skills by your self.