EGR Keep

[Desert Patina]

So here in Arizona they visually inspect for the EGR, so if I want to drive it on the road I need to keep it.

I want to go with a standalone ECU (favoring Speeduino), but they don't control the EGR. I did see some talk about it in the forums, they suggest at a certain RPM and TPS reading, to open the EGR.

But it looks like the EECIV works differently. It simply shuts off the EGR at full throttle for a bit more power, and otherwise the vacuum is what opens and operates the EGR.

That would be fortuitous, as that would be very easy to program into the speeduino. And I also hope that would be easily reflected in the tune as well, just anticipating the EGR to be open under most operating conditions.

Does anyone here know for sure if the vacuum operates the EGR, only to be shut off at WOT by the ECU?

[MikeFleming]

The EEC operates a separate solenoid that controls vacuum to the EGR valve. When under boost, there's not much vacuum available so the valve does not open. There is also a one-way check valve in-line to the EGR diaphragm that prevents it from rupturing under pressure.

The EEC opens it on a schedule depending on temp (not open during cold phases) and only at specific part-throttle conditions. You can easily test it on a hot engine by slowly opening the throttle form closed throttle idle. With a small finger in the opening on the engine side, you can feel the valve open (on a normally functioning system).

The EGR system helps a bunch on to reduce part-throttle pinging so it's a good thing.

[Desert Patina]

Thanks for the reply. I believe that confirms my suspicions.

The vacuum actually operates the EGR, and the ECU effectively shuts off the EGR when the engine isn't at operating temperature, or is at idle or wide open throttle. The ECU never really opens the EGR, it turns on a solenoid that cuts off vacuum to the EGR denying the vacuum the ability to open the EGR.

The only reason establishing it is an EGR shutoff rather than a full driver determining how open it should be (etc...) is important is...

1) I think I can replicate or even port over shutoff logic easier
2) I think the ECU map would "learn" or accommodate for when the EGR is open without having to build a specific "if EGR open" conditional map, or some other kind of direct logic set of conditions and maps

[MikeFleming]

The EEC-controlled solenoid controls vacuum that OPENS the EGR valve. The valve closes from spring pressure when the vacuum is low.

It shuts off at closed throttle, not just at idle. So it's closed during coast-down.

[Desert Patina]

Many thanks! I absolutely appreciate your guidance and wisdom here.