EGR Emulator Circuit

[GriffMG]

Newbie here.

I'm trying to make an electronic emulator for the EGR valves on my 2007 Discovery - which has had the EGRs blanked
but not removed. Currently I have a 'dummy' EGR lashed to the battery box, which works well - but won't work forever.

I have made up the circuit here:
https://www.electronicspoint.com/threads/help-to-design-egr-valve-simulator-cheater.244193/

But I think the 1K resistor across the connectors for the actuator is making the ECU think the EGR is open
circuit - I've dismantled an old EGR and the coil on the actuator measures 8ohm on my multimeter.

Would it be safe to replace the 1K with a smaller resistor - say 470ohm or 200ohm and expect the ECU to be happy.

The actuator seems to be connected to the full ignition voltage on one side and a PWM signal on the other which
effectively 'earths' it (presumably to avoid back-emf?)

I'm reluctant to just try willy nilly in case I damage the ECU.

Any help gratefully received

 

[GriffMG]

Tried reducing the resistor down to 470ohm, but the ECU was having none of it.

Considered using the actual actuator from the broken EGR to test, but then I had a thought this morning; I'm going
to try the coil from a relay - that will have inductance and resistance and be in the right ball park, plus I should hear it at least trying to actuate.

 

[Alec_t]

I think there's more to it than simply using a coil or resistor. If I understand the other thread's OBD graphs correctly (that's a big IF, since I've no experience with OBD ), the second graph relates to the EGR position sensor; so wouldn't you also need to emulate that sensor to keep the ECU happy?

 

[GriffMG]

Thank for that, the circuit I am employing does exactly that - provides feedback as to the sensor position.

I suspect the position is only actually measured just after the engine is cut out, I can see and hear my jury rigged
EGR operate four times after the engine is turned off. It is run from fully closed to open and back, presumably to
check function and get a little messy exhaust gas for 'lubrication'. The position sensor is a simple potentiometer
(I have it on my desk here).