No confusion re the butterfly's purpose. Any old school diesels I have worked on never had one, as to kill a diesel you just shut off the fuel & the engine winds downs nicely. No chains to worry about on most modern engines.

I assumed the actuator was on/off like a solenoid due to the spring return. Why you would use a PWM strain motor instead of a stepper motor is beyond me, possibly for its instant open capability as stepper motor would be slower. Again the whole Euro6 Diesel config is just a fudge & achieves nothing in real terms.

I thought the new SDV6 only uses a low pressure EGR & the takeoff is after the DPF, supposedly to reduce soot ingestion, but does not appear to work well, so I'm working on an EGR gas flow filter idea to capture most of the soot. Apparently the manufacturers know that the soot ingestion kills the engine, why both filtering intake air then allowing hard carbon particles straight in from the exhaust ? Research shows that 5-20um are the worst & that is a lot of the soot that gets ingested!🤷‍♀️ They knew it would be a problem, but decided NOT to add a fine particle filter to the EGR gas circuit, because it would require regular maintenance, by that they mean owner accessible so it can be emptied & reverse flushed. So I'm working an idea for one of these.

 

Just to pipe in on DPF internal gutting, EGR blanking and remapping.

MOT testers currently do not look for these, but there are changes coming supposedly to actually test for the emissions systems being there and working as intended.

it also invalidates insurance (although you could get another remap and remove the blanking, but you can’t refill the guts of the DPF easily) and in the event of an accident would be classed as non-road legal vehicle, which could lead to numerous diff types of prosecutions.