As you suggest the elevated temperatures may not be only from EGR. Looks like the EGR is being operated more like an on/off device instead of modulating. This would be one way of reducing the soot build up as I would expect build up to occur more during the partial opening than full open or full closed.
The elevated temperatures may be by design to reduce fouling of the intake from EGR, not so much for the DPF. I suspect the eleveted temps are from late power cycle fuel addition, which could be a cause of the reduced economy some are experiencing.
Regardless, very interesting for us engineer types.
Last edited by KeithS; 08-30-2012 at 04:26 PM.