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Old 08-30-2012, 04:38 PM
TDIwyse TDIwyse is offline
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Location: Midwest
Join Date: Sep 2010
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Mein Auto: 4 diesels
Originally Posted by KeithS View Post
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.
The EGR goes to 0 under certain conditions like costing in gear or full fuel situations or during DPF regen events. The data points with 0 EGR Duty cycle in the above plots are for coasting are heavy acceleration situations.

The 2 "Post Injection" events have the same behavior pre and post recal. Once the coolant temp hits 140F they end, except for DPF regen events when they are used to maintain DPF temps sufficient to regen.

The only major differences I see in the data pre/post recal is heavier utilization of EGR and slightly increased DPF temps. I really wished they didn't increase the EGR utilization. That's a major cause of intake carbon buildup.
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2011 335d 11.8 sec 120 mph 1/4 mile NHRA certified track

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