EGR rates and efficiency (+ overrun trick)

[robnitro]

I have set up a temperature dependent egr map for my uncooled pd150 egr and it helps a lot with warm up. My egr map is slightly modified from the pd160 one, with ensuring 22 up to 25 afr for efficiency and smoke concerns.

However, by reading many papers on EGR and efficiency, I can't seem to find a consensus on whether low rates of egr help efficiency at low loads. I'd think that the added heat would help mixing of fuel at low loads, especially when cold. (I also wonder how to calculate egr % rate, as an uncooled egr flow less actual CO2 than cooler egr).

For overrun, less engine braking- there is an easy trick. Make the first column fuel axis to 0mg/s. Set up egr values to 250 mg/s for that column. When there is no fueling, egr is mostly open, so very little backpressure and minimal turbo speed. You can even do this w egr delete if you still have the egr valve functional...just make the rest show 850 mg/s.

Opposite of that, for engine braking, set up 0mg/s column in boost request map. Fill it in with a higher boost value (I use 1500 mbar - its abs). When my egr is fully off, I make around 7 psi when lifted off throttle.

 

[Phantomofheat]

I know with gas cars that running EGR at low-light load situations will help with MPG as long as to much is added. The two reasons for that is less pumping loss throttle closed and the second is less fuel needed to maintain 14.7:1 AFR. Diesels do not have those problems.

I do like your ideas but you might want to do some scans and make sure that you are not having any spikes when going from full fueling to no load.

 

[robnitro]

No spikes, for the turbo it slowly rises due to pid.
Even sometimes it doesn't meet 7 psi, at below 2500.
The n 75 map is untouched.

In more papers, EGR seems to be a wash. The added heat gets offset by lower oxygen.