View Single Post
Old 11-29-2011, 02:44 PM   #10 (permalink)
Master EcoModder
Diesel_Dave's Avatar
Join Date: May 2011
Location: Indiana
Posts: 1,194

White Whale - '07 Dodge Ram 2500 ST Quad Cab 2wd, short bed
Team Cummins
90 day: 37.68 mpg (US)
Thanks: 112
Thanked 511 Times in 213 Posts
Originally Posted by UFO View Post
... when the CEL is lit, the ECM will retard the timing to avoid the creation of NOx and mileage will decrease.
Bingo! there's your reason for FE getting worse by removing EGR.

EGR wil improve FE at the same NOx level, however, if all the other engine settings are the same, I have never, ever seen FE improve with EGR on a diesel.

This is the whole reason for the EGR vs SCR debate on diesels (see article here: An engine with EGR has lower NOx emissions, but worse FE. SCR can clean up the NOx after it's left the engine, but not having to use EGR buys you FE. Of course SCR means you have to add DEF (diesel exhaust fluid).

If EGR improved diesel FE, SCR would have both DEF and worse FE, so there would be no point.
Diesel Dave

My version of energy storage is called "momentum".
My version of regenerative braking is called "bump starting".

1 Year Avg (Every Mile Traveled) = 47.8 mpg

BEST TANK: 2,009.6 mi on 35 gal (57.42 mpg):

Last edited by Diesel_Dave; 11-29-2011 at 03:18 PM..
  Reply With Quote