iRV2 Forums

iRV2 Forums (
-   Class A Motorhome Discussions (
-   -   DEF consumption or MPG of DEF? (

G Schulz 03-10-2016 09:39 PM


Originally Posted by jharrell (Post 2971422)
They do different things, DPF is for soot, DEF is for NOx.

They have a relationship in that for an engine to have met NOx emissions up to 2010 without DEF it needed more EGR to run cooler, because heat and pressure is what creates NOx from air. However when the engine runs cooler it creates more soot causing the DPF to need more often regeneration. So DEF helps reduce regeneration indirectly only because the EGR can now be reduced increasing temps, which also helps mileage and power. It doesn't necessarily change how regeneration is done, only how often it's needed.

For 2010 emission engine makers realized they couldn't meet the tougher standards without DEF, they tried everything, Navistar really tried and failed. EPA doesn't care how you get emissions down, just so happens DEF is the only viable way to get NOx down right now. Volkswagen got caught tweaking EGR which reduced power and mileage but only while testing instead of going with DEF, then on the road it ran hotter but no DEF, so it put out 40 times the NOx.

Here is a diagram, notice how the DEF system is after the DPF:

Attachment 121098

Thanks for the info on emissions. You do know your emissions. I didn't know DEF engines used a DPF as well. I thought the use of DEF eliminated the DPF.

2009 Safari Cheetah 40'
350 HP Cat
2014 Ford Focus
Air Force One

lanerd 03-11-2016 07:49 PM

You know, I've never measured mine. The DEF is so cheap and I use so little of it, I just don't see the need for measuring. If I'm doing a lot of traveling, I'll keep it about 3/4 full....if I'm setting for a long period of time, only about 1/4 full.

In any case, I guess i can say....who cares? :cool:

erstanfo 03-13-2016 03:00 PM

I asked the original question since my consumption seems high compaired to what the dealer and Cummins says 2% and wanted to know if I should have it looked at next time I take it to Freightliner for service.
Thanks to all the replies.

All times are GMT -6. The time now is 01:49 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.