EGR - Why So Evil?

[mdadgar]

Each time the topic of EGR comes up it's inevitably followed by some variant of "EGR is a NIGHTMARE on diesels."

So my question is: why?

Why is it so much worse on diesels than on gassers? Should work pretty much the same way. Potentially better, since fuel is the limited factor in a diesel motor, not air.

A technical explanation would be good.

Thanks.

- Mark
02 Sierra 2500HD, D/A, CC SWB, EGR and cats

[AzKevin]

Here's what I've read/heard..... There have been concerns made by the European auto community about bad the US diesel fuel quality is. As an example, VW uses an EGR on the TDI, and although the TDI has a great following, many complain that the EGR can clog within 30k miles or so. One can only assume that this isn't a problem in Europe. Aside from that I've heard some claim EGR gasses degrade engine fluids.

[csimo]

There are many reasons that EGR on a diesel is bad news. The particle size of diesel exhaust cause buildup in the system, and several other problems. Here's a good article on the effects of diesel EGR on engine oil:

http://www.practicingoilanalysis.com/article_detail.asp?articleid=349&relatedbookgroup=Lubrication

[OC_DMAX]

Mark,

The article that CSIMO posted a link to provides a good explanation on how recirculating exhaust gas on diesel engines is affecting the formulation of oils (going to CI-4 for diesels due to EGR's).

My main dislike is all the extra engine hardware required. If you can find a 2001 DMAX, compare under the hood to what you have on your 2002. You have a vacuum pump, three separate solenoids, a vacuum sensor, two diaphram valves and an exhaust gas cooler that is plumbed into the radiator. I probably left out a few things. That is a lot of extra complexity.

Alan