EGR on the KJ CRD

dgeist · **Posted:** Fri Feb 08, 2013 1:09 pm

I typed this up in email for a user recently and thought it might be nice to post it.

The "Exhaust Gas Re-circulation" system on a modern auto is used to help regulate the combustion process by introducing a small amount of exhaust into the combustion process, reducing the overall percentage of oxygen in the combustion and changing the characteristics a little. This is useful at cold startup and at certain other times with a gasoline engine. This does reduce harmful emissions and has some debatable economy benefits, albeit at the expense of some complexity in the engine. On a diesel, and EGR doesn't have the same effect because of how diesel combustion is regulated (not by the amount of air, but by the amount of fuel). Contrary to the intent of the system, mostly bad things happen to diesel engines as a result of EGR plumbing.

Wikipedia has a pretty decent article:
http://en.wikipedia.org/wiki/Exhaust_gas_recirculation

In any case, in our jeeps, the EGR does introduce abrasive soot into the intake, change the acidity of the motor oil (which wears on metal parts) and foul up sensors inside the top end of the engine. Unfortunately, since legislator and lobbyists (and not engineers/scientists) make most laws. The use of EGRs is mandated on ALL passenger vehicles with internal combustion engines (gasoline and diesel alike).

The "quick and dirty" answer for the longevity and economy of our jeeps is to simply block off the EGR valve that lets the exhaust in with a metal plate. Unfortunately, it is illegal to tamper with "environmental engine controls" in many places. Also, disconnecting the EGR entirely makes the engine think it's malfunctioning and in need of repair and throws a check-engine light.

The KJ CRD community has come up with a couple solutions to making the EGR function more appropriately in our jeeps. The most popular are commonly referred to as the ORM (off-road-mod), the SEGR (Synthetic EGR), and the GDE (Green Diesel Engineering) engine tune. I'll explain each:

- ORM
This is a (free) modification that will trick the computer into not using the EGR by disconnecting a MAF sensor (Mass Air Flow) at the top of the airbox, just to the left and behind the radiator as you're looking at the engine from the front. This will get you some performance and economy gains, but also commonly throwns a Check Engine Light.

- SEGR
The SEGR is a product conceived/designed/produced by forum members as a kit (but also available from a couple folks pre-built) that mimics the proper electrical function of the EGR. Its electronic circuit acts just like a properly functioning EGR valve from the computer's perspective. It sits inline between the engine computer and EGR and the computer is happy no matter what the EGR is doing. The EGR itself ends up with no power, so it stays in whatever position it was last in, usually closed. The system requires electronics assembly and some splicing of wires under the hood. This is within scope for the electronics-saavy, but non-trivial for those not experienced with electronics systems.

- Green Diesel Tune
The Green Diesel Tune is actually a combination of changes to the programming of the engine computer. It comes in several flavors, but each makes changes consisting of various tweaks to engine control that accomplish a benefit in both fuel economy and power as well as other small changes requested by customers. The programming also greatly reduces the actuation of the EGR valve from the factory behavior so that it is seldom open during regular driving, reducing the problems with EGRs listed above. This solution does not disable the EGR but has been observed to reduce premature EGR failure. GDE is a private company whose founder is active in the community and supports its products actively in public forums as well as through the company's official methods.

No support or endorsement of one method over another is implied here. Searches of each of the techniques will give you plenty of food for thought as to which you might care to utilize on your jeep.

Dan

EGR on the KJ CRD

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