This article originally published in Issue 64 of the Turbo Diesel Register.

Cummins' Column

Cummins' Column

by Robert Patton, Editor TDR

6.7-LITER ASK THE ENGINEER

Hidden in the closing paragraph of the “Cummins Column” in Issue 62 was the invitation to the TDR membership to “submit your questions regarding the 6.7-liter Cummins engine to the editor and I will forward them to our helpful contacts at Cummins Inc.”

Purposefully, we did not make a big splash about the Q&A format. I have quietly gathered a handful of insightful inquiries, made edits, added past TDR references and then forwarded to Cummins for their response.

Enough preamble. Some of your questions follow:

Q. Soothe the mind. Effective with the 6.7-liter engine’s introduction in January of 2007, exhaust gas recirculation (EGR) was a new exhaust emissions strategy for the Dodge pickup customer. However, EGR for the B-series engine was first introduced in 2002. Please discuss Cummins’ experiences with EGR.

A. In October 2002 Cummins implemented EGR with several engine products: the 5.9-liter ISB; the 11-liter ISM; and the 15-liter ISX engines that were used in on-highway applications. The Dodge Turbo Diesel 5.9-liter B-series engine did not require EGR.

The 5.9-liter ISB vehicles that have used EGR are medium-duty trucks with names that you’ll recognize like Freightliner and Bluebird.
In 2007 Cummins introduced EGR as a part of the emissions package for our 8.3-liter ISC engine, our 9-liter ISL engine and the Dodge 6.7-liter Turbo Diesel engine.

From April of 2002 through December of 2006 Cummins engines with EGR accumulated over 40 billion miles of service.

Q. As an audience, since our ownership of an internal combustion engine (What was your first, a lawnmower?), we’ve been taught that clean air is paramount to the longevity of the piston ring-to-cylinder seal. By now we have all seen the sooted intake tract of an EGR equipped engine. The impression one gets from the photographs does not inspire confidence. Please explain how the integrity of the combustion seal is maintained.

A. While the intake tract does show soot from the EGR, you have to remember that the exhaust gas that is being recirculated into the engine was just created by the combustion event(s) in the cylinder(s). Thus, the EGR is no more detrimental than the exhaust gas that was created by the combustion event. Further, the power cylinder components are engineered with the cooled EGR system in mind to ensure durability.

Q. As the TDR’s editor I see the strong advantage that Dodge and Cummins will have at the January 2010 emissions date. Although the Cummins 6.7-liter audience has struggled through several reflash iterations, the competitive ’07 and newer Ford and GM engines are not without problems too. And, for the 2010 emissions date (that is only 6 months away), they’ll be introducing completely new engines!

Aside from what we’ve read in trade publications, can you elaborate on the competitive products?

A. No comment. But the Cummins engine is well positioned.

Q. We know that the 6.7-liter has already met the January 2010 emissions guidelines. However, other Cummins engines, specifically the larger displacement big-rig engines, will have a different exhaust aftertreatment technology, the use of selective catalytic reduction (SCR) and the corresponding injection of urea fluid into the exhaust stream. The fluid is officially called diesel emissions fluid (DEF) and it will be available under many different trade names.

If I recall correctly, the use of a NOx absorber catalyst (NAC) on the 6.7-liter engine was the key to “keeping it simple stupid” for the diesel pickup customer. Your thoughts?

A. The 2007 Dodge Ram 2500 and 3500 pickup trucks met the 2010 emissions requirements three years ahead of schedule by employing a NOX Adsorber Catalyst. We are excited to continue with this proven package for pickup customers in 2010.

However, a new DEF aftertreatment system will be introduced on chassis cab trucks in 2010. The reason for the difference is twofold. First, Dodge Ram pickups are certified for emissions differently than the heavier trucks, including the Dodge Chassis Cab trucks. Second, many pickup truck customers have different needs and different duty cycles than commercial truck customers, such as those buying Dodge Chassis Cab trucks. When selecting the best aftertreatment solution for the application, these differences lead to two different answers.

It is important to note that DEF systems, called SCR elsewhere, have been in use in Europe for several years, so this is not a new technology. 2010 chassis cab owners will need to refill the DEF tank every few thousand miles, but should expect long-term durability in return.

Q. An astute TDR member noted an air conditioner refrigerant tag on a 2009 Dodge Ram 1500. The tag listed the various gasoline engines that power the Ram 1500 as well as a “5.0-liter diesel.” Can you tell us about the 1500 diesel program?

A. No comment.

Q. I often encounter the question of shutting down when the engine appears to be engaged in one of the regeneration modes. Occasionally, with this new 6.7 engine, the EGT is at 600° or higher as I shift the Aisin six-speed into Park. When the engine is in a regeneration mode, it takes a period of several minutes for the EGT to slowly drop to a tolerable shutdown temperature of 350°. I simply cannot allow myself to twist the key when the EGT is high. Cummins’ response?

A. There is a table in the Diesel Supplement to the Owner’s Manual that provides guidelines on cool-down idle periods after loaded operation. Following that table is all that is needed.

As evidenced by this Q&A section, the “Ask the Engineer” section is open for business.