Abelson reports: Cummins in the SCR camp

At this very moment, Senior Technical Editor Paul Abelson is at the Navistar one-on-one press conference, so he asked us if someone was dashing by the press room, would we post this blog with the Cummins report from MATS. I was headed that way. Here's Paul:

It doesn’t seem that long ago that Cummins introduced the ISX. It was to be the engine to take Cummins through the increasingly stringent EPA emissions regulations of the early 21st Century. And it was only a year ago September that Cummins announced they would meet EPA 2010 WITHOUT NEEDING selective catalytic reduction (SCR).

My, how things change.

The 15-liter ISX was originally designed with two overhead camshafts. One worked all the valves, and the other, with massive lobes, was to exert the forces needed to pressurize fuel injectors to around 30,000 psi. The higher the pressure, the finer the atomization and the cleaner the burn.

Two days ago here at Louisville, Cummins presented their strategies for meeting EPA 2010. They WILL use SCR, and will replace the old ISX with two new engines, the ISX15 and its smaller, lighter sibling, the ISX11.9. No longer is a camshaft dedicated to pressurizing the fuel injection system. Using pneumatic and hydraulic pressure in the new XPI common rail Fuel System, injectors are now pressurized to about 33,000 psi. And within each combustion cycle, each injector can pulse up to five times for an extremely precise burn.

The XPI system with Cummins VGT (variable geometry turbocharger), improved electronic controls, and reduced exhaust gas recirculation (EGR) made possible with SCR means fuel economy is improved by up to 5 percent from the current ISX. ISX15 ratings range from 400 hp to 600 hp, with torque from 1450 to a massive 2050 lbs-ft. As installed, the ISX11.9 is a bit less than 400 pounds lighter than the 15-liter, with dimensions within 1/4-in of the current ISM.

The 11.9 gives Cummins an entry in the highly competitive 12-liter class, with 210 to 425 hp and 1,150 to 1,650 lbs-ft. The smaller engine shares the fuel, air, electronic and emissions technologies with the ISX15. Cummins explained how, by having the SCR take over much of the control of oxides of nitrogen (NOx), they are able to cut back the amount of EGR needed to manage NOx, lessening under hood heat and improving combustion.

Mid-range engines will also benefit from the new strategy. They include the ISB6.7 (200 to 325 hp), ISC8.3 (260 to 350 hp) and ISL (345 to 380 hp).

In addition to the national truck stop and dealer networks that will be selling diesel exhaust fluid (DEF), the urea solution used in the reduction process, Cummins Filtration will be distributing DEF to 8,000 customers with more than 20,000 retail locations, helping to assure availability.

Cummins is now securely in the SCR camp, along with every other domestic engine supplier except International. They stand alone promoting the in-cylinder solution that relies heavily on Advanced EGR without SCR.

The arguments go back and forth, but ultimately you, the user, will determine what technology survives or if each will find its own niche.