NASHVILLE, Tenn. — Heavy-duty Cummins engines will not use selective catalytic reduction (SCR) to meet 2010 nitrous-oxide emissions limits like a handful of other engine makers. Nor will they need any other form of NOx aftertreatment.

Instead, according to Dr. Steve Charlton, Cummins executive director of heavy-duty engineering, the ’10 engine will be a relatively simple evolution of the existing ’07 product, employing cooled exhaust gas recirculation (EGR), a variable-geometry turbocharger, and a diesel particulate filter (DPF).

It’s long been thought that SCR would be needed to meet stringent 2010 NOx limits, though Cummins has been hinting in the last year or so that in-cylinder means could possibly be employed.

Speaking at a press conference here prior to the fall meeting of the Technology and Maintenance Council, Charlton also said the company will introduce two new displacements, at 11.9 and 16.0 liters, to complement the existing 15-liter ISX engine. The three will share common architecture, though the new 11.9 will actually be derived from an all-new 13-litre diesel being developed for the Chinese market.

Cummins medium-duty engines, unlike their big brothers, will use SCR as their NOx-reduction system for 2010, on top of cooled EGR and a DPF. It’s not new technology to the Indiana company, having launched its European mid-range engines certified to the Euro 4 standard using SCR in 2006.

Both Detroit Diesel and Volvo/Mack have long since committed to SCR in 2010, while Caterpillar and others have yet to announce their plans for heavy-duty motors, which must meet even tougher EPA-mandated emissions targets two years from now.

A key component of the Cummins 2010 product will be the XPI high-pressure common rail fuel system developed jointly with Swedish truck and engine maker Scania. Gone are the days of the unit injector. Injection pressures will be about 32,000 psi, approximately the same as now, but the common rail system is much more flexible, allowing multiple injection pulses and pressure on demand.

First field tests of the new Cummins engines in customer hands will likely happen in May 2008.