MOSSVILLE, Ill. (March 12, 2001) — Caterpillar will not be using cooled exhaust-gas recirculation (EGR) to meet 2004/2007 emissions standards, and it has gained a 12-month extension from the October 2002 deadline for the next emissions hurdle.

While the other American heavy-duty engine manufacturers have all come out in favor of cooled EGR, Cat says it will instead concentrate on optimizing in-cylinder combustion and use exhaust aftertreatment — an oxidizing catalyst chamber — to clean up residual emissions. And while Cummins, Detroit, and other engine makers battle to meet an October 2002 deadline, Caterpillar is not set to launch its new engines until the fourth quarter of 2003.

For in-cylinder combustion control, the engine manufacturer said it would use a second-generation version of the hydraulically actuated electronic unit injection (HEUI) technology it has co-developed with International. Along with a new electronic control package with double the speed and more memory for the most precise fuel and air management to date, this would optimize in-cylinder combustion. A bonus from the switch from camshaft-pumped unit injectors to HEUI will be an opportunity to enhance the performance of the engine brake and redesign the heavy valve train of the OHC C-15 and C-16 engines for weight savings.

Caterpillar said it abandoned cooled EGR — the company has been developing the technology alongside the new Advanced Combustion Emissions Reduction Technology (ACERT) — because of the added complexity of the components that have to be added to the engine to enable cooled EGR. This not only impacts potential reliability and durability, said Cat, it also has the potential to present the truck manufacturers with added problems when installing the engines.

Director of Truck Engine Products John Campbell said that the HEUI fuel system has been well proven in current Cat mid-range as well as International Truck and Engine power units. Exhaust aftertreatment devices have been successful in the clean diesel 3126E engines introduced a year ago, and exhaust aftertreatment is a technology widely adopted by Cat for power generation units, he said.

Addressing the installation benefits, Campbell said that the substitution of HEUI for the current electronic unit injector technology and the change of on-engine controller were both “internal” changes that didn’t affect chassis installations of Cat’s emission engines. Furthermore, the modifications made little difference to the heat rejection — unlike cooled EGR engines. This brings two major benefits: no requirement for major increases in cooling system capacity; nor any significant impact on fuel economy.

According to both Campbell and marketing manager Dave Semlow, there would be no effect on fuel economy, maintenance intervals, reliability or durability. ACERT would simply allow Cat to meet the emissions hurdle with no impact to the end user and with two bonuses: improved performance of the engine retarder and a significant lowering of engine noise.

Noise will probably be a function of two changes. One will come from the lower loads on the camshaft, since the fuel pressure loads will be removed to the high-pressure, engine-oil rail system.

The other will come from the electronic controls of the HEUI system. Benefits touted for HEUI are engine-speed-independent fuel system pressure for better low-speed emissions control, and the ability to use split-shot or pilot injection to initiate early combustion in the cylinder. In International engines this slower flame propagation in the combustion chamber lowers NOx, but also reduces the pressure rise for a major reduction in the diesel-knock noise.

Caterpillar is not saying how the system works overall, but guarded responses to questions about EGR indicate that there may well be some in-engine recirculation, probably achieved through exhaust valve timing events. This is one of the secrets of ACERT that Cat is playing close to its chest. In common with EGR engines from competitors, Cat is also looking at variable geometry turbochargers as a way of achieving an identical power rating family to what’s available today. The combustion and aftertreatment are obviously effective. Cat says it will get to the emissions levels needed with the ACERT system without having to go back to the Environmental Protection Agency for further relief with protection strategies, otherwise known as the Auxiliary Emission Control Devices, necessary to keep cooling systems of an acceptable size with cooled EGR. That gives it a leg up on both Cummins and Detroit Diesel.

It may also account for the fact that Cat says it won’t have to meet the emissions regulations till fourth quarter 2003.

Under the Consent Decrees signed in 1998 to settle a lawsuit filed by the federal government, the signatories have to have 2004 compliant engines by 10/02. However, the wording of these decrees involves the number of tons of NOx put out over time by the diesel engines, both before and after the signings. If Cat can show it will overall reduce emissions by its strategies, it can get relief from EPA. No one from Caterpillar is offering details on how the deadline has shifted for Cat, but this is likely the mechanism.

Caterpillar predicts it will have fully compliant engines — all on-highway mid-range and heavy duty diesels — in the marketplace by fourth quarter 2003, and that it will continue to sell EPA-compliant engines from now through 2004. It will also build on the ACERT technology to meet the stringent 2007 emissions requirement, indicating the company’s commitment to a long-term solution that reduces truck engine emissions to only 2% of the levels that were in existence when diesel emission regulation first kicked in 1988.

The achievement is remarkable, said Campbell. For while the engines are now heading to a point where they make only 2% of the NOx and particulates emissions of 1988, they are more reliable, more durable, more economical, and the peak power output today is far higher than a decade ago. And he didn’t say it, but they are more driveable, too.