Stray Cat

While other diesel engine manufacturers plan to use cooled exhaust gas recirculation (EGR) to meet U.S. Environmental Protection Agency 2004/2007 emissions standards, the engine division at Caterpillar will concentrate on optimizing in-cylinder combustion and use exhaust aftertreatment-an oxidizing catalyst chamber-to clean up residual emissions.

For in-cylinder combustion control, the engine company plans to use a second-generation version of the hydraulically actuated electronic unit injection (HEUI) technology it developed with International Truck and Engine. Along with a new electronic control package (with double the speed and more memory for the most precise fuel and air management to date), switching from camshaft-pumped unit injectors to the new HEUI system would optimize in-cylinder combustion. Another bonus: enhanced performance of the engine brake and an opportunity to redesign the hefty valve train of the OHC C-15 and C-16 engines for weight savings.

Caterpillar says it abandoned cooled EGR-the company has been developing the technology alongside the new Advanced Combustion Emissions Reduction Technology, or “ACERT”-because of the added complexity of the components that have to be added to the engine to enable cooled EGR. This not only affects potential reliability and durability, says Cat, it has the potential to create problems for truck manufacturers when installing the engines.

Director of Truck Engine Products John Campbell says the HEUI fuel system has been well proven in current Cat midrange as well as International powerplants. Exhaust aftertreatment has been successful in clean-diesel 3126E engines, and exhaust aftertreatment is a technology widely adopted by Cat for power generators.

Addressing the installation benefits, Campbell explains that the substitution of HEUI for the current electronic unit injector technology and the change of on-engine controller were both “internal” adjustments that do not affect chassis installations.

Furthermore, the modifications make little difference to heat rejection. Unlike engines with cooled EGR, this means no need for major increases in cooling system capacity.

NO ILL EFFECTS

According to both Campbell and marketing manager Dave Semlow, ACERT is similar in that it will present no adverse effect on fuel economy, maintenance intervals, or reliability.

Caterpillar is not saying how ACERT works, but responses to questions about EGR indicate some type of in-engine recirculation, probably achieved through exhaust valve timing events.

Like competitors with EGR engines, Cat is looking at variable-geometry turbochargers to achieve an identical power rating family to what’s available today.

A NEW DEADLINE

An important byproduct of Cat’s strategy is the possibility that it won’t have to meet U.S. emissions standards until fourth quarter 2003.

Under the Consent Decrees signed in 1998 to settle a lawsuit filed by the U.S. government, the signatories said they would have 2004-compliant engines by October 2002. However, the wording of these agreements involves the number of tons of NOx put out over time by 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. Caterpillar says it will have fully compliant engines-all on-highway midrange and heavy duty diesels-in production 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.