To meet the upcoming EPA '02 emission requirements, Mack Trucks will employ two distinct strategies - one for highway vehicles and one for vocational vehicles - with the launch of a new family of heavy-duty diesel engines.

During the Mid-America Trucking Show in Louisville, Ky., last week, company officials said the "application-specific" solutions developed by Mack represent a unique effort to meet the new regulations by matching an appropriate emission reduction technology to the specific application of customers and their vehicles.
The new EPA '02 certified engines will be known as the ASET engine family, which is an acronym for Application Specific Engine Technology. All ASET engines rely on exhaust gas recirculation as the basis for delivering optimum performance while reducing emissions.
For all Mack engines ticketed for highway tractors - including the Vision by Mack and CH Series, the company will use cooled exhaust gas recirculation (C-EGR) technology. For those engines destined for vocational trucks - the new Graniteä Series, RD6, MR, LE, DM and RB models - internal exhaust gas recirculation (I-EGR) will be employed.
"We see no reason why our customers should have to accept a 'one-size-fits-all' approach to engine technology to meet the new regulations," said Steve Homcha, Mack executive vice president of Class 8 programs.
The Mack ASET solution for highway customers will be based on cooled exhaust gas recirculation - in which a portion of gases leaving the engine are diverted from exhaust through a cooling system, and then carefully remixed with air entering the engine for combustion.
C-EGR allows for the best level of performance and emissions benefits in a "steady-state" operating environment - i.e., when the vehicle is operating at relatively consistent speed and load over a significant period of time.
Modifications to the fuel system and software were the initial changes made to Mack engines in developing its C-EGR technology. An improved filtering medium was then added to the oil filtration system, along with a new oil pan that accommodates an additional eight quarts of oil that the C-EGR engines will require.
"We felt that it was necessary to increase the oil capacity levels of the new engines in order to keep our oil change intervals where they are today," added Homcha.
Homcha said the new highway application engine features a number of innovations developed specifically to accomplish C-EGR and deliver optimum performance. They include a new EGR valve, electronically controlled by the Mack V-MACâ system, to regulate the recirculation of exhaust gases, and a Mack Venturi mixing valve that combines inlet air and cooled exhaust gas prior to introduction into the cylinder. A new variable geometry turbocharger provides the pressure necessary to drive the re-circulated gases into the intake valve.
"While these engines employ a number of technological advancements, the underlying process is simple - the exhaust is cooled and burned again to meet the lower emissions levels," Homcha said. "The changes related to the ASET C-EGR solution ensure that these engines will meet our customers' expectations for driveability, performance, durability and maintenance, at the same time that they meet the new emissions requirements from EPA."
Homcha added that the introduction of the ASET family will make it possible for Mack to offer a new MaxiCruise 380/410 ASET C-EGR engine as part of its engine lineup.
Like C-EGR, internal exhaust gas recirculation also will be customer-friendly. I-EGR accomplishes emissions reduction by having a percentage of exhaust gases remain in the cylinders of the engine from one combustion cycle to another, until the targeted emission levels are met. This approach provides a consistent level of emission benefits and performance in the varying and often harsh environments in which vocational trucks operate.
Homcha said Mack engineers developed the ASET I-EGR solution after studying the typical operation of a vocational vehicle. These trucks often perform in a stop-and-go manner over shorter distances, where operational hours are a more important concern than miles traveled.
In response, he said, the Mack engine designers achieved a technical breakthrough by concentrating on optimizing the flow of exhaust gases through the system, in order to make it possible to retain a precise amount of gases in the cylinders for further combustion. That was accomplished through a new camshaft, advancements to the valve system, and precision machining of the exhaust ports to maximize aerodynamic flow.
Homcha also noted that the Mack ASET engine offerings include two new products -Maxidyne 335 and 370 engines -- with I-EGR technology.