Cummins Inc. says it will have a full range of well-performing truck engines ready for sale in October 2002, when the next round of exhaust emissions regulations takes effect. The engines will be as rugged as today's products, but will cost more to buy, perhaps use a bit more fuel, and operate at higher temperatures.
Like most other builders, Cummins says it will use exhaust gas recirculation, or EGR, to reduce the amount of nitrogen oxides, commonly called NOx, which contribute to smog. NOx is formed at high temperatures; mixing exhaust with inlet air reduces the amount of oxygen in the chambers, which lowers combustion temps, which reduces NOx.
Cummins' EGR systems include high-tech "variable-geometry" turbochargers, special plumbing, sensors and valves, and special cooling systems, engineers said at a briefing in April.
All models will be equipped and certified except the N14, which will be withdrawn as a truck engine by October of '02. The first EGR'd engine, an ISX, will appear as early as next March, and others will be phased in as the deadline approaches.
Huge radiators - an expected necessity of "cooled EGR," because heat from exhaust gas must first be eliminated before it goes into the engine - will not be needed, engineers said during a briefing for the trade press in early May.
A special jacketwater cooler will extract heat from exhaust gas before it gets to the engine's inlets. Coolant can handle the extra heat because it will be pressurized to 15 psi, vs. today's 7 psi. And operating temperatures will be 10 to 20 degrees hotter than on today's models.
A sophisticated variable- geometry (VG) turbo keeps the EGR system pressurized as varying amounts of exhaust gas are pumped through special plumbing to the inlet side, engineers explained. The turbo works as needed, even under low loads, so it does not always spool up and down as a driver puts his foot to the floor or backs off.
Good news for drivers is that the VG turbo also boosts acceleration and quickens response. Drivers have good-naturedly protested when it came time to get out of test trucks, engineers said. To prove this, they let me and another editor drive a heavy tractor-trailer rig with an EGR-equipped engine. Sure enough, the 11-liter ISM showed snappier acceleration than its 400-hp rating would seem capable of.
Enhanced electronic controls tell the turbo and special valves in the EGR system what to do. The controls take cues from additional sensors at various points on the engine and its accessories. Among the goals is to maintain current fuel economy levels, but some models may see slight decreases in efficiency.
Developing and testing EGR systems for all models is costing considerable money, and this must be passed on to truck buyers. Like other engine builders, Cummins notes that truck makers will set the final prices. But guesstimates put typical upcharges at $1,500 to $3,000, depending on engine size and truck model.
All domestic builders except Caterpillar say they will use cooled EGR. Detroit Diesel has EGR-equipped Series 50s running in transit buses and says they perform better and get better fuel economy than non-EGR engines. Mack will also use cooled EGR but has given few details.
Volvo Trucks says its 12-liter VED12 diesel will use cooled EGR to meet upcoming emissions limits, but won't need a high-tech, high-cost variable geometry turbocharger. Volvo calls its emissions system "V Pulse" because it will use the naturally occurring pulses from the turbocharger to move exhaust gas to the engine's inlet side. Like most of its competitors, Volvo will also use special plumbing, sensors and valves. But it will stay with today's comparatively simple and inexpensive turbo.
Cat announced in February that it will not use cooled EGR, but instead will employ a system called ACERT. This includes advanced electronics and hydraulically actuated fuel injection, a special catalytic converter, and "a breakthrough in combustion technology." Executives won't say exactly what that breakthrough involves, but do say that their engines will be much simpler and cost "significantly less" than competitors' models.
Like the other domestic builders, Cat is laboring under a Consent Decree imposed by the U.S. Environmental Protection Agency in 1998. The decree punished builders with millions of dollars in fines for allegedly "cheating" on emissions devices, and moved up emissions limits scheduled for January 2004 by 14 months, to October 2002.
Each builder deals separately with the EPA. Cat says the outcome of its ongoing negotiations will affect only what it does. It hopes to coast through the October '02 deadline using "credits" for producing other clean-burning engines prior to EPA deadlines.
Cummins engineers and marketing people say they suspect some of Cat's credits may come feom the ccleaning up of thousands of diesels used in Cat's off-road machinery. That, Cummins people insist, would mean Cat's truck engines won't have to meet the same limits in October '02 that others will. If so, Cummins will sue.
So, along with cleaner exhaust gases, there are also conflict and intruigue in the air.
