A Better Mousetrap?

Caterpillar has taken a lot of heat for its soloist approach to reducing diesel engine emissions. While its rivals have focused on cooled exhaust gas recirculation to meet tougher U.S. EPA pollution standards, the company missed the October 2002 deadline to comply and has been paying a penalty of about $3,500 US for each engine it sells. In the fourth quarter of last year, Caterpillar doled out more than $40 million US in fines. Until the EPA targets are met, that toll will climb every time someone catches the keys to a new truck with a yellow engine.

Caterpillar claims the pain in its wallet will be worth it in the long run and in March offered a glimpse as to why: it introduced five new truck engines equipped with ACERT emission controls, including replacements for the modified 3126E, C10, and C12 “bridge” engines Cat currently sells in North America. The 8.8-litre C9 is available now and has two ratings for on-highway trucks at 335 and 350 horsepower. Production of the C7, a 3126E replacement, will ramp up in June, the same month the heavier-duty C13 and C15 engines will enter the market in limited release (both are scheduled for full production in October). The last in the line, the C11, will replace the C10 for vocational and regional applications. Assembly starts in December.

The 2003 model announcement is perhaps the most definitive statement heard from Caterpillar with respect to ACERT, which combines new air, fuel, and exhaust hardware with updated electronic controls. It is intended to address EPA requirements and meet the performance demands of all Cat diesel engine customers: the company developed ACERT for its construction and mining machines and power generation units as well as its truck engines.

The company also hopes ACERT will assuage on-highway customers with a watchful eye toward even more rigorous EPA restrictions in 2007. In light of concerns about the performance, price, and reliability of EGR engines leading up to the last EPA deadline, Caterpillar claims ACERT will meet the next standards with no major modifications.

Caterpillar has kept details about ACERT–which stands for Advanced Combustion Emission Reduction Technology–closely guarded ever since the company abandoned cooled EGR in early 2001. At the time, Caterpillar director of truck engine products John Campbell said the decision to go with ACERT was made because of the complexity EGR components would add to the engine. But at a glance–which is all journalists were afforded during the March launch–ACERT is hardly an elegant looking solution. The C11, C13, and C15 all have larger displacements than the models they replace, as well as an air-intake system that uses two turbochargers in series (the second has an electronically controlled wastegate). To manage the extra heat from compressing air twice, ACERT requires both a jacket-water aftercooler and air-to-air charge cooling. Cat admits the additional plumbing contributes to a general weight gain: ACERT engines are between 130 and 200 pounds heavier than previous versions.

Another major change is that ACERT engines require exhaust aftertreatment to reduce particulates–an oxidation catalyst incorporated into the muffler, the same system currently used on Cat’s bridge engines. The C11 and C13 also get a new cylinder-head design that allows for integration of an optional, more powerful compression brake.

“I won’t tell you ACERT is simple or even pretty to look at,” says Steve Rutherford, truck engine region manager for Caterpillar Commercial Services in Woodbridge, Ont., “but just about everything that’s gone into it has been used by us before in other applications, which is something we couldn’t say about cooled EGR.”

For example, he says, to meter incoming air precisely and optimize combustion, ACERT includes variable valve actuation that’s controlled electronically, a design principle the company employs on other types of engines (ironically, it recirculates exhaust back to each cylinder, a form of EGR).

As for the twin turbos, Caterpillar uses them on
off-highway engines.

Of the five ACERT models scheduled for production this year, the C15 should interest Canadian owner-operators the most, with ratings from 435 to 550 horsepower and torque from 1,350 to 1,850 foot-pounds. Its displacement is 15.2 litres, up from 14.6, and it’s the only overhead-cam engine in the group. The C13, at 12.5 litres, is aimed at highway fleets that don’t need the heft or horsepower of the C15 but want maintenance intervals to match, plus enough guts to pull 140,000 pounds if need be–things not ideally suited to the current C12.

It’s not known when the market will see 600 horses and 2,000-plus foot-pounds of torque from Caterpillar or anyone else, but Rutherford says Cat is committed to replacing the high-horsepower and torque output of its discontinued C16. One option is to offer the 18.1-litre C18, which Cat sells in Europe under the Sisu brand. Another is to beef up ratings on the C15.

While Caterpillar may have defined its 2003 model rollout and provided hints about how ACERT works, there are still many questions the company will need to answer in the months ahead. The first is performance. Cat claims that ACERT engines will be more fuel-efficient than those from competing manufacturers, but has released no test data to support this idea. Cat expects to complete 10.2-million miles of field trials before full production of its key C13 and C15 models begins, but in Canada, just 10 ACERT engines–a mix of C9s, C13s, and C15s–were in test service at the end of last month.

Meanwhile, truck makers are refining their installation engineering and paying particular attention to any substantial cooling issues that might arise from ACERT.

Since it dropped development of EGR as a way to meet the October ’02 emission deadline, Caterpillar has been aggressive in criticizing it. Competitors have returned volleys of their own, saying ACERT is a technology designed for heavy construction equipment first, with trucks as a secondary application. Cat has been accused by some of its rivals as playing up fears about the reliability, durability, and fuel economy of EGR motors, as well as shorter oil-drain intervals, contributing to a pre-October buying blitz and a severe drop in truck sales in the months after.

Cummins points out that many of its EGR-equipped engines are approaching the 500,000-mile mark in revenue service. The company had sold almost 6,000 of its ISM and ISX engines with EGR by mid-March, representing 45-million real-world miles. By October, Cummins expects to have 25,000 EGR engines on the road. Detroit Diesel says after 8 million miles of testing it has seen an improvement in both liner and ring wear in its ’02 engines–by 49 and 78 per cent, respectively.

Heat-rejection horrors anticipated a couple of years ago never materialized with EGR. Nor did fears about extreme soot-loading in the oil that lubricates and cools an EGR engine. Chevron tests show no change in an ISX engine, for example. Only Cummins dropped its recommended oil-drain interval for normal duty, from 35,000 to 25,000 miles (all the others, Cat included, remain at 15,000 miles), but that may have been unnecessary in hindsight.

Fuel economy, which all EGR engine producers said would suffer, does appear to be poorer by 3 to 5 per cent in most cases. Cat says its ACERT engines will achieve fuel efficiency on par with its 2001 engines, or 3 to 5 per cent better than competing engines. Only real-world testing will prove it one way or another.

“That’s the key for us now, to use the coming months to make sure the engines perform the way we know they can,” Rutherford says. “Customers want to know about price, and we’ve said it will be a premium price. We need to get the miles in and the testing done so we can demonstrate the value ACERT will bring.”

He says that value will be realized over the long haul for customers looking ahead to 2007, and for Caterpillar itself. “Paying fines,” Rutherford says, “is not part of our long-term strategy.”