We’re in a lull between the storms. With the introduction of the 2004 EPA-mandated reduced-emissions engines behind us and the next round of reductions more than a year-and-a-half away, we can catch our breath and contemplate what’s to come. Or can we?

Those who are now running ’04 engines will have experienced (or will soon) the effects of increased under-hood temperatures and will be looking for solutions to those maintenance issues. Could it be any worse come 2007? All the North American engine makers are saying existing technology is up to the challenge.

The reduction of NOx (nitrogen oxides) can be accomplished with expanded EGR capacity — or in Cat’s case, with Advanced Combustion Emissions Reduction Technology (ACERT) plus a new variation on the EGR theme. Dr. Steve Charlton, executive director of Cummins’ advanced engineering group, says the present ratio of about 15 percent EGR will be upped to 20 or 25 percent. Tim Tindall, director of emissions programs at Detroit Diesel, says the EGR function on a Series 60 will be upped to about 30 percent, or double the present ratio.

Mike Powers, Cat’s product development manager, says refinements to the shape and function of the combustion chamber including changes to piston, ring, and liner designs, along with modifications to the fuel and air systems will bring ACERT up to scratch for ’07. Cat will stick with variable valve actuation and series turbochargers as well — the principal features of ACERT.

However, in a somewhat surprising twist, Cat is also using an EGR variation in its ’07 engines to achieve additional NOx reduction. It’s a ‘low-pressure loop’ EGR system in which exhaust gas is drawn downstream of the particulate filter-and thus cleaned of particulates-is recirculated into the intake air. Cat calls this technology ‘Clean Gas Induction’ (CGI) and says the clean air pulled back into the intake distinguishes it from the competitors..

That leaves engine makers with the challenge of cutting PM (particulate matter) from 0.1 to 0.01 g/hp-hr, or 1/10th of the present level. This, they all say, can be accomplished with particulate traps, officially known as diesel particulate filters (DPF).

The engine makers are warning that we’ll likely see further degradation in fuel economy, similar to what we saw with the ’04 engines, and heat rejection will be a huge issue in ’07 engines — as if it isn’t already. But all in all, what’s under the hood won’t be terribly unfamiliar.

A Few New Pipes

For starters, EPA has said crankcase emissions will be treated as engine emissions beginning in ’07, forcing engine makers to develop closed-circuit crankcase ventilation systems. Says Detroit’s Tindall: “We’ll be using oil-driven centrifugal oil-separators to scrub the oil vapour from the crankcase gases.”

And with increased EGR volumes, expect larger EGR coolers. Truck journalists recently had a “sneak preview” of Detroit Diesel’s ’07 Series 60 engine and found an EGR cooler that appeared roughly twice the size of the existing cooler.

The turbocharger is key to the performance of the more demanding EGR ratios. To that end, at least two engine makers, Detroit Diesel and Volvo, have adopted the Cummins-owned Holset sliding-vane VGT. Volvo Trucks North America spokesperson, Jim McNamara, confirmed recently that Volvo’s newly introduced VE D16 engine uses a Holset sliding-vane VGT — “with electronic actuators to provide more precise control.”

Detroit Diesel will also be using the Holset turbo, replacing the current — and in some cases troublesome — Garrett swinging-vane turbo. Both Detroit and Mack have experienced difficulties with that design. In Detroit’s case, we saw coolant lines running to and from the turbocharger — something we haven’t seen before.

But aside from a few new pipes, some bigger pipes, a couple of new sensors, larger fans, radiators, and charge-air coolers, the changes planned for ’07 won’t be obvious. We will, however, see some very different looking exhaust systems.

Diesel Particulate Filters

Having nicked NOx somewhere forward of the firewall, engine makers still face the challenge of a 90 percent reduction in PM output. The DPF will filter the soot out of the exhaust and store it until it can be burned off. Proper function of the DPF will depend on new fuel and lube oil formulations designed to reduce soot in the combustion chamber. New engine lubes will use a reduced ash formulation, while diesel fuel will be refined in a manner that removes almost all the sulfur.

Once trapped by the DPF, the accumulated soot will be reduced to ash using a chemical catalyst, platinum in most cases, and then burned off by elevating the temperature inside the DPF. Caterpillar’s Powers says in most applications, the heat produced under normal load will be enough to remove the particulates from the filter. This process is called passive regeneration. “But in low-load situations where the exhaust temperature isn’t high enough, we’ll rely on a thermal device to provide enough heat to accomplish the filter regeneration,” he says.

This approach is typical across all brands. In a process called active regeneration, diesel fuel will be injected into the exhaust stream to raise the internal temperature to somewhere between 900 and 1300 F, resulting in very high exhaust-outlet temperatures. The process is managed by the engine-control system and is triggered by temperature and pressure changes in the exhaust system as the filter accumulates soot. It will be transparent to the driver, and each event will last about 10 minutes, occur every four to 16 hours, and consume about half a litre of fuel.

These filters will also need periodic manual cleaning to remove accumulated ash from the regeneration process and from oxidized engine oil. The EPA says cleaning intervals must be at least 150,000 miles apart, but actual intervals will vary, said Tony Greszler, vice president of engine engineering for Volvo Powertrain group. “These could easily go to 200,000 miles depending on conditions,” he said.

The engine makers are saying the filters will be integrated into a muffler-type device with a removable filter section to facilitate cleaning or replacement. The filters will not be interchangeable across engine brands, and cost estimates for a “filter change” stand now at US$150. For fleets using different engine platforms, this could create inventory issues as each brand of engine will require a mated DPF.

Undercurrents

With concerns about cost, performance, maintenance, fuel economy, and of course, heat rejection, the obvious question remains: will there be another pre-buy prior to ’07?

All the engine people say there will be engines in customers’ trucks by mid-2006, so we’ll have a chance to see ’em and feel ’em before we buy ’em. Performance results should be well established by D-Day.

Here’s what Freightliner LLC president Rainer Schmueckle said about a pre-buy recently. “With many of the OEMs currently building to capacity, and with little bricks-and-mortar expansion planned, I can’t see how we’d fulfill a major pre-buy,” Schmueckle said. “We’ll have ’07-compliant engines in customer trucks later this year. We hope that will increase the confidence level of the customer, and we’re continuing to negotiate with federal officials for customer incentives to promote early adoption of the new engines.”

As to the cost of meeting 2007 EPA rules, Schmueckle has said the upcharge could be as high as US$4500 to $6000. Others have booted around a figure closer to $10,000. And generally that doesn’t include increases in operating costs or in maintenance and reliability concerns.

Bring on that storm.