Your Next Diesel: The View from 2001
There’s still much more to learn about them, but a couple of recent test drives indicate that the engines you’ll be driving in trucks made after October 2002 may not be so bad at all. In fact, the most difficult part may be getting used to a turbocharger that winds itself up even after you’ve
lifted your foot off the throttle. It’s a little weird, but we’ll get to that later.
The next round of diesel emissions regulations kicks in just over a year from now, and as the accompanying chart shows, they demand a drastic
38% cut in nitrous oxides from present levels. It’s a huge issue, and an incredibly expensive development ordeal for engine makers. Cummins, for example, says the bill so far is about US$250 million. And it’s not over yet, not by a long shot. It’s no wonder, then, that there’s been an enormous amount of politicking just behind the scenes. Not to mention a lawsuit or three. (See ‘Diesel’s Future’, January 2001, for more of the background to this continuing saga).
The U.S. Environmental Protection Agency is the big bad wolf here, and the major engine manufacturers, quite rightly in many eyes, feel
somewhat victimized. Falsely accused of secretly manipulating engine electronics to defeat earlier EPA standards, Caterpillar, Cummins, Detroit Diesel, Mack and Volvo reluctantly signed so-called ‘consent decrees’ in 1998 to avoid extensive legal wrangling with the U.S. Department of Justice. It cost them a lot of money, but it also cost them two years of research and development work because among other things they agreed to move the planned EPA rules of 2004 up to 2002. It’s been a mad scramble ever since.
And then there’s 2007, when NOx and particulate levels must come down to almost non-existent levels. The EPA wants super clean diesels with emissions at a tenth of the values demanded in 2002. Engines that can achieve these levels will likely be cleaner than natural gas or other alternative fuel engines, but the means to do it are not yet cast in stone.
In any case, clean is one thing and practical is another. The questions we’ve been asking on your behalf concern issues like purchase cost, fuel economy, and driveability, which isn’t to mention the keys of reliability and durability. Nobody can answer the last two yet, even for 2002, but it’s pretty clear that you’ll pay more for an ’02 engine by a couple of thousand bucks or so. Thankfully, it looks as if fuel economy might not suffer at all, or perhaps by just a tad. Some 2002-spec mid-range diesels have actually shown a 2% improvement.
In terms of driveability, 2002 engines seem more than OK after brief test drives, with possibly even better throttle response than we have now.
Until a couple of months ago, a technology called exhaust-gas recirculation (EGR) was thought to be the only feasible answer to the EPA’s
October 2002 emissions demand. Most think it remains so, but Caterpillar recently announced that it had stopped pursuing EGR in favor of a
simpler combination of injection and combustion tools with exhaust aftertreatment. Trouble is, Cat also said it couldn’t have engines ready by
October of next year but will need until late in 2003.
The question then becomes, will the EPA allow an extension? Cat thinks so, but it’s not clear, and other engine makers are incensed by that prospect after they’ve invested big money and say they can indeed meet the deadline outlined in the consent decree. That decree, they point out, is a binding legal document with performance penalties built in.
Tina Vujovich, Cummins vice president in charge of environmental policy, told several journalists at a dinner meeting recently that her company would not hesitate to sue EPA if it grants Cat an extension beyond October 2002.
“The level playing field has been defined, and it’s in the consent decree,” she said. “It will be our objective… to see that the consent decree is not
She added that Cummins had once considered asking for an extension itself but is now confident that its EGR solution will work.
What exactly is EGR? An EGR system takes exhaust gas out of the normal exhaust stream, upstream of the turbocharger, runs it through a
separate cooler, and then ships it back over to the intake manifold, downstream of the aftercooler. It’s important to note that this is ‘cooled’ EGR, because there’s also non-cooled EGR which has been seen in some light-duty use for some time (it won’t work in heavy diesels because the
fuel-economy penalty would be large).
Early reports were that the cooling of exhaust gases as they’re recycled back through the engine would place huge loads on the cooling system —
some engineers said there would be up to 40% more heat to dissipate through the radiator. Rads might have to be 10% to 15% bigger, some
said, which would have body ‘packaging’ implications. And the control systems would be more complex, with the need to control the amount of
exhaust gas recirculated, injection timing, boost pressures and more.
These and other issues seem to have been resolved by most manufacturers, though it’s clear that an ’02 engine is more complex, with many
detail changes as well as some big ones. Here’s a rundown on what the major players are doing:
Instead of cooled EGR, Caterpillar says it will concentrate on optimizing in-cylinder combustion, then using exhaust aftertreatment — an oxidizing catalyst chamber — to clean up residual emissions.
For in-cylinder combustion control, it will use a second-generation version of its well proven hydraulically actuated electronic unit injection (HEUI) technology. Also, a new electronic control package will double the processing speed and add memory for the most precise fuel and air management to date. The switch from camshaft-pumped unit injectors to HEUI will be an opportunity to enhance the performance of the engine
brake and redesign the heavy valve train of the OHC C-15 and C-16 engines for weight savings.
Caterpillar says this new Advanced Combustion Emissions Reduction Technology (ACERT) avoids the added complexity of components that have to be added to the engine to enable cooled EGR. Thus reliability and durability are not affected. Without the added hardware, Cat says its
solution saves truck manufacturers from engine installation problems. The technology also adds a significant lowering of engine noise, says
director of truck engine products John Campbell.
The modifications are claimed to make little difference to heat rejection — unlike cooled EGR engines. With two major benefits: no requirement for major increases in cooling system capacity, nor any significant impact on fuel economy.
Cat’s not saying how the system works overall, but guarded responses to questions about EGR indicate that there may well be some in-engine recirculation, probably achieved through exhaust-valve timing events. Cat is also looking at variable geometry turbochargers as a way of
achieving an identical power-rating family to what’s available today.
Cummins will be using cooled EGR to reach 2002 emissions targets. A key part of its strategy will be to use variable-geometry turbocharging developed by its wholly owned subsidiary, Holset. Such turbos are in mass production already and in active use in Europe in Iveco trucks. Some
40,000 have been shipped, so it’s well proven.
This technology has been successfully demonstrated on the next generation of the Cummins B series engine and is also being applied to its
other medium-duty and heavy-duty products, which are currently in field tests.
Cummins says it achieved a 2% improvement in fuel economy compared to its current B-series product, reduced NOx by 50%, and reduced the
time of unaided cold starts by over 80%. In addition, the throttle response of the engine was significantly improved as a result of the
According to John Wall, Cummins vice president and chief technical officer, the cooled EGR path was selected after researching all technical solutions. He says the company concluded that it’s the only feasible technology for meeting the 2.5 gram NOx levels of 2002.
In a recent test drive at company headquarters in Columbus, In., editor Rolf Lockwood took an M-11 engine on the road and found that the variable-geometry
turbocharging does indeed make for excellent throttle response. The overall sound of the engine was a little different, but it was the turbo winding up and down at odd moments that was most remarkable. Its variability means you won’t necessarily hear its whine building up as you stomp on the throttle. It’s a subtle thing, but for people who drive by sound, as all of us do to some extent, the turbo’s noise may be a key part of things like
shift timing. It will take some getting used to but it’s no big deal. Otherwise, you wouldn’t know the difference, and unless you look closely, you won’t see any difference either.
Fuel economy may well not change. “With a heavy-duty engine,” says Wall, “I think you can expect to see the same or slightly worse fuel economy as we have now. That’s not the last word, but that’s where we stand now.”
The next-generation Detroit Diesel Series 60 features cooled EGR as well, and John Morelli, vice president of 2002 engine development, says
they’re right on schedule in the development process. As with other engine makers, the missing piece is still final rulings from the EPA on the
exact interpretations of the consent decrees. Detroit’s program got a boost last year with the launch of the Series 50 bus engine with EGR to
meet accelerated bus-engine EPA rules.
As well as a variable-geometry turbocharger, exhaust cooler and electronic valves to direct the cooled exhaust back into the inlet stream, DDC has added a Bosch common-rail fuel injection system that provides finer control than the previous unit-injector setup.
Removing the bulky injector from the overhead allows for an all-new Detroit Diesel/Jacobs engine brake that lowers the profile of the engine a couple of inches. A secondary benefit is that the overhead will be lashless, saving the current 60,000-mile tune-up requirement. The ’02 Detroits
will have a slimmer front-on aspect, too. This, together with other updates, is anticipated to save as much as 100 lb and make the engine easier to fit into the frame.
Morelli says there will be some realignment of power offerings and engine displacement, because there are some indicators that more
displacement is needed for equivalent power, at least in the short term. Under the hood, as with the Cummins, things look surprisingly normal.
The slick integrated engine brake (IEB) is possible because the bulky unit injector is gone. The timing for the retarder is optimized by a dedicated ‘bump’ on the exhaust cam.
Mack’s 12-liter Mack E-TECH engine will meet 2002 demands with EGR, and with engineering targets that are actually 10 to 20% below those standards, the company says. Even in the most challenging configuration, the high-output 460-hp rating.
EGR will not be the sole technology used, but Mack won’t provide further details yet. It says other new technologies will be progressively introduced in the E-TECH engine between now and 2002. One key element will be a significant evolution of the engine’s unit-pump fuel system, in
which Mack will deploy flexible injection capabilities as early as the second half of 2001.
Mack is also moving forward with the “industrialization” process, namely the re-engineering of the truck as well so that manufacturing can roll smoothly. It’s an advantage enjoyed by a company that makes both trucks and engines. The company should be launching factory builds of both
engines and vehicles equipped with them any time now.
Bottom line, it looks like the engines you’ll be buying after October 2002 will be more or less OK. Time will tell, of course. And you may also get benefits like lower weight, better throttle response, and even improved braking performance in some cases.
But the engine manufacturers may still be at odds with EPA over some key interpretations of the consent decrees. At issue is the industry’s
request for EPA to allow the use of Auxiliary Emission Control Devices (AECDs) to protect heavy-duty diesels in extreme conditions. Essentially, they let engines stray outside the regulated NOx limits when conditions are extreme: high load, high temperature, high altitude. But they are similar in concept to what EPA referred to as “defeat devices” that allowed the engine makers to “cheat” in the late 1990s.
If EPA doesn’t allow them, all bets may be off. That, among a bunch of other things, remains to be seen. — by Rolf Lockwood
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