Reinforcement in red: Cummins launching new generation Tier 3 QSB engines at ConExpo; new engines, new look belies consistent message on emissions technology

Mike Brezonick

Maybe it's because of the industry it's in, maybe it's because of the increased scrutiny all large companies receive these days or maybe it's because its headquarters has always been in the heart of the Midwest--Columbus, Ind. Whatever the reason, Cummins Inc. has always seemed to put a premium on a philosophy that can be summed up as "say what you're going to do, then do what you said."

By that standard, the new generation Tier 3 QSB engines that Cummins will show for the first time at ConExpo are a normal progression, a restatement, albeit in iron, and sporting a dramatic new red livery, of a plan the company laid out more than three years ago.

"It's doing what we said we would do, which is certainly something people have heard us say before," said Dave Crompton, Cummins vice president--MidRange Engine Sales. "But it's a big piece of what drives the engine business.

"Investing in the technology, developing stability in the platforms earlier and planning with an eye toward the future are things that have been driving us for a while. It's played out that way--and not by luck. It's at the heart of where we've been and what we're doing with Tier 3 as well."

Of course, even if it's a restatement, it's an awfully important one for any number of reasons, not the least of which is because of the engine itself.

The B series diesel engine will probably go down in history as the most important engine Cummins has ever built and it has found myriad applications in everything from loaders to boats to Dodge Ram pickups. To date, the company has built more than three million B series engines and set sales records with the engine in several market segments in 2004.

And evolutionary or not, the new QSB diesels are said by the company to offer significant improvements in performance, responsiveness, noise emissions and durability. And of course, the capability to meet EPA's Tier 3 standards well ahead of the required Jan. 1, 2006 deadline.

"Probably the most important thing is that in the context of the most challenging emissions requirement that's ever faced us in off-highway, we've kept that as a requirement, but it's not been the focus of the development," Crompton noted. "Compliance is the end game, but it's not what drove our thinking in terms of the strategy moving forward.

"The strategy was really driven from what our customers and what a healthy market need, which is stability though more challenging and faster emissions cycles, but also a focus on limiting the impact technically and limiting the incremental cost associated with achieving the next emissions hurdle. It was really focused on performance for the customer, cost and complexity for the OEM and stability through the emissions cycle. And it happens to be complaint as well."

The Tier 3 QSB diesels will be available in four- and six-cylinder versions, both of which are electronically controlled. The 6.7 L, QSB engines will span an output range from 130 to 260 hp, with a restricted rating of 275 hp available. The smaller 4.5 L QSB is available in ratings from 110 to 160 hp, with a 170 hp restricted rating. A 4.5 L, mechanically controlled Tier 3 engine rated 80 to 110 hp is in development to meet Tier 3 standards (for that engine size) that become effective in 2008.

The Tier 3 QSB engines are derived from a design developed by Cummins and Iveco as part of their European Engine Alliance (EEA) joint venture, but Crompton emphasized that it wasn't simply a direct technology transfer from the EEA product, which has been sold in Europe for several years by both partners. "There is core technology that was developed within EEA that is available to both partners," he said. "We are not obligated to the same technology solution for Tier 3 and in fact, we will likely take a different path.

"The basic block design is similar, the fuel systems are somewhat similar. But how you specifically get to Tier 3 in terms of combustion and some of the overall approach, Cummins has taken a different tack."

The foundation of Cummins' emissions approach has been what the company calls its in-cylinder emissions solution, which is an analysis-led design encompassing specific proprietary designs of components such as injector nozzles, intake and exhaust ports, pistons, etc., along with engine control software developed by Cummins. This approach--what the company calls its "emissions recipe"--is being carried across nearly all of Cummins engine families and has been refined through thousands of hours of computer-aided combustion analysis.

"We put in almost 18,000 cpu hours generating a piston bowl and injector combination to go out and run in a test cell," said Tim Britt, technical project leader for the Tier 3 B series engine. "We're very proud to say that at the end of this process, in when we cut our first piston bowl, it's at the same piston bowl we're going into production with. That's a huge achievement and a huge savings in time and expense."

The new QSB engines incorporate electronically controlled Bosch common rail fuel systems and four-valves-per-cylinder head designs, with the injector vertically centered for more precise injection. The system, which is similar to the system on the Cummins Euro 3 on-highway engines, is capable of multiple injection events--such as pilot and post injection--within a single injection cycle, which can provide improved responsiveness as well as reduced smoke, particularly in cold-start conditions. The common rail system can deliver injection pressures as high as 23,000 psi, but Britt noted that "we're finding we're not having to go anywhere near that, which is an added bonus in terms of reliability and durability."

The injection system is controlled by a CM850 electronic control module built by Motorola. Cummins uses a common electronics architecture with an identical OEM interface for all of its engines from 4.5 L through 15 L, connected through a 50-pin Deutsch connector. "That's really helpful for OEMs that use several of our engines," Britt said.

All of the electronically controlled Tier 3 QSB engines also incorporate Holset wastegated turbochargers. "It's fairly straightforward turbocharger technology." said Tim Meyer, marketing, Cummins Tier 3 applications. "We offer variable geometry products in on-highway, but in this market, we thought we could do well with wastegate turbocharging. It offers very high reliability because we haven't added a lot of sensors, we haven't added a lot additional technology and componentry.

"The approach we took for Tier 3 was to minimize the impact of installation to our OEMs and our customers, so they don't have a large tear-up of the product line. In most instances, we can slide the Tier 3 engine into where the Tier 2 engines had been. Because they utilize the in-cylinder solution, we don't have a lot of extra hardware hanging on the outside."

Along with exhaust emissions, significant improvements have also been made to the QSB engines with an eye toward the other emission noise. Cummins said that noise emissions have been reduced by as much as 5 to 9 db(A), depending on model and configuration, which is more than a 55% reduction in sound pressure. The block incorporates a more sculpted, ladder flame design for improved stiffness and the geartrain has been moved from the front to the rear of the engine, which reduces torsionals and gear chatter. A bolted bed plate has been added to the underside of the block to reduce lower end flexing and the tappet cavities have been enclosed within the block itself. "There used to be a flat plate that bolted over the top of the tappet cavity," Britt said. "We've closed that in as part of the casting.

"The valve cover is isolated, so there is not a drumming action on the top, and the high-pressure common rail fuel system has relatively lower drive torque, but also the pilot injection is just a huge aid in reducing noise.

"If you look at the no-load noise for our Tier 2 engines, at almost every engine speed our Tier 3 engines are quieter--at full load. It's a huge reduction in noise, like night and day."

Some of the changes have also improved overall engine reliability, Britt added. "The enclosed tappet area was done mainly for noise reduction" he said. "But it's also a leak reduction because that's a lot of surface area for gasketed joints that we've just eliminated now."

Other durability-related improvements include a redesigned oil cooler cavity bolt pattern, a larger tappet wear surface and wider cam lobes, which reduces overall contact stress, the company said.

"We have also reduced our piston temperatures by using directed piston cooling on our Tier 3 product," Britt said. "It's a rifle nozzle that sprays the oil in the underside of the piston and the piston has galleries that direct the oil flow internally on the bottom side of the piston.

"One of the fringe benefits of our combustion system is that we have inherently low soot in our oil. In the past, oil change intervals were often dictated by soot levels in the oil as well as the acidity (total base number, TBN). We have found that we've had to start paying a lot more attention to the TBN side instead of the soot because our soot is so low."

The new QSB engines have been certified to EU Stage 3 emissions standards, according to Cummins, and the company has also sent its emissions certification paperwork to the EPA for its approval. "We have received our certificate from Europe and we are just waiting on EPA," Britt said. "We're way ahead of schedule."

The six-cylinder Tier 3 QSB engines will begin production in June, while the four-cylinder engines will commence limited production late this year. In an effort to more promptly serve emissions-sensitive markets throughout the world, Cummins indicated that the new generation QSB engines will, at launch, be manufactured at three sites--Rocky Mount, N.C.; Oyama, Japan; and Darlington, U.K.

Crompton said that prototype Tier 3 engines have been running in the lab and at "some key OEMs" for nearly two years, and that Cummins was confident in its position for both Tier 3 and beyond that, Tier 4.

"Obviously, given that the date for Tier 3 is fast approaching, we've been very active in prototyping with OEMs in machines," he said. "We believe that moving forward, the in-cylinder solution is as transparent as you can get from Tier 2 to Tier 3 and then from Tier 3 to Tier 4. It's the core of how we're getting there--no cooled EGR, no aftertreatment at Tier 3 and then carrying that stable platform through to Tier 4 with the addition of aftertreatment.

"From an engine development standpoint, there's not a lot left to do for Tier 4. The focus will be how do we integrate, optimize and make it as seamless as possible for the equipment manufacturers and the customers? How do you integrate and take the best advantage of electronics for the machine and not just the engine? How do you do the packaging and support of the engine and aftertreatment together?"

Some of those answers, the company said, can be provided by Cummins' Advisor and PowerMatch software. Both are analytical programs that lead the OEM engineer through an engine selection and installation process that incorporates Cummins requirements and recommendations and provides an assessment of the installation with an eye toward maximizing total equipment operation.

"In terms of aftertreatment" Crompton added, "we have Fleetguard as a part of Cummins and we believe that gives us a significant advantage. We're going to design the aftertreatment, we're going to package it, in some cases we're maybe going to install it and we're going to support it. I don't think there's anybody else in the industry that's going to be able to do all of those things at the same time with a collective statement of confidence that a customer can be comfortable from an engine-out perspective, I'm covered.

"I think it's reinforcing Cummins as a credible, long-term, committed supplier to the off-highway markets. A lot of people have seen our transition from non-emissionized product the last two cycles and built some mist. I think the fact that we are repeating what we said we would do is doing nothing more than reinforcing our commitment and ability to be a long-term leader in this business."

Cummins Tier 3 QSB Specifications

6.7 L QSB

Dry weight--1047 lb. (475 kg)

Overall height above the centerline of crankshaft--25.75 in. (654 mm)

Overall length--41.6 in. (1059 mm)

Overall width at widest point--28.5 in. (725 mm)

4.5 L QSB

Dry weight--817. 9 lb. (371 kg)

Overall height above the centerline of crankshaft--23.4 in. (596 mm)

Overall length--32.2 in. (818 mm)

Overall width at widest point--28 in. (713 mm)

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