Gentlemen, Start Your New Engines

With the on-highway diesel emissions regulations set to change in January '07, it comes as no surprise that it's been standing room only at industry meetings whenever engines are on the agenda. There's a lot to know about them – not least is the fact they are going to cost $7,000 to $10,000 more.

There's more complexity and much misconception.

Basically, the technology path is similar to the changes for the '02 engines: exhaust gas recirculation (EGR) – but at increased flow rates. EGR is used because the spent gases displace oxygen in the incoming air and keep down the flame temperature during combustion, thereby limiting NOx (nitrogen oxides).

The good news: Because EGR has been used for the last three years, experience has allowed the early bugs to be addressed and allowed end users to reach a level of comfort and confidence. The possible bad news: Many fleets are clamoring to get trucks with the current engines before the '07s hit, which could cause a big financial hit to manufacturers in 2007, if sales take a nose dive.

DIESEL PARTICULATE FILTER

The diesel particulate filter (DPF) is a new component that everyone will have to deal with on the '07 trucks, whatever the make of engine.

It's important to thoroughly understand this new piece in the emissions puzzle, because there's a lot of mystery and misconception about DPFs, most of it surrounding the maintenance that will be required and "regeneration" cycles.

The filter is there to deal with the microscopic carbon particles that exit the combustion chamber. Beginning in January '07, they are effectively outlawed in diesel exhausts.

The filter element is a ceramic monolith that is a bundle of ceramic tubes alternately closed at one end or the other. Exhaust enters the open tubes from the engine, and the only way out to the exhaust stack is through the ceramic walls into neighboring tubes open at the other end, leaving carbon particles in the ceramic.

Just upstream of the filter monolith is an oxidizing catalyst stage. This serves two purposes, one of which is to oxidize the nitrous oxide (NO), which is a component of the NOx stream in the exhaust, turning it into nitrogen dioxide (NO2), another NOx component.

The enriched NO2 moves from the oxygen catalyst stage and enters a second process in the filter where the carbon particles and the additional NO2 in the exhaust react in the presence of a different catalyst. The carbon then comes off the ceramic walls as carbon dioxide gas and the NO2 reverts to NO. This process is known as passive regeneration and requires the heat of the exhaust to proceed.

All this goes on without the driver being aware of it, and the filter remains free of carbon build-up. However, this second reaction (of regeneration) only occurs in the hot stream of exhaust typically seen when an engine is under load.

Applications such as over-the-road trucking provide enough load factor and throttle position to permit continuous passive regeneration.

Others, such as vocational applications, dumps, utility trucks, urban delivery vehicle and trash packers, may not have a hot enough exhaust stream, thus requiring active regeneration.

Active regeneration is the oxidation catalyst's other task. If the engine electronics detect a buildup of back pressure as the carbon loads up without passive regeneration, a rich fuel mixture fed into the exhaust comes into contact with the oxidation catalysts and builds up heat in the stream to initiate the regenerative process.

This fuel may come from clever injection timing or it may simply be injected into the exhaust just downstream of the turbocharger.

QUESTIONS & CONCERNS

There's a lot of misunderstanding about active regeneration: Will it set fire to trees? What about a fuel hauler sitting at the fuel rack? What happens if the driver keys off in mid-regeneration? Won't the filter housing get extremely hot?

It's important to understand that although the exhaust heats up, there's no flame. Again, this is undetectable by the driver, and the exhaust is little hotter than the exhaust from an engine working under load (as in the passive regeneration).

One fear – the blown turbo – came up during the question-and-answer session at the February annual meeting of the American Trucking Associations' Technology and Maintenance Council. One fleet manager asked if a blown turbo would also result in a blown DPF. Probably not, he was told, because electronic sensors will detect abnormal temperatures and shut down the engine before damage can occur.

Exhaust gas will be very clean with the new diesels, but will also get very hot at times. Heat during regeneration – estimated by manufacturers to be 1,000 to 1,200 degrees at the tailpipe – caused some consternation among the TMC audience. How will drivers and passers-by be protected from being burned by such hot air? Will a driver be able to stop an active regeneration if he's warned that one is about to occur and he must park the truck for a delivery or pick up? Could a driver or manager order the system to regenerate before a truck leaves the company premises so it won't occur while it's on the streets – something especially wise for a rental truck?

Manufacturer reps said they anticipate such situations and are still formulating their plans. But they also said exhaust temps of the new diesels will be similar to those now experienced with gasoline engines, whose exhausts are hotter than current diesels. So maybe some fears are unfounded.

In any case, some manufacturers' control systems will not allow active regeneration when trucks are standing still. Most reps said they plan to require the truck to be moving at least 10, 20 or 30 mph – none have picked an exact speed yet – before a regen can occur. And it will be interrupted when speed falls below a set velocity. This should prevent personal injuries to anyone near a tailpipe. Even so, manufacturers are designing diffusers that would quickly dissipate hot air as it leaves a pipe.

"Touch temperature" – how hot the surface of the aftertreatment device gets during DPF regeneration – should be about the same as on current mufflers, which is around 500 degrees or less, reps said. This is because devices will be dual-walled to insulate their outer skins from heat, and there will be shields at certain places to keep heat away from critical chassis parts. Stout construction should also make the devices strong, and they'll not be easily bashed by road debris or overhead obstructions.

DPF MAINTENANCE

Another fleet concern is the amount of maintenance the DPF will require.

Along with the spent combustion gases coming out of the engine are minute traces of ash from additives in the oil. These ashes do not regenerate, and build up in the DPF over time. They have to be removed in a cleaning process.

Again, there's good news: This maintenance cycle should only occur somewhere in the 200,000- to 400,000-mile range. For an over-the-road fleet turning trucks at 36 or 42 months, this may be a one-time event. For other applications, maintenance may be required more regularly, but the federal mandate says this cannot be less than 100,000 miles (150,000 miles in California) to the first cleaning.

That maintenance should be relatively easy. If a fresh clean filter monolith is available, the task can be completed in around one and a half to two hours.

There's considerable concern over the cost of the cleaning machines – you are not going to be able to tap the filter on the workshop floor to get the ash out. Most will be cleaned by air-pulsing. Detroit Diesel recommends an ionized water cleaning process, and the machines cost up to $30,000.

So it is likely that dealers and engine distributors will be investing in the cleaning machines, and fleets will carry new or reconditioned and cleaned filters on the shelf.

Caterpillar is taking a different tack, making the filter serviceable while still on the truck. That means removing inlet and exhaust pipes and connecting the filter to what amounts to a very powerful vacuum cleaner. It sounds simpler, but the construction of all the DPFs we've see to date is such that the filter monolith can be very easily removed for cleaning.

So yes, there will be cost for the filter maintenance and a little additional maintenance, but nothing like the fears expressed by fleets in those standing-room-only meetings.

NOT ONLY HERE

It's not only North America that's pursuing the holy grail of clean air. Europe and Japan also have stringent air quality standards that will phase in following a timetable only a year or so later. The standards are different – much to the chagrin of the engine designers, because it means research and development dollars, Euros and yen to meet different emissions targets.

However, since emissions post-2010 here and post-2012 in Europe are both virtually zero, there is a significant convergence that may enable an initiative to develop world standards for the developed nations. These will then provide a road map for other nations as they strive for the same economic and environmental conditions we enjoy.

But these air quality mandates come at a huge price. The development of engines to meet the '07 regulations in the United States has taxed the engineers and the resources of the engine and vehicle manufacturers.

Both Volvo and International say those costs will add $7,000 at a minimum to the sticker prices of a truck, to as high as $10,000.

WATCH OUT FOR 2010

EGR in 2002 was a paradigm change for heavy-duty diesels and brought with it a number of issues that, fortunately, we've worked through for the '07s. But 2010 presents some daunting challenges and calls for technologies that are not even available today – or only at unrealistic and unaffordable premiums.

Technology paths will likely combine solutions currently favored in Europe along with those used here.

Higher rates of exhaust gas recirculation and new combustion processes pose huge issues for both engine and vehicle manufacturers. Engines have to be more robust and reconfigured for higher injection pressures and improved efficiency to offset potential fuel economy losses, both from the technology and from the lower energy content of the ultra-low-sulfur diesel it demands. The trucks have to handle higher heat rejection into the cooling system. And trucks are becoming more aerodynamically efficient, in part to offset fuel economy penalties and higher ownership costs that come with the '07s.

Truly, this year is the time of huge change for the heavy-duty engine manufacturers as several all-new, worldwide engine platforms are introduced. Why worldwide? Because it takes an annual production of 100,000 engines annually to be able to amortize the huge investments in research and development and production tooling. 2007 also will see the introduction of all-new trucks from International and Freightliner, as well as highly modified chassis from every other truck OEM.

Someone said back in the 1980s that the heavy-duty truck market had matured and not a lot of change was going to happen as we go forward. As you will see, that is about as far from the case as can be imagined.

MORE SPEC INFO EMERGES

More spec'ing information on 2007-model diesels has emerged as manufacturers tell customers what to expect after January. The latest forum was the annual TMC meeting, where engine maker representatives outlined changes in their model lineups and, as noted above, answered questions about highway testing and new maintenance procedures for the engines' exhaust aftertreatment devices.

Stricter limits on exhaust emissions are requiring various hardware and software changes, but for the most part, operating ranges will remain the same as now. That means you can continue to specify the same axle gearing and transmissions, representatives said. But some changes might be necessary, so always consult closely with people at your dealer and, if necessary, the factory.

Shop technicians and drivers will have to become aware of the new aftertreatment devices. They'll operate by themselves, engine reps said, but as discussed earlier, will eventually need attention, making that need known through warning lights and fault codes. Crankcase ventilation systems, too, will be new in '07, and many will use filters that need periodic cleaning or replacement.

The new emissions equipment will not be spec'able, but exhaust system configurations might be, according to sessions at the recent National Truck Equipment Association meeting in Atlanta. New aftertreatment devices will remove soot and ash while also acting as mufflers. But the devices will be bigger and heavier and, of course more expensive, and for the most part will not be legally changeable.

Dual exhausts will largely disappear, except for Big Power engines. "Straight pipes," treasured for their mellow-to-loud sound, will disappear because it'll be illegal to remove aftertreatment devices. And "packaging" the systems is a challenge on short-wheelbase tractors and some straight trucks. Each truck builder will offer several exhaust configurations to try to accommodate certain body types. You'll have to look at these configurations and be sure the factory is furnishing the best one.

If you habitually buy trucks off a dealer's lot, you might be stymied, because the chassis he'll have in stock might have exhaust systems that will get in the way of the bodies you'll need. Changing exhaust systems will not be easy, and kits might or might not be available from the factory. Stay tuned on this one.

Following is a breakdown of what each engine manufacturer is planning for '07.

CATERPILLAR

Caterpillar debuted its 2007 emissions solution in detail at the Mid-America Trucking Show, but that was too late to meet our deadline for this issue, so we have no details about ratings or even official word of the updates to the hardware to meet 2007.

Fortunately, though, at the recent TMC annual meeting, Bob Wessels, Cat's manager of customer value, shared a fair amount of information with the audience.

According to his presentation, the C-11 engine goes away, to be replaced by a vocational C13. C7 (190-300 horsepower/520-860 pounds-feet), C9 (275-350 horsepower/860-1,350 pounds-feet), C13 (305-470 horsepower/1,050-1,750 pounds-feet), regular C15 (435-550 horsepower/1,550-1,850 pounds-feet) and a high-performance C15 (600-625 horsepower/1,850-2,150 pounds-feet) comprise the on-highway offering for '07.

At the Cat booth we were able to get a walk-through of a C15, demonstrating the technology to meet the new emissions regulations.

Caterpillar's next-level ACERT technology continues with the system approach of optimized air handling, with – on the bigger C13 and C15 – series turbocharging with wastegate control. Cat explains that this allows for lower pressure ratios across each turbo and lower turbine speeds for better durability and reliability.

Output of the greatly compressed charge (up to 42 psi) passes through a water/air cooler on the engine and then through the chassis-mounted charge air cooler in front of the radiator.

With the initial launch of ACERT, Cat introduced variable valve timing on the inlet side of the C13 and C15, a technology similar to that developed by retarder manufacturer Jacobs. This lowers engine-out emissions in what is suggested is a modified Miller cycle.

The final stage in the earlier ACERT engines was the first use of heavy-duty diesel exhaust aftertreatment in the form of an oxygen catalyst to clear up particulates and soluble organic fractions.

For 2007, Caterpillar is adding its own form of exhaust gas recirculation. Because the company has been an outspoken critic of other technologies, Cat calls its technology clean gas induction (CGI). The word clean refers to the fact that the exhaust is taken from downstream of the diesel particulate filter and is then run back up through a dedicated pipe to another air/water cooler on the engine. The cooled "clean" gas is then introduced into the fresh air stream entering the first-stage turbo from the air filter.

The Caterpillar DPF also differs from the other engine manufacturers'. In addition to the outlet for the exhaust – clean gas – recirculation, Cat says its filter has no oxidizing catalyst stage. On all other manufacturers' engines, a diesel oxidizing catalyst is present ahead of the filter. It's there to raise the temperature of the exhaust through fuel oxidation to assist in active regeneration of the DPF as well as generate NO2 to oxidize the deposited carbon from the filter.

Cat's solution is to raise the exhaust temperature directly by heating it with burning diesel fuel. Word is that Cat engineers feel there is no need for an oxygen catalyst to generate NO2.

On the demo engine at TMC, the active regeneration heating was to be accomplished using a complex-looking combustion chamber just downstream of the second turbo. It is fed with engine coolant in and out – fuel to the combustion and firing chamber and air to purge the latter – in all five lines. There's also a larger pipe to bring in air for the combustion. But the most astounding thing – for a diesel engine – is the sparkplug sticking out of the top of the combustion head.

According to Cat, the combustion process goes on within the firing chamber, so the external walls of this combustor do not get excessively hot. And, most likely, the hottest the exhaust will get is no more than the engine produces under full load – 750 to 1,100 degrees – since this is all that is necessary to ensure passive regeneration in the filter.

As with other '07 aftertreatment solutions, the DPF loads up over time with ash from the lube oil. The filter must be cleaned of this ash – very infrequently – but unlike other aftertreatment solutions, Cat proposes this be done with the filter in place. The company says it will use a device like a giant vacuum cleaner that – with DPF in and out pipes disconnected – will purge the ash from the ceramic filter.

Crankcase emissions are controlled on the smaller engines with a closed system. The C13 and C15 have an oil separator that drains back into the engine and a vent for blow-by gases. These will need service every third oil change. Oil change intervals, using the new CJ-4 oils, are unchanged.

CUMMINS

True to its promise that its 2007 engines will be basically unchanged from the '02 EGR engines, Cummins unveiled ISM and ISX big-bore engines with few changes other than the diesel particulate filter.

Down the scale, though, ISB gets a capacity boost to 6.7 liters from 5.9, and the ISC and ISL now feature cooled EGR for the first time.

In a press conference in conjunction with the TMC meeting in Tampa, Cummins Vice President Ed Pence said the Cummins on-highway line-up comprised these five engines, and that Cummins is ready for 2007.

In fact, he said, Cummins has aggressively gained market share from 21 percent a few years ago to 26 percent today, and production has skyrocketed from 135 a day to 430 plus. Most importantly, through cost efforts, the break-even point is at a 50 percent lower volume. This will provide a major cushion should the market go south following the introduction of the 2007 engines, Pense said.

Describing the 2007 technologies, Executive Director Heavy-Duty Engineering Steve Charlton introduced the subtle changes to the air handling on the ISX. These include a revised Holset variable geometry turbo (VGT) that is now electronically controlled with stepper motor actuation instead of the previous air control. The exhaust cooler has been redesigned, fitting a more efficient package to handle the higher rates of recirculation into the same location on the engine. At the same time, Cummins has relocated the EGR valve from the hot side of the engine to the cold side, a much more favorable environment. And there's a new, more elegant crossover tube at the rear of the engine.

On the fuel side, injection pressure is up again due to an injection camshaft change.

Another added component is the closed crankcase breather, which mounts on top of the cam cover. This is a passive coalescer with a filter element that has to be changed out at every fourth oil change.

Allaying fears about DPF maintenance, Charlton said, according to application, the much-feared cleaning cycle would be anything from 250,000 to 400,000 miles, and that would mean it would be two years or more before DPF removal and cleaning for many operations. Also, the cleaning process is simplified with a filter processor Cummins has developed.

The DPF displayed was configured for vertical installation and was only a little larger than a conventional muffler. It has an oxygen catalyst stage ahead of the monolith particulate filter, with temperature sensors at the inlet, mid chamber and at the outlet. Pressure sensors measure the pressure drop across the filter stage.

As with most other engine makers, the oxygen catalyst oxidizes nitrous oxide in the engine-out exhaust, turning it to nitrogen dioxide, which – if the filter matrix is at a high enough temperature – will react with the carbon to produce carbon dioxide and nitrous oxide, purging the particulate matter from the filter. This continuous purging of the carbon is passive regeneration, and in many applications goes on in normal truck operation. For extreme cold operations or in applications where the exhaust cannot be brought to temperature, active regeneration causes a very small dose of fuel to be injected into the exhaust stream to heat the matrix and promote the chemical reaction that removes the carbon.

The need for cleaning the DPF comes from the ash byproducts of the lube oil additives. The actual amount of ash is very small – hence the long maintenance period – but the ash does collect and does need to be emptied.

The passive regeneration is maximized using the new, more powerful engine electronic controls. More power and speed from the ECU are necessary, because the electronics have to control the VGT, the EGR valve, fuel and the DPF. However, according to Charlton, this additional computing power, plus the electronic controls for the VGT, make the '07 ISX even sweeter to drive than the '02 (see Drive Test on page 68). The difference, he said, is as great as that between '99 and '02 engines. Drivers in the test fleets, he added, were clamoring to drive the beta-test engines in their operations.

According to Charlton, in redesigning parts of the air handling system, Cummins has been able to target areas that may have caused problems, and that engine reliability would be one of the benefits of the model change. Fuel efficiency would not be compromised, he said, and he anticipates no degradation of fuel economy compared to today's engines.

Jeff Weikert, Cummins executive director of Medium Duty Engineering, introduced the medium and light-heavy ISB, ISC and ISL.

The ISB, already an EGR engine, gets a boost in displacement to 6.7 liters, (which will likely please '07 Dodge diesel pickup buyers) and a new top rating of 325 horsepower and 750 pounds-feet. Other changes include the Holset VGT across all power ratings for the B and engine ECU common with the ISC and ISL.

The latter engines will have cooled EGR in '07, along with the Holset turbo.

Because these engines are common-rail fueled, the engineers have developed a very elegant way of initiating the active regeneration. The multiple-event injection gets a final squirt of fuel after the exhaust valve opens, and in the blow-down stroke fuel is pushed out into the exhaust stream. In contrast, on the ISX a water-cooled injector sits on the outlet from the turbo.

All engines feature the Fleetguard crankcase ventilation filter and have the same maintenance requirements. Nothing was said about the ratings for the engines other than none in the lineup today will be lost. Very little was mentioned about the ISM, though it is still very much in the program. Like all the other engine models, it will have the VGT and the DPF. It will also share the more powerful ECU with the ISX and feature the same Fleetguard crankcase filter.

On fuel economy and lifetime costs, Vice President of Sales and Market Communications Jeff Jones said that most engines would be at today's fuel economy levels. Gains made in small refinements would offset the lower density of the ultra-low-sulfur diesel fuel.

As far as maintenance cost, he said, since the additional crankcase filter and the DPF would likely be serviced at today's lube oil change intervals – which will not change – there would be only a small incremental cost over the life of a vehicle. The service channel is ready, he said – with 1,000 dealers currently in training – and will be fully equipped to service the 2007 engines when they start to appear.

DETROIT DIESEL

Detroit Diesel goes into 2007 with three engine platforms and a whole new worldwide engine range in the wings, due to debut in North America late next year.

For the new emissions levels, DDC will retain the 14-liter Series 60 and the 12-liter MBE4000. For lighter applications in Freightliner LLC brands, only the MBE926 will be available as the four-cylinder goes away.

All will adopt additional flow rate, cooled EGR to minimize engine-out NOx and particulate matter. They use a catalyzed diesel particulate filter to reduce PM down to the 0.01 g/hp-hour mandate.

The MBE926 will cover ratings from 190 to 350 horsepower at 520 to 860 pounds-feet of torque. The in-line-6 MBE4000 takes over with 350 to 450 horsepower with 1,250 to 1,650 pounds-feet, a new rating. The familiar Series 60 is rated 425 through 515 horsepower with 1,450 to 1,650 pounds-feet.

Toward the end of 2007, the HDE will bow in, initially at 14.8 liters. This six-cylinder is the first of four displacements that will take DaimlerChrysler through EPA 2010 as well as Euro 6 in 2012 and to Japanese standards in the same timeframe. It is generally thought the HDE, at 9.9, 12.8, 14.8 and 15.6 liters, will replace Detroit Diesel's current lineup as well as Mercedes-Benz and Fuso heavy-duty diesels.

For 2007, though, Series 60 will feature rate-shaped injection with multiple-event capability. The exhaust system is new.

The Series 60 also gets the Cummins-owned Holset variable geometry turbocharger. This is an elegant one-moving-part design, far simpler than swing-vane types that can prove unreliable. It has an electronic stepper motor control. (The Holset turbocharger is, incidentally, also found on Cummins, Volvo and Mack engines next year.)

Detroit Diesel's diesel particulate filter includes a diesel oxygen catalyst stage, manufactured by several different suppliers. The German company, Purem, was purchased three years ago by DaimlerChrysler to fold its technology into engine development and moved last year into space at the Detroit-area plant.

As with competitors' engines, the Series 60 uses diesel fuel in the exhaust stream, introduced by a "doser" located just downstream of the VGT. The fuel makes contact with the oxygen catalyst and heats the exhaust stream when active regeneration becomes necessary. As with other engines, active regeneration is only required for applications with relatively low load-factor or in cold-weather operations. For most over-the-road fleets, the carbon on the filter will be oxidized into CO<->2 in the heat of the exhaust in a continuous passive regeneration.

Active regeneration – like operation of the VGT and the EGR valve – is handled by new-generation, more powerful engine electronics.

The company is recommending the DPF's filter monolith be washed with de-ionized water, rather than be pulse-blown cleaned like other solutions.

To deal with crankcase emissions, Detroit Diesel has a disc-stack centrifuge to return oil to the crankcase while venting into the atmosphere. As such, it requires no maintenance.

Other external changes to the Series 60 include an engine-mounted radiator that allows the cooling fan to draw the maximum air through the matrix.

MBE4000 gets a two-solenoid injection system for injection rate shaping and multiple-event performance. It has the same DPF as the Series 60, but its doser is in common with the MBE926. Unusually for a diesel, the 4000 gets an intake throttle valve to draw in exhaust gas as necessary.

The 4000 gets a simpler electrostatic closed-crankcase breather that drains oil back to the oil pan and requires no servicing.

The 4000 also has an engine-mounted cooling system that minimizes fan-tip-to-shroud gap for optimum efficiency. This uses a smaller fan for the same heat rejection and improved fuel economy.

The 926 sees changes to the injection system for rate shaping and multiple event injection. It can have single or dual turbocharging according to rating and it also features a throttle valve and a DPF.

INTERNATIONAL

International will maintain most of its current line-up of the 4.5-liter V6 (VT 275), the 6-liter V8 (VT 365), the 7.6-liter in-line 6 (DT 466) and the 9.3-liter I-6 (DT 570). The 530 will be dropped.

At the top end, though, International will introduce its 2007 MaxxForce Big Bore, an engine currently being cooperatively developed with MAN in Germany. This engine is based on the MAN D20. There are currently 50,000 D20s running in Europe, and it will be available here later in 2007. The U.S. model comes in two displacements, 11- and 13-liter.

For all but the Big Bore engines, International will increase exhaust gas recirculation rates and system capacity, adding additional electronic control capability and refining fuel controls and calibration. This builds on International's Green Diesel Technology introduced in 2001 and refined in 2004.

This time around, the Green Diesel is complemented by a diesel particulate filter, which is both an oxygen catalyst and a ceramic monolith filter. Like the others, this will mostly regenerate passively with sufficient load factor to keep exhaust temperatures around 750 degrees. In cool ambient temperatures or in low-duty cycles, the filter will load up with carbon and will have active regeneration through heat from a temporarily enriched exhaust. International has not said how this will be done, but the common-rail type of injection allows for an additional injection event during the exhaust blow down – in a similar fashion to Cummins' ISC and ISL. This will result in an elevation of exhaust temperature over today's, in the order of 300 to 400 degrees, says International. Horizontal and vertical tailpipes will both be mounted from the horizontally mounted stainless-steel DPF.

Because crankcase emissions are also limited by the 2007 mandate, all Internationals will have a closed crankcase breather. The V engines have had this feature since 1995, but they will be fitted across the line in 2007.

There's a little more information about the Big Bore. At a recent reveal of the new ProStar over-the-highway model (see story elsewhere in this issue), Tim Shick, director of marketing and field support for the new engine, offered some details. The engine has an extremely tough block and head, cast in compacted graphite iron. According to Shick, it has been extremely difficult to cast CGI engines in high volume until fairly recently. The castings have also been hard to machine, but new processes have allowed MAN to produce an extremely durable yet relatively light engine.

Ribs on the engine increase the block's stiffness, and a wide flange for the laminated oil pan and a de-coupling rubber gasket all make for a quiet-running power unit.

Inside, most of the components are similar to the MAN engine, with one-piece pistons for the 11-liter and two-piece pistons for the 13-liter engine.

A much more sophisticated top end for the overhead camshaft engine features common rail injection that can accommodate up to five injections during a combustion event. The common-rail fuel system means injection pressure is not dependent on engine speed. With more precise control from the advanced electronics, emissions and fuel consumption are both minimized, Shick said.

Ratings have not been decided, but the 13-liter will likely be between 300 and 450 horsepower with torque of 1,000 rpm with the ability to lug down to 900 rpm. The 11-liter is to be the vocational engine with ratings up to 400 horsepower.

The Big Bore will go into customer test fleets early in 2007 and be available later in the year in the ProStar, 8000 and 7000 models.

MACK

Mack's engines for 2007 were announced late last year and included a complete list of Maxidyne, Econodyne and Maxicruise ratings for the MP7 and MP8 engines.

These are shared engine platforms with Volvo. The MP7 is 11-liter and the MP8 is 12-liter. Mack's rollout will be different from Volvo's. The MP7 is available in limited production even now. The MP8 will be available later in 2007. The 16-liter is also slated to get Mack personality and cosmetics, but likely will not appear as the MP10 until 2008.

For the moment, then, the 11-liter will cover ratings from 300 to 405 horsepower with torques ranging from 1,260 to 1,560 pounds-feet. The upcoming 13-liter takes over higher ratings of 415 to 485 horsepower and 1,540 to 1,700 pounds-feet As Mack points out, under 405 horsepower it's the MP7, above it's the MP8.

The 16-liter currently goes to 625 horsepower in the VT880 conventional recently released by Volvo. Mack President Paul Vikner said at the launch he "likes those numbers" for the 16-liter MP10 when it becomes available.

As noted in the Volvo story, the engine platforms are common, so the Mack MPs – which will replace the E7 as they phase in – have the same architecture: overhead camshaft and rear cam drive to absorb the torsionals from the higher fuel pressure on the camshaft.

Other features of note: The Holset variable geometry turbocharger makes its appearance with electronic controls on Mack engines. The Holset turbocharger is currently used in four 2007 engine applications and will likely be included when the upcoming DaimlerChrysler HDE is launched.

Like the Volvo engines, the 11-liter MP7 and the 13-liter MP8 are different engines with different bore centers. The smaller weighs 2,270 pounds and the larger weighs 2,560.

The new engines are a little longer than the E7, but they package more easily because they are 14 inches narrower. Optimized cooling means close fan-tip-to-shroud clearances.

The engines use diesel particulate filters, with the option of a vertical stack replacing the muffler(s) or the "tea kettle" design, which mounts to the frame rail behind the right front wheel. Both have removable ceramic particulate traps that can be changed out in under two hours.

The DPFs feature a diesel oxidation catalyst that functions as a NO2 generator for the oxidation of the trapped carbon into CO<->2 for passive regeneration when the exhaust is hot enough. This DOC also serves to heat the exhaust stream when either engine load or low ambient temperatures are insufficient for the passive reaction to occur. Diesel-rich exhaust from a doser downstream of the turbo makes contact with the catalyst and the fuel is oxidized – not burned – producing sufficient heat to light off the reaction in the ceramic monolithic filter.

Like the Volvo engines, the Macks feature a crankcase oil recovery system with the cleaned blow-by gases vented into the atmosphere.

It's important to note that while there are very close parallels across the Volvo and Mack engine lines, the Mack engineers have made a determined effort through pistons, camshaft and electronics that the "Mack"-ness is preserved and promoted.

Evidence of this are the three different types of ratings: Maxidyne, Econodyne and Maxicruise.

VOLVO

There are three all-new or nearly new engines from Volvo for 2007. Based on the D12 (with 600,000 manufactured since it was introduced in 1993), the new 11-, 13- and 16-liter base engines are shared with Mack and European maker Renault.

However, while the base iron is common, each manufacturer has engineered a different personality into its own engines.

In Volvo's case, the engines are designated the D11, D13 and D16, each number reflecting the displacement. The smallest engine weighs in at 2,175 pounds and offers rating from 325 to 405 horsepower and torques of 1,250 to 1,450 pounds-feet. It is targeted at vocational, regional LTL and P&D applications.

The mid-sized engine is the D13. At 2,550 pounds, it will be the power unit of choice in VN and VHD (though Volvo will continue to offer Cummins ISX as well). The D13 has ratings of 335 to 485 horsepower and 1,350 to 1,650 pounds-feet and is rated for GCW up to 143,000 pounds.

The big 16-liter engine weighs in at 3,070 pounds but delivers 450 to 600 horsepower and 2,050 pounds-feet of torque, intelligently managed by Volvo's i-Torque. It will be available in both VNL and VT models and is targeted at long-haul and high gross weight applications.

In all, the D11 will be available in seven ratings, the D13 in eight and the D16 in seven.

The engines are all designed with similar architecture: overhead cam, in-line 6-cylinder with the camshaft and accessory drive relocated to the rear of the engine. This has been done to accommodate even higher injection pressure for the electronic unit injector (by Delphi). Injection pressure has been increased to 35,000 psi from 29,000 on the D12. As such, there is a tremendous load fluctuation on the fuel cams. To avoid cam/drive/crankshaft torsionals and timing issues, the loads are fed via a damper into the accessory drive and straight into the engine flywheel.

Otherwise, the Volvo engines follow similar emissions paths, with additional flow-cooled exhaust gas recirculation.

In a deviation from the earlier Volvo engine, these new platforms all use the Holset variable geometry turbocharger with the latest electronic stepper motor control. This gives closed-loop control for the Vectro engine management system and – with a poppet-valve EGR valve – precision flow EGR under all conditions for improved fuel economy and performance, says Volvo.

The emissions system has two available diesel particulate filters (both to be manufactured by Cummins' Fleetguard division). One is designed to replace vertical mufflers with a single exhaust that includes both ceramic monolith filter and a diesel oxidizing catalyst stage. An alternative is the "teakettle" design that mounts on the frame rail right behind the right front wheel. This is an excellent location, because it allows for very quick and easy removal of the particulate filter monolith for cleaning out the oil-additive ash that accumulates in the filter and does not regenerate with the carbon.

Because the DPF has an oxidation catalyst stage, the Volvo units are passively regenerated in typical over-the-road driving, but need the rich-fuel active regeneration for applications that either don't keep exhaust temperatures in the range needed, or are in cold weather conditions.

With electronic controls that monitor engine performance and exhaust temperature, the active regeneration is kept to a minimum. Volvo says fuel economy on the D13, for instance, could actually be improved over the earlier D12. However, that 2 percent or so improvement could be lost to the lower energy of ultra-low-sulfur diesel fuel.

As with competitors' engines, the Volvos have crankcase emissions controls that return oil to the oil pan before venting into the atmosphere.