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PLATFORM FOR THE FUTURE
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There were one or two surprises in store
for Ivan Stjemqvist when he visited
DaimlerChrysler to see its neration HDEP engin
project managerThomas Harr is the person at DaimlerChrysler with the greatest knowledge of the new HeavyDuty Engine Platform (HDEP), the foundation of the group's future engine development. In a highly interesting interview with (almost) no information held back, he gave CM the full story of the engine range that will be the future joint platform for DaimlerChrysler's heavyduty engines and will supersede all the existing heavy-duty diesel engines in the global engine range.The six-cylinder in-line HD EP series will eventually have four engine sizes.10.6. 12.8, 14.8, and 15.6 litres.The first example to he launched is the 14.8-litre version with High EGR. turbo-compounding and active particulate trap.
Against the trend
It seems slightly paradoxical that the first HDEP engine is equipped with EGR,when the present trend is for SCR after-treatment.
"Perhaps," admits a smiling Harr while showing us a test model of the first engine in the series. "At the same time it shows a little about the flexibility of a genuinely global diesel engine. In North America (NAFTA countries) AdBlue has not yet been accepted, and to comply with EPA07 requirements, we must do as the other engine manufacturers in this important market. And that means: High EGR to fight NOx and an active particulate trap to reduce PM . Those are the conditions just now in NAHA, hut this will change by the next environment step in 2010.
"Our existing EPA07 engines have been ready for a long time, hut we are expecting a steep decline in sales in 2007 and plan louse this time for a slow implementation of the new HDEP engine generation into the awareness of the American truck owners.
"It's the very engine we arc looking at here: it is a six-cylinder in-line engine of 14.8-litre displacement.This is the engine size that will be most widely distributed and the one that will appeal particularly to the big fleet owners. Maximum power and torque are 560hp and 2.600Nm respectively for NAFTA. For later applications it is planned to have 600hp and 3,000Nm.There will be an additional downrated 'fleet owner' version of 455hp and 2.100Nm."
Our interview began in one of the technical engine development workshops. where several test engines were under preparation. For a journalist to be allowed in here at all is like letting a child into a toy shop. And there it was, right in the middle of the floor, the new 14.8-litre HDEP engine.
Together we went through the engine from A to Z. and practically nothing was kept secret.There are no big surprises in the basic engine design.The change from V-engine to in-line engine had, after all, been announced long ago, and the timing gear location on the flywheel end is now normal.Two overhead camshafts on a heavy diesel engine are no longer unusual and when, as in this case, they do not activate the unit injectors, the dimensions are relatively modest.The entire HDEP range abandons unit pump injection in favour of common-rail injection.
Great flexibility
Common-rail injection provides far greater flexibility when the same engine is to be used globally and certified in many countries.The 'small' two-cylinder high-pressure pump is driven directly from the timing gear and delivers a constant rail pressure at a modest 900 bar, says Harr, but the actual injection pressure may vary all the way up to 2,100 bar.
The final pressure increase takes place in the individual injectors, where the pressure is electronically-hydraulically intensified by a factor 012.3 and controlled by two solenoid valves.
The common-rail system is supplied by Bosch. and DaimlerChrysler will he the first customer for the new Amplifier Piston Common-Rail System (APCRS).The biggest advantage of the new system is that the injection characteristics can vary within the engine map to always get the best fuel consumption.The benefit is that the lower rail pressure requires less pumping energy, the large pressure increases happen only in the injector itself and only when needed and provide different flexible rate-shape characteristic modes such as ramp, boot or square.
All the EPA07 engines seen so far have used VGT or two-stage turbo-charging. hut not this engine. It has a conventional turbo, and when we express our surprise. Harr merely points to the heat shield after the turbo. It's behind this heat shield that the 'secret' is hidden. At a time when other engine manufacturers are, surprisingly abandoning the turbo-compound principle. DaimlerChrysler is introducing it for the first time. In connection with the High EGR, which needs a high exhaust backpressure, it finds the turbo-compound highly suitable. "We need the back pressure, and we need the added efficiency supplied by the turbo-compound to convert the increased efficiency into fuel savings. Frankly, we'd rather avoid the VGT as well as the two-stage turbocharging," Harr admits. "We tested both options, but so far the reliability and fuel consumption in the two systems are not satisfying .Turbo-compound is stable and gives an added fuel saving."
While looking at the exhaust side, we also notice there is no exhaust brake throttle in the outlet.There is also a rather unusual throttle in the air-inlet. "Of course, we have a highpowered engine-brake built-in," says Harr. "but it operates without exhaust-throttle. It's a decompression brake working according to the same principle as a J-Brake. It is so highly powered that we do not need an outlet throttle to shut off the airflow.We are talking braking power of above 500hp."
EPA07 has been a challenge for all engine makers in the US, and without use of SCR technology, there is no getting round the High EGR needed to manage the low NOx-values. For sufficient reduction of the PM, it has additionally been necessary to have an active particulate trap (DPFfilter).The first part of the two-piece DPF filter is an oxidation catalyst with full flow, while the last part is a ceramic PM trap retaining more than 90% of the soot particles. It is this part of the filter that intermittently needs to regenerate. This happens automatically by adding hydrocarbon (HC) from an HC closer, thus increasing the exhaust temperature. Active regeneration takes 1010 15 minutes and is not noticed by the driver.The new DPF filter does, however, require ultra-low sulphur diesel fuel, something the American industry has been able to comply with.
Multiple names
'HDEP' is just a project-name.Naturally, we would like to have a hint of what the real name will be." Unfortunately it can be no more than a hint," says Harr." Partly because it is not a topic the project team is engaged in and partly because we wish to keep it secret until the opening. It is, however, quite certain that we will use different names for the different markets. In Europe it will definitely be a Mercedes-Benz name, whereas in NAFTA it is more likely to lean towards the Detroit Diesel Corporation (DDC). In the Far East we will make use of the family ties to Mitsubishi Fuso."
The first Freightliner model to have the new engine will be the newly presented Cascadia. It has gone through extensive wind tunnel testing at the new facility in Portland. and the results are very promising.
In North America truck speeds are significantly higher than in Europe, therefore aerodynamics have a much greater impact on fuel consumption.With the reduced airresistance, the new HDEP engine will give the new Freightliner long-haul trucks unprecedented low fuel consumption,giving it a head start in the US and the whole NAFTA area.
Following a hopefully successful introduction onto the North American market, it will come to the rest of the world, above all Europe.When will we be able to test the first Actros with an in-line six? "In Europe the change from V-engine to in-line engine plays a significant role." says Harr."The present Actros cabin and chassis were after all practically built for aV-engine, and changing to the in-line engine does involve major intervention in the cab and chassis design. Therefore, the change to the HDEP engine is inextricably connected with the new truck generation.
The introduction in Europe is also closely connected to the emission standards. As it is well known, thanks to Bluel'ec [AdBlue]. our existing engines also comply with Euro-5 demands, this will be sufficient until 2012.Well ahead of time we will need. howevecto be ready with the Euro-6 engines, and that will definitely be IIDEP engines.The problem is that we do not yet know the final Euro-6 standards to the last detail, and that is crucial for the design we will end up using.
"Our primary design is BlueTec aftertreatment, but we cannot deny that it may become necessary to combine it with EGR. This will depend on the final NOx and PM values, and it is actually about time that the EU takes a clear stand and announces the requirements.
Bus versions
"For the Mercedes-Benz and Setra bus ranges we are preparing 10.6 and 12.8-litre versions. Seen from a manufacturing viewpoint, we are hoping that the bus people will not want a horizontal engine.This has not yet been finally decided.The engine strategy for buses should be as close as possible to the truck engines to generate a maximum of synergies.
"When the change to the HDEP engine series has been carried out for the entire range, we are following the same strategy for medium-duty engines; light-duty is still under discussion.
"It is not a coincidence that the first HDEP engine has its premiere in the US. In North America, DaimlerChrysler and Freightliner LLC are still deeply into the phase of convincing the customers that they should choose a diesel engine developed and manufactured by the truck manufacturer itself —just as it is done in Europe. For this process the DaimlerChrysler owned DDC is a key factor, which will pave the way for the HDEP heavy-duty engine in the NAFTA countries. DDC has been very successful with the legendary Series-60 engine recently upgraded to EPA07.A reasonable acceptance in the US of the new 14.8-litre heavy-duty engine is therefore very important and may create the final breakthrough for the European driveline philosophy.
"Development of the largest HDEP engines has therefore taken place at DDC, at the facility in Redford,Michigan.This is also where the first 14.8-litre engines will be produced, and it is our hope that the customers will transfer the confidence earlier shown to the DDC products to the HDEP. Engines for Europe will be produced in Mannheim,which, like Detroit, has proud engine traditions.
"Mitsubishi Fuso in Japan will handle the engines for the Far East as competence centre and assembly plant," says Harr, whose working place is constantly changing between Europe. Japan and the US.
It is not planned to produce the HDEP in Brazil's Sao Paulo facility so far.The facility will be very busy for a long time to come as it will supply all the markets that are not in the forefront of tough environment requirements and the current 0M457 LA for Europe. What will happen later has not yet been decided. •