The new OM 473: The man behind the engine

Vehicle & Technology

Power centre.

The new OM 473 is the most powerful unit of the new generation of engines for Mercedes-Benz trucks. The man behind it: Dr Elmar Böckenhoff, Chief Designer Global for Truck Engines and Powertrains at Daimler Trucks.

Dr Elmar Böckenhoff, Chief Designer Global for Truck Engines and Powertrains at Daimler Trucks in an interview with “Transport” editor Lars Rauscher (photo on the right).

When you design a new engine, where do you start – is there a blank sheet in front of you?

Böckenhoff: Yes – that’s the great thing about this engine family. We essentially began with a blank sheet. It was filled with the result of what we elaborated in basic research. The specified targets we had from markets and planned applications were also integrated. And, of course, the tremendous wealth of experience that the Daimler Trucks colleagues here have. The OM 473 is the most recent member of what is now a complete family of engines for on-road use.

The proven V6 and V8 engines were exemplary in terms of reliability and efficiency. Why is it now important to construct a new in-line engine?

Böckenhoff: There are very concrete technological reasons for this. When it comes to exhaust gas recirculation for example there are many arguments in favour of the in-line engine. The clear separation of the cold and the hot side of the engine is possible here, but not in the case of the V engine. In addition, our goal was to design a series that would be accepted in Europe, the USA and Japan. The in-line six-cylinder engine offers a huge potential in this respect. The advantage is that the development expenditures can be set in relation to a much larger quantity. This means that we can offer a technological leap that could never have been sustained by a single market.

What are the fundamental strong points of the new OM 473?

Böckenhoff: The same ones that characterise the entire series – robustness, quality and reliability. On top of that, it has the biggest displacement, the highest torque and the greatest output of our new engine generation. It is made for heavy-duty applications that require a high transportation speed with a high load.

Despite Euro VI the OM 473 is more economical than its predecessor. How did you achieve this?

Böckenhoff: The engine is designed in such a way that it can operate with extremely high combustion pressures. This is the basis for an efficient combustion. After all, above the 230 bar that we have selected, the internal engine friction increases dramatically. We are exactly in the optimal range, and that’s where we wanted to be.

Which injection system did you decide to choose?

Böckenhoff: The engine series has a highly innovative common rail system with very high injection pressures. Furthermore, we have the possibility to shape the profile of fuel injection. This means that we inject varying amounts of fuel in several stages during the injection duration of several milliseconds. This has an optimal impact on consumption in all rpm ranges.

You have given the engine a second turbocharger…

Böckenhoff: …and we’ve done so as turbocompound technology. It enables a clear improvement in efficiency at all loads and outputs. With a second turbocharger we regain further energy from the exhaust gas following the first stage of turbocharging. We transfer this to the crankshaft.

What do you find particularly fascinating about the OM 473?

Böckenhoff: Leaving aside the turbocompound technology, the unique selling proposition in Europe and in itself is impressive. What fascinates me is the combination of technologies. Each of them by and large fully exploits its possibilities. Peak pressures, injection system, injection modulation, the engine brake – all of this has been outstandingly put into function. My fascination also includes a respect for the achievements of my team. Impressive individual solutions were created here. A perfect package was then developed with the participation of many more people. This also relates to the powertrain and the exhaust gas system.

The engine of this displacement class was already available in the USA. Do customers in Europe benefit from this?

Böckenhoff: A very clear yes. We are introducing this engine family in stages. We began in the USA, then it was Europe’s turn. Now the first technologies that we further developed in Europe are being launched on the U.S. market. Thanks to this intensive exchange, we already achieve a previously unparalleled quality when sales start. Through the fine-tuning and work on the details, as this is not just about the basic concept. The OM 473 benefits tremendously from the experience in the USA – in heavy-duty applications, but also in completely normal fleet operations.

In its most powerful version the OM 473 generates 460 kW. It that enough as the top-of-the-range engine?

Böckenhoff: We are not taking part in a power race simply for its own sake. The goals of this engine are functionality, heavy-duty capability and application – not showroom and marketing. As part of the engine family this top engine is not only identical in design, but also shares all the standards in terms of reliability, service life and durability. We are not willing to accept compromises on this point.

Venturing an outlook – will be have a hybrid drive as the standard solution for heavy-duty trucks in 20 years time?

Böckenhoff: In comparison to the other engine systems the diesel engine has achieved an extremely high degree of efficiency. In addition, the demands as regards power density are extremely high for commercial vehicles. For this reason the diesel engine will be represented in a large segment of the market in the foreseeable future. Furthermore, there will also be fields of application in which the hybrid drive can bear the additional costs.

Are there development possibilities for the diesel engine?

Böckenhoff: Basically yes, but this will be decided by two factors. One is the statutory framework. It has for example led to a situation in which there are now Euro VI engines whose exhaust gas may even be cleaner than the air intake. The second factor is the profitability for the customers. There are a number of technologies that have enabled us to make further efficiency leaps – for example exhaust gas heat recovery. Whether and when this technology will come, however, depends on the development of fuel prices, as the investment must pay off in the end. All future technologies must prove this. The diesel engine, particularly the OM 473, has already done so.

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