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Mercedes introduces hi-tech pistons made from steel


August 19, 2014

An aluminum piston (left) and one of the new steel pistons (right)

An aluminum piston (left) and one of the new steel pistons (right)

In 1936, Mercedes-Benz became the first company in the world to launch a diesel passenger car – the 260D. Over the years, diesel automobiles became renowned for their efficiency and fuel economy. Now, the manufacturer is building on that success with the introduction of high-tech steel pistons.

The steel pistons will debut in the V6 diesel engine of the Mercedes-Benz E 350 BlueTEC. With the new pistons in place, the car will deliver the same engine output as would be achieved with aluminum pistons (190 kW/258 hp) yet will only use around 5.0 liters of fuel per 100 kilometers (47 mpg) – that's an improvement of about three percent.

The use of steel pistons improves efficiency, as steel has a lower level of thermal conductivity when compared with aluminum, meaning higher temperatures are reached within the combustion chamber. This, in turn, leads to increased ignition quality, while the combustion duration is reduced. The overall result is lower fuel consumption and pollutant emissions.

An additional advantage of using steel is that it allows the piston to be smaller in size, while also offering a greater resistance to mechanical stresses. The use of steel has also allowed engineers to reduce the gap between the cylinder wall and the piston – resulting in the reduction of untreated emissions.

Steel pistons are already found in certain commercial vehicle engines, where they are combined with heavy cast-iron crankcases. Meanwhile, aluminum pistons are normally found in passenger car diesel engines. But the steel pistons developed by Mercedes-Benz will reportedly harmonize perfectly with a car's much lighter aluminum engine housing.

Diesel engines have come a long way since the first Mercedes-Benz 260D. There was the introduction of turbo technology in the 70s, the first particulate filter system in 1985 and then the arrival of the common-rail diesel in 1997. Now, some engines even combine diesel and gasoline, such as that of a 2009 Saturn at the University of Wisconsin-Madison.

Source: Daimler


Pistons were steel a hundred years ago. How are these pistons different?

19th August, 2014 @ 12:07 pm PDT

I think titanium would be better but the cost...

@ MBadgero

Better alloy, better shape, tighter tolerances.

19th August, 2014 @ 03:15 pm PDT


Bill Bennett
19th August, 2014 @ 09:19 pm PDT

A ceramic face to the piston would seem to be better yet, just a matter of being able to attach it well to the rest of the piston.

Siegfried Gust
20th August, 2014 @ 08:25 am PDT

Maybe now CARB won't get their panties in so tight of a bunch.

Bruce H. Anderson
20th August, 2014 @ 12:10 pm PDT

@ Bruce H. Anderson

CARB is all about their power science and air quality has nothing to do with their actions.

20th August, 2014 @ 01:06 pm PDT

Wouldn't the ideal be to make the piston and cylinder from the same metal so they'd have the same coefficient of expansion?

That's why it's so bad to lose cooling in an engine with an iron block or iron lined cylinders and aluminum pistons. The pistons will expand more than the cylinders and seize in the bores.

Gregg Eshelman
20th August, 2014 @ 02:56 pm PDT

Any details on the piston pin on the new steel piston?

Mike Johnson
20th August, 2014 @ 03:13 pm PDT

@Siegfried Gust

I would not want ceramic anywhere inside an engine. Even a single loose grain can ruin an engine. If you want you can try the following experiment.

Take a ceramic plate (dish). Invert it. There should be a base ring of unglazed area. Take any kind of knife and use this unglazed ring area as a sharpening device. You will be surprised at the result.

I do remember International Harvester petrol engines using cast iron pistons some 45 years ago.

30th August, 2014 @ 12:18 am PDT
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