Benz announces petrol engine with diesel characteristics

It doesn't really roll off the tongue, but 'DiesOtto' is the new name for an engine type under development by Mercedes-Benz.

The name is derived from the surnames of two German inventors, Rudolf Diesel and Nicolaus Otto.

Diesel invented the compression ignition engine and Otto invented the four-stroke petrol engine.

Benz's latest development is a petrol engine with direct injection and turbocharging, variable valve timing and variable compression. Spark ignition fires the air/fuel charge during start-up and when the engine is working under full load, but at low to medium revs and during light load, the charge combusts through 'controlled auto ignition', which Benz describes as a "process similar to that of a diesel."

This type of combustion is highly efficient and will result in diesel levels of torque and fuel economy, combined with petrol engine quietness and low emissions.

A 1.8-litre four-cylinder currently under evaluation (pictured) develops 175kW of power and peak torque of 400Nm. Fitted with this engine, an S-Class Mercedes could be expected to return a fuel economy figure as low as 6.0lt/100km.

Optimising power and torque in a small capacity engine is easier than making a larger capacity engine more economical, according to Prof. Dr. Herbert Kohler, Head of Group Research & Advanced Engineering Vehicle and Powertrain; Chief Environmental Officer of DaimlerChrysler.

"Our next goal will now be to make the gasoline engine as economical as a diesel. All the preconditions for this are provided by our DiesOtto concept, which incorporates the foremost strengths of both the gasoline engine and diesel engine," the Professor said.

Both diesel and petrol engines are under active consideration in hybrid-drive applications (more here and here). One vision for the future is a hybrid vehicle with an integrated starter/alternator which is also the electric drive unit.

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