| New Engine Technology | Mercedes-Benz DiesOtto |

Mercedes-Benz claims to have created an engine that combines the performance and emissions attributes of petrol engines with the high torque and fuel economy of a diesel. The DiesOtto concept relies partly on controlled auto ignition (CAI), a heat-retaining combustion system that has been heavily researched by car manufacturers of late because of its potential.

CAI works by retaining large quantities of burnt gas in an engine cylinder from a previous piston compression cycle, which then heats the new incoming fuel-air mixture after compression and causes an auto-ignition. Mercedes has designed the system to operate at low and medium engine speeds when a spark plug is unnecessary, subsequently achieving much lower nitrogen oxide emissions.

Using conventional petrol to fuel it, the DiesOtto concept is a four-cylinder, 1.8-litre unit, but despite its modest size (a result of the need to lower fuel consumption), produces 238bhp with maximum torque of 295lb.ft thanks to an additional turbo. The special unit works in conjunction with an electric hybrid integrated starter/generator to aid the search for even greater fuel consumption and lower emissions.

Herbert Kohler, Head of Group Research & Advanced Engineering Vehicle and Powertrain; Chief Environment Officer of DaimlerChrysler is confident of success: "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".

Kyle Molyneux - 25 Jul 2007