17 Jun 08
The Diesotto design philosophy is to combine the low emissions typical of petrol engines with the fuel economy of diesels. It's all about downsizing and maximising efficiency.
Firstly, the engine can work on a low fuel:air ratio which alone cuts fuel consumption by around 10% compared with a conventional unit. It has variable valve control and a variable compression ratio that adjusts according to the demands on the engine. Then there's the diesel-style automatic ignition at low and medium engine speeds, with conventional spark plugs working only at initial start-up or when the engine is being used hard. And it's ridiculously clean, too - only tiny amounts of nitrous oxides are released after combustion, necessitating only a standard three-way catalytic converter. But power and torque aren't forgotten: the extra boost comes courtesy of a pair of turbochargers.
Further 'eco' technologies are included, too. An electric motor-generator works with the petrol engine for stop/start and power regeneration; the engine automatically cuts out when idling, and when the car brakes, energy is recovered, stored in a high-voltage lithium-ion battery, and used to assist the engine when accelerating. This is a so-called 'mild' hybrid set-up, as the car cannot run on electric power alone. There are also low rolling-resistance tyres, and plenty of aerodynamic enhancements to keep air drag to a minimum.
Jurgen Hirsch, Manager of Vehicle Concept at Daimler, has been at the heart of the F700 development. He said: 'The car is powerful, it's got good fuel economy and low emissions - that sounds too good to be true, doesn't it? Already we are using some of the Diesotto technologies on current models, but it'll take some time before the full package is available to us. We still have quite a few things to work on.'
