Click Thumbnails to Enlarge
First official green pictures
11 September 2007 03:00
So, another big lumbering Mercedes saloon then?
Not a bit of it. Although the F700 might be 5.17m long – somewhere between the S-class and long-wheelbase S-class – the F700 is supposedly cleaner and more frugal than any current S-class. This is thanks to its innovative ‘Diesotto’ engine. The F700 also features a hybrid drive and suspension that reads the road ahead. And, for those who are familiar with the online world Second Life, there's an avatar too.
Diesotto? Sounds like a mix of diesel and the Otto cycle...
Bingo. That’s just what this engine is. The F700 has a 1.8-litre four-cylinder engine that is supposed to combine the low emissions of a petrol engine with the consumption of a diesel. With the Diesotto engine, this very large F700 manages 55.3mpg and emits just 127g/km of the dirty stuff. But don't think this engine lacks power, as there are two sequential turbochargers, plus a hybrid system to assist when the car moves off. The hybrid system allows stop/start running. There's also direction injection, variable valve lift and a variable crank. This crank allows for the especially clever bit: the ignition. Running on conventional petrol, the Diesotto engine operates with spark ignition under start-up and full loads, but under partial loads (low and medium speeds) it switches to diesel-style compression ignition. Mercedes calls this controlled auto ignition (CAI) and it means lower operating temperatures. This in turn means fewer nitrogen oxide emissions, while a three-way catalytic converter mops up the rest. The Diesotto engine makes 235bhp and 295lb ft, and the electric motor adds another 20bhp. This means a 0-62mph time of 7.5 seconds, and the aforementioned impressive consumption and emission figures. And not only is the engine very clean and efficient, but because it's smaller and lighter, it helps the F700 weigh 1700kg, whereas a base S280 is 1880kg.