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Mercedes-Benz Re-Thinks Direct Injection

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Khatir Soltani
Benz Now Back On Track with CGI Direct Injection

Believe it or not, gasoline direct injection is a technology that's near
Direct injection, as we know it in the automotive world, started here, with the 300 SL. (Photo: Mercedes-Benz Canada)
sixty years old. Sixty years old? It makes you wonder what automakers were doing all the while with less efficient, conventional port fuel injection. It's funny how only now, in the middle of the first decade of the 21st century, we're starting to hear about this alternative injection method, employed in Mitsubishis, Mazdas, Volkswagens and BMWs, among others. The real innovator, however, was Mercedes-Benz, which, way back in 1954 employed the world's first fuel injection system in the classic 300 SL 'Gullwing' coupe. It also happened to be the world's first gasoline direct injection system, which was derived from the Benz-designed engine featured in a Messerschmitt fighter aircraft a decade earlier.

The term gasoline direct injection, incidentally, comes from the process
CLKs like these were the first modern non-diesel Benzes to feature CGI. (Photo: Mercedes-Benz Canada)
in which fuel is delivered to the engine; it is injected directly into the combustion chamber, through a common high-pressure fuel rail. About three years ago, when gasoline direct injection technology was still in its modern-day infancy, few cars featured it. At the time, the leading automaker was Mitsubishi, with its Carisma compact sedan and a few European-market Pajeros, while Volkswagen and Audi had just started featuring their version, called FSI. Of course, not one to be left behind, Mercedes-Benz once again invested in direct injection, developing its own version called Stratified-Charge Injection Gasoline, or CGI for short. Benz applied this technology to one engine, a 1796 cc (1.8L) inline four-cylinder that made 168-horsepower. It was available in the CLK and the C-Class as a sort of mid-range engine, but it was neither quick nor glamorous, and the power that was produced wasn't particularly smooth nor was it delightful to listen to. It did what was expected of it, namely, cut back on tailpipe emissions and fuel consumption. Needless to say, almost everyone forgot about CGI.

Outside of Stuttgart's inner circle, no one knew exactly
Stunning. Beautiful, Powerful. I'm not just talking about the CLS exterior, I'm talking about the new CGI engine. (Photo: Mercedes-Benz Canada)
why Mercedes-Benz didn't advance this technology during the three years that it was on the market. It was unexplainable why Benz didn't scale up CGI production for its class-leading twin-turbo V12s, or its big, burly V8s, or at least employ it in more engines to compete with Audi and BMW. Instead, they did something much better with their time, something that Mercedes-Benz used to be very good at; they strove for perfection behind closed doors. At this year's Geneva motor show, alongside a slew of 63-series AMG muscle sedans and coupes, Mercedes-Benz brought out its first vehicle to feature its all-new direct injection technology, the CLS350 CGI.

So,
Ceramic and metal piezoelectric injectors are what make the new CGI system so impressive. (Photo: Mercedes-Benz Canada)
what new thing does the new and improved CGI bring to the world of direct injection? A surprising number of new things, actually, and much came from M-B's long history building common-rail turbodiesels, namely piezoelectric injectors. You may have heard this term being mentioned once or twice in the news - always with reference to diesels - but it's never meant a whole lot to anyone in North America. While they're an essential part of the modern performance diesel motor, they have little value on this side of the Atlantic, as North American regulators are too busy banning them to welcome the cutting edge diesel technology. Nevertheless, piezo injectors differ from the injectors used in standard gasoline direct injection engines in that they're made of metal and ceramic which change their state in a matter of milliseconds, when subjected to an electrical current. When an electrical current passes through the injectors, the characteristics of the injectors change, enabling them to quickly start and stop injecting fuel.
Khatir Soltani
Khatir Soltani
Automotive expert
As a car enthusiast, he tests and compares vehicles from different categories through the eyes of the consumer, ensuring relevant and objective reviews.
  • Over 6 years experience as a car reviewer
  • Over 50 test drives in the last year
  • Involved in discussions with virtually every auto manufacturer in Canada