Mercedes-Benz Revives Its Inline Six Engine

It has taken nearly two decades, but Mercedes-Benz is finally thinking straight again. The automaker is working on a new family of inline six-cylinder engines, its first since the late 1990s.

The gasoline-powered straight six, likely to arrive with the 2017 Mercedes-Benz E-class, displaces 3.0-liters and has an output as high as 400 hp with turbocharging. There will also be a turbodiesel version displacing 2.9 liters, which should top 300 hp in top spec.

Mercedes last offered a straight six in the late 1990s, abandoning it for a new, cheaper V-6. This was the era of the cost-cut E- and C-class models that were designed to broaden the brand’s appeal to new-car customers.

It seems ironic, then, that Mercedes is developing the new engine for the same reason – to save money. The new six-cylinder has been developed off Mercedes’ 2.0-liter four-cylinder engine, with which it shares its bore spacing and 60 percent of its parts. That cuts production expenditures by nearly 35 percent.

Mercedes’ new engine strategy is reminiscent of General Motors’ Vortec inline engines of the past decade, which spawned a 2.8-liter I-4 and 3.5-liter I-5 for midsize pickup trucks and a 4.2-liter I-6 for body-on-frame sport/utilities. Conversely, BMW was rumored to be working on a V-6 replacement for its venerable inline-six family at the time, but any thoughts of making such a change were scrubbed.

Enthusiasts love straight sixes for their inherent balance and silken power delivery. These qualities have in recent years been singly identified with BMW, but Mercedes has a long history of its own with straight sixes. It developed a 3.0-liter inline six in the 1950s that powered everything from the 300 sedans of the day to the 300SL.

The new engine will likely be just as widely applied. After the debuting in the E-class, the new engine will find its way into the S-class and C-class, and then on to the rest of the lineup. The V-6 will likely disappear. We can also expect to see several hybrid and plug-in hybrid models incorporating the new six-cylinder, including a high-performance variant that features a 110-hp electric motor. It’s not clear yet which versions of the engine will be offered in the United States. A Mercedes spokesperson says it is not yet ready to comment on any new engines.

The powerful inline-six also foretells further declines in V-8 sales at Mercedes and across the industry. An internal forecast expects the take rate for V-8 E-class models to be under two percent. There will, however, be a new 4.0-liter V-8 built off the same engine architecture—in essence it shares cylinder heads with the turbocharged four-cylinder. That will arrive in 2017, just in time for the next E63 AMG.

jlewisbarned
@richardaucock @automobilemag Love a good straight-six. So silky...
sstvp
At last. I'll have mine without the troublesome turbo,  variable valve-timing capable of switching from Atkinson cycle to Otto cycle, and three cylinder with valve-locking to provide variable displacement, and no throttle valve.

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