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Mercedes prepares to crush all rivals

The fuel economy wars are heating up, and we can partially thank (or blame depending on your view point) the U.S. government for increasing fuel efficiency. According to Edmunds, Mercedes Benz is looking to significantly boost fuel efficiency for the turbodiesel variant of its restyled 2014 E-Class luxury sedan.
The outgoing 2013 E350 Bluetec features a 3.0-liter V6 turbodiesel that produces 206 hp and 400 lb-ft of torque. It's enough to give the 4,000-lb sedan EPA ratings of 22 mpg city and 32 mpg highway.
However, the new 2014 E250 Bluetec 4Matic gives up two cylinders and a bit of power and torque to significantly boost highway fuel economy. The 2.1-liter, 4-cylinder turbodiesel engine uses twin sequential turbochargers to generate 195 hp and a still impressive 369 lb-ft of torque, however, highway fuel economy skyrockets to 45 mpg.

2014 Mercedes E-Class
Projected city and combined fuel rating are not available, but we expect those figure to rise sharply as well.
The 45 mpg highway rating makes the E250 Bluetec 4Matic even more fuel efficient than the lighter, less powerful Volkswagen Passat TDI which has an EPA highway rating of 43 mpg. And as its name implies, the E250 Bluetec 4Matic manages that lofty figure with the added heft of an all-wheel-drive system.
Mercedes has yet to announce pricing for the 2014 E250 Bluetec 4Matic, but the 2013 model starts at a $52,200 and lacks AWD.

Source: Edmunds

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RE: More info?
By 91TTZ on 5/20/2013 3:13:07 PM , Rating: 2
Sequential configurations also allows variable boost while cruising because you can have a dual-stage wastegate that will reconfigure the boost path. This means while cruising at low-rpm, the small turbo could be completely bypassed and the larger, quieter turbo could continuously feed a regulated ~5psi, something that can't be done in a single turbo application where efficiency is wasted by over boosting at highway RPM.

You can still have variable boost with a single turbo. The wastegate's job is to allow exhaust to bypass the turbine and control boost. Why would you have the wastegates set at a fixed setting when a boost controller is able to vary it?

For instance, on my 300ZX the turbos have integrated wastegates which are set to open at 7 psi. However, the vacuum lines running to the wastegates have a T with another line running to a boost solenoid. When the ECU detects that the engine is running correctly, it opens up the boost solenoids which allows some of the pressure to bleed out of the system. This allows the turbos to boost to 9 psi.

If you install a boost controller in place of the boost solenoids you can have even more control of the boost. The boost controller will come with a servo controlled actuator that can bleed off the air more precisely and allow you to have different boost setting configurations. Many newer cars have the boost controller logic integrated into the ECU. They therefore have variable boost.

RE: More info?
By Spuke on 5/20/2013 3:39:35 PM , Rating: 2
They therefore have variable boost.
On GM's LNF engine (2.0L DI turbo), the ECU has a torque target and varies boost to meet that target based on load, elevation, temperature, fuel octane, etc. I would imagine other engines perform similarly.

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