Say Hello To Compound Turbocharging Thanks To 48 Volt Electrical Systems


Compound turbocharging will be coming to more of tomorrow’s vehicles thanks tot engineers at Borg Warner. Turbochargers are compressor powered by the energy of hot exhaust gasses as they rush out of the engine after the power stroke — energy is wasted in non-turbocharged cars. They are vital in the quest to make internal combustion engines more efficient.

Mercedes with compound turbocharging
Mercedes 6 cylinder engine will be first to offer compound turbocharging using Borg Warner e-booster.

Conceptually, they work the same as fanning the flames of a camp fire. More oxygen makes a hotter fire. Cram more of it into a cylinder nearing the top of its compression stroke and you get more power with fewer emissions. If that sounds like magic, it is. But there’s a catch. At low engine speeds, exhaust gas flow is low. It usually takes a few seconds after the driver whistles down to the engine room for more power before the turbo is spinning fast enough to make a noticeable difference. The period leads to what is known as “turbo lag.”

Volvo is leading the way in compound turbocharging systems that uses an electric supercharger to provide boost as soon as the throttle pedal is pressed and before the turbo spools up. The result is the best of both worlds — nearly instantaneous power at slow speeds and lots of extra power at higher engine speeds.

Borg Warner has just introduced what it calls its e-booster, an electric supercharger about the size of a cantaloupe. The company says it can improve fuel economy by 10 percent with no loss of performance. The e-booster is little more than a really powerful hair dryer that pushes more air through the intake tract.

The e-booster can spin up to its full 70,000 rpm operating speed in just three fifths of a second. Borg Warner says it improves torque by 85 percent at 1,500 rpm  and by 55 percent at 2,000 rpm.Thanks to electronic engine management systems, the supercharger and the turbocharger can be managed so the driver feels nothing but a smooth, continuous flow of power all the way from idle to red line.

The e-booster needs up to 6 kilowatts of power — more than a traditional 12 volt system can supply. But a 48 volt electrical system can supply the needed juice and power other vehicle systems like electric steering, electric brake boosters, heated seats, and electric water pumps.

On Friday, BorgWarner announced that Mercedes Benz will introduce the e-booster on a 3.0-liter six-cylinder engine that will be used in an as yet unnamed model. CEO James Verrier says two more automakers will use the e-booster system soon but won’t name the other companies yet. “It’s going become relatively mainstream over the next five years,” he says.

“There’s very little that’s new under the sun when it comes to most engine technologies,” says Stephen Ciatti, a mechanical engineer at Argonne National Laboratory. “What changes is our ability to either manufacture them cheaply and effectively … or the need for a more expensive approach to solving a problem when market demands or regulatory pressures don’t force it.”


Source: Wired



About the Author

I have been a car nut since the days when Rob Walker and Henry N. Manney, III graced the pages of Road & Track. Today, I use my trusty Miata for TSD rallies and occasional track days at Lime Rock and Watkins Glen. If it moves on wheels, I'm interested in it. Please follow me on Google + and Twitter.
  • Ed

    Now retired from having been a supplier to the auto industry for over 40 years, I am now pondering the remarkable complexity we have added to our engines to make them clean and drivable. The list of “emissions stuff” is very long….and getting longer, as this story shows. What is striking is that no matter what Mercedes vehicle this electric turbocharger goes into, that vehicle will pollute more just driving off the dealer lot than an electric car will in driving 100,000 miles. Does the list suggest we are nearing a tipping point for internal combustion engines?

    Since the 1960s:
    Positive crankcase ventilation (PCV) valves
    Exhaust gas recirculation (EGR) valves
    Vacuum amplifiers
    Electronic ignition
    Lead-free gas
    Oxidizing catalytic converters
    Air injection systems
    Electronic Engine Controls
    Fuel injection
    Barometric Pressure Sensor
    Reducing catalytic converters
    Sealed fuel tanks
    Vapor recovery systems
    Vapor recovery fuelers
    Cam and crank timing sensors
    Knock sensors
    Mass airflow sensors
    Manifold Absolute Air Pressure Sensors
    Free oxygen sensors
    Electronic throttle control – pedal and throttle position sensors
    Variable valve timing
    Low sulfur fuels
    Diesel particulate traps
    Cylinder Deactivation
    Hybrid ICE/battery electric vehicles
    High Multi-Speed transmissions
    Continuously variable transmissions
    Multi-Clutch transmissions
    Urea injection and selective reduction catalysts
    Direct fuel injection

    …and most recently:
    48V mild hybrids with start/gen units and electric turbochargers
    Continuously variable compression ratio crankshafts
    Quad turbocharging

    …and, soon:
    Opposed piston engines?
    Homogeneous Charge Compression Ignition?
    Camless valve systems?

    • Steve Hanley

      When I saw the photo of that Merc engine, my first thought was, “Wow. That’s a very complex, complicated machine! Wouldn’t it be easier and cheaper to just use an electric motor?”

      • Ed

        Ain’t it the truth?!

  • kevin mccune

    Hey the steak eating Guys love the noise of an “infernal ” combustion engine, the world is our oyster to swallow , right ?

    • Ed

      Just had a lovely filet a few hours ago!

      • kevin mccune

        That kind of reminds me of some my acquaintances, who just had to have frog legs , they have hunted our native bullfrogs into extinction and the lack of respect the “University of Barbecue” wank displayed when he was grilling beef a fence over from a herd of grazing cows- you do believe in “abiotic oil “, I take it ?