BMW files patent for electric-powered turbocharger: Tri-turbo M3 still a possibility

2015 BMW M3
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The first rumors about the future BMW M3’s engine sent chills through the automotive industry. Apparently, BMW had plans to put in a tri-turbo V6 engine with an output of about 450 HP in the M3. This new engine would combine two conventional turbos with one electric turbo to help the vehicle’s fuel economy. Those rumors were later squashed by new rumors about a new twin-turbocharged 3.0-liter, six-cylinder engine currently under development. But, alas, the tri-turbo engine returns with a new patent filed by BMW for electric-powered turbocharger technology.

This new electric turbocharger seems to have addressed the age-old concerns engineers have had about turbochargers and the size of their turbines (apparently size does matter). You see, small turbines spool up quickly and provide boost via a compressor, but end up running out of steam at higher RPMs. Big turbines do just the opposite; they provide more power at high RPMs, but take too long to spool up, this creating turbo lag. BMW’s new technology doesn’t take on the traditional mechanical turbo layout because the turbine and the compressor aren’t fixed on the same axle. Thanks to two clutches, both the turbine and the compressor can be uncoupled from the turbine axle. When these two clutches are opened, the electric motor can operate without any load.

Hit the jump to see more details on the new technology and a list of the electric turbo’s individual parts.

When the driver hits the acceleration pedal the clutch will close and the electric motor will connect to the compressor and give it enough air to make for a fast engine response. When the turbine has reached a certain speed, the clutch closes and both the turbine and the electric engine are used to run the compressor.

When maximum boost is attained, the electric motor acts as an alternator by generating more power for the battery. This, in turn, eliminates the need for a wastegate because the electric motor limits the amount of boost created.

Maybe now some people won’t think the idea of BMW having an electric turbocharger is ridiculous after all.

2015 BMW M3 Exclusive Renderings
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The electric turbo’s individual parts (as labeled in the diagrams):

  • 1) turbo layout
  • 2) turbine
  • 2’) turbine axle
  • 3) compressor
  • 3’) compressor axle
  • 4) electric motor (and alternator)
  • 5) turbo axle
  • 6) (turbine axle) clutch
  • 7) (compressor axle) clutch
  • 8) gearing
2015 BMW M3 Exterior Spyshots
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Source: F30 Post

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