Monday, May 30, 2016

Going Electric: The Next Phase in Forced Induction

2018 Audi SQ7 TDI (Euro-spec)

Not long ago, the only info about electric supercharging in these pages was in the classified section next to a male-enhancement ad. Only one of those products actually worked.

Electric supercharging, long rumored but never fully realized, is finally happening. Audi’s upcoming SQ7 TDI pairs an electric supercharger with sequential turbos on the SUV’s 4.0-liter diesel V-8. It’s a first for a production vehicle.

As with a conventional centrifugal supercharger, an e-supercharger uses a traditional compressor wheel but drives it with an electric motor rather than a crank-driven belt. E-superchargers draw their power from batteries or capacitors, which can be charged via regenerative braking or, in the case of the SQ7, a beefy generator and a 48-volt sub-system.

Going Electric: The Next Phase in Forced Induction

The biggest benefits of e-supercharging are power and response, particularly at low engine speeds. Because an e-supercharger’s ability to create boost is not coupled to exhaust energy or engine rpm, it offers flexibility not found in alternatives. Though traditional turbocharging remains a more efficient means of adding power, it has drawbacks such as lag.

As engines downsize and pressurize, e-supercharging offers the ability to size a compressor for a power target without sacrificing low-rpm drivability. It does so by filling in the torque-less void below the turbo’s threshold for creating boost. This is exactly how Audi is using the Valeo-supplied electric supercharger in the SQ7 TDI.





Electric superchargers won’t replace turbos, but they allow for the optimization of turbos and other technologies. For example, deactivated cylinders can remain dormant longer when supported by e-supercharging. And in Miller-cycle engines, which have a longer-than-normal expansion ratio, an electric blower can replace a traditional supercharger to reduce parasitic losses. Valeo describes its e-supercharger as an enabling technology, which gives it at least one thing in common with those male-enhancement products.


from Car and Driver Blog http://blog.caranddriver.com/going-electric-the-next-phase-in-forced-induction/


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