Editorial: Tri Turbo and Electrical Assist

Interesting | July 9th, 2011 by 15
458417.1 lg1 750x500 Editorial: Tri Turbo and Electrical Assist

The triple turbo talk continues unabated, this time with a bit of a twist, electric turbo. Not so fast! Electric turbo? If a turbo was …

The triple turbo talk continues unabated, this time with a bit of a twist, electric turbo. Not so fast! Electric turbo? If a turbo was powered electrically (rather than with exhaust gases) it would be a centrifugal supercharger.

And a quick interwebs search on ‘electric supercharger’ will bring up the same level of snake oil stupidity since ‘high mileage’ magnets. But if you look for ‘electrically assisted turbochargers’, a completely different set of information comes up.

What the electrical assist does is spin the turbine up to speed in very light to no load conditions. And the term ‘light to no load’ is the critical piece. Under load, you have to supply massive quantities of
amps to the electric motor to generate the boost levels needed. But if all that is required is for the turbine to be spun up then an existing automotive electrical system will work just fine.

458417.1 lg1 655x495 Editorial: Tri Turbo and Electrical Assist

A random electric supercharger featured here

Knowing that, where the electrical assist in a tri-turbo setup resides is just a matter of deduction (as opposed to ‘induction’). The speculation is that the engine would continue to use two small turbos (one for cylinders 1-3, the other for cylinders 4-6) as the N54B30 does. They have minimal lag, and provide decent performance right off idle. But they suffer at higher engine RPMS. It’s at this juncture that the third turbo would be employed, picking up the compression of air at higher RPM/load tan the two smaller turbos won’t handle as efficiently.

It’s that third turbo that would benefit from electrical assist. As engine RPM rose, the circuit to spin the third turbine with the small electric motor would kick in and the turbo would be ready to provide
boost with virtually no lag. (Even more fun is grabbing the electrical output from the motor when under boost and applying that to the battery.)

In thinking about how that would be accomplished, I imagined a pancake motor housed between the turbine and compressor side of the turbocharger. Et voila, electrical assist! But, Garrett has been down this road before with their e-Turbo, and I suspect electrically assisting the turbine was conceived prior to 2005.

But before jumping on the band wagon, there is one major caveat. What it boils down to (all puns intended) is how do you protect the electric assist motor, living on the shaft that joins the turbine and compressor, from the intense heat produced by the turbocharger.

I suspect they have an answer to that, and that’s why they are titled engineers and I’m a scribbler. Regardless, chalk another new thing up as EfficientDynamics.

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