e-turbo
An electrified turbocharger; a turbo with electrically assisted ramp-up, using an accessory electric motor, to bring the turbine up to speed, reducing turbo lag. (When operating in electric mode, the turbo functions like a supercharger, driven by input power instead of exhaust gas.)
e-turbo: turbocharger with electric motor assist
An e-turbo is a turbocharger fitted with an electric motor that drives the turbine shaft independently of exhaust gas flow. The motor, typically rated between 10 and 20 kilowatts, spins up the turbine during low-speed running and acceleration, delivering boost pressure when exhaust energy alone cannot. Once engine speed and exhaust volume are sufficient, the motor disengages and the turbo operates conventionally, driven by hot exhaust gas flowing across the turbine wheel. This hybrid arrangement eliminates turbo lag, the delay between pressing the throttle and feeling boost arrive.
The electric motor is powered by the vehicle's high-voltage battery, the same pack that supplies the main drive motor in hybrid and battery electric vehicles. Clutches or overrunning mechanisms ensure the motor does not drag once the turbo is self-sustaining. The turbine and compressor wheels remain conventional, but the shaft housing and bearing structure must accommodate the motor attachment and the additional loads it creates. Integration with engine management requires careful tuning: the motor must cut out cleanly to prevent surge, and the transition from electric to exhaust-driven operation must be seamless to avoid drivability faults.
Where e-turbo sits in the market
E-turbo technology is most common in mild-hybrid and plug-in hybrid vehicles where a battery is already present. It appears in diesel and petrol engines, though diesel applications are more frequent because diesel engines produce substantial exhaust heat at low revs, making the lag problem acute. Full battery electric vehicles rarely use turbos of any kind, rendering e-turbo unnecessary. Conventional cars without onboard electrical storage cannot use this technology cost-effectively.
E-turbo differs from a supercharger in that it exploits exhaust energy passively once the motor has done its work, making it more efficient than a belt-driven blower at steady cruise. It differs from a simple turbocharger in cost and complexity: the motor, inverter, clutch mechanism, and software add several hundred pounds to the vehicle bill and introduce additional failure points. The name reflects the electrical motor assist, distinguishing it from older concepts like variable geometry turbos, which adjust turbine vane angles but still depend entirely on exhaust flow.