Electric Turbo and E-Compressor

Turbo lag — the delay between pressing the throttle and the turbo building boost — has been the curse of turbocharging since the technology was invented. Electric turbos and electric compressors eliminate lag by using a high-speed electric motor to spin the compressor independently of exhaust gas flow. Instead of waiting for the exhaust to spool the turbine, an electric motor instantly spins the compressor to deliver boost pressure in milliseconds.

There are two designs. An electric turbo adds a small electric motor to the turbocharger shaft, between the compressor and turbine wheels. The motor spins the shaft at low RPM to eliminate lag, and once exhaust flow is sufficient, the turbine takes over and the motor can even act as a generator to recover energy. A separate e-compressor is a standalone electrically driven compressor placed in the intake tract before or after the turbocharger. It provides instant boost pressure independently of the turbo — when the turbo catches up, the e-compressor reduces its output.

Spinning a compressor fast enough to make meaningful boost takes serious power. These systems require a 48-volt electrical system at minimum — the motor draws too much current for a 12V system. Mercedes-AMG, one of the first to production, uses a 48V-powered electric turbo on their latest engines. The electric motor can spin the compressor to over 100,000 RPM in under one second. Audi uses an e-compressor (separate unit) powered by 48V on some RS models.

Mercedes-AMG uses an electric turbocharger (motor on the turbo shaft) in the M139l engine in the C43 AMG and in the M176 engine in the AMG S63 and GLS63 models. Audi uses a separate electric compressor on some RS models and the SQ7/SQ8 with V8 TDI. The technology is still limited to high-end performance applications because of cost, but 48V mild hybrid systems are making it easier for manufacturers to add electric compressors to more mainstream engines in the future.

Electric turbo and e-compressor systems add electrical components to an already hot environment. The 48V motor, its wiring, and cooling system are the primary service concerns. Check for DTCs related to the electric motor, power supply, and speed sensors. The 48V system must be in good health for the electric compressor to function — a failing 48V battery or DC-DC converter can prevent the e-compressor from operating. You may also see DTCs for boost pressure targets not being met if the electric compressor is not spinning up correctly.