Brought to the US market for the first time in the 2020 Audi S6 and S7, Audi’s Electric-Powered Compressor (EPC) comes paired to the 2.9-liter, twin-turbocharged TFSI V6 engine. It consists of an electric motor with a small turbine that helps quickly build turbo boost pressure, sharpening throttle response and reducing any noticeable turbo lag.
The EPC takes advantage of the latest-generation 48V mild hybrid electrical architecture, supplying electric energy generated during coasting and recuperation to the vehicles’ 9.6 Ah lithium-ion battery. From there, the battery provides the electric motor energy to accelerate the turbine located downstream of the engine’s turbochargers to quickly increase pressure, aiding engine responsiveness and torque delivery.
The entire EPC system adds just 10 kg (22 lbs) to the vehicles’ overall weight and reduces response time to less than 250 milliseconds, faster than an average human’s reaction time.
The compressor is located downstream of the engine’s parallel twin turbochargers and upstream of the air-to-water intercooler, pushing cooler air through the engine’s two throttle bodies and into its cylinders with higher force. At lower engine speeds, the EPC activates at speeds up to 70,000 RPM. This helps the engine operate similar to the smoothness of a naturally aspirated, non-turbocharged, engine.
When the V6 TFSI engine is operating at higher speeds, a valve for the EPC closes, leaving a parallel path for air to move throughout the engine. However, the EPC is always operating, even when idle, ready to respond to the driver’s needs for more power.
Both the Audi S6 and S7 are rated at 444 horsepower and 443 lb-ft (600 N·m) of torque—37 lb-ft more than their V8 TFSI-powered predecessors. In internal tests that simulate real-world standing starts, the latest powertrain exhibits response characteristics that rival Audi’s torque-rich, turbocharged 4.0-liter TFSI V8. Yet, the 2020 S6 and S7 offer 22% greater EPA-estimated fuel-efficiency with its downsized V6 engine compared to their predecessors without sacrificing performance.