Audi RS5 B8 4.2 FSI Stage 1 ECU Tuning

The Audi RS5 B8's 4.2 FSI V8 is one of Audi's most iconic naturally aspirated engines. For this project, we developed a Stage 1 ECU calibration for the Bosch MED17.1.1, focusing on extracting additional performance while keeping the calibration appropriate for a high-mileage engine with over 200,000 km.

ECU & Engine

• Engine: 4.2 FSI V8
• Engine code: CFSA
• ECU: Bosch MED17.1.1
• Software: 8T1907560D / Version 0008
• Hardware: 8T1907560

Calibration

Before tuning, we recommend inspecting and cleaning the intake valves, as carbon deposits are common on FSI direct-injection engines and can affect airflow and performance.

The Stage 1 calibration included optimization of:

• Ignition timing
• Fueling
• High-load operation
• Airflow and throttle limitations
• RPM limiter
• Cold-start catalyst heating

The airflow/load limitations were adjusted to prevent unnecessary throttle intervention at maximum load, allowing the engine to use its available performance more effectively.

For the modified downpipe setup, catalyst-efficiency diagnostics associated with P0420 were also disabled.

Results:

Stock: Power 422hp Torque 434Nm

Stage1: Power 449 hp Torque 471Nm

Gain: hp+27 and +37 Nm

That's an increase of approximately 6.4% in power and 8.5% in torque.

For a 200,000+ km naturally aspirated V8, the results are particularly strong. The calibration focuses on delivering real, usable gains while maintaining the character of the legendary high-revving 4.2 FSI.

Final result: 449 hp / 471 Nm.