B4x Performance Upgrade Guide
View the ideal performance upgrade paths for your B48 or B46 engine. These infographics show recommended modification stages for all compression variants including B48E.
Power figures are community averages and not tied to any specific tuner or brand. Actual results may vary based on conditions, fuel quality, and supporting modifications.
Stock Fuel System Capabilities (Ethanol)
Understanding your fuel system limits is critical when planning ethanol-based builds.
Methanol Injection Guide
Methanol injection can provide additional cooling and octane for high-power builds.
Gen 1 Low Compression (10.2:1) Upgrade Path
Performance upgrade guide for B48/B46 engines with 10.2:1 compression ratio (typically 30i models).
Gen 1 High Compression (11.0:1) Upgrade Path
Performance upgrade guide for B48/B46 engines with 11.0:1 compression ratio (typically 20i/30e models).
B48E/B48T1 (M-Lite 9.5:1) Upgrade Path
Performance upgrade guide for B48E engines with 9.5:1 compression ratio (M135i, M235i, etc).
B48TU (Gen 2) Upgrade Path
Performance upgrade guide for B48TU/B46TU Gen 2 engines (2018+ models).
Expected Power & Torque Figures
Community-observed average power and torque figures for B48/B46 at various stages. These are not tied to any specific tuner - just what has been observed across the community. Figures are based on wheel horsepower (WHP) measured on Dynojet dynos - other dynos typically read closer to crank figures.
