BMW 335i performance guides
Choose the correct engine/trim guide below, then match mods to your goals (street, track, daily reliability).
Engine / trim guides
FAQ
Does my BMW 335i have an N54 or an N55?
It depends on generation/build date. Many E90/E92/E93 335i models started with the twin-turbo N54, while later years moved to the single-turbo N55. Confirm by generation/VIN/build sheet before buying parts.
This hub links to the 335i N54 guide — what if I have an N55?
Use engine-specific guidance. N54 and N55 share some concepts, but their common issues, fueling/ignition needs, and mod priorities differ. Always match parts and tune strategy to your exact engine.
What should I fix first before tuning a 335i?
Start with a leak-free baseline (vacuum/boost), healthy ignition (plugs and coils), and stable fuel delivery. On N54 cars, injector health and fuel system maintenance are especially important before adding boost.
Upgraded twins vs single turbo: which makes sense for my goals?
Upgraded twins keep a more OEM-like feel and packaging, while single-turbo setups can support higher peak power but require a more involved build plan. Choose based on your power goal, budget, and how much fabrication and tuning complexity you want.
What should I log after a tune?
Log boost target vs actual, timing corrections, fuel trims, AFR/lambda, fuel pressure (when available), IAT, and any misfire indicators. Repeat the same test in similar conditions to compare changes.