Tuning · BMW M135i (F20 / F21)
M135i
N55
The N55 hot-hatch sleeper in F20/F21 form. Hand-calibrated from Stage 1 through to hybrid and big-turbo builds.
Engine
N55
Stock
322 bhp · 450 Nm
Stage 3 ceiling
322 bhp
About this tune
The F20 / F21 M135i (2012-2016) is the pre-LCI 1 Series hot hatch, N55 single-turbo straight-six in the smallest possible body. Stock is 322 bhp / 450 Nm (BMW Performance Power Kit trim), sent rear-wheel via the ZF 8HP. Available as the F20 5-door and F21 3-door, both sharing the identical drivetrain. The N55 predecessor to the B58 M140i, and one of the most popular N55 tuning chassis in the UK.
BMW M135i tuning
The BMW M135i (F20 / F21, 2011–2019) runs the N55 and leaves the factory at 322 bhp · 450 Nm, Rear-wheel drive, 8-speed ZF automatic. Samuel tunes the F20 5-door and F21 3-door to the same standard — every map hand-calibrated for the specific car, its fuel grade and its installed hardware, not a base file loaded and left. M135i Stage 1 alone takes it from 322 bhp · 450 Nm to 380 bhp · 500 Nm on the standard turbo, flashed over OBD on BM3, MHD or MG Flasher.
Add the Stage 2 hardware and the M135i targets 420 bhp · 550 Nm; from there the N55 stretches to around 800 bhp on a hybrid or big-turbo build with supporting fuelling. Whichever stage suits the M135i, the file is delivered within 24 hours and is fully reversible to the supplied stock calibration.
Configurator
Build your M135i tune
Choose your stage — Stage 1, Stage 2 or Stage 3 — add the options that fit your car, and send the full build to Samuel for a custom remote remap. He'll quote, schedule, and personally calibrate within 24 hours of confirmation.
Add a stage or add-on
£0
Engine guide
BMW M135i tuning, stages, hardware and what to expect from the F20 N55
The F20 / F21 M135i (2012-2016) is the pre-LCI 1 Series hot hatch, the N55 single-turbocharged 3.0-litre straight-six in the smallest possible body. From the factory, BMW set the M135i at 322 bhp / 450 Nm (BMW Performance Power Kit trim); the hardware ceiling sits considerably higher and is shared with the rest of the N55 family. BMW M135i tuning with Samuel applies the same N55 Stage 1 / Stage 2 / Stage 2+ map family used on the 335i, 435i and M235i, same engine, same MEVD17 DME, same hardware ceiling.
Stage 1
380 bhp · 500 Nm
No hardware required. The MEVD17 DME is flashed via the OBD port. BMW M135i Stage 1 unlocks 380 bhp and 500 Nm from the OEM hardware (up from 322 / 450 stock). The BMW M135i chip tuning starting point and the most cost-effective change you can make to the F20 / F21 N55 hot hatch.
Every M135i tune Samuel produces is calibrated individually for the specific car, fuel grade and installed hardware, not a base map loaded and left. BMW M135i tuning done correctly accounts for the F20 chassis behaviour, the gearbox calibration and UK fuel quality; the map is reviewed against your data logs after the first flash and revised before sign-off.
Compatibility
Platform and hardware compatibility
Bootmod3 (BM3)
Full N55 support across every chassis in the family (M135i, M235i, 335i, 435i, 535i, 135i, X3 / Z4 35i, M2 N55). MEVD17 DME OBD flashing, realtime monitoring via the BM3 app. One of the most mature N55 tuning platforms.
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MHD
Full N55 support, historically the dominant platform on the N55 before BM3 caught up. Suitable for Stage 1, Stage 2 and Stage 2+. Excellent data-logging toolset.
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MG Flasher
Full N55 support. Clean interface and reliable flash process on the MEVD17 DME. A common alternative to BM3 / MHD for owners who prefer the MG ecosystem.
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xHP Flashtool
Compatible with the ZF 8HP gearbox fitted to F-series N55 cars (M135i, M235i, 335i F30, 435i, 535i, X3 35i F25). Strongly recommended at Stage 2 and above. E-series N55 cars (135i E82, 335i E90 / E92 / E93, Z4 35i E89) use the ZF 6HP automatic or a 6-speed manual, xHP does not cover those gearboxes in the same way.
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ECU: MEVD17.2 DME across most N55 production. Accessible via OBD port for Stage 1, Stage 2 and Stage 2+; bench-flash only required for some Stage 3 hybrid setups.
M135i specs & stage targets
BMW M135i tuning at a glance
- Engine
- N55
- Body styles
- F20 5-door · F21 3-door
- Chassis codes
- F20 / F21
- Production
- 2011–2019
- Drivetrain
- Rear-wheel drive
- Gearbox
- 8-speed ZF automatic
- Stock output
- 322 bhp · 450 Nm
- Tuning ceiling
- ~800 bhp on the right hardware
| Stage | Target |
|---|---|
| Stage 1 | 380 bhp · 500 Nm |
| Stage 2 | 420 bhp · 550 Nm |
| Stage 2+ | 440 bhp · 600 Nm |
| Stage 3, Hybrid Turbo | Up to 800 bhp depending on spec |
| Stage 3, Big Turbo Kit | Up to 800 bhp depending on spec |
FAQ
M135i tuning — frequently asked questions
M135i Stage 1 lifts the N55 from a stock 322 bhp · 450 Nm to 380 bhp · 500 Nm, with no hardware required. The map is flashed through the OBD port on BM3, MHD or MG Flasher and is the starting point for almost every M135i owner — broader torque and sharper throttle response from the factory hardware.
This page covers the F20 5-door and F21 3-door (F20 / F21). They share the N55 engine and run the same core calibration, but every M135i tune Samuel delivers is tailored to your exact car, fuel grade and installed hardware — never a base map loaded and left.
Stage 2 on the M135i targets 420 bhp · 550 Nm and needs downpipe + intake or panel filter + intercooler. Everything else — turbo, fuel system, intercooler — holds within the Stage 2 figures on the N55.
On the right hardware spec the N55 in the M135i reaches around 800 bhp. Stage 1 and Stage 2 run the standard turbo; beyond that needs a hybrid or full big-turbo conversion with supporting fuelling, and the calibration is built bespoke per car.
Remotely. Once Samuel has your build details, the calibrated M135i map is delivered to your flashing tool account (BM3, MHD or MG Flasher) within 24 hours and you flash it yourself over OBD in about 15 minutes. It's fully reversible — the original N55 stock file is supplied before you flash, so the car can return to factory at any time.
A factory warranty can be voided if BMW shows a tune caused a specific failure, so it's a personal call. Samuel's M135i maps are calibrated to stay within the mechanical limits of the N55 hardware, and because the tune is reversible to stock before any dealer visit, many owners run a tuned M135i without issue.
Keep exploring
Keep exploring M135i tuning
Other N55 models we tune: M2 (N55), M235i, 135i, 335i, 335i (E90), 435i.
Engine guide
N55 tuning
Every N55 BMW we calibrate, with the full Stage 1, 2 and 3 breakdown for the engine.
Learn moreStages
Stage 1 & Stage 2 explained
What separates Stage 1 from Stage 2 on the M135i, the real-world gains and the hardware each one needs.
Learn morePricing
How tuning is priced
How the licence, off-the-shelf maps and custom calibration are priced. We quote your exact spec, never a fixed menu.
Learn moreGuide
What is bootmod3?
New to remote flashing? A plain-English explainer on the platform and how a custom map reaches your car.
Learn more