Tuning · BMW M340i (G20 / G21)
M340i
B58 Gen 2
The Gen 2 B58 in saloon and Touring form. Hand-calibrated from Stage 1 to a fully bespoke big-turbo build. Choose your package, send your build to Samuel, and get a tune that fits the way you actually drive.
Engine
B58 Gen 2
Stock
374 bhp · 500 Nm
Stage 3 ceiling
374 bhp
About this tune
The G20 / G21 M340i (2019-present) is the M-Performance variant of the 3 Series with the B58 Gen 2, the revised, smoother, more efficient version of BMW's single-turbo straight-six. Stock is 374 bhp / 500 Nm, sent through the ZF 8HP with xDrive standard in most markets. Available as the G20 saloon and G21 Touring; both share the identical drivetrain and respond to the same Stage 1 / Stage 2 map. The M340i is one of the most popular B58 Gen 2 chassis worldwide and the closest thing to an M3 you can buy without paying M-car money.
BMW M340i tuning
The BMW M340i (G20 Saloon, G21 Touring, 2019–present) leaves the factory at 374 bhp · 500 Nm. Stage 1 moves that to 440 bhp · 680 Nm without touching any hardware — Samuel maps the MG1CS003 DME via OBD on BM3, MHD or MG Flasher, every file calibrated to the specific car and its fuel grade. Stage 2 targets 480 bhp · 700 Nm with a downpipe (OPF delete on 2018+ cars) and intake; from there the B58 Gen 2 runs to around 1000 bhp on a hybrid or big-turbo build with supporting fuelling. Every file lands in your flashing tool account within 24 hours and is fully reversible to stock.
The G20 / G21 M340i is the M-Performance 3 Series, built around the B58 Gen 2 — BMW's revised single-turbo straight-six, smoother and more efficient than the Gen 1 unit it replaced. Standard fit is xDrive with a ZF 8HP automatic; RWD is available in select markets. Both the G20 Saloon and G21 Touring share the same drivetrain and run the same calibration. Stock output of 374 bhp sits noticeably short of what the hardware can handle.
Configurator
Build your M340i 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 M340i tuning, stages, hardware and what to expect from the G20 B58 Gen 2
The M340i runs the B58 Gen 2, BMW's revised 3.0-litre single-turbocharged inline-six fitted to the G20 saloon, G21 Touring, M440i, M240i G42, Z4 M40i, X3 / X4 M40i and the Toyota Supra 3.0. From the factory, BMW set the M340i at 374 bhp / 500 Nm; the hardware ceiling sits considerably higher. BMW M340i tuning with Samuel targets that headroom with a calibration matched to the G20 / G21 chassis behaviour and 8HP gearbox. BMW M340i G20 tuning and BMW M340i G21 tuning use the same map; only the Touring exhaust geometry differs slightly further back.
Stage 1
440 bhp · 680 Nm
No hardware required. The MG1CS003 DME is flashed via the OBD port, boost, ignition timing, fuel delivery and torque limiters all revised. BMW M340i Stage 1 unlocks 440 bhp and 680 Nm from the OEM hardware (up from 374 / 500 stock). The BMW M340i chip tuning starting point and by far the most popular single modification on the G20 / G21 platform, the most cost-effective change you can make.
Every M340i tune Samuel produces is calibrated individually for the specific car, fuel grade and installed hardware, not a base map loaded and left. BMW M340i tuning done correctly accounts for the G20 chassis behaviour, the 8HP gearbox calibration and UK fuel quality; the map is reviewed against your data logs after the first flash and revised before sign-off.
Compatibility
This M340i tune runs on Bootmod3, MHD or MG Flasher — all three flash the B58 Gen 2 over OBD. Compare platforms or see full B58 Gen 2 compatibility.
M340i specs & stage targets
BMW M340i tuning at a glance
- Engine
- B58 Gen 2
- Body styles
- G20 Saloon · G21 Touring
- Chassis codes
- G20 / G21
- Production
- 2019–present
- Drivetrain
- xDrive (RWD in some markets)
- Gearbox
- 8-speed ZF automatic
- Stock output
- 374 bhp · 500 Nm
- Tuning ceiling
- ~1000 bhp on the right hardware
| Stage | Target |
|---|---|
| Stage 1 | 440 bhp · 680 Nm |
| Stage 2 | 480 bhp · 700 Nm |
| Stage 3, Hybrid Turbo | 550-1000 bhp depending on spec |
| Stage 3, Big Turbo Kit | 550-1000 bhp depending on spec |
FAQ
M340i tuning — frequently asked questions
The B58 Gen 2 in the M340i goes from 374 bhp · 500 Nm stock to 440 bhp · 680 Nm at Stage 1 — no hardware required. The map is flashed over OBD on BM3, MHD or MG Flasher; the result is a broader torque spread and a noticeably sharper throttle from the factory hardware.
Stage 2 targets 480 bhp · 700 Nm and needs a downpipe (OPF delete if your car is 2018 or later) and an intake. The standard turbo and fuel system hold within Stage 2 on the B58 Gen 2 — no pump or intercooler changes required to reach those figures.
Once Samuel has your build details, the calibrated map is delivered to your BM3, MHD or MG Flasher account within 24 hours of payment. You flash it over OBD yourself in about 15 minutes — no bench flash, no dealer visit.
Yes. The stock B58 Gen 2 file is supplied before you flash, so you can return the M340i to factory calibration at any time.
The ZF 8HP in the M340i responds well to xHP calibration once torque increases. At Stage 1 it's optional but noticeable; at Stage 2 and above, where the torque jump is significant, it's strongly recommended. Available as an add-on above.
Keep exploring
Keep exploring M340i tuning
Other B58 Gen 2 models we tune: M240i, M440i, Z4 M40i, X3 M40i, X4 M40i, Supra 3.0.
Engine guide
B58 Gen 2 tuning
Every B58 Gen 2 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 M340i, 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