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 / G21, 2019–present) runs the B58 Gen 2 and leaves the factory at 374 bhp · 500 Nm, xDrive (RWD in some markets), 8-speed ZF automatic. Samuel tunes the G20 Saloon and G21 Touring 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. M340i Stage 1 alone takes it from 374 bhp · 500 Nm to 440 bhp · 680 Nm on the standard turbo, flashed over OBD on BM3, MHD or MG Flasher.
Add the Stage 2 hardware and the M340i targets 480 bhp · 700 Nm; from there the B58 Gen 2 stretches to around 1000 bhp on a hybrid or big-turbo build with supporting fuelling. Whichever stage suits the M340i, the file is delivered within 24 hours and is fully reversible to the supplied stock calibration.
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
Platform and hardware compatibility
Bootmod3 (BM3)
Full B58 Gen 2 support on the MG1CS003 DME across every Gen 2 chassis (M340i, M440i, M240i G42, Z4 M40i, X3/X4 M40i, Supra 3.0). OBD-port flashing, realtime monitoring via the BM3 app. The most widely used platform for B58 Gen 2 tuning.
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MHD
Full B58 Gen 2 support. Suitable for Stage 1 and Stage 2. Strong data-logging toolset and active community support.
Read more →
MG Flasher
Full B58 Gen 2 support. Clean interface and reliable flash process. A common alternative to BM3 for owners who prefer the MG ecosystem.
Read more →
xHP Flashtool
Compatible with the ZF 8HP gearbox fitted to every B58 Gen 2 chassis. Gearbox calibration matched to the ECU map, strongly recommended at Stage 2 and above where torque jumps significantly. Available as an add-on.
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ECU: MG1CS003 DME across all B58 Gen 2 production. Accessible via OBD for Stage 1 and Stage 2; bench-flash only required for some Stage 3 hybrid setups.
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
M340i Stage 1 lifts the B58 Gen 2 from a stock 374 bhp · 500 Nm to 440 bhp · 680 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 M340i owner — broader torque and sharper throttle response from the factory hardware.
This page covers the G20 Saloon and G21 Touring (G20 / G21). They share the B58 Gen 2 engine and run the same core calibration, but every M340i 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 M340i targets 480 bhp · 700 Nm and needs downpipe (OPF delete if 2018+) + intake. Everything else — turbo, fuel system, intercooler — holds within the Stage 2 figures on the B58 Gen 2.
On the right hardware spec the B58 Gen 2 in the M340i reaches around 1000 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 M340i 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 B58 Gen 2 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 M340i maps are calibrated to stay within the mechanical limits of the B58 Gen 2 hardware, and because the tune is reversible to stock before any dealer visit, many owners run a tuned M340i without issue.
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