Tuning · BMW 420i (G22 / G23 / G26)
G22 420i
B48
The entry-point B48 in coupe and Gran Coupe form. Hand-calibrated from Stage 1 to a hybrid-turbo build. Choose your package, send your build to Samuel, and get a tune that fits the way you actually drive.
Engine
B48
Stock
184 bhp · 300 Nm
Stage 3 ceiling
184 bhp
BMW 420i tuning
The 420i is the car you buy for the shape — a G22 coupé, G23 convertible or G26 Gran Coupé with the entry engine under the bonnet — and that mismatch between styling and output is exactly why so many end up on Samuel's books. The car looks quicker than it is from the factory, and a calibration is the cheapest way to make the two match.
BMW ships the 420i with 184 bhp and 300 Nm. Stage 1 rewrites the standard calibration to 280 bhp and 450 Nm, hardware untouched, transforming how the coupé pulls out of corners and down a slip road. Downpipe and intake fitted, Stage 2 raises the goal to 320 bhp and 500 Nm — at which point the 420i is quicker on paper than a factory 430i.
For owners who want more, hybrid and big-turbo conversions calibrate up to roughly 500 bhp with the right fuelling behind them. Nothing about the software side needs a workshop visit: your file is hand-built and delivered to BM3, MHD or MG Flasher within a day, flashed via OBD on your driveway, and reversible to the stored factory map at any point.
Configurator
Build your G22 420i 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 420i tuning, stages, hardware and what to expect from the G22 B48
The G22 420i runs the entry-spec B48, the same 184 bhp / 300 Nm software calibration as the G20 320i, in the slightly larger 4 Series coupe body. The engine block, head, turbo and fuel system are identical to the 430i's; only the software limiter and a slightly smaller injector spec separate the two. BMW 420i tuning with Samuel exploits that, Stage 1 alone unlocks more torque than a stock 430i makes. BMW 420i G22 Coupe tuning, G23 Convertible tuning and G26 Gran Coupe tuning all use the same map.
Stage 1
280 bhp · 450 Nm
No hardware required. The MG1CS003 / MEVD17 DME is flashed via the OBD port, boost pressure, ignition timing, fuel delivery and torque limiters all revised. BMW 420i Stage 1 unlocks 280 bhp / 450 Nm from the OEM hardware (up from 184 / 300 stock). One of the largest single-software gains available on any modern BMW because the factory 420i limiter is so conservative.
Every 420i tune Samuel produces is calibrated individually for the specific car, fuel grade and installed hardware, not a base map loaded and left. BMW 420i tuning done correctly accounts for the G22 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 B48 support across every chassis in the family (320i, 330i, 420i, 430i, 530i, Z4 sDrive20i). OBD-port flashing on the MEVD17 (early) and MG1CS003 (later) DMEs. Realtime monitoring via the BM3 app, the most widely used platform for B48 tuning.
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MHD
Full B48 support. Suitable for Stage 1 and Stage 2 across the family. Strong data-logging toolset for verifying lambda, ignition correction and intake temperatures after each flash.
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MG Flasher
Full B48 support. Clean interface and reliable flash process on the MG1CS003 DME, a common choice for owners who prefer the MG ecosystem.
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xHP Flashtool
Compatible with the ZF 8HP gearbox fitted to every modern B48 chassis (G20 / G22 / G30 / G29). Available as an add-on, strongly recommended at Stage 2 where torque jumps significantly for a 2.0-litre four. Manual-gearbox cars do not need xHP.
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ECU: MEVD17 / MG1CS003 DME across B48 production. Accessible via the OBD port, no bench flash required for Stage 1 or Stage 2.
G22 420i specs & stage targets
BMW 420i tuning at a glance
- Engine
- B48 · 2.0L turbocharged inline-four
- Body styles
- G22 Coupe · G23 Convertible · G26 Gran Coupe
- Chassis codes
- G22 / G23 / G26
- Production
- 2020–present
- Drivetrain
- Rear-wheel drive
- Gearbox
- 8-speed ZF automatic
- Stock output
- 184 bhp · 300 Nm
- Tuning ceiling
- ~500 bhp on the right hardware
| Stage | Target |
|---|---|
| Stage 1 | 280 bhp · 450 Nm |
| Stage 2 | 320 bhp · 500 Nm |
| Stage 3, Hybrid Turbo | Up to 500 bhp depending on spec |
| Stage 3, Big Turbo Kit | Up to 500 bhp depending on spec |
FAQ
G22 420i tuning — frequently asked questions
Because the numbers favour it. At Stage 1 the 420i makes 280 bhp and 450 Nm, clear of the 430i's factory 255 bhp and 420 Nm, and the two cars share their bodyshells. If the shape already suits you, a £350 remap gets you past the car you might have traded up to.
The G22 coupé, G23 convertible and G26 Gran Coupé all carry the identical B48 and DME, so the starting point is shared. The finished file never is: Samuel calibrates each 420i individually around its fuel grade, its fitted hardware and the owner's brief, so two body styles rarely leave with byte-identical maps.
Two parts: a downpipe and an intake. Once fitted, Samuel calibrates the standard turbo to 320 bhp and 500 Nm. No further parts are needed at this stage — the requirement list is deliberately short so the cost stays in the calibration, not the parts catalogue.
You configure the package, send Samuel the car's details and any fitted parts, and he writes the calibration by hand. Within 24 hours it is released to your BM3, MHD or MG Flasher account and you flash it yourself through the OBD port. Any later revisions are handled the same way, wherever the car happens to be.
Around 500 bhp. Getting there means a hybrid turbo or a full-frame conversion, plus downpipe, intake and fuelling that can feed it, with the calibration written specifically for the assembled hardware. It is a proper project rather than a single flash, so list the complete setup when you enquire and Samuel will scope it honestly.
Keep exploring
Keep exploring G22 420i tuning
Other B48 models we tune: G20 320i, 330i, 330e, 430i, 530e, 530i.
Engine guide
B48 tuning
Every B48 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 G22 420i, 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