B58 Bolt-Ons: M340i, M440i, M240i, Z4 M40i & 540i

The B58 is the 3.0-liter turbo six in the G20 M340i, G22 M440i, G42 M240i, G29 Z4 M40i and G30 540i. It's strong from the factory and responds well to a tune, so most people end up modifying one. The trick is doing it in the right order, so every part you buy supports the next one instead of being replaced later.

How the B58 makes boost

From the air filter to the exhaust:

1. Airbox and intake: the filter and the box it sits in.
2. Turbo inlet pipe: the pipe from the airbox to the turbo. On G-series cars it's plastic.
3. Turbo: a single twin-scroll turbo bolted to the head.
4. Charge pipe: carries pressurized air from the turbo to the intake manifold. Also plastic from the factory.
5. Charge-air cooler: the B58 has no front-mount intercooler. The cooler is a water-to-air core built into the intake manifold, cooled by its own low-temperature circuit and a heat exchanger up front.
6. Downpipe: carries exhaust out of the turbo and holds the main catalyst.

Which B58 do you have? Most G-series cars use the updated second-generation B58 (often called Gen 2 or B58TU). Early G30 540i cars use the first-generation engine, and the M340i and M440i got another update for 2025. Fuel parts, some downpipes and tunes are specific to the engine version, so check the listing or send us your VIN.

Shared parts vs chassis-specific parts: the G20, G22, G42, G29, G30 and the A90 Supra share a lot of B58 parts, especially fuel and turbo parts. Intercoolers, downpipes and charge pipes are often chassis-specific, so use the page for your car (links at the bottom) to see what fits.

Intake and turbo inlet

An intake mostly adds induction sound and helps a tuned car breathe. The factory plastic inlet is the part worth upgrading when you start adding boost.

• Dinan cold air intake: a reworked, larger lower airbox for the M340i, M440i and M240i. Z4 owners get the Z4 M40i version.
• Eventuri carbon intake: a carbon housing built for a smoother flow path and low intake temperatures.
• aFe Momentum GT Pro 5R: an intake built for the G30 540i.
• CTS high-flow turbo inlet or the Dinan carbon turbo inlet: replace the plastic inlet before it cracks.

If you want to keep the factory box, a VTT drop-in filter is the simplest step.

Charge pipe: do this before you tune

The plastic charge pipe is the weak point once boost goes up. A metal pipe removes that risk, and it's the part we'd put on any B58 that's getting a tune.

• Spool charge pipe kit: covers Gen 1 and Gen 2 B58 cars, including the 540i.
• Active Autowerke G-chassis charge pipe: for the M340i and M440i.
• FTP G20 B58 charge pipe: a direct replacement with silicone couplers and a water-injection bung.
• FTP G30 540i charge pipe and intake pipe combo: the 540i-specific version.

Charge-air cooler

Because the cooler lives in the intake manifold, upgrading it means swapping the manifold, not hanging a bigger core behind the bumper. It's the upgrade for cars that see heat soak, track days or a lot of boost.

• CSF Gen 2 charge-air cooler manifold: a billet replacement for second-generation B58 cars. The Race X version is for builds going further.
• Wagner EVO1 intake manifold: an intake manifold with an integrated intercooler and more volume than stock.
• Supporting cooling: the Dinan heat exchanger or the Forge chargecooler radiator give the cooler circuit more capacity.

Downpipe: for tuned cars

The downpipe holds the main catalyst right after the turbo. A high-flow catted downpipe helps a tuned B58 spool and hold boost. On a stock car it mostly adds volume. Downpipes are chassis-specific, so pick the one listed for your car.

• Active Autowerke GESI catted downpipe for G2X/G4X: for the M340i and M440i through 2024. The wider-fitment version covers the M240i and 540i, and there are 2025+ versions for the updated engine.
• Fabspeed sport cat downpipe: uses HJS catalytic converters. Z4 owners need the Z4 M40i version.
• Scorpion 5" downpipe with high-flow sports cat: a large-diameter catted option.
• Catless race downpipes, like the CTS race downpipe, are for off-road and competition use only.

Active Autowerke says its GESI downpipe doesn't need a tune, but most downpipes do, and every one of them works best with one. Plan the two together.

Fuel: when you go past a basic tune

A stock fuel system handles a basic tune on pump gas. Ethanol blends and bigger turbos need more fuel, and every part here needs a tune set up for it.

• Spool Stage 3 low-pressure fuel pump (Gen 2): the usual first fuel upgrade. The 540i has its own kit.
• Spool FX350 high-pressure pump: for Gen 2 cars running more ethanol.
• Spool IFX350 injectors: larger direct injectors for Gen 2 cars.
• CTS port injection kit: adds a second set of injectors for big-turbo builds.
• Spool wireless ethanol analyzer: shows ethanol content and fuel temperature on your phone.

Tune

The tune is what turns these parts into power. The options we carry:

• Burger Tuning JB4: a piggyback for Gen 1 and Gen 2 B58 cars, with a Gen 3 version for the latest engine.
• Active Autowerke software: a flash tune. Cars built from mid-2020 on have a locked ECU that has to be unlocked first; the listing explains how.
• DTE PowerControl X: a plug-in module that connects to the factory sensors.

What we'd do

• Daily driver: a charge pipe and a tune. Add an intake if you want more sound.
• Weekend car: charge pipe, turbo inlet, intake, a catted downpipe and a tune. Add a charge-air cooler manifold if the car sees track days or hot summers.
• Tuned car chasing power: all of the above plus a low-pressure fuel pump and ethanol. Then high-pressure pump, injectors or port injection if you go to a bigger turbo.

Find every part that fits your car on the M340i, M440i, M240i, Z4 M40i and 540i pages. For charge pipes and downpipes, go straight to the M340i intercooler and M340i exhaust pages, or the same sections on your car's page.