Best Performance Upgrades for the BMW F30 340i in Australia
Best Performance Upgrades for the BMW G20 M340i in Australia
The G20 M340i is one of the best performance sedans on the market. From the factory it makes 285kw, sounds good, and pulls hard. But if you’ve owned one for more than six months, you already know it can do more. The B58 engine under the hood is one of the most tuneable platforms BMW has ever built, and the factory calibration is deliberately conservative.
Here’s where to start if you want to unlock what the M340i is actually capable of.
1. Downpipe Upgrade
The single best bang-for-buck modification on the M340i. The factory downpipe is heavily restricted to meet emissions regulations, and it’s one of the biggest choke points in the entire exhaust system.
An upgraded downpipe — specifically a high-flow catted unit for street use — reduces backpressure, allows the turbo to spool faster, and improves power delivery across the entire rev range. On a stock tune you’ll feel a noticeable improvement in mid-range response. Paired with a remap, a quality downpipe is worth 25-40kw at the wheels.
It’s the first modification most serious B58 owners do, and for good reason. Nothing else at a similar price point moves the needle as much.
2. ECU Remap
The B58 in the M340i is running a conservative factory map. BMW calibrates across multiple markets, multiple fuel grades, and with significant safety margins built in. A remap tailored for Australian 98 RON fuel removes those margins and calibrates the engine for your specific setup.
On a stock car, a remap alone is worth 30-50kw. Combine it with a downpipe and you’re looking at a genuinely different car — one that pulls from 2500rpm all the way to the limiter with authority.
The key is using a reputable tuner. The B58 is a well-supported platform with plenty of proven tune options available in Australia. Don’t cheap out here — a bad tune on a good engine is an expensive mistake.
3. Intake Upgrade
The factory airbox on the M340i is reasonably well designed but still restricted. An upgraded intake improves airflow into the turbo, which works in combination with a downpipe to reduce restriction on both the inlet and outlet sides of the turbocharger.
Intake upgrades on their own produce modest gains — typically 5-10kw. But as part of a package with a downpipe and remap, they contribute meaningfully to the overall result and improve the induction sound noticeably.
4. Charge Pipe Upgrade
The factory charge pipes on the B58 are plastic. They’re adequate at stock boost levels but become a weak point when you start pushing more pressure through the system. An upgraded charge pipe kit replaces the plastic factory components with aluminium, which holds boost more consistently and eliminates the risk of a blow-off under hard acceleration.
This is less about peak power and more about reliability at higher boost levels. If you’re tuning the car, charge pipe upgrades are worth doing at the same time.
5. Exhaust System
If you want more sound without going catless on the downpipe, a cat-back exhaust is the answer. The M340i’s factory exhaust is well-suppressed — BMW fits active exhaust flaps that open under load, but even with those open it’s fairly subdued by performance car standards.
An aftermarket cat-back opens up the exhaust note significantly, especially in combination with a downpipe. The result is a sound that matches the performance — deep, purposeful, and aggressive under load without being antisocial at low speeds.
What Order Should You Mod In?
For most M340i owners in Australia, the logical order is:
Downpipe first — biggest single gain, sets the foundation for everything else
Remap — unlocks the full benefit of the downpipe and pushes the engine to its potential
Intake + charge pipes — supporting modifications that compound the gains from the remap
Cat-back exhaust — the finishing touch for sound and aesthetics
You don’t have to do them all at once. The downpipe alone is a worthwhile first step, and you can build from there as the budget allows.
What Kind of Numbers Are We Talking?
A fully built street M340i — downpipe, intake, charge pipes, and a quality tune on 98 RON — typically lands in the 380-420kw range at the wheels depending on the tune and conditions. That’s a near 50% increase over the factory figure, from a car that still looks stock and drives comfortably every day.
The B58 platform has proven it can handle these power levels reliably. There are M340is in Australia running these numbers daily with no issues.
The Bottom Line
The G20 M340i is an exceptional starting point. With the right modifications in the right order, it becomes a genuinely fast car that competes with vehicles costing significantly more.
Start with the downpipe. Everything else builds from there.
Eurospec stocks B58 downpipes and performance parts for the G20 M340i in Australia. https://eurospecau.com/shop or get in touch to discuss your build.
