BMW M240i G42: unleashing the B58, the complete exhaust system guide
The M240i G42 is a worthy heir to BMW's compact coupés: rear-wheel drive, a 374 hp B58 and a compact footprint. Many buyers pick it as the smart alternative to the M2. Only one thing is missing to complete the picture: a real voice, which the factory exhaust locks away entirely. Here, point by point, is how to choose the exhaust for your BMW M240i B58 G42, and what each option really changes.
Written by ROG Motorsport · Updated
Your ROG exhaust for the BMW M240i B58 G42
From €2,490 in stainless steel, €2,990 in titanium
Configure my exhaust- Vehicles
- BMW M240i B58 G42 3.0T (2021-2023)
- Engine
- B58 · 374 hp · 500 Nm
- Exhaust
- Valved cat-back, built for your VIN
- Material
- 304 stainless steel or titanium
- Front section
- Optional: catted downpipe with 200 or 100 cells, or decat
- Valves
- ROG remote, or factory control if your vehicle has it
- Lead time
- 20 working days from order confirmation to delivery
- Warranty
- 3 years, parts and workmanship
Closely related versions have their own guide: BMW 230i B48 G42 2.0L, BMW 340i B58 F30 3.0T, BMW 540i B58 G30 / G31 3.0T, BMW 840i B58 G16 3.0T.
The B58: the benchmark modern straight-six, muffled at the factory
The 3.0L turbo B58 is regularly named among the best engines of its generation, so much so that Toyota chose it for the Supra. Very stiff closed-deck block, twin-scroll turbo, instant response and exemplary reliability: it is a sound base that takes tuning remarkably well. Its only flaw is not mechanical but down to type approval: a particulate filter and oversized silencers reduce its natural, rounded, metallic sound to almost nothing on your M240i G42.
The ROG exhaust replaces that system with a free-flowing layout and controllable valves. The straight-six gets its voice back, from the deep rumble at idle to the full note at high revs, and you stay in total control.
How the exhaust on your BMW M240i B58 G42 is put together
An exhaust system is best understood in two parts. Here is what each one does, and what ROG replaces.
The cat-back is the complete exhaust system
It is everything you can see under your BMW M240i B58 G42, from the outlet of the front section to the tips: pipes, silencer, valves. Routing, silencer, valves: this is where the sound is shaped, and where we focus our research and development.
The front section, where the catalytic converter sits
On your BMW M240i B58 G42, this is the downpipe, the pipe that leads away from the turbo. It contains the factory catalytic converter: the second restriction in the exhaust, after the silencer. Changing this part remains a choice: it pays off mainly with an ECU remap, which turns the freed-up flow into power.
Your BMW M240i B58 G42 in figures
What an exhaust changes straight away is the sound, the engine's breathing and the weight at the rear. For more power, add an ECU remap.
Power
Torque
Published factory and Stage 2 figures.
With or without an ECU remap, the exhaust fits and works. But it is an ECU remap at an approved tuning centre that truly unleashes your BMW M240i B58 G42, and that is what we recommend.
Let's be frank, as always: on a modern turbo engine, the exhaust alone brings a moderate gain by reducing back pressure. The true potential of the B58 is unlocked at Stage 2, the exhaust plus an ECU remap at an approved tuning centre. It is one of the most responsive engines on the market, with reliability preserved thanks to a block that is heavily over-engineered from the factory.
Configuring your exhaust, step by step
4 choices, in the same order as the product page configurator.
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Step 1 of 4: Material: stainless steel or titanium
For your BMW M240i B58 G42, the exhaust costs €2,490 in stainless steel and €2,990 in titanium.
304 stainless steel
€2,490
- Weight
- Baseline
- Sound
- Full and rounded
Durable, corrosion-resistant, with a rounded, full sound: the most popular option.
Titanium
€2,990
- Weight
- Around 40% lighter
- Sound
- Metallic, crystal-clear
For the same design, it weighs around 40% less than stainless steel. A more metallic note at high revs and a look all of its own, from brushed to blued.
Both materials age well: 304 stainless steel copes with winter and salt, and titanium does not rust. Stainless steel or titanium: what really changes.
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Step 2 of 4: Front section: downpipe and catalytic converter
Optional: the downpipe on your BMW M240i B58 G42, with its catalytic converter. Sound rating out of 10, valves open: the factory exhaust sits at 3.
Cat-back only
Included
7/10Factory emissions control
Nothing changes at the front: the cat-back alone is already enough to change the car.
200-cell sports catalytic converter
+€650
8/10Road use and inspection
The everyday compromise: emissions control is still there, and breathing improves noticeably.
100-cell sports catalytic converter
+€650
9/10Inspection: depends on local rules
One step further: more flow, a more aggressive sound, reduced emissions control.
Decat
+€420
10/10Track use
Everything unleashed: maximum flow and unrestrained sound, for the track.
Sound intensity, on a scale of 0 to 10
- 10/10Decat downpipe + ROG cat-back
- 9/10100-cell sports catalytic converter + ROG cat-back
- 8/10200-cell sports catalytic converter + ROG cat-back
- 7/10ROG cat-back only, factory catalytic converter retained
- 3/10Factory exhaust, for comparison
Valves open. With the valves closed, every configuration becomes discreet again.
What about the engine warning light? It can appear with a sports catalytic converter: the downstream oxygen sensor reads a different level of cleaning from the factory unit. It is not an engine fault, and it is dealt with by an ECU remap or a diagnostic tool. With a decat, an ECU remap becomes necessary. If it happens to you, call us and we will point you in the right direction. Passing vehicle inspection with a sports exhaust.
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Step 3 of 4: Valves: ROG remote or factory control
Two ways to control the valves on your BMW M240i B58 G42.
ROG remote
The simplest solution: a control unit in the boot and a remote, open or closed at the press of a button, whatever mode you are in. A question while fitting? We will get back to you.
Factory control
- Only for vehicles fitted with factory valves
- Controlled by the drive modes
Does your vehicle have factory valves? The exhaust keeps their existing control: the drive modes operate the valves, as before, with no added electronics.
On a long journey, what matters is the absence of drone at a steady speed. With the valves closed, the exhaust keeps the cabin calm; the show is still there whenever you ask for it. More about exhaust drone.
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Step 4 of 4: Tips: the visual signature
Match the tips to the style of your BMW M240i B58 G42, understated or bold. A particular finish in mind? Send us a photo and we will look at it together.
- Stainless steel
- Black
- Carbon
- Blued titanium
- M Performance style carbon
The ROG sound signature on the B58
With no resonator or unnecessary mid silencer, our exhaust frees the natural voice of the B58: a round, metallic bass note at idle, a full and even build through the revs, and crisp crackles on the overrun with the valves open. It is the BMW straight-six sound at its noblest, never tipping into tiresome drone, and with the factory discretion available with the valves closed.
From order to fitting
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Configuration
You choose the options for your BMW M240i B58 G42 and enter its VIN, found in box E of the registration document or at the base of the windscreen.
-
Check
We confirm compatibility with your car before we build it.
-
Manufacturing
Made to order, for your BMW M240i B58 G42.
-
Delivery
Free, insured delivery, with tracking sent on dispatch.
-
Fitting
Clamps and gaskets, no welding: two hours on average at the garage of your choice.
20 working days from order confirmation to delivery
- Warranty
- 3 years, parts and workmanship, from the date of delivery
- Payment
- In instalments with Klarna
- Installation
- At the garage of your choice
What about the manufacturer's warranty? In Europe, fitting a part from another brand is not enough on its own to void it; the manufacturer has to prove the link between that part and the fault. Our article on the manufacturer's warranty.
Our recommendations for your BMW M240i B58 G42
-
Daily driving
€2,490
- Stainless
- Cat-back only
- ROG remote
Your BMW M240i B58 G42 stays easy to live with, the factory emissions control is retained, and you open the valves when you decide.
View this configuration -
Fast road
€3,640
- Titanium
- 200-cell downpipe
- ECU remap
For great roads: more voice and more response, while staying road-friendly.
View this configuration -
Track
€3,410
- Titanium
- Decat downpipe
- Stage 2
The most extreme configuration, for track use only.
View this configuration
These profiles are starting points. The right choice is often made in five minutes on the phone.
BMW M240i B58 G42: your questions
How much power does an exhaust add on the BMW M240i B58 G42?
As standard, the BMW M240i B58 G42 produces 374 hp and 500 Nm. Without a remap, the exhaust transforms the voice and lightens the rear; it is the ECU remap that increases power. With a Stage 2 build, the published figures reach 440 hp and 620 Nm.
Stainless steel or titanium: which material for the BMW M240i B58 G42?
For the BMW M240i B58 G42, the ROG exhaust costs €2,490 in stainless steel and €2,990 in titanium. Choose stainless steel for value for money and a rounded sound, titanium to save around 40% in weight and get a clearer tone.
Do you need to replace the catalytic converter on the BMW M240i B58 G42?
No, the cat-back alone already does most of the work on the BMW M240i B58 G42. The downpipe option is for those tuning the engine: 200 cells to stay road-friendly, 100 cells or decat for the track.
Will a ROG exhaust pass vehicle inspection on the BMW M240i B58 G42?
The cat-back only and the 200-cell sports catalytic converter both keep emissions control: that is the configuration to present, with the valves closed. The 100-cell brings more sound and flow, and whether it is accepted at the emissions test depends on the car and local rules; the decat version is intended for track use on the BMW M240i B58 G42.
How is the ROG exhaust fitted on the BMW M240i B58 G42?
Fitting needs no welding or cutting and takes two hours on average on a lift. We check compatibility with the VIN of your BMW M240i B58 G42 before manufacturing.
What price and lead time for a ROG exhaust on the BMW M240i B58 G42?
From €2,490 to €3,640 depending on the configuration. Allow 20 working days from order confirmation to delivery. Free delivery, 3-year warranty.
Unsure about your configuration? Give us a call.
Stainless steel or titanium, cat-back only or the complete system: the right choice depends on how you use your BMW M240i B58 G42. We take the time to talk it through before you order, with a reply within 24 hours. We are not here to sell to you over the phone: we help you choose, even if that means a cheaper option because it suits the way you drive.
Behind every ROG exhaust is a French team you can actually reach, who know the cars they talk about. More than 500 exhaust systems fitted and a rating of 4.9 out of 5.
Further reading
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