Mercedes A45 S AMG W177: the M139 unmuzzled, the complete exhaust system guide
421 hp from a series-production four-cylinder: the M139 in the A45 S still holds the title, and it is hand-built like an AMG V8. Its factory exhaust, however, lets almost none of this achievement through. Here, point by point, is how to choose the exhaust for your Mercedes-AMG A45 / A45 S W177, and what each option really changes.
Valved Exhaust System for Mercedes-AMG A45 / A45 S W177 2.0 turbo (2020-2022)From £2,459 · free delivery · 20 working days
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Your Rog exhaust for the Mercedes-AMG A45 / A45 S W177
Price shown on the product page, in your currency
Configure my exhaustThe short answer.
- Vehicles
- Mercedes-AMG A45 / A45 S W177 2.0 turbo (2020-2022)
- Engine
- M139 · 387 to 421 hp · 480 to 500 Nm, depending on the version
- 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: Mercedes-Benz A200 W177 1.3 turbo, Mercedes-AMG A35 W177 2.0 turbo, Mercedes-AMG A45 W176 2.0 turbo, Mercedes-AMG CLA45 S C118 2.0 turbo.
The M139: the most powerful series-production four-cylinder in the world
The engine in your A45 S AMG W177 holds an official title: it is the most powerful series-production turbocharged four-cylinder in the world. The M139 produces 421 hp at 6,750 rpm and 500 Nm, which is more than 200 hp per litre. On the S version, the single twin-scroll turbo runs at 2.1 bar of boost pressure. An architectural detail unique to it: the engine is rotated 180° compared with the usual layout. The exhaust manifold and turbo sit on the bulkhead side, at the rear, and the intake is at the front: shorter air paths, fewer detours, better breathing.
Like the V8s from Affalterbach, every M139 is hand-assembled according to the “One Man, One Engine” principle. Behind it sit the AMG SPEEDSHIFT DCT 8G dual-clutch gearbox and 4MATIC+ all-wheel drive with AMG TORQUE CONTROL, whose two electronically controlled clutches distribute torque between the rear wheels. An exceptional engine, and a factory exhaust that, particulate filter included, makes it pass for an ordinary hatchback. The Rog system sets it free without touching the stock electronics.
How the exhaust on your Mercedes-AMG A45 / A45 S W177 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 Mercedes-AMG A45 / A45 S W177, from the outlet of the front section to the tips: pipes, silencers, 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 Mercedes-AMG A45 / A45 S W177, it is the downpipe, the pipe leading 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.
The figures for your Mercedes-AMG A45 / A45 S W177
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. Factory figures vary by version; Stage 2 figures published for the 421 hp version.
With or without an ECU remap, the exhaust fits and works. But it is an ECU remap at an approved tuning centre that truly unlocks your Mercedes-AMG A45 / A45 S W177, and that is what we recommend.
Let's be frank: the exhaust alone brings a moderate gain, through the reduction in back pressure. The true potential of the M139 is unlocked at Stage 2, the exhaust plus an ECU remap at an approved tuning centre. It is one of the most responsive four-cylinders on the market, and the figures above stay well within its working range.
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
Titanium costs more than stainless steel; the price of each version is shown on the product page, in your currency.
304 stainless steel
- Weight
- Baseline
- Sound
- Full and rounded
Durable, corrosion-resistant, with a rounded, full sound: the most popular option.
Titanium
- 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 Mercedes-AMG A45 / A45 S W177, 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
8/10Road use and inspection
The everyday compromise: emissions control is still there, and breathing improves noticeably.
100-cell sports catalytic converter
9/10Inspection: depends on local rules
One step further: more flow, a more aggressive sound, reduced emissions control.
Decat
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? With a sports cat, it can come on with some engines: the sensor placed after the catalytic converter measures a different level of emissions control from the original. It is not a mechanical failure, but a warning light should never be masked or cleared without dealing with its cause: the right answer is a catalytic converter suited to the engine, with a map by a tuner who takes it into account. The decat version, for track use only, almost always triggers it. If this happens to you, write to 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 Mercedes-AMG A45 / A45 S W177.
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 Mercedes-AMG A45 / A45 S W177, 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
Your choices carry over to the product page: only the finishes, your VIN and the cart remain.
The Rog sound signature on the AMG 2.0
Our exhaust gives the M139 back its racing engine character: a furious, full tone, an aggressive climb to the redline and rich crackles on lift-off with the valves open. With the valves closed, your hot hatch becomes perfectly civilised again. The contrast is where all the fun lies: the car does not change its nature, it changes its volume, whenever you decide.
From order to fitting
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Configuration
You choose the options for your Mercedes-AMG A45 / A45 S W177 and enter its VIN, from box E of the registration document or the base of the windscreen.
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Check
We confirm compatibility with your car before we build it.
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Manufacturing
Made to order, for your Mercedes-AMG A45 / A45 S W177.
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Delivery
Free, insured delivery, with tracking sent on dispatch.
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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 purchase
- Payment
- Card, PayPal or bank transfer
- 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 Mercedes-AMG A45 / A45 S W177
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Daily driving
- Stainless
- Cat-back only
- Rog remote
Your Mercedes-AMG A45 / A45 S W177 stays easy to live with, the factory emissions control is retained, and you open the valves whenever you decide.
View this configuration -
Fast road
- Titanium
- 200-cell downpipe
- ECU remap
For great roads: more voice and more response, while staying road-friendly.
View this configuration -
Track
- 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 a few messages.
Mercedes-AMG A45 / A45 S W177: your questions
How much power does an exhaust system add to the Mercedes-AMG A45 / A45 S W177?
As standard, the Mercedes-AMG A45 / A45 S W177 produces from 387 to 421 hp and 480 to 500 Nm, depending on the version. 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 for the 421 hp version reach 490 hp and 600 Nm.
Stainless steel or titanium: which material for the Mercedes-AMG A45 / A45 S W177?
The Rog exhaust comes in stainless steel and titanium, at the price shown on the product page in your currency. 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 Mercedes-AMG A45 / A45 S W177?
No, the cat-back alone already does most of the work on the Mercedes-AMG A45 / A45 S W177. 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 Mercedes-AMG A45 / A45 S W177?
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 Mercedes-AMG A45 / A45 S W177.
How is the Rog exhaust fitted to the Mercedes-AMG A45 / A45 S W177?
Fitting needs no welding or cutting and takes two hours on average on a lift. We check compatibility with the VIN of your Mercedes-AMG A45 / A45 S W177 before manufacturing.
What does a Rog exhaust cost for the Mercedes-AMG A45 / A45 S W177, and how long does it take?
The price depends on the configuration and is shown on the product page, in your currency. Allow 20 working days from order confirmation to delivery. Free delivery, 3-year warranty.
Valved Exhaust System for Mercedes-AMG A45 / A45 S W177 2.0 turbo (2020-2022)
From £2,459 · 3-year warranty
Configure my exhaustUnsure about your configuration? Write to us.
Stainless steel or titanium, cat-back only or the complete system: the right choice depends on how you drive and on your Mercedes-AMG A45 / A45 S W177. We take the time to talk it through before you order, with a reply within 24 hours. We are not here to push a sale: we help you choose, even if that means a cheaper option because it suits the way you drive. Write to us: we reply in writing, in English.
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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