The amazing engine in the Mercedes-AMG A45 S – TopAuto
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Wednesday / 10 August 2022
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The amazing engine in the Mercedes-AMG A45 S

The Mercedes-AMG M139 engine in the A45 S puts out 310kW, and it’s “just” a four-cylinder.

For context: the powerful 4-pot from the BMW 135i puts out 225kW, the Honda Civic Type-R 228kW, and the new Golf R 235kW.

Currently, there is nothing that comes close to the power unit from Mercedes-AMG when it comes to a two-litre, turbocharged, four-cylinder recipe.

So, how exactly did Mercedes-AMG achieve this?

The one development that AMG claims contributed greatly towards the bump in power was optimising the engine for efficiency.

In many turbocharged cars, the exhaust and turbo sit on the front side of the engine – requiring an extended intake on the inlet side at the back of the engine and a longer exhaust that routes under the engine block to the back.

Flipping the engine 180 degrees makes accessing the hot components trickier, but it shortens both the inlet and exhaust – and allows the engine to be placed lower in the engine bay.

Low-friction roller bearings – a concept carried over from AMG’s turbo V8 engines – assist the turbo in spooling faster for more responsiveness, while clever duct engineering in the manifold feeds the twin-scroll turbo in a way that makes sure the pressure to the turbo is more consistent with the cylinder firing order.

The result: near-instantaneous throttle response and a bump in torque.

However, powerful engines make lots of heat.

To combat this, Mercedes-AMG used a heavy-duty cooling system featuring air, water, and oil-cooling to make sure the engine doesn’t grenade itself.

F1 technology is used in the cylinders, too, and comes in the form of a super durable, low-friction coating – while the electronic water pump can adjust the rate of flow depending on the engine’s requirements.


The M139 engine in the Mercedes-AMG A45 S is a marvel of engineering that rivals have not been able to match.

It comes at a price, however, and the hot hatchback it drives is over R1.1 million.

With developments like this in engine technology, Mercedes-AMG also alluded that the new C63 could lose half its cylinders – favouring a hybrid four-cylinder system with more than 370kW over a V8 engine.

Mercedes-AMG A45 S – Photos

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