Skip advert
Advertisement

Posaidon boosts the Mercedes-AMG GT S to 690bhp

New hardware and software gives GT S Huracan-trumping performance

You could say that the Mercedes-AMG GT S’s standout feature is its deep bellowing V8. That’s not to say the chassis is lacking, but the twin-turbo unit was certainly a key ingredient in securing victory against the Porsche 911 Carrera GTS in the car's first head-to-head test (evo 204). And now, thanks to German tuning house Posaidon, that V8 is available with substantially more firepower.

Advertisement - Article continues below

Swapping the standard inboard turbos for uprated items, increasing the size of the intercooler and fitting a freer-flowing exhaust system has enabled Posaidon to fine-tune the ECU’s mapping so the engine now produces 690bhp and 553lb ft of torque.

This represents a substantial increase of 187bhp and 74lb ft of torque over the standard car, and ensures the Posaidon GT S shaves six tenths from the factory model’s claimed 3.8sec 0-62mph time. Top speed also grows to 216mph, 24mph more than standard, ensuring the car now has enough grunt to out-drag a Lamborghini Huracan. 

Posaidon says that it could have upped torque even further, but it chose to cap the number at Mercedes’s recommended torque limit in order to ensure the mechanically unmodified seven-speed dual clutch gearbox remains reliable – though admittedly, Posaidon does offer a ‘box remap and will, if provided with a written request to do so, up torque beyond the recommended limit.

The German tuner also offers uprated brake components, but no new parts for the car’s chassis setup are currently available. But with all-round double wishbones, adaptive dampers and an electronically controlled limited-slip differential part of its standard armoury, the AMG GT S is arguably already well placed to handle more power. 

Interestingly, owners of the non-S AMG GT can also be catered for, because Posaidon’s engine performance upgrades are also available on its less potent V8 – in this case the car’s final output would represent a 234bhp and 111lb ft of torque over standard. It’s worth noting that the GT doesn’t receive the S’s electronic LSD however, instead making do with a mechanical system – so Posaidon tuned GT owners might find that this output increase requires gentler throttle applications…

So what’s the price of all of this engine work? Posaidon says that it’ll supply and fit all of the parts for €25,000 (this price includes Germany’s 19 per cent sales tax). While that might initially sound like a lot, let us not forget that a Posaidon AMG GT S’s output would rank it alongside the likes of the Lamborghini Huracan – and that car starts at £186,760.

Skip advert
Advertisement

Recommended

Mercedes-AMG GT review – better than the original, but a match for the Porsche 911?
Mercedes-AMG GT – front
In-depth reviews

Mercedes-AMG GT review – better than the original, but a match for the Porsche 911?

A sophisticated new chassis, up to 805bhp and a more practical cabin provide the AMG GT with everything it needs to take on the best in the business
9 Jan 2026
Mercedes AMG GT Track Sport testing – special with GT3 RS-rivaling road potential shapes up
Mercedes Concept AMG GT Track Sport
News

Mercedes AMG GT Track Sport testing – special with GT3 RS-rivaling road potential shapes up

Mercedes-AMG has skipped right past any new GT R or black series to a track-spec race car for the road. We hope it makes production…
28 Oct 2025
Skip advert
Advertisement

Most Popular

Living with the Toyota GR Yaris, a homologation hot hatch for £20k
evo Fast Fleet Toyota GR Yaris
Long term tests

Living with the Toyota GR Yaris, a homologation hot hatch for £20k

As the mystery of the GR’s true fuel tank capacity is solved, a new enigma emerges
27 Jan 2026
New Toyota GR Yaris Aero Performance review – more aero, still brilliant
Toyota GR Yaris Aero Performance
Reviews

New Toyota GR Yaris Aero Performance review – more aero, still brilliant

A wilder-looking winged variant of the GR Yaris joins Toyota’s GR range – and the best news is it’s coming to the UK
28 Jan 2026
Looking for a used Mercedes-AMG V8 bargain? These are our picks
Mercedes-AMG V8s
Features

Looking for a used Mercedes-AMG V8 bargain? These are our picks

Mercedes-AMG is rectifying its down-sizing strategy and working on a V8, but while you wait here’s four used V8 AMG icons we’d take a punt on
29 Jan 2026