You won’t believe how powerful the Mercedes-AMG GT 4-Door 63 S 4Matic has become

Mercedes-AMG’s GT family is a lineup of filthy performance machines, none more imposing than the 730-horsepower GT Black Series. But before the GT Black Series arrived, the 639-horsepower AMG GT 4-Door 63 S 4MATIC+ held court as the most powerful member of the AMG GT family.

Just because that’s the case now, though, that doesn’t mean there’s no room for the four-door powerhouse to reclaim that throne with some help from the aftermarket world. Enter Posaidon.

What’s so special about the Posaidon GT 63 RS 830+?

2020 Posaidon GT 63 RS 830+ Exterior
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If you want power, the Mercedes-AMG GT 4-Door 63 S 4MATIC+ already packs a lot of it. The performance four-door is equipped with a 4.0-liter twin-turbocharged V-8 engine that produces 630 horsepower and 664 pound-feet of torque. The V-8 is capable of helping the fastback accelerate from 0 to 62 mph in 3.2 seconds before peaking at a top speed of 196 mph. These figures show the potency of the AMG GT 63 S 4MATIC+, and that’s without the help of any aftermarket outfit like Posaidon.

But what if you crave for more power, or at least more power than the 730-horsepower Mercedes-AM GT Black Series? If you’re looking for a tuner that’s capable of addressing those needs, then you might as well get to know Posaidon, the German tuner that has a long track record of developing and building aftermarket for Mercedes and Mercedes-AMG kits.

What kind of power and performance upgrades are we looking at?

2020 Posaidon GT 63 RS 830+ Drivetrain
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This is where the fun starts, especially if the goal is to unlock staggering amounts of power from that V-8 unit.

The first order of business? Replacing the two turbochargers in the engine with new ball-bearing performance turbochargers.

That’s just the beginning. The V-8’s intake system, interceding system, and cylinder heads also received extensive overhauls to keep up with all the upgrades that Posaidon has set in place. Even the stock exhaust system has been canned in favor of an entirely new flow-optimized exhaust system.

2020 Posaidon GT 63 RS 830+ Exterior
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Posaidon even added water/methanol injection to help improve boost pressures without putting too much thermal load on the engine. All the new pieces in place require a delicate balancing act from all the modifications that Posaidon has added. The latter also includes software modifications to the V-8’s engine control unit, drive control unit, and drive chain.

The results speak for themselves, or at least the performance figures do.

With all the upgrades, updates, and changes in place the RS 830+ now boasts a 4.0-liter twin-turbocharged V-8 engine that’s cable of producing a knee-buckling 940 horsepower and 942 pound-feet of torque.
2020 Posaidon GT 63 RS 830+ Exterior
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That’s 300 horsepower and 279 pound-feet of torque more than the standard AMG GT 4-Door 63 S 4MATIC+. The power gains show up in the car’s performance times, too. With all the setup complete, the RS 830+ is capable of accelerating from 0 to 62 mph in just 2.8 seconds. It can also hit 124 mph from 62 mph in just 5.9 seconds and reach a top speed of “over 211 mph.” That’s supercar-like levels of performance for a four-door missile that weighs a whopping 4,758 pounds.

How much damage to the bank account should I explain to the misses?

2020 Posaidon GT 63 RS 830+ Exterior
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Posaidon didn’t say how much financial damage the RS 830+ will cause. We do know that the powerful sedan starts at over $160,000. More importantly, you also need to vector in the complexity of this build and the results that came from it. A total cost of around $200,000 isn’t impossible.

Final Thoughts

2020 Posaidon GT 63 RS 830+ Exterior
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If you know Posaidon, you know that the German tuner doesn’t go half-assed with its tuning programs. Every program the firm develops is dialed to 11. That sentiment applies to the kit the tuner developed for the AMG GT 4-Door 63 S 4MATIC+. Here’s the thing: Posaidon could have achieved its goal of coaxing more power out of that twin-turbo V-8 by taking the software tuning route.

A tweak here and a tweak there would have achieved the desired results. But this is Posaidon. Software engine upgrades aren’t as exciting as overhauling most of the drivetrain and then adding the software upgrade in the end.

  • Leave it
    • Too much power for most people
    • No exterior and interior upgrades
    • Could be expensive
Kirby Garlitos
Automotive Aftermarket Expert - kirby@topspeed.com
Kirby’s first exposure into the world of automobiles happened when he caught Knight Rider on television as a five-year old boy. David Hasselhoff didn’t leave much of an impression on him (that happened later on in Baywatch), but KITT certainly did. To this day, Kirby remains convinced that he will one day own a car with the same ‘spirit’ as the original KITT (not the 2008 monstrosity). He doesn't know when that will be, but until then, he’s committed to expressing his love for KITT, and all cars for that matter, here at TopSpeed.  Read More
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When the AMG GT Black Series was launched, the 730 hp super sports car deposed the Mercedes-AMG GT 63 S 4MATIC+ as the most powerful car in the AMG portfolio. The previous title-holder, a four-door motor with an elegant coupé roofline, boasts 639 hp – while the former AMG sports car superstar, the GT R, lags even further behind at 585 hp.
Yet the engineers at POSAIDON in Mülheim-Kärlich have remedied the situation with modifications of the highest level – in the truest sense of the word. They have given the most extreme level of their performance improvements for the four-door GT-series X 290 the name GT 63 RS 830+. The spec sheet includes a brutal 940 hp and incredible peak torque of 1,278 Nm – some 300 hp and 378 Nm more than the already potent series vehicle!

Unlocking figures of this magnitude in this 4.0-liter twin-turbo V8 naturally involved comprehensive and carefully considered changes to the hardware and software of the AMG drive system, based on required extensive and utterly precise development work.

The POSAIDON engineers replaced the two turbochargers in the M177 DE 40 AL engine with new ball-bearing performance turbochargers connected to an entirely new exhaust system, complete with new downpipes fitted with motorsport catalyzers. The eight-cylinder engine’s intake system, intercooling system and cylinder heads also enjoyed an equally extensive overhaul. The intake and exhaust ports have been expanded and flow-optimized. POSAIDON also optimized the valve positions.
The additional water/methanol injection introduces thoroughbred motorsport technology to the RS 830+. This system, supplied by a tank integrated in the base of the trunk, allows significantly enhanced boost pressures without subjecting the motor to higher thermal load, successfully combining the maximum possible performance enhancements with dependable and enduring operation.
In order to squeeze everything possible from the new hardware, the developers at POSAIDON made extensive optimizations in relation to the software programming of the control units for the engine (ECU), drive (TCU) and drivechain (CPC).

Of course, these performance enhancements are reflected by impressive driving performance. Although the sprint from 0-100 km/h in just 2.8 seconds is eye-catching, anyone who knows their stuff will be even more impressed by the continued acceleration shown by the 2.1 ton all-wheel drive, which powers from 100 to 200 km/h in just 5.9 seconds! When it comes to the top speed unlocked by all the software optimizations, the POSAIDON team have stated a reserved figure of “over 350 km/h”.

By the way: While the 830+ version is for export only, POSAIDON also offers tuning levels that are ever so slightly “tamer” – but come with TÜV approvals. In Germany, the official TÜV seal is available for vehicles with up to 830 hp and 1,100 hp.

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