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.

2020 Posaidon GT 63 RS 830+

Specifications
  • Make: Array
  • Model: 2020 Posaidon GT 63 RS 830+
  • Engine/Motor: V8
  • Horsepower: 940
  • Torque: 942
  • [do not use] Vehicle Model: Array
Pros
Cons

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

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?

This is where the fun starts, especially if the goal is to unlock staggering amounts of power from that V-8 unit.

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.

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.

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?

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

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.