Noted Mercedes tuner Renntech isn’t averse to building all sorts of tuning programs for vehicles bearing the Silver Arrows badge. In recent months alone, the German tuner has released programs for the Mercedes-AMG GT S, Mercedes S550, and even the already departed SLS AMG Black Series. Now, Renntech is back with a new aftermarket kit for the Mercedes-AMG S63 Coupe that peaks in excess of 700 horsepower and almost 850 pound-feet of torque.

The program is defined by the engine upgrade that is being offered in a number of levels depending on what a customer wants. There’s an ECU upgrade that already adds power by itself. There are also new downpipes and sports mufflers that tacks on even more power. And there’s a choice to get all of it put together in order to maximize the program’s full potential. It’s not evident because the car’s body didn’t receive anything other than the decklid spoiler. But that’s the beauty of this Renntech program. The substance of the kit is mostly felt away from the eyes of the customer so it would be hard to identify it as a Renntech kit unless the car gets going.

Once it does, though, well, that’s when the magic happens. The AMG S63 S’s 5.5-liter bi-turbo V-8 engine may be good for 577 horsepower and 664 pound-feet of torque on its own. But thanks to Renntech, there are a lot more horses coming out of that V-8. It will be most certainly felt when the owner pushes the car to its performance limits. That’s power and output taken to an entirely new level, things that a tuner like Renntech has proven to be very good at when it comes to Mercedes models.

Continue after the jump to read the full review.

Exterior

Exterior modifications on the Mercedes-AMG S63 Coupe are limited to the tuner’s prototype decklid spoiler. The matte black paint isn’t included in the program itself, but Renntech added it for show purposes to give the AMG S63 Coupe a stealthy and more aggressive look that complements the impressive engine upgrades given to the coupe’s V-8 engine.

Interior

No interior upgrades are included in this particular program.

Drivetrain

In standard form, the AMG S63 Coupe is powered by a 5.5-liter bi-turbo V-8 engine that produces a tight 577 horsepower and 664 pound-feet of torque. Those are impressive numbers, at least for a standard model is concerned. But Renntech took it a step further by modifying the coupe’s ECU unit, installing new sport mufflers with electronic valves, and tweaking all the parts together to produce an impressive 708 horsepower and 839 pound-feet of torque at the crank. Considering that the ECU upgrade alone is already good for total of 669 ponies and 734 pound-feet of twist, the extra dose of power from the bolt-on parts is a welcome addition.

The tuner also put the AMG S63 Coupe on the dyno to get the car’s actual power while taking into account an estimated drivetrain loss of 17 percent. The results showed that in stock form, the AMG S63 Coupe has a maximum power of 445 horsepower and 489 pound-feet of torque. With the tuner’s upgrades installed into the V-8, the max power goes up to 588 horses and 697 pound-feet of torque on the wheels.

Performance numbers were given based on the power improvements brought about by the ECU upgrade. With that mod in tow, Renntech claims that the AMG S63 Coupe would be able to sprint from 0 to 60 mph in just 3.4 seconds to go with a quarter-mile time of 11.37 seconds at 125.01 mph.

Chassis and Suspension

Somewhat surprisingly, Renntech left the car’s chassis and suspension intact, free of any aftermarket parts.

Pricing

The full price for the tuner’s proprietary ECU upgrade is around $3,495 while the downpipes and catalytic converters retail for an extra $4,490. That brings the total up to $8,435. not including the cost for the prototype decklid spoiler.

Competition

Mercedes-AMG S63 Coupe by G-Power

G-Power presented its own tuning kit for the Mercedes-AMG S63 Coupe back in March 2016. Just like Renntech, G-Power opted to keep the mods minimal in the exterior and interior as it focused more on giving the full-sized luxury coupe a notable increase in power and performance. The tuner accomplished that by installing its own Bi-Tronik 5 V1 power upgrade to bring the output up to 705 horsepower and 738 pound-feet of torque. The program helps the AMG S63 Coupe improve its sprint time to 60 mph to just 3.8 seconds to go with a top speed of 205 mph, thanks in large part to the removal of the car’s Vmax limiter.

Read our full review here.

Mercedes-AMG S63 Coupe by Mansory

Another tuner that has put in the aftermarket work on the Mercedes-AMG S63 Coupe is Mansory. Unlike Renntech and G-Power, Mansory pulled out all the stops with an extensive aero kit and a lavishly appointed interior. More importantly, the Swiss tuner added a bevy of new performance components, including connecting rods, big end bearings, crankshaft, bearing bushings, a turbocharger, and a suction and compressor system. The result is an output of 887 horsepower and 960 pound-feet of torque, enough to beat out Renntech and G-Power’s respective upgrades. With the upgrades in place, Mansory was able to improve the coupe’s 0-to-60-mph time to just 3.2 seconds to go with an electronically limited top speed of 186 mph.

Read our full review here.

Conclusion

Renntech isn’t going to blow anybody away with its program for the AMG S63 Coupe. Then again, a posted output of 708 horsepower and 839 pound-feet of torque is still impressive in every way a customer looks at. Add to the fact that the whole kit costs less than $10,000 and this is about as good a tuning purchase of the AMG S63 Coupe at that price point.