Renntech Mercedes-Benz S700 - 485HPA Fine-Tuned Teutonic TerrorThere's something to be said for sheer size, especially for a 2.5-ton two-door that's quicker in the quarter mile than most production sports cars, more comfortable than the Elvis suite at the Las Vegas Hilton, and decorated with the savoir-faire of any Cary Grant movie in which he wears a tuxedo. There's also something to be said for a 48-valve DOHC 12-cylinder engine displacing seven full liters and producing approximately 485 horsepower and 510 pound-feet of torque. And it's all built like a Mercedes because it is a Mercedes.
RENNTech is the brainchild of Hartmut Feyhl, who left both the renowned AMG tuning firm and his native Germany to settle in Delray Beach, Florida. From there Feyhl has been expanding the Mercedes-Benz performance envelope significantly. The most popular of the RENNTech conversions is his 6.0-liter version of the factory 5.0-liter V-8 used in the S500 and SL500. But it's the company's work on the Mercedes flagship V-12 powerplant that's the subject here: Through the magic of a 90-millimeter bore and 91-millimeter stroke, RENNTech inflates the 6.0-liter V-12 found in the S600 and SL600 up to a lofty 7.0 liters and then caps the assembly with delicately ported combustion chambers and four custom-ground camshafts.
To showcase this engine, RENNTech installed it in a '95 S600 Coupe (resulting in what the company calls an S700) outfitted with RENNTech's stainless-steel cat-back exhaust system, a four-speed automatic transmission modified to handle the torque and consistently launch in first gear, a suspension slightly lower than stock and incorporating a larger-diameter front anti-roll bar, a custom rollbar, a four-point harness for the driver, and anti-penetration security glass. The most impressive, and likely necessary, modifications made to the S-Coupe are 14-inch front and 12-inch rear diameter Alcon vented disc brakes and a set of 18x8.5-inch Speedline wheels surrounded by 265/40ZR18 Pirelli P-Zero Asimmetrico tires.
Despite all its power, the best thing about the RENNTech engine is what doesn't change from Mercedes' original design. The V-12 is an inherently balanced, uncannily seductive arrangement, and Mercedes maximized that advantage with every trick in the book to produce what may be the quietest mega-displacement engine in production. If there's a deterioration in that mausoleum silence and equilibrium because of RENNTech's extra displacement, we didn't notice it. The only extra noise is a distinctive, intoxicated howl from the new exhaust system-a performance sound we'd seek out anyway. Even the large tires are muffled to silence within the big coupe's passenger vault.
Quiet but deadly, the S700 rocketed down the quarter mile in 13.7 seconds at 108.0 mph, defied logic by sprinting 0-60 mph in 5.3 seconds, and then left us slackjawed by hauling its dreadnought tonnage back down to 0 from 60 mph in only 112 feet. There is virtually no sensation of speed; it's as if inertial dampeners in this big ship drain any untoward motion that might interrupt the skeet tournament being held on the fantail.
It looks like a luxury car, it's outfitted like a luxury car, but when pushed, it scoots like a sports car. Nevertheless, the car's bulk is inescapable-you're always aware of just how enormous the thing is-and the steering wheel is mated to relatively slow but ultimately precise steering gear. With so much torque on tap, it's simple to balance the car's natural understeer with an instant helping of power-induced oversteer (as long as the Mercedes traction control is turned off). The only glaring omission on this car was the lack of a limited-slip differential, which would have improved the acceleration times. Take this car to Montana, and it'll go across America's speed-limitless state more comfortably, and maybe faster, than a Gulfstream V.
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