Taming the torque

In case you haven’t been following our S600 project, it spawned from a golden find in Sunshine Kids and the company’s high quality, yet very narrow child seats. Instead of needing three-row seating we were able to stuff the entire Mazlumian family of five comfortably in the two rows of the S600. I didn’t have to purchase a minivan I’d eventually wear a skirt in.

I wanted performance and with this S600 I got more performance than I bargained for thanks to Renntech, whose Level 3, “650 bhp” upgrade, comprised of engine and transmission ECU upgrades, a carbon-fiber intake and intercooler kit took our stock 5.5-liter V12 powerplant from a crazy stock 472 whp and 570 lb-ft of torque to a laughable 527 whp with 703 lb-ft of torque (Proven, Oct. ’11)—to the wheels, and through the automatic transmission.

We also upgraded the factory 18-inch AMG wheels to Renntech’s 9x19 Monolite wheels wrapped with General Tire’s GMAX AS-03 tires, going up one size in the rear to 275mm. We lost 15 pounds per corner there. We also got rid of the spare wheel and jack—shedding another 60 pounds—with the addition of TyreShield USA’s tire puncture protection system to all four of our GT tires, bringing the total weight loss to about 120 pounds.

All told, using our GPS-based PerformanceBox from VBox USA, our performance went from a respectable zero-to-60 in 4.4 seconds with a 12.7-second quarter-mile at 114 mph baseline, to zero-to-60 in 4.1 seconds and the quarter-mile in 12.2 seconds at 119 mph. This was at 1,000 feet of altitude, too—subtract a tenth and add 1 mph for sea level correction. The car’s the ultimate executive family hauler, yet a total sleeper.

Unfortunately, our S600 was suffering from what many of today’s high-performance cars do—not enough grip for the power. So much torque is transferred to the rear wheels at low speeds that it’s next to impossible to get a consistently good launch.

High-performance car manufacturers are combating this issue today with sophisticated automatic transmissions and launch control mechanisms to optimize digs from anything under 20 mph (think Ferrari 458 Italia, Porsche 911 Turbo, Lambo LP 560-4), netting easy 3-second blasts to 60 mph consistently, if not quicker. Drag radials would easily get this Benz into the low 3-second range. In fact, Renntech’s test car logged zero to 60 in 3.3 seconds and a mid 11-second quarter-mile at 120 mph at the strip with the same upgrades. However, streetable drag radials aren’t desirable in a family car used year-round on the streets in the Midwest. We needed to maximize performance using our all-season tires.

Without launch control, you would think the next best thing is the widest and tallest tire possible, but we’re pretty maxed-out with our 275s on 19-inch wheels—yet it’s still not enough. To put it into perspective, in order to achieve low 4-second blasts with traction control off, we had to part-throttle First gear to 4000 rpm, short shift, and from 3000 rpm ride the torque through Second gear. That’s a lot of torque left on the table. Standing on it only caused so much wheelspin that it slowed acceleration times.

Thankfully, Renntech had the answer: a differential upgrade built exclusively for them by none other than OS Giken. In the world of driveline components, these guys are in a league of their own. Because of their costly raw materials and patented designs, OS Giken is able to stuff up to twice as many plates—in the case of the S600, 20—inside the pumpkin. This not only achieves the smoothest transition between running nothing to 100 percent full lock, it’s also able to withstand an exorbitant amount of torque. They’re also extremely reliable, many times outlasting the lifetime of the cars they go in, and to this day OS Giken reports zero failures from its U.S. customers.

If there is one slight drawback, it’s the added weight. With so many plates, our diff shipped out a hefty 119 pounds and returned to us a whopping 19 pounds heavier. It was a fun install (make sure you’ve got a friend to help).

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