That not only continued once AMG was fully in the fold as Mercedes’ official performance sub-brand, but actually became even more mental when the engine bay of the first generation C63 AMG found itself stuffed full of M156 V8 motor displacing 6,208cc.
Two generations of C63 later, the swept capacity of the M178 V8 measures just 3,982cc, but with a pair of turbochargers nestled between the cylinder heads this small block V8 can potentially make more horsepower and torque than its larger, naturally aspirated predecessor.
“Turbocharging makes tuning much easier, with a remap of the fuel, ignition and boost maps all that it takes to see significant gains in output,” says Andreas Ehret, the boss of Väth.
The basic Väth C63 power upgrade delivers 612hp with 800Nm of torque, a substantial increase over the 510hp and 700Nm produced by the ‘S’ variant of the C63 AMG. This ECU only conversion comes with German TÜV certification.
“The key to reliable power with this engine is keeping temperatures down so the first thing we do for our Stage 2 conversion is install an additional intercooler with a larger aluminium core,” Andreas explained. “We were seeing temperatures of 120 degrees C with the standard intercooler, but our more efficient unit can extract up to 45 degrees, which gets the intake temperatures down to the 80 degrees region.”
“However, that is not the end of it. With a big power increase you also need to keep the gearbox cool as temperatures will soar into the 110 to 120 degree C region, which is not good,” he continued. “We use an independent gearbox oil cooler to reduce the oil temperature to no more than 80 degrees as well.”
Exhaust backpressure creates a lot of heat both in the exhaust as well as the exhaust valves, and that is not good for either combustion or power output. “Our free flow exhaust downpipe and 200-cell metal catalytic convertors reduce backpressure and heat build up in the system so the engine runs cooler and more efficiently,” he said.
The Väth V63 RS ECU remap and free-flow exhaust downpipe really opens the taps and the result is a rousing 645hp and 880Nm of torque. “We knew we could get even more power due to our success with our high efficiency intercooler and gearbox oil cooler, but we also knew that the standard turbochargers were right on the limit at this point,” said Andreas. “So we swapped them out for a pair of our bespoke turbocharger units that can flow a lot more air. We recalibrated the ECU mapping to suit and the dyno showed a very satisfactory 680hp with 900Nm of torque.”
As the test car started life as a standard C63 T rather than the S-model, Väth fitted the electronic rear differential from the S. “This works perfectly from zero to the cars delimited 325km/h top speed,” says Andreas.
Although Väth normally use KW coilover suspension as a matter of course, this time they went with H&R who provided a coil-over kit with adjustable spring pans, with active dampers that plug into the factory electronic damper selector control.
“The KW suspension works brilliantly on the C43 4Matic, but when we were doing back-to-back testing with the C63, we found that the H&R set-up was better with the rear-driven car,” Andreas explained. “The differences between the low and high speed ride and handling characteristics are not so big and with less traction and more power this is important on the C63.”
With the ride height set 35mm lower than standard the Väth V63 RS estate looks nicely hunkered down on its 8.5J and 10.0Jx20-inch V2 GT alloys, shod with 255/30ZR20 and 285/30ZR20 Continental SportContact 6 tyres.
Half the emotion you get from an AMG V8 motor comes from its soundtrack and here Väth has played a new card. Unlike the stock exhaust, which explodes with sound when the engine fires up the Väth sound valve exhaust system has a default switch that ensures Comfort mode is engaged when you start the car. The counterpoint is Sport mode, which delivers a full dose of basso profundo NASCAR grade bent crank V8 growl.
“There is a limit to how much noise you can make, and you don’t want to wake up the whole neighbourhood unintentionally,” said Andreas. “In fact we recently modified a factory Aston Martin Rapide exhaust for a client to make it quieter. He told us it was far too noisy for the golf club or when he went shopping.”
As is an estate car this V63 RS is a real Q-car, and with not far off 700hp under its bonnet has the potential to really upset drivers of the odd supercar you might encounter on the autobahn.
I was actually surprised how much traction the car had considering the amount of grunt going through the rear wheels, but on a dry road at least there is no problem getting the power to the tarmac so long as you are sensible with your right foot.
On some of the bumpy country roads I used as my test route it quickly became apparent that Andreas was right about the H&R suspension, which breathes well over bumps, thus keeping the wide rubber on the deck.
On the autobahn this car is a real weapon, and just a whiff of throttle sends the speedometer needle soaring from 140 to 200km/h in the blink of an eye. Back on normal roads you have to be really careful, as this cars ability to add velocity in seemingly 20km/h increments per second is quite un-nerving to anyone looking to hold onto their licence.
Potent is a suitable word that describes the performance of the Väth V63 RS, while wolf in sheep’s clothing describes its appearance. On the other hand a car that can carry the family, and blow off the odd supercar along the way is perhaps best described as a good all-rounder.