Full Blown Performance: MTM Tuning’s Supercharged RS4 Clubsport

By: Chris Ostberg

We knew from the start that it was going to be a trip we would not soon forget. While hustling our Golf TDI along the winding rustic backroads which lie just outside of Ingolstadt in Bavaria, we couldn’t help but think about the great day ahead. We had an 8:30 am appointment with MTM – one of the most well respected Audi tuners in Europe – and no intentions of being late. The carrot: MTM had set aside some of their best offerings and promised ample testing time.

FLASH!

Huh? What was that? But we already knew exactly what it was. Immediately after seeing the intense orange light our peripheral vision caught a glimpse of the unmarked VW Vanagon parked to the left in the bushes. The Polizei of the “Freistadt Bayern” had set up a speed measuring camera just to the side of the rural two lane “Bundesstrasse”.

After glancing down at the speedometer needle, which proudly displayed approximately 40 km/h north of what was allowed, a calm feeling approached. Normally there would be panic or guilt. Normally the impending license suspension notice in the mail would cause a good deal of stress. Not today. We were on the way to pick up the keys to the supercharged, fire breathing, 535 horsepower MTM RS4 Clubsport. Nothing else mattered.

MTM is short for Motoren-Technik-Mayer GmbH (roughly translating to Engine-Technology-Mayer LLC) and was founded by Roland Mayer, a former Audi engineer, in 1985. At the time, Mayer worked on the development of the legendary turbocharged inline-5 engine which brought Audi to many subsequent motorsport victories. The knowledge and the connections from Audi would become invaluable for Roland and his quickly growing tuning company. Simply put, no other third party tuner has the in-depth knowledge and working relationship with Audi that Roland Mayer at MTM maintains to this day.

Settled in the small Bavarian town of Wettstetten just outside of Ingolstadt, MTM resides in a two building facility staffed by over 20 full time employees. Almost everything from R&D, testing, and installation is done in house. Upstairs (which is very tastefully decorated with 600+ hp 2.7 liter engines and various Italian motorcycles) is Roland’s office along with a few CAD workstations where parts are designed and modeled. The downstairs is the main sales/office area.

In back is a workshop area used for installation and service. Perhaps the most impressive sight is the climate controlled chassis dyno room. It includes two side-by-side MAHA 4-wheel dynos each with huge vane axial fans which could make a Learjet jealous. It’s one serious setup.

Roland recognizes that in order to properly test and tune modern cars with forced induction, air delivery representative of real world driving conditions is required to keep intercoolers cool and intake temps low. His high powered ventilation system is capable of producing large volumes of air combined with high wind speeds which accurately simulate highway driving. The MAHA dynos are also renowned for their accurate (even conservative) and repeatable figures. They feature a “rolldown” function to determine driveline losses in order to differentiate between wheel and crankshaft power figures. All of this allows MTM to develop and test its products as thoroughly as possible.

Upon our arrival at MTM we are given a quick tour of the facility by the very cordial and knowledgeable press coordinator, Karla. She leads us out to the garage area. Two cars, a supercharged MTM RS4 Clubsport and a turbocharged R-TT 3.2 DSG are currently up on post lifts and being attended-to by a flurry of mechanics. The RS4 Clubsport was in fact receiving its final inspection before the keys are handed over to us.

The MTM RS4 Clubsport. What praise can we possibly give to the regular RS4 that hasn’t already been said? It’s simply a phenomenal and highly-capable 4-door unlike anything else available. In stock form it’s good enough to lap the Nürburgring Nordschleife quicker than any other 4-door sports sedan on the market. It’s exceptionally luxurious and well equipped. It also comes with the tried and proven all weather conquering quattro driveline now with a rearward torque bias. It’s not perfect to all people though. And so where there’s room for improvement MTM steps to the proverbial plate.

The centerpiece of the MTM RS4 Clubsport package is the liquid-to-air intercooled, Lysolm-type, belt driven supercharger that resides directly underneath the carbon fiber bulge on the hood and feeds the car with 0.45 bar (6.5 psi) of fresh air. This cleverly designed package sits smack dab between the cylinder heads within the “V” of Audi’s 4.2 liter V8 and boosts power levels to a very impressive 535 horsepower and 428 ft-lbs of torque. The engine internals and compression ratio remains 100% stock. A special carbon fiber vent on the hood gives extra clearance to the supercharger and helps keep underhood temperatures checked. The blower assembly completely replaces the stock variable length intake manifold.

It’s important to note that the RS4 Clubsport is still a prototype, meaning it is quite clearly a work in progress. The final version will certainly be finely finished and up to OEM standards and aesthetics, as with all MTM vehicles. The particular supercharger on this press car has actually been adapted from a standard S4 application, which is evident by the holes in the intake runner where an IDI fuel injector would normally reside. This same system is available on the normal S4 and can produce up to 503 horsepower.

Roland has set the development durability goal of 50,000 km for this Clubsport RS4. This means he is not going to release the kit into production until the test car reaches 50,000 trouble free kilometers on the stock engine internals. Currently, the press car has seen roughly 15,000 km, so there is a ways to go. However, press cars tend to see slightly more, ummm, “wear and tear” than the average car so one can rest assured that it has been thoroughly tested and developed under all conditions. We drove this car hard, and it ran well without a hiccup.

Development of MTM’s supercharger system was far from easy. Three important factors contributed to the overall difficulty of the project; size (component packaging), heat, and ease of installation.

Audi has already used up nearly all available space by just fitting a V8 into the A4 chassis. They’ve shortened the engine length as much as possible by using smaller than usual bore-to-bore spacing and fitting the accessory/cam drive to the back of the engine. This didn’t leave Roland much real estate to work with on the front side.

A supercharger setup works by turning an air compressor (blower) mechanically with a belt and pulley system. The extreme revving capability of the RS4 engine means the entire belt drive system must be able to withstand high speed and high torque operation. At full boost, the supercharger can require 50 or more horsepower from the engine to spin itself, which must be transmitted through this belt. Considerable effort went into designing the belt/drive assembly to fit into the small space and function without slippage under all conditions.

The additional heat generated by this setup necessitated the carbon fiber scoop which peeks menacingly from the hood area. MTM also concluded intercooling was vital for safe and consistent power delivery. Trials without intercooling showed that intake air temperatures would climb too high, which in turn would decrease power output as the ECU pulls back ignition timing to compensate. Higher temperatures also increase the likelihood of engine knock, not something welcome to an owner when a $30,000 RS4 engine is in stake. The water-to-air intercooling system taps cleanly into the factory cooling system adding an additional heat exchanger before passing through the supercharger.

“Power is nothing without control”. This cliché statement holds especially true with MTM’s RS4. Simply adding more power to a stock RS4 would result in a less rounded vehicle, perhaps not as effective overall as what originally rolled off the line at quattro GmbH. The remainder of the modifications were therefore designed to make maximum use of the additional power produced by the supercharger. Weight saving measures bring the curb weight of the Clubsport down to a claimed 1660 kg (3650 lbs). This is about 350 lbs less than a US-spec RS4 even while counting larger brakes and additional safety features.

Audi’s DRC suspension system was designed to bridge the gap between ride and performance, two suspension attributes which lie on opposite ends of the design spectrum. The DRC system does an admirable job of controlling body motions on the stock RS4. The hydraulic connections which link the front/rear opposite corners of the car together allow a softer than normal spring rate to be used which increases the ride comfort. Under most conditions the system works exactly as intended. However, some strange behaviors can be observed from time to time with the DRC setup. Under hard braking, for instance, the soft springs in conjunction with the heavily front-biased weight distribution can cause the rear of the car to “waddle” from side to side. This unsettling feeling is not very confidence inspiring to most drivers and limits control during threshold braking.

While the stock RS4 is an excellent all around performer, the RS4 clubsport takes more focus on the performance side of the scale. MTM has attacked the dynamic shortcomings of the stock RS4 suspension head-on to increase the handling ability and adjustability of the car. The stock DRC system is disabled and the springs/dampers are swapped for MTM’s own coilover suspension system. This firmer setup, which no longer relies on the DRC system for pitch and roll control, is better suited to aggressive cornering and race track driving. Hard braking becomes noticeably more stable. The only downfall is the tendency to spin an inside rear tire under slow speed sharp corners. With so much power at tap, a rear LSD (limited slip rear differential) unit should be strongly considered.

The RS4’s Lamborghini-derived 8-piston front braking system does a good job of slowing down a nose-heavy RS4 under normal conditions. As with most things, there’s still room for improvement. We’re talking about 535 horsepower here and brake capacity is something one can almost never have too much of. MTM upgrades to an 8-piston caliper system of its own spec and increases the rotor size from 365 mm to 380 mm. The MTM rotors are also directionally vaned (unlike Audi’s) to improve cooling at speed. The MTM RS4 Clubsport is fitted with MTM’s trademark “bimoto” wheels measuring a 19-inches in diameter. The result is a stunning look that compliments the incredible performance.

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