The heavily modified turbocharged 2.7-liter dohc 20-valve V6 underpins the action with a deep and powerful growl at low speeds, turning into a purposeful cry at higher rpm. The Cosworth-made motor already produces an impressive 142 bhp per liter, the highest specific output of any current production car. The MTM version pushes this into orbit with 223 bhp per liter, more than double the 100-bhp/liter benchmark for high-performance engines!
While Cosworth retained the 2671cc (81.0 x 86.4mm) capacity of the basic Audi motor, the rest of the engine around it was totally redesigned. The block was strengthened, the crankshaft beefed up and lightened, lighter, stronger pistonsand con-rods fitted along with sodium-cooled valves.
The cylinder heads were redesigned to optimize gas flow. With larger intake and exhaust ports than the S4 heads, these heads are manufactured by a specially developed casting technique. Special manifolds were cast for the two KKK K04 turbos, which work with the Bosch Motronic ME7 sequential fuel-injection system and 9.0:1 compression ratio. The engine benefits from a pair of larger, more efficient intercoolers, and the turbos are said to produce 2.2 bar absolute on overboost.
The bigger bore exhaust system is also bespoke. The center and rear silencers were designed to minimize backpressure-very important with turbocharged engines, and free-flowing metal catalysts are used.
To get 602 reliable horses from this already tuned engine, MTM goes back to first principles. The engine is stripped and every component that will be re-used is checked for dimensional accuracy, weight and balance. Then new forged and machined connecting rods are used with the original pistons. The standard valves are now paired off with uprated valve springs, allowing higher sustained revs.
The original oil cooler is retained, but the sump is given internal baffles to keep the vital lubricant in the right places when the car is being driven hard. The cylinder head is ported and polished, and the compression ratio reduced from 9.0:1 to 8.5:1 by both some subtle machining work and a thicker head gasket.
The inlet system is modified to admit more air, and the exhaust manifolds are also new. "The standard KKK K04 turbos are only good for 458 bhp with just two metal catalysts, sports exhaust and ECU conversion," Roland Mayer said. "You can get up to 470 bhp with modified KKK K04 turbos," he said. "But to get over 600 bhp, we need to go up to the next turbo 'group,' so we put a pair of KKK K16s on the manifolds. These are internally modified to our own requirements and flow a lot more air at high revs." Bigger fuel injectors and a second fuel pump cope with the maximum boost pressure of 1.6 bar, rising to 2.0 bar on overboost.
The complete exhaust system is replaced with MTM's own chrome-nickel cast-iron manifolds, four free-flowing metal catalysts and larger bore 70mm-diameter twin-pipe stainless-steel system. "There is some movement because of torque reaction, so we use expansion joins on the manifolds to prevent any cracking,"Roland stated.
The ride height is 20mm down from the standard car with uprated springs and KW dampers. After receiving complaints about the harsh ride of Audis from previous model owners, Audi did some of its suspension development work in the UK and came up with a fairly comfortable ride and handling compromise for the UK. On the other hand, German drivers complained that it was too soft. The MTM car is much stiffer, which is fine on long autobahn sweepers and indeed on the track, but it might be borderline on UK roads.