Would it make "Quattro" purists cringe or wonder why? Sure, but back in 2010, nobody else was doing it, so we set off to take one of our biggest 2.7T B5 S4 builds to a totally different experience and ditch the front axle components and transmit all of that energy to just the rear wheels.
We started with our VAST Hybrid Borg Warner S200 twin turbo build, all hand-built from the stainless log manifolds back to the 3" downpipes, collecting to a 4" exhaust system. The engine was our "3.0T" stroker setup with a forged Audi 3.0 crankshaft, VAST 3.0 short billet connecting rods and forged pistons and big port cylinder heads with all Audi RS4 supporting hardware for the intake system and oversized turbo inlets and dual open element intakes running without a MAF sensor on our custom tuning for the Bosch ME7 Motronic ECU.
Compression Ratio: 9:1
Intercooling: AWE Tuning, NO methanol or alcohol or E85 tricks
Cylinder Heads: 2.8L ATQ large port, Supertech titanium valvetrain hardware, oversized intake valves, oversized inconel exhaust valves.
We retained use of the vehicle speed sensor by a custom relocation to the rear differential. The rear differential spider gears were welded in place to test the concept in preparation for a larger conversion one day.
All parasitics were removed wherever we could (front axle outer CVs were disassembled to give a torque preload for the front wheel bearings, front axle flanges removed, front differential removed, air-conditioning system removed).
Gear oil capacity was increased with the extra volume found in the transmission with the front differential removed and the center diff delete coupling element.
The result: 723rwhp/630rwtq at 34psi for the very first dyno tuning day without going back to improve it, which is not too shabby. Mind you, this is 2010 we're talking about here on a factory control unit we custom remapped for a race gas file.
This vehicle was sold sometime around 2012 and had a long life thereafter, the last we heard.
The VAST RWD Drivetrain Conversion Kit:
Center Diff Delete, 4340 Chro-moly with more robust SAE conversion spline system for the output shaft: