Audi Tuning | VW Tuning

… Or is it?

Jim is an architectural photographer and spends a lot of time on the road, sometimes with and sometimes without his B7 Audi S4 Avant. While he was away on a recent trip, he arranged to have the car picked up from Barrier Audi where it was getting worked on and brought to us for a STaSIS center-diff install and an APR full exhaust consisting of higher flowing cats, down-pipes, and cat-back. An increase of 25 hp and 35lb-ft of torque have been seen on APR’s dyno with this set-up – typically the most amount of power you can squeeze out of the V8 without spending big money on a super-charger.

The rear valence had likely been removed for installation of the hitch we noticed just beneath the bumper. Makes sense considering Jim uses his Avant for cross-country trips and likely hauls quite a bit of gear. The differential and exhaust were just the beginning stages of Jim’s performance goals as this car also sees the occasional High Performance Driving Event. We hear a rear differential upgrade is also planned as soon as STaSIS has one available. Ohlins suspension and brakes are likely going to follow shortly after. Stay tuned for updates!

After a few weeks in the shop, we installed the STaSIS 4:1 center differential on my B6 S4. The stock differential provides 2:1 torque distribution, with the modified STaSIS unit we’re able to provide 4:1 just like the B7 RS4.

I have not had a chance to take the car to an HPDE yet, but I have noticed an immediate difference coming out of the apex of a corner. Typically when you’re exiting, the car begins to under-steer; with the diff the moment you begin to under-steer the power is transferred from the front to the rear and we can neutralize some of this under-steer.

There has been no odd behavior from ESP or ABS. The only thing I’ve noticed post-diff has been some Quattro binding at low speed turning, such as in parking lots.

This modification is available for 5 and 6 speeds, manual A4/S4s.

The install was simple, expect approximately one hour for the install and reinstall. Start by disconnecting the center drive-shaft. The drive-shaft is held in by six allen key head bolts, be careful not to strip these. We heated the bolts with MAAP gas to loosen and burn off any Loctite.

Once the bolts are out, the Torsen housing can be removed, and the differential can be removed. Slide in your new unit, refill the transmission fluid (it’s shared with center diff) and you should be good to go!