You own a Quattro MK1 TT?
Did you know you’re actually driving a “front wheel drive” Quattro? Well almost.
Some say the rear wheels get only about 5 to 20% of the torque. This means you’re driving a car that has the potential of 50-50 split but electronically controlled way, way lower.
The TT does not have a differential like the “real Quattros” but an Haldex system. This is apparently due to the fact that the engineers were lacking space and opted for the Haldex system. Mechanically, the TT cannot send over than 50% of the torque to the rear wheels, since the front wheels are always engaged.
The only way to change the torque distribution is to change the Haldex controller. And to the best of my knowledge, there is only two manufacturers that carry the performance haldex controllers. The “best” being: HPA. Mk1 TTs have only one option as the MK2 have 3 options which are switchable from the inside. (December 2010: See my update on HPA’ Haldex Controller)
Here’s a link to HPA’s Haldex Controller page: http://www.hpamotorsport.com/haldex.htm.
Here’s what it says.
The sophisticated Haldex based all wheel drive system used in the VW R32 and Audi TT Quattro monitors throttle input, ABS wheel speed sensors, steering angle, etc to anticipate and distribute torque transfer from the engine to the driveline.
Specially prepared Haldex control units are able to alter the time in which the system reacts to these dynamic changes and and how it reacts to them; creating more favourable or aggressive handling characteristics.
This upgrade increases torque transmission at acceleration providing consistent performance with increased over-steer. The torque-transmission is influenced by how fast you press the accelerator down. The Haldex system can transmit torque before the engine delivers torque. At greater speeds the torque will decrease enabling less over-steer and safer driving properties.
The advantages of this HPP upgrade are it’s ability to predict the onset of torque. This upgrade takes into account the TPS signal more so than the OEM software and therefore can proactively begin applying power to the RWD clutch packs before wheel spin begins. As power is increased, more power lock occurs in the RWD unit until full lock is achieved. To summarize, the new HPP is more aggressive with how it transfers power and does so much more proactively than the OEM system. This is ideal for autocross, road racing, and street driving as well as enhancements to poor weather driving.
Gen 1 Competition Controller
Applications: Mk4 R32, Gen 1 Audi TT
Developed by racers for racers; the Competition Controller, now in a stealthly look, identified with an engraved “Competition” marking, transforms the Haldex equipped 4-Motion platform into a weapon on the track. Similar in principle to the standard performance Haldex upgrade, the Competition Controller features one MAJOR difference.
Back in the ’80s the Audi Quattros dominated the race track with their unbelievable ability to brake late when entering the corners. This ability was a result of the rear axle staying engaged under full braking allowing for a combined mechanical and frictional stopping force to be applied across all 4 wheels. The Competition Haldex Controller offered from HPA mimics this by keeping the rear axle fully engaged while under braking. Where the stock Haldex and HPP units release the rear axle into a free wheel situation as the brakes are applied, the Competition unit keeps the rear axle engaged, generating additional mechanical force to assist in slow down and maintain dynamic chassis balance.
The Competition Controller is a must for modified vehicles with high torque outputs. The experienced driver will benefit from the additional chassis control afforded by the equal deceleration rates of the front and rear axle. This allows the driver’s input to dictate the vehicle dynamics under braking, corner entry and exit rather than falling victim to the abrupt disengagement of the rear axle. This added stability and control translates directly to faster lap times; making the Competition Controller a must for the competitive driver.
You can also follow a Forum thread on the subject at: http://www.audiforum.ca/audi-tt/56157-2004-tt-s-line-esp-light-2.html