The biggest complaint that I've seen about the Audi TT's handling is that it has the 95/5 Haldex split and only uses awd when the front wheels slip.

Has anyone had experience with remapping the Haldex ECU to provide a better split (60/40)?

wak-tt.com/mods/haldexpp/haldexpp.htm]Waks Wide Web

I'd like to get it done but I don't want to ruin the traction control or do damage to the hardware if it wasn't meant to operate like a normal AWD system.

 

I don't have any AWD updates done but many have changed controllers and are very pleased with the reuslts I've read. It's suggested you do the Haldex filter and oil change a little more frequently if you change the controller as the wet Haldex clutches get more activity. The stock Haldex split is more then 95/5 from what I've read, and the most popular way to change the characteristics is to purchase the different controller for the Haldex unit. The controller is located under the car at the haldex unit itself.

From VWvortex in the MK1 TT forum pages:
The stock system is mostly FWD until sensors throughout determine that power needs to be sent to the rear, which, in stock form, happens with hard acceleration or loss of traction. The Haldex system averages about 80% front / 20% rear distribution, and it can never go beyond a 50/50 split because the front half-shafts are permanently powered.

If you want a more constant 50/50 power distribution, you can purchase a Haldex Performance controller. This swap will allow more power to go to the rear in many more conditions. There are two replacement controllers in the form of either a Blue or Orange controller; with the Blue controller, more power is sent to the rear wheels earlier, but the controller unlocks once the gas is released, or if the clutch or brake pedals are pressed. The more expensive Orange controller, however, stays locked at all times. What this all means is that the Blue is good for improved street driving because of a more neutral power distribution, whereas the Orange is more track-oriented because a locked AWD system is always applying power, which allows drivetrain braking but takes away a safety net on the street.

I believe the replacement controllers go for about $800 - $900 bucks.

 

This is some good reading:

HPA Motorsports Inc. - Haldex Controllers

 

Alan,

Thanks for the response. It sounds like what I'm looking for is just the controller. Seeing as I have a MK1 TT it looks like my only option is the competition controller which isn't switchable. Ideally I'd like better launch control (currently it's a little bit jerky when launching from a stop, I think the front wheels begin to spin and then the Haldex begins supplying more power to the rear wheels.

I will be driving my car in Chicago this winter, do you know if this mod poses any safety concerns for bad weather driving? It seems like engine braking being applied to the rear wheels would be a good thing in the snow but I don't want to not fully understand the technology and end up in Lake Michigan!

.

 

The stock front:rear split is around 70:30 IIRC. There is a hardware limit of 50:50 on the early Haldex systems.

Alan is correct in the functions of the two authorized-aftermarket Haldex controllers, but I'd like to add that the big advantage is that their reactions are predictive rather than reactive, as the stock controller is. The Blue and Orange controllers can also send power to the rear based on throttle input, whereas the stock one is based only on wheel slippage. I recommend the Blue for everyone but the hardcore track-junkies.

 

I'd definitely lean more toward everyday usage versus track junky. Is there a website that sells the Blue Haldex?

 

Yeah, to take advantage of the Orange, you're going to have to be pretty skilled at road-racing. Otherwise, it will just be a liability - with the possibility of binding the differential - on the street.

I don't know of anyone other than HPA that sells them new in North America. You can always sit on the classifieds (on higher traffic sites than this one) and hope that a used one pops up.

 

I had mine done at rpi in Vancouver - I think you can get them through newspeed as well.

 

Does anyone know the difference between the orange Haldex controller and HPA's?

 

HPA only sells the equivalent of the orange controller. There is no "locked in" situation as some claim. There are a lot of myths on some forums, and maybe they apply to some other versions. The rear only engages on hard acceleration and deceleration, otherwise it is supposed to be FWD. I've read on other forums about mild binding or hopping getting into parking spots, but I've only been able to get that to happen if I'm really aggressive - like beating someone to that last spot in the mall during holiday shopping . My Talon with LSD all around was worse for binding than this, and even that didn't get in my way.

The difference between the blue and the HPA Performance is only that the latter will also engage the rear wheels during hard braking. Normal braking is still supposed to be FWD. Not sure where the threshold is, since it can't be monitored with the diagnostic tools.

Talk to Nik at HPA and he'll tell you all about it. I was skeptical too based on all the mis-information on some of the forums. I've been driving with the HPA Performance for over 2 months and I've never noticed any problems. I'll see how it handles in the winter, but for normal driving, you wouldn't know it is there. So far, I'd recommend it for daily driving, not just track use.

Mike

P.S. Regarding being a safety hazard while braking, that sounds like a myth. As long as the ABS is working, it is supposed to do what it does on the front wheels. Supposedly the rest of the DSP still works with the Performance controller, but I haven't tested it myself yet. I'll know when the snow comes. My old Talon engine-braked all 4 wheels unless I pushed the clutch pedal in. If you have a 6M, how can the engine be connected to the rear wheels and not the front when you push in the clutch pedal???