HPA Holiday Special on Haldex Controllers
12-05-2006, 03:41 PM
#14
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Steve --Not quite sure I understand...
I can see how this controller would make ESP ineffective if it did not allow the rear to disengage like OEM. The ESP system would tell the car to do one thing, but the controller would be doing its own thing. That would be bad and make ESP worthless. I can also see how it would effect ABS "if" ESP was on.
But what about with ESP off? Or better yet, how would the "competition" controller effect ABS in a car without ESP?
Also, while I understand how this controller would negatively effect ESP and could cause someone to loose the rear end of the car in a situation where ESP would keep things right, I don't understand what you mean when you said the not disengaging like OEM woud cause the tail to "drag".
Could you explain a little more?
But what about with ESP off? Or better yet, how would the "competition" controller effect ABS in a car without ESP?
Also, while I understand how this controller would negatively effect ESP and could cause someone to loose the rear end of the car in a situation where ESP would keep things right, I don't understand what you mean when you said the not disengaging like OEM woud cause the tail to "drag".
Could you explain a little more?
12-05-2006, 04:11 PM
#16
The other quattro
The TT and A3 use a Haldex center differential. The other A cars (A4, A6, A8) use a Torsen center differential. The Q7 I think uses the same diff as the Cayenne and Touareg and the R8 uses a Lamborghini VT differential.
Torsen is a full time system where at a steady state it is distributing torque to both axles. Typically it's setup for 50/50 altho they're starting to run slightly rear bias in the S and RS cars. Haldex is normally a FWD bias sending power to the rear axle only when a front wheel is slipping. The orange controller is more permanently locked than the stock setup tho and there's maybe some issues with how that effects the car under braking. But, since Torsen based cars are always delivering torque to the rear axle and they don't have issues with braking it's not clear why an orange controller Haldex would have any issues.
Torsen is a full time system where at a steady state it is distributing torque to both axles. Typically it's setup for 50/50 altho they're starting to run slightly rear bias in the S and RS cars. Haldex is normally a FWD bias sending power to the rear axle only when a front wheel is slipping. The orange controller is more permanently locked than the stock setup tho and there's maybe some issues with how that effects the car under braking. But, since Torsen based cars are always delivering torque to the rear axle and they don't have issues with braking it's not clear why an orange controller Haldex would have any issues.
12-05-2006, 04:35 PM
#17
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oh yeah... other Audi's - I am just TT Centric
you said that "Haldex is normally a FWD bias sending power to the rear axle only when a front wheel is slipping."
do you mean that power is sent to the rear wheels when under engine power, not when the front wheels are slipping... that is how the left/right power is distributed
do you mean that power is sent to the rear wheels when under engine power, not when the front wheels are slipping... that is how the left/right power is distributed
12-05-2006, 04:54 PM
#18
The driveshaft is always spinning to the haldex diff
but the diff itself is not always engaged. With stock programming the clutchpack in the Haldex engages when there is a difference in rotational speeds between the front and rear axles (ie a slip). The difference in speed drives an oil pump which increases oil pressure which causes the clutches to engage and power is transmitted to the rear axle. Under normal situations where the front axle is spinning at the same speed as the rear axle (no slip occuring) the car is FWD. There's some debate as to whether it's 100% or 95% FWD but it's predominantly FWD.
The blue controller activates an electric oil pump in the differential proactively when it thinks there might be a slip (ie the driver just mashed the gas and there's alot of torque going to the front wheels). This will engage the clutch a bit earlier than the stock programming but otherwise it functions the same.
Left/right power distribution is controlled by an "electronic diff". The front and rear diffs are open and when there's a slip at one side the brake on that wheel is engaged to cause power to transfer to the other side. That functionality doesn't really have anything to do with Haldex and functions the same on Torsen cars.
The blue controller activates an electric oil pump in the differential proactively when it thinks there might be a slip (ie the driver just mashed the gas and there's alot of torque going to the front wheels). This will engage the clutch a bit earlier than the stock programming but otherwise it functions the same.
Left/right power distribution is controlled by an "electronic diff". The front and rear diffs are open and when there's a slip at one side the brake on that wheel is engaged to cause power to transfer to the other side. That functionality doesn't really have anything to do with Haldex and functions the same on Torsen cars.
12-05-2006, 06:55 PM
#20
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Re: how hard is the install?
Not tough, kinda an extra PITA Haldex filter change. Lotsa install links. Here's one from Steve.<ul><li><a href="http://public.fotki.com/ttschwing/haldex_mods/mods/">http://public.fotki.com/ttschwing/haldex_mods/mods/</a</li></ul>