Rolling Road Day at QST
Hi, it is good that kim will run the S3's and TT's in 4x4 mode because I emailed Haldex about it and they said only run in 2wd mode if the prop shaft is removed because there could still be a drive through the rear diff because of the oil drag when the car is flat out on the rollers at about 100mph+, can you put me down please, Cheers Martin
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johneroberts
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Surely that would only be an issue if the rear wheels were prevented from rotating. I'd always assumed that on a 4WD RR the rear rollers were just in "free rotate" mode if it's running 2WD.... but I don't know. Does anyone know for sure?martins3 wrote:Hi, it is good that kim will run the S3's and TT's in 4x4 mode because I emailed Haldex about it and they said only run in 2wd mode if the prop shaft is removed because there could still be a drive through the rear diff because of the oil drag when the car is flat out on the rollers at about 100mph+, can you put me down please, Cheers Martin
Cheers, Clive
I don't know if they run with the rear rollers running free but if Haldex themselves say don't try it without removing the prop shaft I wouldn't try it on my car, I spoke to Mike at Jabba Sport about it before and when they tried there 4x4 scoda on there rollers in 2wd mode they measured a higher drag through the transmition than running in 4wd mode, this must be the drag in the Haldex diff oil, Haldex said in there email to me you can get over 7ibft of torque transfer through the diff when the fuse is out running in 2wd mode through the oil drag and more at speed when the car is on the rollers at 100mph+clived wrote:Surely that would only be an issue if the rear wheels were prevented from rotating. I'd always assumed that on a 4WD RR the rear rollers were just in "free rotate" mode if it's running 2WD.... but I don't know. Does anyone know for sure?martins3 wrote:Hi, it is good that kim will run the S3's and TT's in 4x4 mode because I emailed Haldex about it and they said only run in 2wd mode if the prop shaft is removed because there could still be a drive through the rear diff because of the oil drag when the car is flat out on the rollers at about 100mph+, can you put me down please, Cheers Martin
Cheers, Clive
HOW THE HALDEX UNIT WORKS
HOW THE HALDEX WORKS
The design of the Haldex LSC is based on a Swedish patent acquired by the Haldex Group.
The unique design of the Haldex LSC comprises three functional parts
- The hydraulic pump driven by
- the slip between the
- axles/wheels.
- The wet multi-plate clutch
- The controllable throttle valve
- with its electronics.
The unit can be viewed as a hydraulic pump in which the housing and an annular piston are connected to one shaft and a piston actuator is connected to the other.
The two shafts are connected via the wet multi-plate clutch pack, normally unloaded and thus transferring no torque between the shafts.
When both shafts are rotating at the same speed, there is no pumping action. When a speed difference occurs, the pumping starts immediately to generate oil flow. It is a piston pump, so there is a virtually instant reaction with no low-speed pumping loss.
The oil flows to a clutch piston, compressing the clutch pack and braking the speed difference between the axles. The oil returns to the reservoir via a controllable valve, which adjusts the oil pressure and the force on the clutch package.
In traction/high slip conditions, a high pressure is delivered: in tight curves (i.e. parking), or at high speeds - a much lower pressure is provided
The design of the Haldex LSC is based on a Swedish patent acquired by the Haldex Group.
The unique design of the Haldex LSC comprises three functional parts
- The hydraulic pump driven by
- the slip between the
- axles/wheels.
- The wet multi-plate clutch
- The controllable throttle valve
- with its electronics.
The unit can be viewed as a hydraulic pump in which the housing and an annular piston are connected to one shaft and a piston actuator is connected to the other.
The two shafts are connected via the wet multi-plate clutch pack, normally unloaded and thus transferring no torque between the shafts.
When both shafts are rotating at the same speed, there is no pumping action. When a speed difference occurs, the pumping starts immediately to generate oil flow. It is a piston pump, so there is a virtually instant reaction with no low-speed pumping loss.
The oil flows to a clutch piston, compressing the clutch pack and braking the speed difference between the axles. The oil returns to the reservoir via a controllable valve, which adjusts the oil pressure and the force on the clutch package.
In traction/high slip conditions, a high pressure is delivered: in tight curves (i.e. parking), or at high speeds - a much lower pressure is provided
Martin, I *think* that what Haldex are saying is "don't run with the fuse out with the rear wheels unable to turn, or else that torque has no-where to go and will heat up the Haldex". Be interestesting to know if the rear wheels are free to / do turn with the fuse pulled!
Clive
Clive
B7 S4 Cab
B5 RS4: MRC custom remap, Milltek 100cpi cats and rear system, RS6 8-pots, H&R PCS coilovers, H&R ARBs, AWE DTS, Tanoga Shortshift, Dynaudio / Focal / Genesis / iPod audio: SOLD, and still missed. One day....
B5 RS4: MRC custom remap, Milltek 100cpi cats and rear system, RS6 8-pots, H&R PCS coilovers, H&R ARBs, AWE DTS, Tanoga Shortshift, Dynaudio / Focal / Genesis / iPod audio: SOLD, and still missed. One day....
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