Haldex and ESP seperate.. correct?

[Rebellionelite]

Hey guys, the Haldex and ESP systems in our cars technically have nothing to do with each other from what I understand... though I could be wrong...

Basically my question is, if we shut off TC in a slippery situation (such as ice and snow), how does the Haldex system transfer power to the wheel with grip? Does it have its own brain seperate from TC? If so, how the hell would that work? How would it limit traction to the wheel thats slipping?

[_leo_]

it has a controller and theres obviouslly sensors for it how it works i cannot tell you but its different then ESP which uses your brakes so it would need an ABS sensor

[feels_road]

Both systems make use of multiple and overlapping sensor information, but obviously have completely different algorithms based on when and what they are intended to do. If you switch off TCL, then you will have more spin from left to right (and less interference from the brakes, which can bog the car down at low speed in very slippery conditions - which is the reason it is sometimes a good thing to switch TCL off). On the flip side, you may have more power sent to the back, since the front will slip more. So, I'd think the car can get more squirrelly.

[BC R]

How would it limit traction to the wheel thats slipping?

I think you are confusing Haldex with LSD. R has two open diffs- front and rear. The "limitation" works exactly the opposite of what you expect- traction on the stronger wheel is limited by the traction of the weaker wheel. This is why selective braking is supposed to help- by increasing "traction" on the slipping wheel it allows the stronger wheel to get more torque from the diff.

Regarding how Haldex transfers torque- it does it based on accelerator pedal position I believe.

[Rebellionelite]

I think you are confusing Haldex with LSD. R has two open diffs- front and rear. The "limitation" works exactly the opposite of what you expect- traction on the stronger wheel is limited by the traction of the weaker wheel. This is why selective braking is supposed to help- by increasing "traction" on the slipping wheel it allows the stronger wheel to get more torque from the diff.

Regarding how Haldex transfers torque- it does it based on accelerator pedal position I believe.

The selective braking is based on information from the ESU system? Or is the haldex relaying information to the brakes itself? This is my main confusion.

[BC R]

The selective braking is based on information from the ESU system? Or is the haldex relaying information to the brakes itself? This is my main confusion.

Haldex does not control braking. Haldex is simply a clutch that robs power from the front diff and transfers it to the rear diff. When it is open only the front diff is engaged to the transmission. When it is closed the rear diff gets almost as much torque as the front diff. Traction control and stabilization control do selective braking. I was just trying to explain why braking is used by traction control- to compensate for the open diffs at the front and rear. Stabilization control swings the car around the wheel it is braking to counteract sideways momentum that it detects.

[Rebellionelite]

So, if I turn off my TC fully (which I can, as I have a Canadian R) and sit on ice. The system won't be able to compensate for one of the wheels slipping, do to the fact that we have open diffs. Interesting.

[BC R]

So, if I turn off my TC fully (which I can, as I have a Canadian R) and sit on ice. The system won't be able to compensate for one of the wheels slipping, do to the fact that we have open diffs. Interesting.

Any R can turn off TC. It is the ESC that not every R car disable.

Any loss of traction cannot be magically "compensated" no matter what car you have- you would need something like an airboat prop for that When the slipping wheel gets selective braking applied it compensates for the open function of the diff not for the slip. For example if you had separate motors driving each of your wheels you would not need braking to improve torque distribution to any of the wheels, but your slipping wheels would still have no traction.

You can install a front limited slip differential into R. This will help by mechanically distributing torque between front wheels without having to apply braking or limiting engine power output. For example with a 2:1 LSD if your left front loses 50% of traction relative to what the right has the right front wheel will still get 100% of the available torque (assuming available torque does not exceed available traction). But if your left loses 75% of the traction then your right will be limited to 50% of the torque. If one of your wheels is freely spinning then the opposing wheel won't have any torque on it no matter whether you have an open diff or a mechanical LSD.

Notice that with LSD and properly tuned Haldex you won't need to disable TC unless you are trying to have fun on slippery surfaces with summer tires. LSD will limit the need for TC to engage. ESC is another story though- once the car goes sideways LSD might help you pull it out in the right direction but ESC will help you swing it around and keep it on course. In daily driving ESC is a really good idea both for the passengers of your car and for people around it...

[Rebellionelite]

Any R can turn off TC. It is the ESC that not every R car disable.

Any loss of traction cannot be magically "compensated" no matter what car you have- you would need something like an airboat prop for that When the slipping wheel gets selective braking applied it compensates for the open function of the diff not for the slip. For example if you had separate motors driving each of your wheels you would not need braking to improve torque distribution to any of the wheels, but your slipping wheels would still have no traction.

You can install a front limited slip differential into R. This will help by mechanically distributing torque between front wheels without having to apply braking or limiting engine power output. For example with a 2:1 LSD if your left front loses 50% of traction relative to what the right has the right front wheel will still get 100% of the available torque (assuming available torque does not exceed available traction). But if your left loses 75% of the traction then your right will be limited to 50% of the torque. If one of your wheels is freely spinning then the opposing wheel won't have any torque on it no matter whether you have an open diff or a mechanical LSD.

Notice that with LSD and properly tuned Haldex you won't need to disable TC unless you are trying to have fun on slippery surfaces with summer tires. LSD will limit the need for TC to engage. ESC is another story though- once the car goes sideways LSD might help you pull it out in the right direction but ESC will help you swing it around and keep it on course. In daily driving ESC is a really good idea both for the passengers of your car and for people around it...

Now that sir is a post! Very much appreciated!

[feels_road]

So, if I turn off my TC fully (which I can, as I have a Canadian R) and sit on ice. The system won't be able to compensate for one of the wheels slipping, do to the fact that we have open diffs. Interesting.

Well, if it is a back wheel that is slipping, it won't matter much, and if it is a front wheel, Haldex will fully lock up and all of your power will be available at the back (until that slips ).

You can install a front limited slip differential into R. This will help by mechanically distributing torque between front wheels without having to apply braking or limiting engine power output.

Actually, I think for Haldex a back LSD is a better idea. In that case, you improve your traction in the rear when the front has problems and Haldex sends power to the back, and at the same time you will gain traction for steering forces available in the front. Conversely, a front LSD reduces steering forces available.

Unfortunately, last time I looked, no back LSD was available yet for the R (this might have changed).

[Rebellionelite]

Unfortunately, last time I looked, no back LSD was available yet for the R (this might have changed).

Hopefully that will soon change

[BC R]

Porsche makes it sound cool

"Porsche Torque Vectoring (PTV) in conjunction with the manual gearbox, or and Porsche Torque Vectoring Plus (PTV Plus) with Porsche Doppelkupplung (PDK), is available as an option for the 911 Carrera 4 and fitted as standard in the 911 Carrera 4S. Both systems actively enhance vehicle dynamics and stability. Operating in conjunction with a mechanical (PTV) or electronic (PTV Plus) rear differential lock, they work by applying brake pressure to the rear wheels as required.

Specifically, this means that when entering a corner at high speed, moderate brake pressure is applied to the inside rear wheel. Consequently, a greater amount of drive torque is transferred to the outside rear wheel which supports the steering motion of the car, thereby improving its cornering dynamics. This ensures remarkable lateral stability and outstanding traction."