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I have a 99 C2 Cab with Tip and Traction Control.

I wanted to see if anyone could explain how the traction control system works? I have had several instances on wet roads where the back end of the car broke free and I didn't really feel like anything "kicked in" to help correct the issue. This happened at slow speeds (like turing a corner and accelerating) and also under medium/hard acceleration at about 60mph (on a straight road that was pretty slick).

I'm just wondering what I should expect out of the system under different condition (i.e. wet roads)



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The traction control on the 99 models used the ABS system to sense slippage in the rear wheels under acceleration and then reduced ignition timing or applied the brakes to control the slip. On a wet road, it should help you get the car going in 1st gear without spinning tires and it will help you under acceleration in a corner even on a dry road. It is not PSM and therefore will not do anything to save the car if you take a corner too fast. It will only help under acceleration in a corner or on a wet surface.

If you can break the rear tires loose under acceleration in a straight line on a wet road, it doesn't sound like the TC is working. You may want to have it checked by a dealer or good independent shop.


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my traction control doesn't kick in unless there is some quasi traction situation. If feather the throttle out of somewhere for instance if you do it smoothly it won't kick in. Basically it needs to be a jarring type traction issue, i.e. not constant or absent. and BTW in the dry it is invasive and annoying if you are really getting on it.

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According to the 99 911 Carrera Owner's Manual;

Traction Control (TC)

TC prevents spinning of the driven wheels when starting and accelerating. Driving stability and traction are improved over the whole speed range.


The increased safety that is provided should not induce you to take greater risks with your safety.

Risks of accident due to inappropriate speed cannot be reduced, even by the TC.

The TC is ready for operation every time you start the engine.

The TC information light in the instrument panel is lit while the TC is performing a regulating action and warns you to adjust your drving style to road conditions.


Driving stability control:

If the TC detects an excessive difference in rpm between the front and rear wheels (spinning) the engine power is automatically reduced.

Brake regulation:

Besides reducing the engine power (driving stability control), the TC brakes the driven wheel that is spinning.

There is some further information but that is the meat.

Edited by fourtaylor
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A note about PSM may apply to Trac. Porsche's approach to these systems is not exactly the same as most other manufacturers. Porsche allows the driver more leeway, say to let the tail hang out.

Delayed activation.....

If, you almost immediately turned into the skid, as most of us likely would, then Porsche's Trac version would likely never activate.

Along this line, my 92 LS400 would apply the rear brakes and simultaneously dethrottle the engine upon detection of even minor wheelspin. The 2000 GS300 I had would immediately apply the brakes but the onset of dethrottling was delayed 1-2 seconds to give the driver time to react and lift/feather the throttle.

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