Larry Cable

Also I dont think that the TC light is lit when either ABD or EDC are activated...

C.J. Ichiban

correct me if I am wrong but ABD uses the brakes and TC uses ignition and fueling timing to achieve their purposes.


therefore- your brakes get worn out when you destabilize the rear during braking, not accelerating, at least not accelerating at high speeds.

Larry Cable

ABD (Active Brake Diffirential) certainly does use the brakes! I believe that it applies the brake to one or other of the rear wheels to restore traction to the wheel that is spinning faster (skidding/slipping) than the other...

EDC (Engine Drag Control) uses the throttle control to avoid loss of traction under 'throttle-closed'/deceleration situations... over-simplified it applies more throttle to keep both wheels turning
rather than slipping while slowing down due to the drag of the engine overcoming tire to road surface traction/friction causing the wheels to effectively 'skid' ...

ASR (Acceleration-Slip-Regulation) similarly uses throttle control under 'throttle-open'/acceleration circumstances to avoid loss of traction ... over-simplified it applies less throttle to increase traction
reducing wheelspin caused by the torque of the engine overcoming the tyre road surface traction/friction and causing the wheel to spin as a result

What I dont know is how, or if, ABD combines with either EDC or ASR ...

Larry Cable

Obviously ABD will punish the rear brake pads ... which is why I drive dry tracks with TC off to avoid this

Larry Cable

Apparently ABD detects the "spinning" wheel (via ABS sensor) and applies the brake to that wheel, causing it to lockup, under this situation apparently the mechanical LSD will transfer the power the the other wheel ... I could imagine that with ABD kicking in a lot your rear pads would suffer, but as I recall ABD only functions below a certain road speed which was pretty low ...

I could be wrong!

Also I think that the TC light only comes on when either ASR or EDC is functioning not when ABD is ... you might feel ABS fire when ABD does not sure ....

fun huh?

C.J. Ichiban

is TC the umbrella corp of all those others or is ABD and ASR type stuff independently programmed and induced?

you are right about the definition of ABD and from my understanding of the TC system it is the ASR segment but not necessarily the EDC in your definitions

I was under the impression that TC off just turns off TC- not abd or that other stuff.

Larry Cable

I *believe* (but honestly this is just a guess) that "TC" refers to "at least" EDC & ASR, and may also apply to ABD but I am less sure about that.

So with TC off - both ASR and EDC are no longer functioning ... ABD may be

Also, after a little more googling I believe that both ASR and EDC can also in addition to throttle regulation also momentarily brake individual wheels to re-establish traction. All of these systems
are refered collectively as Porsche Stability Management or PSM (as opposed to PASM which is the
Active Suspension Management)

Further in the GT3 (unlike other PSM equiped models) when TC is off, it is OFF not in "standby for emergency" mode, so it wont rescue you in an emergency as in other PSM cars when ABS kicked
in PSM would turn back on ...

Larry Cable

but when it comes down to it; if indeed the 997 does have a more aggressive (and possibly initial) rear brake bias this is indeed probably the #1 (unavoidable) root cause of increased rear temps and pad/rotor wear ... on the upside it probably makes the car stop a lot better ...



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Larry Cable

oh and I forgot that with sport(on)+TC(on) TC thresholds increase, that is it's even less intrusive than Sport(off)=normal

mdrums

At certain turns at Sebring I can get into having the ABS come on, basically just tickling the ABS and PSM will come back on if turned off. Also it was my understanding that is PSM is off and the car get sideways it will come back on...although I personally have not tested that yet.

Larry Cable

in a regular 997 yes it will, not in a GT3, it's off until the engine is cycled or a finger presses the button on the center console

mdrums

Thanks for clearing that yp for my Lary. Although I thought only the new GT2 had the new PSM that would stay off no matter what. That is what they made it seem like in the magazine reviews and on the Porsche website.

thanks! Mike

BKSPN33

It looks like you guys have covered this topic, but I found a big difference between having the TC on and off. Use of the sport button should be different depending on your sway bar settings and what track you are at. There are certain tracks and set-ups where "normal" will be faster, although I typically have it on "sport." I used the TC for the first couple events and didn't feel it intervene hardly at all. But as I learned the car and started to drive more aggressively, I felt it come on quite a bit. I have never turned it on again and find it much better. It is a great system and most guys without a ton of experience probably wouldn't know it was helping. It certainly does limit your ability to rotate the back end when desired and mask the true movement of the car.

As noted earlier, when it is off, it is off until the car is restarted.