Here are the conditions of my questions: '02 Coupe, 6 speed transmission, 4750 miles, 100% stock, standard suspension, traction control is on, tires are cold, Chicago location, 20 degrees above Zero outside temp, tires show 24 pounds of air pressure because they are cold, dry pavement - except for minor salt dust, I am at a stop light, it turns green, I fairly hard hit the gas - not floored by any means, the car takes off, the rear tires spin, I let off of the gas, the car comes back, I hit the gas again, and the rear end almost comes around on me until I let off on the gas and the car straightens out again.

On several occassions, whether standing still or traveling along a slower -say 30 MPH - speeds, if I hit the gas the rear tires will spin until I let off on the gas.

Am I misunderstanding the purpose of traction control or what? I thought the car always monitored the speed of all four wheels and if the rear tires are turning at a greater speed than the front tires - the computer will take control of the gas pedal and correct the condition. Someone surely must have some advice for me! :confused:

Thanks in advance for your input!

 

Next time keep your foot in it and let us know what happens. :)

vetterdstr :cheers:

 

strshp:

Sounds like you are letting off to soon -- before traction control can do it's job. I assume you have stock tires and wheel sizes?

Also, at 24 psi -- your tires are WAY underinflated. 30 psi cold. No matter how cold. This may cause traction control to react more slowly -- it's probably frozen stiff.

 

EHS - I respect your opinion. I will be out within the hour to up the air and will be ready to report back ASAP! :steering:

 

:lol: :lol: :lol:

vetterdstr :cheers:

 

My traction control usually cuts in so quick that it kills the power if one of the rear wheels goes over a bump without spinning. When I autocross and forget to turn the TC off the car will die on the line. However, there are times (like the conditions you describe) where I can get the rear tires spinning and get a little fishtailing (usually controllable) on full throttle acceleration. I can tell the TC is working since the DIC message says it is but TC is just applying the rear brakes vs killing the power. The brakes probably keep wheel spin close to optimum since the acceleration is pretty strong. If it would act like that on dry hot pavement it would be fantastic.
Bill

 

One other thing to consider --


the AH/TC program was revamped for, I believe, 2001 and again 2002, to make TC kick in more progressively than earlier years.

If you drove and earlier C5 it may have felt differently and more aggressively applied than on yours.

 

2001 coupe is acting just like yours in the cold Conn. weather. I think the combination of cold air, cold tires, cold dusty roads is making it act like it does. In summer it will go back to normal.

 

OK, so here is the scoop!

I added air to the tires and brought them all up to 31 pounds per tire. I went back and attempted the same stunts and viola . . . TC kicks in immediately. I still find it strange that the air pressure in the tires could have such an effect on the TC system. I would think that it is monitoring the wheel spin RPMs and as a result would always be comparing the difference per wheel regardless of air pressure. - ???

Thanks for the input! :cheers:

 

strshp -- glad the suggestion worked. I don't know the magic of AH/TC, but it does expect a certain number of parameters to work effectively, like tire diameters, etc.

Guess you've discovered that tire pressure can now be added to the list.

Thanks for being the test pilot.

Take care.

 

My 2002 Coupe A4 does the same thing when its cold (ie: below 50 degrees).

When it was stock, it would break loose around 5700 RPM or so in first...

When I had just a Blackwing, it would break loose around 1950 RPM or so in first and second... traction control would kick in about .5 second later..

I currently have just Corsa Pace Car Exhaust, and it breaks loose at 4000 RPM (in first & second )... then traction control goes crazy... blink blink blink on the dash... haha... it was nuts on Saturday / Sunday... It's also crazy loud over 4000 rpm. :reddevil

I'm waiting to see what happens when I put the blackwing back on, I'll probably be pounding traction control all through first when it's cold.

 

Bill, I am not completely sure on this but I don't think TC modulates the brakes at all. All it does is modulate the throttle(thru the computer and not the pedal). Active Handling does modulate brakes and not the throttle. I think this is how it works.

John

 

I believe that was one of the changes for the last few years (afer 2000). Not completely sure, though.

 

ROGER, TC is the engine only, just drove in the snow, floored it, RPMs stayed at 1500 and the car moved forward. AH is the brakes.

 

From Hib Halverson's article on the new Z06 on http://www.idavette.net:

"The final handling upgrade is a revised Active Handling system. "AH2" is a significant improvement in a system that was already good. A full discussion of it requires space we don’t have, but the key changes are: sideslip angle rate control, rear brake stability control, improved coordination with traction control and a change in the procedure to enable "competitive mode."

Sideslip angle control means AH2 can now sense if the driver is too slow to react or overreacting to vehicle dynamics during transient maneuvers that exceed the car’s limits. The revised Active Handling enables just the right amount of differential braking to assist in maintaining vehicle balance. AH2’s control over rear brake intervention is more precise during high lateral acceleration combined with light braking, such as a driver surprised by a decreasing radius turn. AH2’s response to that situation is more seamless and predictable. AH2 is better coordinated with traction control which uses either rear brake intervention and engine torque limiting to control rear wheel spin. Compared to AH1, the revised Active Handling’s use of traction control is skewed more towards rear brakes than engine controls. The result is less engine "sags" and better engine response after a traction control incident. Lastly, the Active Handling software has been changed such that "competitive mode" (Active Handling without traction control) can be enabled while the vehicle is moving. Previously, you had to come to a full stop."

That's what I meant. Hope this helps.

:smash:


[Modified by EHS, 4:27 PM 1/14/2003]

 

EHS:

Once again, (prior to this you helped greatly with a headlight decision that I needed to make), you are a wealth of information. I appreciate you answering one of my other questions that I just hadn't had a chance to get on the board.

Thanks :thumbs:

 

So, what happened when you kept you foot in it? :confused: Did TC kick in? :eek:

vetterdstr :cheers:

 

I stand corrected. The TC does use rear brakes per Mr. Halverson and confirmed by the owner's manual.

John

 

Thanks, I even have that article saved. So TC is a combo of engine and brake intervention. When I drove in the snow yesterday, got some slip, in a straight line at 20mph, the RPMs dropped very fast. I think the PCU choose the engine. If the rear brakes had come on, then the ABS would have kicked in, I was in an inch of fresh powder. So I floored it and the RPMs stayed at 1,500.

 

If the T/C cuts back on the throttle you lose control of the throttle. The situation you describe indicates the brakes were being applied. By the way the Traction Contol and ABS are in the same module called the EBTCM. In 2001 they changed the TC calibration to reduce the cut in. As I said in my previous post there are places where it will completely kill the throttle when it the wheels hit certain road conditions. Where I pull out of the plant parking lot the road is raised about 4 inches. As I turn right going over this crown at slow speed the TC will kick on once the right rear wheel is the only one not yet on the higher section. It almost stalls the car every time it happens and it takes several seconds for the throttle to come back.

If anybody is interested in mods, has the right tools and wants to experiment all of these calibrations can be changed and could make for some very interesting TC implementations like F1 uses. Imagine TC holding the wheel spin to the absolutely best amount on a specific track surface. Not too little and not too much. Just dump the clutch and go. At the next track just change the calibration.

Bill