question about traction/stability control

[Norm Peterson]

A few things,

If your goal is to progress as a driver and find the limits of the vehicle you can approach that in a few ways. Many drivers who don't track their cars regularly simply don't push the cars hard enough all the way around in order to approach the limit.

Cars (and tires) are so good any more that it's hard to get anywhere near their limits without entailing considerably greater risk than it took, say, 40 years ago to approach the limits of most cars then (911 Porsches and swing-axle cars being intentionally excepted here).

Stockish Corvettes of the late 1960's could only dream of having the performance metrics of an S550.


Norm

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[GTP]

A few things,

If your goal is to progress as a driver and find the limits of the vehicle you can approach that in a few ways. Many drivers who don't track their cars regularly simply don't push the cars hard enough all the way around in order to approach the limit.

Traction control and stability control absolutely changes the "balance" of the car in a few phases of cornering and also changes where the limit occurs. If you can't feel the difference than that's probably due to the way your driving, which isn't necessarily a bad thing.

If your slowly building up your confidence in the car feeling for the limit it ( and I cant believe I'm saying this) could be beneficial for you to keep traction control on during HPDE events. Reason being is that the mustang understeers pretty heftily from the factory, and until you throw some big sway bars and a lot of front camber at the car it will continue to understeer. Traction control and stability control help "de-yaw" the car and promote stability. What I mean by that is that these programs essentially keep the car understeering longer and make it harder for you to lose it on corner exit.

So point being keep driving the car harder until you feel that understeer in full affect, that should indicate your close to the limit (maybe under, maybe over). This should occur in corner entry, then play with your steering angles, steering rates, braking rolloff rates etc to try and get the balance sorted out a bit better for corner entry and rolling into the mid corner phase. Once you can get the weight to settle onto both the front and rear tires and maintain that limit balance through the first three phases (corner entry, turn in and mid corner) then you have a pretty good idea of where the limit is and should turn off all the nannies.

Advance track and the like are really intrusive at times and cause you to have really exaggerated throttle inputs to get what you want out of the car, they form bad habits for the driver and most of all they dont let the car smoothly rotate the way you would like.

Once you do turn these programs off though be very careful with your throttle application for phases 3,4,5 of the corner (mid corner, turn out, corner exit), as it is very likely that the same throttle input will send you for a spin, or instead more understeer if the car isnt balanced properly. Remember these cars are heavy and so once you make a mistake it takes a lot more distance on the track to correct that mistake. But then its just practicing what you just mastered on phases 1-3 while now slowly adding more and more throttle through phases 3-5 until youve got your balance down perfectly.


Theres more than one way to skin a cat but this is just one idea of a beginner technique to find the limit of the vehicle while staying safe and keeping the traction control on until you can really feel the difference and/or are ready to utilize the abilities of the car with the traction control off.

Have fun at the track!

Such a great post, [MENTION=19010]EcoBlue68[/MENTION]. I'm glad search found this thread for me, as my question was "Does Sport Mode cause a bit of understeer?"

I wish I had switched to Track Mode earlier in the day for my last track day. I had changed over to a full GT350 suspension, better alignment settings, etc., and yet the car seemed to understeer more than the previous time at that track.

The car was not nearly as much fun, because I could not steer with the throttle as much as last time, due to too much push during stages 4-5 of corner exit.

The irony is, I had pad fade at the end of the straight with just a couple laps left on the day, and of course, that was the session with TC off. What a hairy scary time getting the car to make it through turn 1, avoid the sand trap, keep two wheels on the short chute, and then claw back on before turn 2.

In short, I was being less aggressive than last year, so I used Sport Mode perhaps longer than I needed. But then, I also forgot to turn off my AC for most of the day! :lol:

 

[F0J]

I would recommend you read up on how those systems modulate your inputs but I think the best advice is to find some slippery area (e.g. snow) to get a "feel" for what they do. It took me one winter season to appreciate how much I hated those systems. They don't always behave in expected ways and the fact that they might put extra stress on your diff/tires/brakes is a big negative. If you turn them off on the track, it does mean you have to be a little more careful when you throttle up (turn exit, blips, shifts) but those are things you should practice anyways.

 

[GTP]

I'm actually pretty good at it. I'm kicking myself for not using track mode earlier bc it is a lot more fun to feel the slip angle of all four wheels instead of just the fronts.

Plus this track had generous runoff at 8 of its 10 turns.

 

[Norm Peterson]

If you turn them off on the track, it does mean you have to be a little more careful when you throttle up (turn exit, blips, shifts)

This ↑↑↑ . . .

but especially this ↓↓↓

when you throttle up (turn exit, blips, shifts) . . . those are things you should practice anyways.

because things can happen unexpectedly that take any or all of those systems out of operation especially on the track. But do go easy when you're first experimenting with turning any of them off.

I'm not kidding, and this isn't from my more usual position of not wanting to be dealing with any potentially intrusive electronic co-pilot either. I'm going to add braking and ABS - or the lack of it - to the above lists.

This past Tuesday at a TNiA event I found myself lined up in grid for session #3 with the TC and ABS lights both showing solid (not flashing, error of some sort, =inop). Running a shutdown/restart cycle didn't clear the problem either and the line started to move onto pit lane. So I went out anyway (advanced run group).

Yes, you have to be aware that the car will behave a bit differently and ready to act accordingly. I did manage to briefly lock up a tire under hard braking a couple of times . . . but the datalogs show that the mean lap time for session #3 was about the same as for session #2, just with more scatter in the individual times than when the ABS was working properly. On the other hand three of my four fastest laps came during session #3.


FWIW, the situation seemed to fix itself after three or four re-starts on the way back to the hotel. Well, at least the lights went out and haven't come back on since (except for when I do my usual 'turn the TC off').


Norm

 

[Norm Peterson]

Electronic Braking, Traction, and Stability Controls, Volume 2

Available through the SAE bookstore for $20. I don't know how long either the price or the supply will last. My copy has been shipped.


Norm

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