FT86 VSC and TRAC Overview

[Deslock]

From pages 213-217 of the BRZ owners manual:

Vehicle stability control (VSC):

Helps the driver to control skidding when swerving suddenly or turning on slippery road surfaces

TRAC (Traction Control):

Helps to maintain drive power and prevent the drive wheels from spinning when starting the vehicle or accelerating on slippery roads

The 6MT has six modes that I'm aware of:

1. Default: VSC and TRAC on
   
   
2. Press VSC SPORT: Allows for more slippage than normal
   
   
3. Press TRAC OFF: For getting unstuck in mud, dirt, or snow (TRAC reengages at ~31 MPH)
   
   
4. Press VSC SPORT and TRAC OFF: Both #2 and #3 above
   
   
5. Hold TRAC OFF for 3 seconds: Disables VSC and TRAC (unless really excessive/bumpy driving condition occur)
   
   
6. Pedal Dance: Completely disables VSC and TRAC. Read more here, here, and here.

Words of Caution:

1. Leaving VSC enabled (default or SPORT) on public roads is recommended. This [ame="http://youtu.be/j8qggahGNH0"]video[/ame] illustrates the effects.
   
   
2. VSC is intended to help recover when something unexpected happens. Relying on VSC to drive faster (than you could without it) when conditions are good is especially risky (since running into leaves, oil, water, ice, sand, etc could result in an even higher speed accident).
   
   
3. Consider learning a vehicle's dynamics and limits at track days, AutoX, or even sliding around in big empty parking lots (at low speed, when/where it's safe).
   
   
4. Use common sense, don't overdrive conditions/visibility, and be prepared.

[TSY]

Originally Posted by Deslock

1. Use common sense, don't overdrive conditions/visibility, and be prepared.

Good advice overall. Unfortunately, common sense may not be so common in everyone who buys these cars.

[jeebus]

I find that sport allows for a good amount of slip while having fun on twisty roads. And it brings the car back in line without feeling too intrusive or artificial. Everything on is terrible, especially with the stock tires. You can trigger the system far too easily and it can pull enough power to be dangerous when merging in traffic. I almost always have sport on, or everything off. At autoX, obviously everything is off.

[WhiteFR-S]

Great post Deslock. I've been confused on exactly what each mode does even after reading the manual numerous times.

[Deslock]

Originally Posted by WhiteFR-S

Great post Deslock. I've been confused on exactly what each mode does even after reading the manual numerous times.

Yeah, Subaru and Toyota chose puzzling combinations of buttons and indicators:

[dori.]

the only thing that makes sense is that skid and traction are different? dunno

maybe one cuts throttle (trac?) and the other uses the abs (skid?)

[gmookher]

turn off
learn to control your throttle

[grst1]

I wish they would have allowed more slip in "sport" mode at lower speeds, when you go through tight corners and then progressively reduced slip it once speed increases. Too intrusive for my taste.

[RYU]

Any difference for 6AT? My guess is no, but we do have an additional Sport button which I believe is exclusively for the shifting/throttle algorithm.

Please folks... Stop encouraging turning off VSC/TRAC. All these crashes are causing all of our insuranc rates to skyrocket.

[brewksy]

Invariably, every time anyone discusses VSC or TRAC or any of the derivatives, there's always a couple people that argue that its unsafe to have these nannies on because they were almost in an accident because it pulled the plug on some safety manoeuvre they were doing.

Let's be clear: no safety manoeuvre on normal driving on normal roads requires additional throttle. But here's the line of reasoning people use:

"I'm merging onto a highway and VSC cuts the power to my wheels, preventing me from merging safely": Why do you need more power here? So you can "drift" the car sideways into traffic? And how is that safer than merging at a slower rate with less wheelspin and more control?

"I needed to speed up to avoid an accident and VSC prevented me from doing that": In no way do you need to use speed to avoid an accident. In every safety manouevre, having traction at the wheels means you have more control and the faster you scrub your speed off (with control), the better your chances are of not injuring yourself or anyone else.

The only argument for turning these off during normal driving is that you may "feel" as though you're better than the systems themselves because you've raced professionally or semi-professionally and you know your car inside and out. I won't judge that - if you think your skills trump the nannies, then by all means turn them off. But coming onto a public forum and extolling the virtues of how unsafe these features are to other, less-experienced drivers does a disservice to everyone.

[res]

[ashtray]

Here's the thing - ever need to turn onto a busy high speed road from a complete stop - with no help from any traffic control (traffic light, etc)? There's some roads at certain hours, you'd need to wait a few hours for a "lazy" opening.

Anyways - so you're waiting for a few minutes and a slight break in traffic appears. Here's your window. You know how fast your car can accelerate, so you know you can make it. You hit the gas and... flashing yellow light on dash. You're not going nearly as fast as you need to and traffic is quickly approaching. (solutions include quickly hitting VSC button, throttle lift then back on it to fool the system that traction is regained, short shift and hope you can get full power in 2nd gear.). Hitting gas harder may have the opposite effect you want (more nanny intrusion and less power to wheels).

Remember, this car has a torsen diff. A little wheel slip is ok - inside wheel slips a bit, more power sent to outside wheel where you need it, and actually helps you accelerate quicker (than an open diff). If the car had an open diff, sure, bring on some traction control nannies - at least in the form of applying brakes to the wheel slipping, but not reducing engine output unless both tires were lit up.


As a funny side story - I had a '72 Buick GS. Was at a stop sign trying to make a right turn and was on a hill. Saw an opening in traffic, nailed the gas and the car went about 5' forward before pretty much losing all forward momentum as my rear tires were smoking away! Doh! Instinct says "you're going to get hit - floor it!" but I had to lift (a few times) before I got enough traction to get the car through the turn then could hit the gas in a straight line and take off. I really underestimated that incline.

[brewksy]

Originally Posted by ashtray

Here's the thing - ever need to turn onto a busy high speed road from a complete stop - with no help from any traffic control (traffic light, etc)? There's some roads at certain hours, you'd need to wait a few hours for a "lazy" opening.

Anyways - so you're waiting for a few minutes and a slight break in traffic appears. Here's your window. You know how fast your car can accelerate, so you know you can make it. You hit the gas and... flashing yellow light on dash. You're not going nearly as fast as you need to and traffic is quickly approaching. (solutions include quickly hitting VSC button, throttle lift then back on it to fool the system that traction is regained, short shift and hope you can get full power in 2nd gear.). Hitting gas harder may have the opposite effect you want (more nanny intrusion and less power to wheels).

Remember, this car has a torsen diff. A little wheel slip is ok - inside wheel slips a bit, more power sent to outside wheel where you need it, and actually helps you accelerate quicker (than an open diff). If the car had an open diff, sure, bring on some traction control nannies - at least in the form of applying brakes to the wheel slipping, but not reducing engine output unless both tires were lit up.


As a funny side story - I had a '72 Buick GS. Was at a stop sign trying to make a right turn and was on a hill. Saw an opening in traffic, nailed the gas and the car went about 5' forward before pretty much losing all forward momentum as my rear tires were smoking away! Doh! Instinct says "you're going to get hit - floor it!" but I had to lift (a few times) before I got enough traction to get the car through the turn then could hit the gas in a straight line and take off. I really underestimated that incline.

Great scenario, but one hitch: How do millions of cars do just that every day without disabling traction control?

[ashtray]

Originally Posted by brewksy

Great scenario, but one hitch: How do millions of cars do just that every day without disabling traction control?

Low power, heavy car, FWD.