VSC Sport and Trac Off don't work

[Ultramaroon]

Originally Posted by Stang70Fastback

I have found that the degree of misunderstanding over these two buttons, how they are used, what they do, etc... is far-reaching in the Twin community. I have no idea why. I may create a guide on the 86owners website I have just to try to provide a single resource for everyone.

People won't read that either. :|

I'd love to be proven wrong, though.

[Stang70Fastback]

Originally Posted by Ultramaroon

People won't read that either. :|

True, but it would be much easier to paste a link than have to type these things over and over for the zillionth time all over the internet, lol.

[bkharmony]

Originally Posted by Stang70Fastback

I have found that the degree of misunderstanding over these two buttons, how they are used, what they do, etc... is far-reaching in the Twin community. I have no idea why. I may create a guide on the 86owners website I have just to try to provide a single resource for everyone.

I understand the two buttons have different functions, but to the end user, it just seems like "drift mode" and "drift mode light". It was absolutely thick-headed for Toyota/Subaru to do it this way. Just give us a dial with 3 modes, or a single button that selects between the three.

[thomasmryan]

If you run a couple extra PSI up front and drop the rear a couple PSI, the system is less intrusive on more technical corners.

[Stang70Fastback]

Originally Posted by bkharmony

I understand the two buttons have different functions, but to the end user, it just seems like "drift mode" and "drift mode light". It was absolutely thick-headed for Toyota/Subaru to do it this way. Just give us a dial with 3 modes, or a single button that selects between the three.

I disagree with you. People just need to learn to read their Owner's Manuals and understand how their vehicles work. Those two buttons control two very different (though closely-related) systems. I would NEVER want them combined into one "dumb people" button; especially on a sports car. There are more than 3 modes when these buttons are used in combination.

Mode 1: VSC On, TC On
Mode 2: VSC On, TC Off (to 31 MPH)
Mode 3: VSC Sport, TC On
Mode 4: VSC Sport, TC Off (to 31 MPH)
Mode 5: VSC Off, TC Off (unlimited)

Stability Control, and Traction Control are two very different things, and people need to learn this.

[COBlue]

Doesn't help that the manual references "trac" and "track" buttons...

Just to clarify:
Mode 1: VSC On, TC On - normal/no buttons pushed
Mode 2: VSC On, TC Off (to 31 MPH) - Trac button pushed briefly
Mode 3: VSC Sport, TC On - "Track" button held >1 sec
Mode 4: VSC Sport, TC Off (to 31 MPH) - ?trac button briefly and "Track" button > 1 sec?
Mode 5: VSC Off, TC Off (unlimited) - Trac button held > 3 seconds

True that VSC and TC have different uses, I think part of the confusion may be that Toyota notes that VSC does use the TC functionality (braking drive wheels), but also can brake non-drive wheels as well as adjust power.

My simple brain just separates the two as: VSC for stability (aka saving my butt from over controlling), TC for preventing (on) or allowing (off) spinning the drive wheels when slippery (mud/snow).

At least that's how I understand it - Stang?

[bkharmony]

Originally Posted by COBlue

True that VSC and TC have different uses, I think part of the confusion may be that Toyota notes that VSC does use the TC functionality (braking drive wheels), but also can brake non-drive wheels as well as adjust power.

I could write a 5,000 word essay on all the problems with the UI/UX of the VSC and TRAC functions on this car, but I'll just make two quick points:

1. The display should indicate better if TRAC, TRACK, VSC, and/or squiggly line are ON or OFF. Just really basic usability stuff here.

2. The manual never explains what VSC actually does, which makes an already confusing situation worse. RE: Stang70Fastback's last comment, I'm a huge believer in RTFM. I read the entire thing front to back before I did anything more than drive the car home. The section on VSC/TC is a garbled mess. That's on Toyota.

Yes, you figure all his stuff out eventually, but it took me several articles, forum threads, YT videos and experimentation before I understood what was actually going on. That is no way to treat your customer - especially one buying a car that is often used for spirited driving.

[COBlue]

+1 on RTFM and your two points.

Also doesn’t help that the same button turns off TC and/or VSC, just depends on how long you push it...

FWIW: I just turned off both at 55mph with long press on trac (vs track) button...

[thomasmryan]

yep. traction control uses the wheel speed sensors to limit the drive wheels from spinning in tangent with the torsen differential.


the stability program uses a gyro, steering angle sensor and relative wheel speeds to keep under steering and over steering from becoming excessive.


less is more

[reeves]

So does VSC/Traction Control even monitor the front wheels?

Because I just did a 15-20 ft slide with my (almost bald) front tires while (intentionally) doing a sharp turn at 35-40 mph.
I was testing out my new MPSS tires I got for my rears.
Fronts will be replaced soon too, but I just wanted to have a little fun in the rain in the meantime.

With stickier rear tires and no one around me, I downshifted and took the turn alot sharper than I needed just to see what the nannies would do during an understeer slide.. And the nannies did NOT interfere at all. I let the car slide its front tires for a second or two until I got close to the curb before letting off the gas pedal (the fronts caught on as soon as I did).

I wasn't going that fast so the rears stuck like glue. And I didn't touch any of the VSC/traction buttons.
So no slipping in the rear = no nannies?

[Stang70Fastback]

Originally Posted by reeves

So does VSC/Traction Control even monitor the front wheels?

Because I just did a 15-20 ft slide with my (almost bald) front tires while (intentionally) doing a sharp turn at 35-40 mph.
I was testing out my new MPSS tires I got for my rears.
Fronts will be replaced soon too, but I just wanted to have a little fun in the rain in the meantime.

With stickier rear tires and no one around me, I downshifted and took the turn alot sharper than I needed just to see what the nannies would do during an understeer slide.. And the nannies did NOT interfere at all. I let the car slide its front tires for a second or two until I got close to the curb before letting off the gas pedal (the fronts caught on as soon as I did).

I wasn't going that fast so the rears stuck like glue. And I didn't touch any of the VSC/traction buttons.
So no slipping in the rear = no nannies?

The system monitors EVERYTHING. Throttle position, brake position, wheel speed at all four corners, steering angle, slip angle, yaw, lateral forces, etc... It absolutely pays attention to what the front wheels are doing. The system can easily identify understeer, which it knows is happening when lateral forces, and vehicle yaw don't align with the expected values based on your speed, and the steering angle. It will definitely respond to a situation where you lose traction at the front end. Typically the response is for the car to brake the inside rear wheel, which helps pull the vehicle into the correct orientation. It will also reduce throttle, which serves to both shift weight forward, and reduce excess speed. If your vehicle did absolutely nothing during a very obvious slide, then either you had the systems off, or something is wrong with the vehicle. However, keep in mind that there isn't any "true" way to fix understeer. If you're going too fast for the turn, you are going too fast, all the car can do is brake the inside wheel, and reduce engine power, and hope the front end starts turning.

Also, why do you have new MPSS tires on the rear, and almost bald tires in front? Why did you not replace all four?

[Geese1]

I'll be the first one to admit that I don't really understand the differences between the 2 systems and what they're used for. I've even read the manual in its entirety and I don't even have my car yet (downloaded the pdf and put it on my iPad).

I'd love to have a nice and clear explanation on what the 2 systems are used for, how they're used, and what the differences between the 2 are.

I'd actually like to learn so that I don't feel so ignorant when it comes to how the car works, and what turning certain features on/off will do for how the car behaves.

[Stang70Fastback]

Originally Posted by Geese1

I'll be the first one to admit that I don't really understand the differences between the 2 systems and what they're used for. I've even read the manual in its entirety and I don't even have my car yet (downloaded the pdf and put it on my iPad).

I'd love to have a nice and clear explanation on what the 2 systems are used for, how they're used, and what the differences between the 2 are.

I'd actually like to learn so that I don't feel so ignorant when it comes to how the car works, and what turning certain features on/off will do for how the car behaves.

There are really three core systems you need to understand. I'll try to make things as simple as possible, but still thorough.

ABS: This system is designed to prevent wheel lockup under hard braking, or braking on slick surfaces. The basic way it works is that each of your four wheels has a wheel speed sensor, which measures the rotation speed of the wheel. The car is always comparing the rotation speeds of all four wheels, and it uses these sensors to detect when a wheel has "locked up" (stopped spinning) due to a loss of traction; either you slammed on the brakes too hard, or one of your tires hit some snow/ice/oil/etc... When it detects this, the car can individually cycle the brakes on the wheel(s) that have lost traction. This is done VERY quickly - many times a second - and is basically the car releasing and re-applying the brakes over and over. (That's the buzzing you feel in the brake pedal when ABS is operating.) This lets the wheel keep rotating, rather than simply letting it lock up and skid, which in turn allows it to maintain some degree of grip on the road, and therefore allows you to maintain control of the car. ABS actually increases stopping distance, since you're basically cycling the brakes on and off, but in exchange, you retain the ability to steer the car, which is generally more critical in an emergency situation.

Traction Control: This system is basically the opposite of ABS. Rather than monitoring for wheels that lock up, it uses those same wheel speed sensors to detect TOO MUCH rotation, which is a result of applying too much throttle for the situation. Doing a burnout, for example, or accelerating and spinning your wheels on a wet/snowy/icy road. Traction control resolves this situation in two ways. First, it cuts engine power. You can have the throttle pedal completely buried to the firewall, but the car will basically step in and say, "You're being an idiot. You're just spinning the rear wheels. Let ME manage this," and it will reduce engine throttle until the rear wheels stop slipping. Remember modern cars are drive by wire, so there is no mechanical connection between the gas pedal and your throttle body. So even if you have the throttle pedal fully depressed, traction control allows the car to override that command and say, "He wants 100% throttle, but he is on ice, and we are only going to allow 7% throttle, because any more than that just spins the rear wheels." In addition, Traction Control can also leverage the car's ABS system, to individually brake either one of the rear wheels if they are spinning too quickly.

So far, we have two systems that work in tandem, doing their best to basically ensure your wheels are always spinning at the same speed that your car is moving.

Stability Control is the most advanced system. Its job is to keep the entire CAR pointed in the direction that the driver intended at all times. At its most basic level, it is designed to monitor for two things: understeer and oversteer. Understeer is when you turn the steering wheel, but the front wheels lose traction, and the car continues in a straight line, or turns maybe a little bit, but not as much as it should. For example, if you've ever driven in snow and tried to make a left turn and the car just didn't want to turn and you almost slid straight into a curb... that's understeer. Oversteer is the opposite of that. Basically the car turns TOO much, and the rear end steps out. Think drifting. Or if you've ever tried to swerve and wound up spinning the car around. Or doing donuts!

Stability control's job is to prevent either of those things from happening. It does this by monitoring a whole host of things. It knows how fast you are going (wheel speed sensors), it knows the angle of the steering wheel, throttle position, etc... Based on those things, it knows exactly how much lateral (side) force, and how much rotational (yaw) force it should be experiencing. The car has accelerometers on board that allow it to detect all of these forces. If you turn the steering wheel, and the front wheels lose grip, that will be immediately identified by the car, as it won't "feel" the car turning as hard/quick as it should be. Basically the car says, "We are going 30 MPH, and he just turned the wheel XXX degrees. My math tells me that should result in YYY G's of lateral force, and we should be turning at ZZZ degrees per second. But my sensors are reading much lower numbers, so clearly the front tires aren't turning us as much as they should be." So it responds by doing a whole host of things. It can cut throttle, which helps shift more weight back to the sliding front tires. It can also brake your inside rear wheel, which helps to "drag" the car around the turn, to help it turn better. It continues to do this until everything checks out, and the car is pointing where the driver wanted it to point.

If it detects oversteer (the rear end coming out too far and starting to slide) it will also cut throttle, and it can brake various wheels to help control that slide and bring the rear end back under control.

In normal mode, these systems are SO sensitive, that they generally step in almost before anything even happens. You won't get a massive burnout going before the car steps in and stop it. Instead, you simply won't get more than maybe a slight chirp from the rear wheels. Even if you rev the engine all the way up and dump the clutch, as SOON as the rear wheels start to slip, the car will cut all engine power, and brake the rear wheels. Same goes for stability control. In normal mode, it will detect the rear sliding even really before the rear tires fully lose grip. They are VERY good systems for someone who doesn't know what they are doing, though more skilled drivers often find them too overbearing. However, between those three systems, it's VERY difficult to completely lose control of the car unless you do something monumentally stupid. Generally speaking, there is no solution for too much speed. If you plow into a corner going faster than your tires have grip for, even the most advanced driver aids can't do anything to help you. These systems help you regain traction, but they don't magically give your tires MORE traction. If you are stopped on ice, and you floor the car and swerve violently, the car will manage all that stuff and keep the car under control. If you are stopped at an intersection, on a snowy road, and you want to make a right turn, and you just bury the throttle and turn the wheel, the car will cut power, and manage your wheelsping, and you will make the turn as fast as the car will allow you to. However, if you plow around that turn at 60 MPH, the aids will do their best to help you complete that turn without losing control, but your tires won't have enough grip to do so. So the result will be a nice, controlled, accident where the car just doesn't turn enough and you slam straight into the curb on the far side of the road.

Hopefully that makes some sense...?

[reeves]

Originally Posted by Stang70Fastback

If your vehicle did absolutely nothing during a very obvious slide, then either you had the systems off, or something is wrong with the vehicle. However, keep in mind that there isn't any "true" way to fix understeer. If you're going too fast for the turn, you are going too fast, all the car can do is brake the inside wheel, and reduce engine power, and hope the front end starts turning.

Well I was only sliding for like a second (maybe two at the longest). Maybe traction control is more aggressive towards the rear wheels?

Originally Posted by Stang70Fastback

Also, why do you have new MPSS tires on the rear, and almost bald tires in front? Why did you not replace all four?

I love to try new things & play around with my car, especially when it's wet outside! (When no other cars are in sight of course)
I've put bald tires on the rears before with new tires in the front just to see how much the rear end will easily slide out too.

New tires are coming for the fronts, but I wasn't going to pass up an opportunity to play with my car in the rain.
It never gets old, even after 5+ years!