Car Advice

How the electronics on the Toyota 86 and Subaru BRZ work

VSC, B-LSD, TRC, ABS and EBD – Toyota 86 and Subaru BRZ is/are constantly working hard to keep you on the road.  

TRACTION CONTROL ON OR OFF? Well, life is not that simple. What is often referred to as “traction control” is in fact several different sub-programmes that each have a specific purpose, and to get the best out of your 86/BRZ you need to understand how they work.

First, some background. As you drive, sensors gather a range of information – each wheel speed, engine output, throttle position, vehicle yaw, brake application, steering wheel angle, gear selection and more. All this data is fed back to a computer which decides whether or not the car doing what it should be, which generally means “are you about to die”.

If the computer decides things are getting out of shape then it takes action through a series of programmes. This may involve braking each wheel individually to correct the car’s course or maximise braking effectiveness, reducing the throttle or restricting it to idle, or even helping you brake. We’ll call these aids Electronic Driving Aids (EDAs), although there’s no official collective 86 term for the, although Subaru group them under the term VDC, or Vehicle Dynamics Control. 

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The EDAs are all designed to keep the car under control regardless of driver behaviour, which is what you want for road driving, which is why these aids are much lauded by safety authorities. But for performance driving some of fun comes from handling the car yourself, particularly when it’s an 86/BRZ. 

The good news is your car provides various methods of turning off the EDAs to some degree or other.  The bad news is that the Toyota explanation and interface is woefully full of unexplained and semi-accurate descriptions, which is where this post comes in. Here’s a list of the important EDAs:

EDA

Purpose

VSC (vehicle stability control, often known generically as ESC or electronic stability control)

This programme identifies understeer (running wide, needing more and more lock to turn) and oversteer (back slipping out). It then corrects the car’s course by braking individual wheels, and in extreme cases, also reducing throttle to avoid making things worse.

Subaru called VSC by the generic term of ESC.

TRC (engine traction control)

If you have both rear wheels spinning this system figures out you’re going nowhere and reduces the throttle. The 86/BRZ refers to this as TRC, or Traction Control, although it is a distinct programme from brake traction control (below). In 86-speak, TRC stands for “Traction Control System”. No, I don’t know why. Subaru call it TCS, or Traction Control System.

B-TRC (brake traction control)

Brake-LSD (name from MY17 onwards)

If one drive wheel spins up faster than the other this system detects that spin and brakes the spinning wheel which sends torque (“drive”) to the other wheel, so you can keep moving forwards. There is no official acronym for this system because it is not mentioned anywhere, but nevertheless it exists. For the purposes of this guide it’ll be known as B-TRC, because it is traction control operated via brakes as opposed to traction control by modulation of the throttle. This system is also known as an ‘LSD mode’, or limited-slip differential mode. That’s technically true but massively confusing because it’s not an LSD, it just acts a like one in some respects, and most 86/BRZs have a true, mechanical limited-slip differential in the form of a Torsen unit on the rear axle.

Subaru’s term is TCS Limited Slip Device. Except it’s not a device, it’s just software. I did mention the names were confusing.

ABS

Anti-lock brakes. Detects that a wheel is about to lock and momentarily reduces brake pressure on that wheel to prevent the wheel locking up. Both Subaru and Toyota agree on this name.

EBD & EBA

Electronic Brakeforce Distribution. Cars are naturally designed to brake the front wheels more than the rear for safety reasons. Unfortunately, this means there is unused braking capacity on the rear wheels. EBD distributes braking force between all four wheels for maximum braking efficiency. Plain ABS just stops a wheel locking. There’s also EBA, Electronic Brake Assist and this helps you apply the brakes hard in an emergency by detecting how quickly your foot moved from accelerator to brake and if you don’t push the pedal all the way to the floor, it’ll help you. Both Subaru and Toyota agree on this name.

Just to be clear, stability control is not the same as traction control, and there are two types of traction control, engine and brake. And the limited-slip Torsen differential (LSD), if fitted, is a purely mechanical device that is always in operation and cannot be turned off; it helps prevent all the power going to one wheel, for example when cornering hard, and is useful for general performance driving as well as initiating and maintaining drifts. The Torsen LSD does not apply brakes because it can’t, and it is not computer controlled.

Controls

Here are the controls for models before MY17 and the EDA operation light common to all model :

TRC Switch

VSC Switch

EDA operation light *

 trc-switch     vsc-switch  slip-indicator-light

*The official name is ‘Slip indicator dashboard light’. But because it flashes whenever an EDA is in operation, which isn’t necessarily when there is any slip, it’s been given here a more appropriate name that is more relevant to driving, as opposed to arcane vehicle dynamic theory.

The MY17 models have the same switches, but VSC Sport has been renamed Track mode. The photo below is of an automatic, so it has the Sport/Snow modes which change only the gearshift points, not the EDAs.

vsc-track-mode

The EDA operation light is the same.

The different EDA modes are…

The car can be run with quite a number of combinations of these aids. Here are the most common settings. ABS/EBD/EBA are on for all modes.  Note that you get a dash light when the system is off, not on. Most car controls are the reverse, you get a dash light when they’re on, not off. B-TRC/Brake-LSD are either on or off, but VSC and TRC have degrees of sensitivity.

Mode & dash light

Main use

How to activate

Effect on driving

VSC

TRC

B-TRC / Brake LSD

Normal

(no dash light)

Road driving, safe performance driving

This is the default mode and is activated as you switch the engine on.

Wheelspin is limited as TRC is enabled – the car will throttle back. Any under/oversteer is instantly corrected by VSC.

Fully on

Fully on

On

VSC Sport / Track Mode

img_6166-2

Track driving

Press the VSC Switch or Track Mode (MY17) switch.

Same as ‘Normal’, but permits a little extra slip before the system intervenes. It will correct before you can maintain a drift.  Correction of understeer is very similar to that of the normal mode. Wheelspin is limited.

vsc-track-mode-closeup

Reduced sensitivity

Reduced sensitivity

On

TRC Off

trc-off

Getting the car unbogged…maybe

Press the TRC Switch.

Disables TRC so you can spin the wheels, which may help in slippery situations. However, VSC is still enabled as per Normal mode. TRC is re-enabled if you exceed 57km/h, or if you drive the car such that VSC is activated, e.g. understeer or oversteer.

Fully on

Off

On

TRC Off + VSC Sport / Track Mode

img_6167-2

Getting the car unbogged

Press the TRC Switch and then the VSC Switch

Exactly the same as VSC Sport except you can spin the wheels more as TRC is totally disabled.  Note points above about automatic re-enabling of TRC. VSC Sport does not disable other than manually.

Reduced sensitivity

Off

On

VSC and TRC off

img_6168-2

Performance driving, drifting

Hold down the TRC  switch for three seconds.

VSC is totally disabled as is TRC, and neither will come back on unless you switch the engine off. You can drift as much as you like. As B-TRC is still on you may see the EDA Indicator flash.  This will not interfere with your sideways action in any way. You can still hit the armo backwards.

vsc-closeup

Fully off

Off

On unless MY17 manual which if off

Notes

  • ABS, EBA and EBD are not disabled by any of these controls.
  • There is also the ‘pedal dance’ which switches all electronic aids off entirely except ABS, explained below.
instruments-all
MY17 dash showing all-off mode. Note that there is no “track mode” icon.

How it feels and looks

Whenever any one of these aids activates the EDA Operation light will flash. There is no indication which programme has activated, just that the computers Are Doing Something. You may also feel and hear the electronics nudge the car into shape as the brakes are applied to one or more wheels, or the engine is modulated without you doing anything. This particularly applies to VSC and TRC. All this is entirely normal and just shows the system operating properly. Operation of Brake-LSD/ B-TRC is not noticeable.

The MY17 manual is different, and about that Torsen LSD.

For some reason – and we have asked Toyota – the MY17 manual disables Brake-LSD in all-off mode, and the MY17 auto doesn’t, which is the same as the previous auto and manuals.

You may think yay, electronics all off…but Brake-LSD is a good thing. All it does is stop a single driven wheel spinning madly while the other one does nothing. But, I hear you say…the car has a mechanical LSD! Problem solved! Well, not so fast. It’s a Torsen LSD, which means that it needs the tyre with less traction on the rear axle to have some traction, otherwise the Torsen diff behaves like an open diff. That is why you don’t see them used in the axles of 4X4s, only between front and rear axles (centre diffs). 4X4s often have one wheel on an axle in the air, and Torsens would be useless unless they are combined with a normal clutch LSD.

In the case of the 86 this matters. We managed to get a “one-tyre-fryer” on a wet skidpan in the manual while donuting; there was so little resistance to the inside wheel it was in effect in the air, so the outside wheel got the same amount of torque. It took a bit of experimenting, but we made it happen. Had Brake-LSD been enabled then that spinning inside wheel would have been momentarily braked and the outside wheel would have got more torque, and we’d have been donuting.

So, deleting Brake-LSD in all-off mode is, in my view, a backwards step. It never got in the way when drifiting and only ever helped. If Toyota wanted to do that they should have fitted a clutch pack to help the Torsen.

The automatic retains Brake-LSD in all modes, but it is disabled if you do the pedal dance.

Incidentally, if you want to feel how the Torsen LSD works there’s a simple way to test it.  Find a slight gradient where you have to turn on full lock ninety degree so you’re facing uphill.  From a standing start across the gradient, immediatley turn full lock and head up hill. You should feel and hear the LSD resisting the turn. Then, do exactly the same again but use momentum to make the turn; coast with clutch down in the manuals, or minimal power/in neutral with the autos. Because there’s less torque through the rear axle the LSD won’t work, and it’s an easy turn. A clutch type LSD has preload regardless of torque.

What’s the “86/BRZ pedal dance”?

It is a hidden diagnostic mode that turns EDAs off. This is how you activate it:

  • Warm the car up to normal operating temperature.
  • Pull the parkbrake 3 times, on the third pull hold the parkbrake up.
  • Push the foot brake three times, on the third press hold the brake pedal down.
  • Pull the parkbrake on another 3 times, hold on third pull.
  • Push the foot brake twice and the TC and VSC should be lit in orange on your dash.

You now cannot disable this mode unless you switch the car off. Pressing buttons has no effect.

It is not exactly clear what this mode does. It certainly leaves ABS active, and it definitely disables VSC, TRC and Brake-LSD/B-TRC. It may disable EBD.

More to the point, is it worth activating? I’d suggest not, based on my own motorsports 86 experience. I can drift perfectly well with and without it as VSC and TRC are entirely off. I want ABS on, and EBD as it helps me stop and trailbrake, and as described above Brake-LSD is beneficial given the Torsen rear LSD. Of course, we have asked Toyota but as it’s not an official feature they have no answer.

So, what to use when?

Does your head hurt after all that? Want a quick guide to the quick guide? Here it is.

  • Public roads – leave everything on. You should not be driving in a manner where the EDAs interfere.
  • Track work – you can drive with all on, VSC Sport / Track Mode, or all off. Novices are strongly advised to use all-on as most of the time the driver is the limit, not the electronics. Then, progress to VSC Sport / Track Mode. This is because to go fast you’ll need to be ever so slightly sliding the car which the the all-on mode will resist. However, be sure you’re comfortable with oversteer, understeer and general skid recovery before you take this step as the 86/BRZ can, and will bite in this mode. On faster tracks, particuarly with MY17 models, there will be little if any difference with VSC Sport on. On tighter, slower tracks there will be more of a difference as there you’d slide the car a fraction more.
  • Motorkhanas and skid pans – slow speed, first and second gear work where the only thing you’d hit is a cone. Switch it all off and have fun!

The modes that just turn TRC off (TRC Off and VSC Sport/TRC off) are of no practical use for performance driving as TRC re-enables itself at speed or after VSC intervention. 

Further reading

 


Robert Pepper

Robert Pepper

Robert Pepper is a motoring journalist, offroad driver trainer and photographer interested in anything with wings, sails or wheels. He is the author of four books on offroading, and owns a modified Ford Ranger PX which he uses for offroad touring. His other car is a Toyota 86 which exists purely to drive in circles on racetracks, and that's when he isn't racing his Nissan Pulsar. Visit his website: www.l2sfbc.com or follow him on Facebook https://www.facebook.com/RobertPepperJourno/ or buy his new ebook!