Traction Control System (TRAC)-How/What /When/Where ?? '07

If by TRAC you mean traction control, then you should be able to find it in you owner's manual. It's what kicks in when the car senses that one or both wheels are spinning without gripping the ground (e.g. steep dirt driveway, one wheel hitting ice or a metal place and the other on asphalt, etc.). It will stop the wheels from spinning so as to protect the motor/generators.

TRAC also stands for Toyota Rent A Car, which is how some people get to drive a Prius for a few days or a week before deciding to buy (if their dealership has one on the lot!). When the hatchback first came out, the TRAC car was usually the only one you could see because everything else got snapped up as soon as the boat docked!

 

<div class='quotetop'>QUOTE(dorf @ Jun 24 2007, 07:50 AM) [snapback]467198[/snapback]</div>

It senses wheel speed and notes that a drive wheel is turning faster than in should based on the speed of the vehicle.

Too often! :lol: The traction control on the Prius is pretty protective. The electric motor has so much low speed torque it could spin the tires off the wheels. Toyota's engineers have tried their best to keep us from breaking the car. One of the main issues is over-speeding MG1, which is the small motor-generator.

An indicator lamp lights on the dash and you feel a loss of power.

Tom

 

TRAC is short for train tracks. The TRAC system allows you ABS-modulate yourself into an intersection after crossing some train tracks while braking - while all you wanted to do was to stop at the stop light.

It's the same implementation of traction control I had on my 2004 Land Rover Discovery. It's too sensitive and potentially dangerous.

 

Seems like the traction control on the Prius is dangerous, at least in my experience. Have almost gotten hit by another car when my car suddenly stops accelerating out of a stoplight, or changing lanes on the freeway and hitting a bump. I wish there was a switch to turn it off.

 

<div class='quotetop'>QUOTE(wiiprii @ Jun 25 2007, 11:02 AM) [snapback]467598[/snapback]</div>

Many Land Rover Discovery owners will remove the ABS fuse, especially off road where you could find yourself sliding down a loose gravel hill right into a tree. The unfortunate side-effect is reduced control in other dangerous situations. If the Prius is anything like the Rover I owned, the ABS and traction control are likely too integrated to allow for a simple mod that would disable the TRAC and still leave the ABS functioning.

 

<div class='quotetop'>QUOTE(wiiprii @ Jun 25 2007, 12:02 PM) [snapback]467598[/snapback]</div>

You would still get hit when MG1 fails from over-spin and leaves you sitting in the intersection. Your only recourse is to drive the Prius within its limits.

Tom


<div class='quotetop'>QUOTE(Les Gas @ Jun 25 2007, 12:15 PM) [snapback]467611[/snapback]</div>

Traction control is not only integrated, it is implemented by the very core of the HSD. It's all firmware in the control system.

Tom

 

<div class='quotetop'>QUOTE(qbee42 @ Jun 25 2007, 01:39 PM) [snapback]467643[/snapback]</div>

I think mine kicks in when I go over speed bumps, but the car doesn't stop.

 

<div class='quotetop'>QUOTE(priusmaybe @ Jun 25 2007, 02:46 PM) [snapback]467690[/snapback]</div>

That's correct; it won't stop. If you loose traction over a speed bump, the traction control will kick in, keeping the wheels from spinning too fast. You will also get the wavy line traction control idiot light. Traction control on the newer Prius will never stop you from going, but if you do stop, it can keep you from moving again. As an example, say you are driving up a snowy hill and the driving wheels start to slip. The traction control light will flash on, and the Prius will apply power to the driving wheels in short bursts: "rumph, rumph, rumph..." With any luck, you can spin your way slowly up the hill, but if it's really slippery, you may slow to a halt. The slower you go, the less power it will apply to the driving wheels. Eventually you will just hang there on the hill with the wheels pulsing slowly to the sound of "rumph, rumph, rumph..." while not moving forward at all. The older Prius behaved in this same manner, but completely gave up when you stopped moving.

The key to Prius traction control, other than better tires, is to keep moving and apply the throttle. Previous experience with non traction control cars will cause most drivers to back off the throttle when the drive wheels start to slip. With the Prius on really slippery stuff, you need to mash the accelerator down and keep it there. That tells the drive by wire system to try a bit harder, and indeed it will. You won't spin the tires uncontrollably, the traction control prevents that, but you will spin them a bit more, and many times that is just enough to make a difference and keep moving. Try to carry some speed; if you can keep moving, traction control won't be a problem.

Tom

 

Two separate - ironic - problems with the Prius traction control.

1. It can leave you without power to accelerate.

2. It can leave you without braking power to stop at your intended point.

It's not a matter of just like-it-or-lump-it. The programming logic of how the system operates is flawed. It is possible to do what is necessary for the Prius and not end up with these side-effects. It needs improvement, and I doubt it's out of reach for Toyota's engineers.

 

<div class='quotetop'>QUOTE(dorf @ Jun 25 2007, 06:49 PM) [snapback]467857[/snapback]</div>

What you did was good, since you still had plenty of speed and power. The mash on the gas technique is for crawling up slippery hills or other tough going.

Correct. If you need more uumph, put the throttle to the floor. It still won't be a lot of uumph, but it will give you all its got.

Tom