Monday, June 4, 2012
Star Safety System - Part One
Toyota has a group of safety features that make up the Star Safety System. They are as follows: anti-lock brakes (ABS), traction control (TRAC), vehicle stability control (VSC), brake assist (BA), electronic brake force distribution (EBD) and smart stop technology (SST). I will go through each one of them and explain what they are and how they work. The first two systems that I will cover will be ABS and traction control. If it wasn't for the first of these systems, ABS, the rest of them would not be possible.
Anti-Lock Braking System
Most people today have owned a vehicle with ABS or have at least heard about ABS. ABS is an electronic braking system that prevents the wheels from locking up and skidding thus allowing the driver to maintain steering control around an obstacle/object on the roadway. With an ABS equipped vehicle, it is not necessary to "pump" the brakes, especially in an emergency situation. The vehicle will do it for you and much faster than any person would be able to do on their own. The driver will feel a "pulsing" in the brake pedal and this is the valves in the system opening and closing. Some anti-lock braking systems can cycle as many as 16 times per second.
There are a few different types of ABS. I will cover the three most popular. The best system is what is referred to as a four-channel, four-sensor system. This system has valves and wheel speed sensors for all four wheels. It will monitor each individual wheel to make sure it has maximum braking force possible applied to it. This is the type of system that Toyota uses in its vehicles. The second type of system is referred to as a three-channel, four-sensor system. This type of system has wheel speed sensors for all four wheels but only one valve for both rear wheels so both rear wheels will have the same brake pressure applied no matter what amount of load/traction they have. The third type of system is called a three-channel, three-sensor system. This is normally found on pick up trucks, but not current Toyota's (Toyota uses 4-channel, 4-sensor). This system has two wheels speed sensors and valves for each front wheel and one sensor and a valve in the rear axle for both rear wheels. The downside to this system is that one of the rear wheels can still lock up and skid before the rear ABS kicks in and therefore increases the stopping distance. In summary, not all ABS are created equal!
Here's an example of what an ABS modulator will look like under the hood of your car. It is typically mounted near the front, left of the engine compartment. It will have a bunch of brake lines coming in and out of it.
Traction Control
Traction control is an electronic system that works with a vehicle's ABS and throttle control units. Traction control will engage when one of the drive wheels is spinning significantly faster than the other. For example, one tire is on a patch of ice and the other is on the normal road surface. Without traction control, the wheel that is on ice would just keep spinning. With traction control, the wheel that is on ice is spinning faster than the other (if the other wheel is moving at all), and the system will apply the brakes (ABS) to the spinning wheel to force power to the other wheel that is on the normal road surface. Once the power is transferred to the "wheel with grip", the vehicle will move forward . In cases of severe traction loss, the traction control system may also reduce spark and fuel to one or more cylinders, apply ABS, and/or close the throttle on electronic throttle controlled (drive-by-wire) vehicles, which most are today.
Traction control can make getting a vehicle "un-stuck" more difficult. In a front-wheel drive vehicle, if you would be stuck in snow or whatever, it's usually best to get the vehicle to rock back and forth to free it up. Traction control would make this action more difficult. Luckily, most new vehicles will have a button (see picture below) to disable the traction control system that will allow the wheels to spin freely and may make getting the vehicle out of a difficult situation a little easier. For normal driving though, leave traction control engaged because it will usually help you more than you may even know it.
Here's a picture of what a typical Toyota traction control button will look like.
Anti-Lock Braking System
Most people today have owned a vehicle with ABS or have at least heard about ABS. ABS is an electronic braking system that prevents the wheels from locking up and skidding thus allowing the driver to maintain steering control around an obstacle/object on the roadway. With an ABS equipped vehicle, it is not necessary to "pump" the brakes, especially in an emergency situation. The vehicle will do it for you and much faster than any person would be able to do on their own. The driver will feel a "pulsing" in the brake pedal and this is the valves in the system opening and closing. Some anti-lock braking systems can cycle as many as 16 times per second.
There are a few different types of ABS. I will cover the three most popular. The best system is what is referred to as a four-channel, four-sensor system. This system has valves and wheel speed sensors for all four wheels. It will monitor each individual wheel to make sure it has maximum braking force possible applied to it. This is the type of system that Toyota uses in its vehicles. The second type of system is referred to as a three-channel, four-sensor system. This type of system has wheel speed sensors for all four wheels but only one valve for both rear wheels so both rear wheels will have the same brake pressure applied no matter what amount of load/traction they have. The third type of system is called a three-channel, three-sensor system. This is normally found on pick up trucks, but not current Toyota's (Toyota uses 4-channel, 4-sensor). This system has two wheels speed sensors and valves for each front wheel and one sensor and a valve in the rear axle for both rear wheels. The downside to this system is that one of the rear wheels can still lock up and skid before the rear ABS kicks in and therefore increases the stopping distance. In summary, not all ABS are created equal!
Here's an example of what an ABS modulator will look like under the hood of your car. It is typically mounted near the front, left of the engine compartment. It will have a bunch of brake lines coming in and out of it.
Traction Control
Traction control is an electronic system that works with a vehicle's ABS and throttle control units. Traction control will engage when one of the drive wheels is spinning significantly faster than the other. For example, one tire is on a patch of ice and the other is on the normal road surface. Without traction control, the wheel that is on ice would just keep spinning. With traction control, the wheel that is on ice is spinning faster than the other (if the other wheel is moving at all), and the system will apply the brakes (ABS) to the spinning wheel to force power to the other wheel that is on the normal road surface. Once the power is transferred to the "wheel with grip", the vehicle will move forward . In cases of severe traction loss, the traction control system may also reduce spark and fuel to one or more cylinders, apply ABS, and/or close the throttle on electronic throttle controlled (drive-by-wire) vehicles, which most are today.
Traction control can make getting a vehicle "un-stuck" more difficult. In a front-wheel drive vehicle, if you would be stuck in snow or whatever, it's usually best to get the vehicle to rock back and forth to free it up. Traction control would make this action more difficult. Luckily, most new vehicles will have a button (see picture below) to disable the traction control system that will allow the wheels to spin freely and may make getting the vehicle out of a difficult situation a little easier. For normal driving though, leave traction control engaged because it will usually help you more than you may even know it.
Here's a picture of what a typical Toyota traction control button will look like.
In my next post, I will cover vehicle stability control (electronic stability control) and how it works and it's many benefits. Bookmark my site or subscribe to my blog via email or your RSS reader to get the update when I finish the next article and any future articles. You can bookmark my site by pushing CTRL+D on your keyboard.
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