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Old 01-22-2012, 05:44 AM
59,585 posts, read 61,634,879 times
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we started discussing this in another thread and were going off topic so i decided there is enough confusion about these as to start a new thread.

i dont think any other systems in a car gives us as much wonder as to what they are about and when to manually fiddle with them.

so after researching them a bit i think i finally got it straight in my head.

ESC or electronic stability control keeps your car on track while moving.

computers make sure that for any given speed the wheels never go faster then an amount that maches your speed. if your wheel or wheels do then thats a sign your path may alter very quickly from where your headed lol.....

if the wheels are going faster than they should because they are slipping then engine braking and pulsating the brake to just whatever wheel or wheels happens so it whips the car back on its intended path.

thats easy to grasp.

now the harder part to grasp.

the traction control also monitors wheel speed but with different criteria.

the traction control doesnt care about the speed matching the rpms ,it only cares if the wheel rpms on an axel are the same . traction control strives to deliver equal rpms to both wheels.

traction control looks at individual driven axles and tries to keep the wheels turning at the same speed. it does not try to limit how fast the wheels turn, just that they turn at the same speed

this comes into play not so much when your moving as it does when stuck or taking off from a stop.

picture one wheel on ice and 1 wheel on dry ground

the wheel on ice starts to spin . it takes very little torque to make that wheel spin as its almost spinning freely on its own.

the drive shaft transmitts its torque to the rear differential which splits that torque 50/50 to each wheel.

when one wheel is slipping or in the air very little torque goes to the spinning wheel and hense because its split 50/50 very little torque goes to the wheel on the ground.

if 10 ft lbs go to the spinning wheel then 10 ft lbs go to the other wheel too.

that may not be enough though to propel the vehicle though.

in comes traction control.

the traction control will apply the brake to that spinning wheel increasing torque demands . the more torque goes to the spinning wheel the more torque goes to the wheel on the ground.

if the engine can develop enough torque because dont forget you need 2x the torque to move the car through that one wheel then you typically do with both wheels on the ground then you will propel forward.

the truth is many cars have trouble developing enough torque to get to that point and so many times you remain stuck.

a 4x4 has a low range which an awd does not. that can multiply torque many times so you get far more torque going to the spinning wheel as the brake gets tighter and tighter and its easier to get more torque at the other wheel now to propel you.

Last edited by mathjak107; 01-22-2012 at 06:32 AM..
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Old 01-22-2012, 05:46 AM
59,585 posts, read 61,634,879 times
Reputation: 38871
so how do we use this stuff?

in normal conditions use your esc on . stability control is there to protect you.

if stuck you may want to turn stability control off as now you dont want engine braking cutting the torque your trying to create. cars usually have a manual button to turn it off.

you want only traction control working when stuck.

in 4 low on a 4x4 stability is usually automatically turned off keeping just traction control on.

dont confuse poor traction with an issue of lack of torque. you may be able to get full torque but if you got tires that cant grab thats another story. thats where winter tires help or all terrains help. they couple that power to the ground better under slippery conditions.

every system is different, some maufacturers have better systems than others . im very impressed with the one in my 2012 jeep sahara. i was not so impressed with the one in the nissan murano .

hope this helps you understand it better.

Last edited by mathjak107; 01-22-2012 at 06:35 AM..
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Old 01-22-2012, 11:40 AM
Location: Winter Springs, FL
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When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go. Braking is automatically applied to wheels individually, such as the outer front wheel to counter oversteer or the inner rear wheel to counter understeer. Some ESC systems also reduce engine power until control is regained. ESC does not improve a vehicle's cornering performance; instead, it helps to minimize the loss of control.
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Old 01-22-2012, 04:02 PM
59,585 posts, read 61,634,879 times
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exactley all the reasons some times you need to turn it off to get unstuck.

that engine braking can really kill your efforts to get going again as it cuts engine torque at just the wrong times .

certainly though keep it on when your not trying to get unstuck .....
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Old 02-29-2012, 10:55 PM
Location: Minneapolis
1,617 posts, read 4,374,481 times
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In a nutshell: Traction control limits engine power (and sometimes applies one brake) when it senses that one or more tires is spinning faster than the vehicle is moving. The system uses the ABS sensors to detect this condition. Without additional sensors, it can do little more.

Stability control does all of the above, and adds two more sensors: a steering angle sensor, and a yaw rate sensor (a type of gyroscope). The steering angle sensor tells the system what direction the driver intends to go, and the yaw rate sensor tells the system what direction the vehicle is actually moving. As long as the two sensors' data is in reasonable agreement, the system does nothing. If all of the sudden it detects a skid, it applies a calibrated amount of braking on only one side of the vehicle in an attempt to both slow you down, and help "steer" the vehicle back toward the driver's intended path (like sticking a canoe paddle in the water to use as a rudder, if that analogy makes sense).

Turn the traction control off if it limits engine power so much that you lose your momentum in deep snow. In deep snow, you sometimes need some momentum to make it through a tough spot, and the traction control can definitely work against you.

Stability control is probably best left active, unless you're just having some fun. It can hit the brakes unexpectedly on an experienced winter driver, when trying to keep some momentum through a corner, but in general, if it does hit the brakes, you were probably going too fast anyway.
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