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The mkiv Supra Owners Club

Why do Supra's with no LSD fitted have traction control?


Alex_GT
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Not sure if this is a stupid question, but my understanding of an LSD is that it controls the amount of horsepower through each driven wheel so that it is impossible for one wheel to turn faster than the other thus preventing wheel spin?

 

In an open differential car, when one driven wheel loses traction it will naturally turn faster than the other driven wheel, thus making driving in low traction conditions extremely difficult. In a situation where one wheel is spinning and the other is not turning at all, how does the traction control make any difference?

 

An open differential has the already inherent mechanical problem of the wheels potentially turning at different speeds that surely cannot be overcome physically by moderating power to the wheels?

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Almost there, with an open diff 100% of the power will go to the wheel that is easiest to turn. Imagine one wheel on ice and the other on tarmac, when you apply power (assuming the ice is smooth and provides no resistance) only the wheel on the ice will turn and the car will move very little. This is why cars with open diffs will only leave 1s instead of 11s after a burnout.

 

An LSD will allow the wheels to turn at different speeds (a locking differential will tie them to the same speed) within a set tolerance; this ensures some of the power will go to the wheel with grip. An electronic diff will do the same by braking the spinning wheel to make it more difficult and thus move power to the wheel with grip.

 

I'd imagine traction control was seen as more necessary on a car that can light up one tyre with relative ease in the right circumstances......

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When an open differential car is travelling in a straight line on a flat road, is only one of the wheels being driven even then? The thing I am worried about is that if the open differential is transferring all of the power to one wheel, surely this would damage the drive shaft?

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When an open differential car is travelling in a straight line on a flat road, is only one of the wheels being driven even then? The thing I am worried about is that if the open differential is transferring all of the power to one wheel, surely this would damage the drive shaft?

 

No, both wheels are driven at the same speed.

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Almost there, with an open diff 100% of the power will go to the wheel that is easiest to turn. Imagine one wheel on ice and the other on tarmac, when you apply power (assuming the ice is smooth and provides no resistance) only the wheel on the ice will turn and the car will move very little. This is why cars with open diffs will only leave 1s instead of 11s after a burnout.

 

An LSD will allow the wheels to turn at different speeds (a locking differential will tie them to the same speed) within a set tolerance; this ensures some of the power will go to the wheel with grip. An electronic diff will do the same by braking the spinning wheel to make it more difficult and thus move power to the wheel with grip.

 

I'd imagine traction control was seen as more necessary on a car that can light up one tyre with relative ease in the right circumstances......

 

ahhhhhhhhhhhhhhhh! always wondered this! thanks craig :D

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