What exactly does the torque converter do to the car? Is that thing related to final drive gear ratio?

Also, for cars with electronic traction control (e.g. VSA), limited slip differential does not help?

Just want to get to know my TL better. Thanks.

 

A torque converter in an automatic transmissioned car takes the place of a clutch in a manual transmissioned car. The torque converter these days is actually a misnomer carried over from the traditional automatic transmission from ages ago. Way back when, automatic transmissions shifted mechanically based on the torque differential between the driveshaft of the engine and the driven wheels. These days, automatic transmissions are controlled electronically based on input such as vehicle speed, engine load, pitch of the car (slope) etc. In any case, think of a torque converter as a perpetually slipping clutch. A lockup torque converter has the ability to lock the "clutch" so that there is no slippage unless it meets certain parameters such as initial throttle application beyond a threshold.

A limited slip differential prevents one drive wheel from spinning freely if has less traction than the other wheel - hence the name limited slip. With Honda's VSA and the newer TCS systems, individual brakes are applied to reduce or eliminate the slip in the wheel with less traction. So, in essence, it replaces the LSD. However, the difference is that with high performance driving, the LSD are predictable - they always behave the same way. VSA and other such systems take many parameters into account and make it harder for the driver to predict what it is going to do.

Under most track conditions, a skilled driver can hustle a car around a track or autocross course faster with VSA turned off.

 

Imagine a plate with a bunch of fins on it attached to a tube . Imagine dipping the plate in a tub of Mazola. Try spinning the tube slowly - you will find that it moves freely in the oil. Now try spinning it faster - it gets harder - at some point you will rwch a point where considerable force is needed. If that vat were itself another plate attached to a tube, it would tend to begin to spin.

That is how a torque converter works - it is based on the principles of fluid dynamics, and at some point the torque converter causes a flywheel to spin, driving an axle and moving your vehicle.