I'm "learning" more about oversteer on my 2010 GT. What I cannot find is which rear wheel is the primary and which receive more power as slip occurs.

Anyone know this answer and have a current link (older links on the site are 401) to the current Tochigi LSD information that the RX8 uses?

 

Google is your friend.

 

Except the video you posted shows how a Type I Torsen works. The LSD in the RX8 is a Tochigi Fuji, and the only thing it has in common with a Torsen is the name people sometime call it.

A TF LSD works by using the spreading force of the spider gears to engage a cone clutch which limits the speed differential between the axles. It's a step above an open diff, and nowhere near as effective as a Type I, II or IIR Torsen.

In operation it acts more like a clutch LSD with a small torque bias ratio to the wheel with more traction.

See the attachement for the description of operation from the FSM.

 

So, three questions:

1. What are the wear implications? Will this type last like a legit Torsen diff, or will it be more like a plain-Jane clutch-type LSD?

2. How is this "nowhere near as effective as" the other diff types? Is it just that it has a low-ish TBR?

3. What are the advantages of this type? Surely no one's proposing that it has zero redeeming qualities.

 

1: A TF LSD will wear out since it relies on a friction plate to work. A true torsen will not wear out in this manner since it relies on gears to work.

2: A TF isn't necessarily a bad diff, and for a street car it's perfectly fine. It does have some drawbacks for a track car. Since it has a relatively small clutch area it will tend to overheat and lose its ability to limit slip when pushed hard on a race track. I've also seen several instances on RX8s and Miatas with TF LSDs of the tabs on the friction cone breaking off which at best would turn the diff into an open diff and at worst destroy the diff and ring and pinion.

3: The advantage is it was cheaper for Mazda than a Torsen, and for 95% of consumers the TF is good enough. It's quiet, and barely noticeable when it's working. It doesn't require special friction modifiers to be added to the gear oil like a clutch pack diff to prevent chattering.

 

Torsen diffs rely on friction too, though. Are you saying there's more friction in a TF diff, or that it's concentrated in a smaller area or something?

On the rest, thanks for the explanation. Makes sense to me.