i'm confused on how to even ask this question so that it makes sence!! at what kind of speed would a 2.5 str star getting pulled by let's say a 1.8str?? or would it?? i've heard that higher str hitd harder off the line but then gives up some on top end??? (yes i am a confused person!)

 

STR = Stator Torque Ratio. It is the torque multiplier at the stall speed of the converter.

Typically the higher the STR the less efficient it is up top. Why that is I do not know. Somewhere around 2.2-2.6 should be more than suficicent for a street vehicle.

Take this for instance...

If your car makes 350tq X 1.8STR = 630tq; now if you hae 350tq X 2.25STR = 787.5tq just from multiplying the input torque.

It will "hit harder" as there is more torque available but typically overwhelms street tires. Lower STR will "hit softer" and be a bit more nice to street tires are the torque is not too high to roast them.

Hope that helps!

 

FYI www.yank.cc they have an awesome FAQ section that describes how it works

Also www.howstuffworks.com has a good article about how torque converters work and goes over the STR

 

Maximum stall torque ratio occurs when the car is not moving. By that I mean the converter pump is spinning at full stall while the turbine (which is attached to the trans input shaft) is not moving. Once the turbine starts to rotate and the car starts moving forward, stall torque ratio begins to fall off quickly.

What this all means is, converters with high stall torque ratios only have an advantage when racing from a dead stop. When racing from a roll, converters with lower STRs will typically have longer torque multiplication and higher efficiencies, making them faster once they're moving. Moral to the story...don't buy a converter soley on stall toque ratios. Most converter companies don't have the resources to be able to afford testing all their converters on a transmission dyno. Because of this, most advertised STRs are wild-*** guesses. Yank gets their converters checked with GM's $1 million tranny dyno. Other companies? Who knows?

 

addy above was wrong... it's www.converter.cc