A torque converter has what is called a stator or reactor. Below stall the efficiency of stator to direct oil onto the pump, determines torque multiplication.

When a stator is added to a fluid coupler, it becomes a torque converter.

What you're describing is a fluid flywheel or coupler.

I think what we’re touching on is the difference between stall and flash. When Rietow says power is the only thing that affects stall he means that when you take the 2 step out, hit the trans brake and mash the gas that stall value is only dependent on engine power.

Scott’s great example and also what I talked about is the flash, which is the rpm the engine climbs to right after the trans brake is released during a run. This is obviously affected by load via weight and gear ratios as Scott pointed out.

Describe the phenomenon which takes place within a torque converter below stall to change stall, according to gear?

quote:

Originally posted by 00 DEAD ON:
In the same dragster, same tune up, same day, same everything. With only a gear change what will the stall do? More or less and why.
Let’s say with the 389’s it stalled 6100 rpm’s. What would it change if anything with the 430’s? WHY?
1. With 389 gears
2. 430 gears
Thx in advance

Brian, the first three guys answered your basic question. On ours the difference between 4.10 and 3.89 is right at 100 maybe a little more stall rpm (3.89) with a wheel speed car. Dead hooked my guess would be about the same. Yes it does take away converter efficiency at peak but it’s very minimal and no speed loss.
Hope this helps.
BP

If power is the ONLY thing that determines where a convertor will stall, I wonder why Marco always asks me silly questions about gear ratio's and weight in the beams, etc.?

Not taking anything away from the other responses either. I’m not here to stir up S h y t..

Don’t go there Moe....

quote:

Originally posted by Mitch H:
If power is the ONLY thing that determines where a convertor will stall, I wonder why Marco always asks me silly questions about gear ratio's and weight in the beams, etc.?

I think that's because Marco might know a bit more about it.....jus sayin....

Gearing effects the centrifugal force of the oil making the pump more efficient above stall,transferring energy to the turbine. This is the phenomenon above stall to get the turbine close to being 1 to 1 with the pump, relatively speaking.

Now describe the phenomenon below stall. Are ya'll claiming centrifugal force inhibits torque multiplication below stall? That's what you're claiming when you say a converter has less stall geared higher numerically.

I think i'm with Mike here. Even with the analogy of the 500 lb gocart and the 4000 lb land barge, the torque the motor makes is what acts on the torque converter. In this analogy with zero tire slippage, the net result is the go cart accelerates much faster than the land barge, but as far as the torque converter goes, it's still flashing to its stall or flash point. Flash/Stall as it relates to the converter is a function of the internals and its physical attributes (diameter, stator configuration, internal clearance, pump fin angle, etc.) vs the torque that it sees, not whats downstream of the converter. Only exception here is a true no load situation.

Changing gears to numerically higher (moving from 4.11 to 4.56) will shorten the time the converter stays on its flash RPM. IE the drive shaft speed gets closer to the 1:1 with the motor input (in the case of being in low gear its FIRST GEAR RATIO:1) and therefore less shear occurs in the converter and its able to move beyond the flash point quicker. This in turn puts less heat into the trans fluid and its able to maintain its viscosity and the torque converter couple is more efficient (lower converter flash point). The closer converters get to 1:1 the less heat is transmitted into the trans fluid.

The same phenomenon can be seen when you yank the chip out the 2 step and mash the throttle, the longer you hold the pedal on the floor the higher the rpm will drift. I've seen the creep up 1-200 RPM depending on how long i hold the motor on the floor with the transbrake engaged. This explains why you see less flash rpm when you go to numerically higher gearing.

How much rpm change will you see for a given gear change, who knows.