What is the role of

[odd boy]

Hi,

Any one knows what is the importance of TCC?

What shall I do if I installed a new converter?

Is it okay if I make it get applied after the fourth gear only?

[joecar]

TC = Torque Converter

The TC is a fluid coupling between engine and trans with the ability to multiply engine torque into the trans. The amount of torque multiplication is somewhat proportional to the amount of slip; at cruising speed (above the TC's stall speed), the TC is slipping very little so the multiplication is almost 1.0; at launch the TC is slipping a great deal, so torque multiplication can be as high as 2.5... (400 ftlb going into TC, 1000 ftlb coming out)...

Power = Speed x Torque + Heat

Some power is lost as heat (the TC and ATF get very hot when the TC is slipping/multiplying)... Torque is increased, but transmitted speed is reduced.

The TC also allows engine RPM to stay up immediately after an upshift... this allows the engine to still be in its torque band (i.e. prevents low torque bogging down after an upshift)... some people call this "shift extension".

The stall speed of the TC is the speed at which it starts to couple rather than slipping...
the stall speed is influenced by the amount of engine torque applied.

The TC's ability to slip/multiply allows for hard launches when the TC's stall speed RPM is matched up with the engines peak torque RPM... on launch, a properly matched TC allows the engine to rev into the start of the engine's torque band... this improves vehicle acceleration.

When installing a cam, typically the peak torque RPM is raised, and you want to install a "stall" converter to match your cam... can you see why...


TCC = Torque Converter Clutch

This is a clutch device inside the TC that when applied prevents the TC from slipping/multiplying... same concept as the clutch in front of a manual trans...

When the TCC is applied, the TC does not slip and so does not multiply torque... the importance of this is that the ATF is not being heated while the TCC is locked, fuel economy improves, and the car drives like a manual trans car.

A motor with sufficient torque is able to overpower the TCC and cause the friction plate to slip instead of holding... this is different than TC slip/multiply, and TCC slip is bad because it burns/glazes/damages the TCC's friction/plate faces, and damages the ATF... this is why the PCM releases the TCC at WOT.

When shopping for a stall converter, get one where the builder has increased the surface area of the TCC.

It's ok to apply the TCC in 3rd and 4th gears... the PCM releases the TCC at WOT.

[joecar]

When you install a stall converter, the engine may hit the rev limiters instead of shifting (not sure exactly why)...

you then edit down the WOT RPM and WOT MPH parameters until you get shifting at your desired actual MPH or RPM.

[odd boy]

thanks a lot, that's a fabulous explanation.


What do u mean by "TC's stall speed"?

When shall I allow the TCC to lock during upshifts?

[FeetDry]

The stall speed of the TC is the speed at which it starts to couple rather than slipping....

...

[joecar]

It's ok to allow the TC to lock during PT upshifts... most calibrations unlock it during PT upshift to get the "smooth" feel.

The stock TCC part throttle apply/release curves should be good...
the apply curve should be at least 5 MPH higher than the release curve...
usually the release curve can be quite low for a car (Camaro/Firerbird/Corvette/GTO) since the LS1/2 has lots of torque down low to be able to pull along at low RPM's).

[odd boy]

thanks boss

[joecar]

No worries chief...

[charcold-bowtie]

higher stalled converter can really wake a vehicle up IMO. I think the stock stall is aroun 1600, mine is a bit smaller than I wanted at around 2600 rpm.