bjamick

iTrader: (31)

Ok i hear yall talking about how converters lock and are unlocked what exactly does that mean when it is unlocked and locked?? like what exactly happens at these times? i know yall are prob thinking im just stupid but i really do not know.

joecar

That's not stupid; you came here to learn.

Stupid is when a person doesn't know AND doesn't ask.

The torque converter (the TC) has a clutch in it (the TCC);
the PCM can command the TCC to apply or to release.

When the TCC is applied, the TC stops slipping (TC always slips a little otherwise).
When TCC is released, the TC slips.

When TC slips (TCC released), the TC is able to mulitply up engine torque into the trans;
this puts more torque thru trans (accelerate car quicker), and the slipping allows engine to rev a little higher into it's torque/power range (i.e. making more torque/power, accelerates car quicker);
this is important at the end of each gear shift, allows engine rpms to sit higher (not drop so low) so there's more torque available to pull the car with in the next gear.

When TC is locked (TCC applied), the TC transmits engine RPM straight into trans with no slip, so fuel mileage improves.

Cheers
Joe

bjamick

iTrader: (31)

so why do people say like when an a4 goes to a dyno they say was that with it locked or unlocked? can you keep it locked or unlocked by using a computer programmer like HPtuners or something??

RICEETER

iTrader: (49)

well, most converters can be manually locked up on the dyno

i say "most" because my 4000 wouldnt lock up (at WOT) on the dyno (i was told that it was because of my 3.23 gears). my car made 375rwhp unlocked and would've made 405-410 locked, but its still gonna run the same at the track because you dont want it to lock up at WOT anyway. basically, the only reason i can see to lock one up on the dyno is to get better #'s because the guy at Yank told me that it was good for me that it didnt lock up because its not good for the converter to get manually locked.

so, all i can get out of it is: the lock up takes place at part throttle and works kinda like a cruising gear (an overdrive if you would).

if im wrong, someone please correct me. im here to learn also

bjamick

iTrader: (31)

ok so when the TQ locks it is kinda like an overdrive gear ok it seems i have heard that somewhere else to, so are TQ unlocked until they reach their stall limit or what?

12secSS

iTrader: (30)

The TCC is applied and released at a programmed MPH in your ECM, based on how much throttle input is given (TPS%), which can be altered by tuning programs. When the TCC engages, it feels like another gear to some people ... hence they think they have an A5.

bjamick

iTrader: (31)

ok so any converter i get will be able to lock and unlock wont it? or will it?

joecar

No, not any, it has to have a clutch in it (a "locking converter").

joecar

Might feel like a gear change when it locks, but technically it's making a direct connection between engine and trans., eliminating the 500 RPM (or so) slippage.

Like 12secSS said, your PCM has MPH vs TPS tables (one for each of 2nd, 3rd, 4th gears) to lock and unlock the TCC.

Some scan tools can command the PCM to lock the TCC.

bjamick

iTrader: (31)

oh so they do this just for the fuel economy and stuff like that and if you plan on getting like 3.73 gears or maybe 4.10's it would be wise to get a locking converter i am correct aren't i?

Joel_SS

iTrader: (8)

Yes the lockup helps with gas milage and also helps cool the tranny. When it is unlocked it is generating lots of heat especially at high RPM.

This a a great read...

http://auto.howstuffworks.com/torque-converter.htm

bjamick

iTrader: (31)

that is a nice write up thanks alot guys im trying to learn in depth more about everything and ls1 tech is helping alot thanks again guys!!

RICEETER

iTrader: (49)

ditto, it has definately helped me out alot. alot of great people here

joecar

Good point, when the TCC slips (multiplying torque) it heats up the ATF.

The howstuffworks link mentions the stator riding on a one-way clutch...
please be aware that this is not the TCC lock up clutch;
the TCC lock up clutch is mentioned in the last page.