Driving with torque converter lock up switch.

[2JZR31]

I just installed a lock up switch for my converter (I just ground the SLU solenoid on the Aristo trans with a switch tapped in at the ECU).

I have been told it will be bad for the trans if you keep it locked then let it shift at high power. That makes perfect sense as the fluid coupling would act as a shock absorber to the trans.

But does it hurt the trans to shift with a locked converter at light loads? It feels a little harder between shifts. But the 3rd to 4th shift seems OK. I reckon there would be pretty good gains in economy to be had especially with a high stall convenor. Even if you just kept it locked on the highway so it wouldn't unlock every 5 seconds with every slight pedal movement.

Some people have told me they lock it at the drags when they hit 3rd gear (I assume they aren't letting it change into 4th?) And also use it for dyno work. So I assume the lock up mech itslef is quite sturdy if it can lock up under WOT at the drags?

I was thinking of making a torque convector controller that locks up when certain conditions are met. I am thinking these conditions for gains in economy.

1: Must be in 3rd and 4th only. (as this shift is very soft and you don't really need or want it locked in 1st or second. Use trans solenoids as an input)

2: Must not lock below a certain speed (I think condition 1 will take care of this automatically)

3: Must not lock above a certain load point. (use a voltage switch set to the 0 psi voltage of the MAP sensor for a turbo car, less for a NA)

4: Must not lock above a certain throttle opening (I think condition 3 will take care of this, if not use a voltage switch on the TPS)

For gains in performance there could be a setup which allows lock up at WOT in 3rd gear, but this must be setup so it cant happen while the trans shifts.

Thoughts? With this blow anything up?

[brett_celicacoupe]

if you want to see how toyota controls the TC lockup then have a look at the MKIII TSRM.

alternatively there is a good article here

http://www.autoshop101.com/forms/h16.pdf


as for your questions, i was wondering similar things in a thread i made last week

http://toymods.net/forums/showthread.php?t=19267

im trying to figure out if downshifting and locking the TC will provide engine braking, but alas no one replyed

if you ever get the urge to put switches on your other solenoids then it would be cool if you could let me know what happens.


one thing though, im not sure if the solenoid will disengage the lockup quick enough if you use a sense from the oem ecu. this sense would be when solenoid 2 goes from ON -> OFF (3rd to 4th on a a340e). electronically it would happen instantaneously but it would take a fraction of a section for the pressure to drop. there would be no way to anticipate when the ECU decides to change gear

[2JZR31]

I get "severe engine braking" anyway when I down shift with stock operation. I get rear wheel lock up if I shift into 1st at 60.

I was going to allow a change from 3rd to 4th with the converter locked as long as the light load requirements were met. It feels fine I don't think it would hurt anything? But that's what I would like to find out for sure.

Also, "when solenoid 2 goes from ON -> OFF" for a gear change. This will also take time for pressures etc to build and the shift to occur. Going by how slow the changes are when you shift compared to how quick the converter unlocks when you flick the switch, I don't think it would be a prob anyhow? Not sure though.

[brett_celicacoupe]

I get "severe engine braking" anyway when I down shift with stock operation. I get rear wheel lock up if I shift into 1st at 60.
.

yeh thats with manually grabbing the stick and reefing it into 1st?


they say that electronically selecting 1st (stick in D mode) at top speed does nothing

apparently the car just coasts along, freewheeling if you will.

so im wondering if locking the TC while in 1st gear at 100 will do anything?

[2JZR31]

yeh thats with manually grabbing the stick and reefing it into 1st?

Yeah, just when moving the stick on mine.

they say that electronically selecting 1st (stick in D mode) at top speed does nothing

apparently the car just coasts along, freewheeling if you will.

so im wondering if locking the TC while in 1st gear at 100 will do anything?

ouch. That sounds dangerous man!

If its just coasting along, its obviously not even going into gear is it? Will it go into second?

[brett_celicacoupe]

lol

i dont think you understand. i didnt for a while but i understand what they were saying in my thread (posted above) - i think anyway

id expect it has something to do with the one-way clutch. much like a bike freewheeling in 1st gear while your travelling at 50km/h


AFAIK they say it happens in 1st or second gear. basically if you select 1st OR 2nd at a higher speed capable of that gear, then the car just glides along not under power, with the engine idleing.

this is mainly coming from what sideshow said so im yet to get my hands dirty with a A340e and see for myself

[2JZR31]

OK. So you mean the box wont go into low gears when the speed is too high, no matter what you do? So you are relying on this safeguard to still be in place if you accidentally select first with the lookup engaged?

[brett_celicacoupe]

what im saying is, the gear is selected 100%

ie where
solenoid 1 = on
solenoid 2 = off

the car may be doing 200km/hr but the gearbox doesnt create any engine braking. the motor would just idle and the car would keep travelling at 200km/hr yet 1st (or second) gear is selected.

analogy of a bike;
you are riding flat out in top gear, going 60km/hr. you then select 1st gear, the gear is selected 100% (chain moves to correct sprocket etc) but your pedals dont suddenly start spinning at a zillion RPM. you just freewheel.



so what im wondering is what will happen if the TC is locked in this scenario

using the bike analogy, it could be like changing the freewheel sprocket mechanism to a locked sprocket/hub?

[2JZR31]

I think I have understood what you are saying. However, the same effect would occur at lower speeds too then wouldn't it? I don't think it happens like that.

If I select 1st at 60, the input shaft IS moving faster than the engine but 1st still hooks up somehow. (so the bike wheel IS initially spinning faster than the pedals, but the pedals will still speed up)

Why should the effect change at higher speeds? I don't think the gear is being selected despite the solenoids being in the right position for that gear at high speeds. Well not unless the stock arrangement uses the lock up for engine braking which I doubt.

[brett_celicacoupe]

If I select 1st at 60, the input shaft IS moving faster than the engine but 1st still hooks up somehow. (so the bike wheel IS initially spinning faster than the pedals, but the pedals will still speed up)

you need to remember we are talking about full manual shift kits.

in your case you are moving the gearstick which most likely disables freewheeling.


but anyway ill need to do some experiementing before i go further.

you could try experiment also if you hook up 2 toggle switches to the other 2 solenoids.

the shift sequence is in that pdf

gear________solenoid1__________solenoid2
1 __________on________________off
2___________on________________on
3___________off________________on
4___________off________________off

toyota have sequenced it such that you only ever change one solenoid in each gear change. meaning you only need to toggle one switch. similar to the grey code concept in electronics