Why/when Does A Torque Converter 'lock Up'?

[Abo Bob]

Does it lock up at low speeds or higher?

What speeds/rpm does it lock up?

Why does this thing exist?

I know how a toque converter works but can't seem to find anything on this aspect of them.

Thanks.

[Bleach1]

I cant give exact specifics for the skyline but the lock up function of the torque converter is basically a fuel consumption or cruising aid. There is always a bit of drive lost through the oil in the converter during normal use but at cruising speeds the converter will lock up to give a direct drive from the engine to the transmision.

[Guilt-Toy]

The 33 auto will lockup in top gear on crooze. Normally happens over 80ks an hour which is there to help fuel economy.

When driving the car you can count the gears...

1st

2nd

3rd

overdrive

when your in overdrive and croozing you will notice the revs dropping 200rpm and the revs will feel more direct manul like. The converter locks up so that there is no slip in the engine revs which wastes fuel.

So it kinds feels like the 33auto is a 5 speed because you get 5 changes if you know what i mean.

They are a pretty good auto...

[Abo Bob]

I see. I can feel mine lock up in 3rd gear also.

I was just wondering if there was any advantage in locking it up earlier or later than usual cos I can see how to control that function?

Do you think maybe it doesn't lock up under full power?

[Guilt-Toy]

It only does it under light load for croozing as soon as you load it up it will unlock.

Maybe if you can change it i would go another 300rpm lower for better fuel economy.