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Old 05-15-2008, 02:01 PM   #14 (permalink)
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Originally Posted by blackjackel View Post
Just came back from a quick wikipedia read of torque converters, and with my basic and limited understanding I ask: How can I tell if my torque converter has locked? How can I tell when it has unlocked? And are you saying that I should drive as slow as possible with it locked (highway)?

Also, for city, are you saying I shouldn't accelerate slow? I should give it a good push to get the torque converter to lock early? (not floor it, but yeah).
As you probably read a torque converter is basically a subsitute for a manual clutch, so it allows you to idle in gear, gives you a smooth start from a stop.
They basically work like a turbine connected to the engine throwing oil at a turbine connected to the transmission. As you can imagine their is always some difference in the speeds of the two turbines which is wasted energy. So to get good mpg they have converters that lock the turbines together and have no waste. Most cars only do this in top gear although I believe some do this in every gear (old mazda 626's).
Watch your rpms as you get up to speed on the highway, your car will shift into top gear and then shortly after the rpm's will drop a couple hundred rpm more and now the converter is locked. Now rpms move in lockstep with the speedometer. There is no slippage so your not losing hp into the converter.

Also torque converters are more efficient at higher rpms so using 30% throttle gets some revs going and less slippage therefore less waste and you get up to top gear and locked quicker.

With the automatics we can't give 60% throttle at 2000rpm in every gear like many here so we can't always run our engines in the most efficient way but we can pulse and glide just as efficiently in top gear if the converter is locked.
Once you know what to look for you will easily be able to tell when the converter is locked.
Your car might lock the converter in every gear too which is much harder to detect so an Xgauge showing this would be useful. I think you'd find that you get lock at 3000rpm for example then you know to make the engine rev more on acceleration.
Hope this helps,

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