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  #1  
Old 12-07-2004, 06:21 PM
oab_au oab_au is offline
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Torque Converter......How???????

Torque converter,,,,,HOW??????.

There are plenty of descriptions of how a torque converter works, in books and on the net.
The one on “How stuff works” is one that most people have read. It does show pics of the three components, and describes their function. If you have a good idea of its operation then you will understand the rest. If not check out their description first.

As we know the Impeller is a centrifugal oil pump, driven by the engine. It draws oil in the center and expels it out the outside edge. The oil enters the outside edge of the Turbine, that is attached to the gearbox mainshaft, driving it around, to exit out the center, into the center of the Impeller, to go around again.

They describe the Stator or Torus, between the two halves, that changes the direction of the oil, coming from the Turbine so that it does not go against the rotation of the Impeller to slow it down. The blades on the Stator change the direction of the oil flow to assist the rotation of the engine.

Well that is as far as they go. The Work Shop Manual states “ This direction is then changed by the Stator so that the oil will assist Impeller rotation. With this action the torque is multiplied” ..I don’t know about you all, but that tells me nothing about Torque multiplication. It like saying “100 ftlbs of torque go in one end, of the black box, and 190 ftlbs comes out the other end. I mean there has to be more than that. Torque is multiplied by gears in a gear box, there is nothing in the torque converter to do this, or is there?

The book states the ratio as 1:1.9, so how does it do it. The way I see it is this. with the Turbine held stationary, as when you are doing a stall test, the Impeller draws oil in the center to force it into the Turbine blades, this imparts energy to the blades, as the blades won’t move, the oil flows around out center of the Turbine, striking the Stator blades to enter the Impeller again. This means that the Impeller, that would have had to suck the oil in, now has a forced feed.

This changes the amount of force applied to the oil in the Impeller, not only does in impart centrifugal force to the oil, it now is applying centrifugal force to the resultant flow from the Turbine, so we have a higher force acting on the Turbine, which flows around to enter the Impeller at a higher force again, to be accelerated by the Impeller to increase the force acting on the Turbine. The end result is, of the 100 ftlbs that left the impeller, 90 ftlbs was returned to it, to go around again, building to 190 ftlbs acting on the Turbine as torque multiplication.

This state only exists while the Turbine is stationary, as soon as it starts to rotate, more energy is removed from the oil flow, so that the return oil has less force, to be multiplied by the Impeller, so that the torque multiplication factor is reduced, till finally the oil flow reduces to almost zero, along with the multiplication ratio.

Hopefully that explains where the torque increase comes from, but where does the HP go? At 2500 rpms when full torque conversion takes place, the engine is putting out say 90 HP, we have accounted for the torque, but the rotation of the Impeller and the stationary state of the Turbine means that the HP has disappeared? Physics tell us it can’t, it must have changed state. Well sure enough it has gone up smoke, heating the ATF. 60 K watts of heat fed into the oil while is locked up. How do you now feel about doing a ‘full stall start’ at the drags. Not a good idea ?

Harvey.
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Old 12-07-2004, 07:47 PM
lee lee is offline
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thanks Harvey, putting your words with other things I've read makes it sink in slightly deeper into my thick skull.

Your last bit of advice is a good message for those sitting at a stop light all loaded up... that's why a tranny tech won't run a stall speed test for longer than about ten seconds...
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Old 12-07-2004, 07:54 PM
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Chiketkd Chiketkd is offline
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Good info and great advice Harvey. I think you just filled in the blanks that 'How Stuff Works' left out...

I'll still do my stall speed launches at the track but I never leave it power braked for longer than 5-10 seconds. The heat built up in the trans from launching like this is why I normally wait at least 1/2 hour between my runs - if not longer...

-Chike
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Old 12-08-2004, 05:13 PM
oab_au oab_au is offline
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Quote:
Originally posted by Chiketkd
Good info and great advice Harvey. I think you just filled in the blanks that 'How Stuff Works' left out...

I'll still do my stall speed launches at the track but I never leave it power braked for longer than 5-10 seconds. The heat built up in the trans from launching like this is why I normally wait at least 1/2 hour between my runs - if not longer...

-Chike

Thanks Chike, I hate not knowing the full story.

Yes I would just be aware of whats happening, when you do start like that. I don't think you achive much by taking it that high. Sure the wheels spin, but that does not get you forward motion. As soon as the Turbine starts turning, the torque ratio reduces.

I have suggested, in the past, that the transmission is loaded up to launch. This is only to raise the line pressure and take up all the slack in the drive line, to prevent shock loading. I would just hold the brake on and raise the rpms to about 1700 rpm, then floor the throttle as the brake comes off.

Maybe it could be checked against the G-tec to see if there is a difference in times. No point in stressing the box, if it is not needed.

Harvey.
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  #5  
Old 12-08-2004, 07:39 PM
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Chiketkd Chiketkd is offline
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Harvey,

I'll be buying a new G-Tech from Svxfiles over the winter (he just bought three new ones). When I get it, I'll do some testing to see how much of an improvement in time I get from launching at stall speed vs 1700 rpms.

-Chike
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Old 12-08-2004, 07:44 PM
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I have the G-tech and I tend to do a little better(1-2 tenths at most) just mashing the gas at the line.
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