i know i'm making myself sound like an idiot. but i've been trying to figure out how exactly these things work and what exactly they're for. cause i see how they go hand in hand with cams for autos. but why? this is like the one thing i don't know! can someone clear this up for me? i had someone tell me what it did. but it didn't make sence.

thanks

 

anyone

 

Here it is in a nutshell. When you go from a stop light your car will move launching at any rpms whether it be 600 rpm by taking foot off the brake or full throttle. However your rpms will be low when you initially put the pedal down and climb rapidly. However no matter what the rpms your car will launch. Now what a stall does is raise your stall speed. So if you have a 3200 rpm torque convertor, when you gun it your car will launch at 3200 rpm so essentially you are launching well into your power band instead of launching and watching the rpms climb into your powerband. Thus by starting in the powerband you will gain .5 in the 1/4 mile since you no longer have to wait to pick up power while moving.

 

You ever been to the ocean? Felt the current against your legs while standing in the water?

That's how they work.

Or try this:

Take two fans, put them face to face as close as you can get them without the blades touching.

Now turn one on. Notice how the other blade spins?

That's how a torque converter works.


You have one "fan blade" attached to the motor and one fan blade attached to the transmission. (I'm oversimplifying here, but bear with me.)

The motor spins the forward fan blade. The rear fan blade spins in response. Also, instead of using air to transfer the power, we use tranny fluid.

At low speeds it doesn't transmit much power. At higher speeds the tranny fluid becomes almost solid. Well, it behaves like that anyway. Which means that the faster you spin the motor the better the tranny fluid can spin the rear fan blade.

That's about it. For the basic concept anyway.

 

thanks for the responce. and for confirming my guess. that's what i thought it was but i never was sure.

so you guys with autos.. do you just hold down the pedal before moving from a stop. or do you guys set your idle right under the stall speed. wouldn't a high stall get to be annoying on the street? lets say like a 3000 stall? cause you're not just getting the car to move gradually. you're just launching out from the stop sign at 3000 rpm!

 

well here is a link for you, it has lots of answers to your questions
http://www.carcraft.com/techarticles/80098/index.html It doesn't really touch to much on lockup vs non lockup, but in general a lockup keeps heat way down thus giving longer tranny life, it also keeps the RPMs down on the highways by about 200-300 RPM. They are bigger in diameter and much heavier. I had both types for my 700r4 which is just about the same as the trans your running and the lockup was about 20 pounds heavier. your not supposed to have your non lockup rpm below your freeway cruise rpm, as it takes away tranny life. If I were to choose one again I would stick to the non-lockup as it has better throttle response and felt quicker, although I have no time slips to validate it.

 

lol, that was funny.

so let me get this straight, torque converter's rev up your rpm's while your stopped, and it's used for a fast launch? so if you were to press the gas and brake at the same time while stopped, let the rpm's go up, and let off the brake, this is essentially the same thing?

 

anyone?

 

Start here...

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

 

jimlab's link to How Stuff Works is excellent. Understand it first.

Thoughts:

It's the stator that allows torque multiplication. Most of the other basic explanations were describing a fluid coupling, which is only a portion of what a TC is.

As for the 3000 launch, that would be at wide open throttle (WOT). Even a 3000 stall converter will allow you to move away from a stop at part throttle without engine going to 3000.

If you are currently driving an automatic, compare the tach and speedo reading as you accelerate normally in traffic. Depending on how "loose" your stock converter is, rpm might stay between 2000-3000 from a stop to 70 mph under moderate acceleration. My stock 4.3 V6 pickup (4L60Eand about a 2000+ stall) stays between 2600 and 3000 just after it gets rolling. C5 Vette has a "tighter" converter (1800 stall) so it has a 6-700 rpm working range in traffic conditions.

Inutero, you described a "brake torquing" launch. That might or might not be faster than just matting it from idle. It depends on engine, trans, weight, traction, etc. You could try either way and see what's quicker.

High stall TCs do a couple of things:

1) they allow the engine to get closer to it's maximum torque area during launch (3000 vs maybe 1800 stock), and it's torque at the wheels that accelerates.

2) the higher the speed differential between the pump (attached to the flywheel) and the turbine (attached to the transmision input shaft), the more the possible torque multiplication as long as the stator and other internal parts are correctly designed. A 3000 stall TC probably has a torque multiplication of 2.2 or 2.4 to 1 at stall when the vehicle is stationary and engine is at 3000. This drops off rapidly toward 1:1 as the vehicle accelerates, but there is still some multiplication to maybe 4500 or so on a 3000 stall.

 

thanks again.

 

so why do people say anything over a 3000 stall isn't suitable for the street? why isn't it?

 

Big stalls feel like a slipping clutch. In a laymans assesment, that's what you're doing. Where a stock TQ'verter (under normal driving conditions) is like fully engaging your clutch by about 1800-2200 RPMs, a bigger stall is essentially, slipping the clutch till near whatever its rating is (this depends on how much you've got your foot in the gas). The reason big stalls are a PITA on a street car is its kinda like driving around w/ the clutch pedal half depressed until you get up near its stall point in rpms, or the 'verter locks up. For example, my car is kind of a pain to back out of a parking spot. Try revving your motor on a manual car to about 1,000 rpms then just barely engaging the clutch but rapidly engaging it after that. That is why you hear guys w/ torque coverters "blipping" the throttle when they're backing up.
Before anyone flames, I realize that this, much like other explanations, is rather vague and layman...even not entirely proper.