How Does a Torque Converter Work?

torque converters what they do and how they work today on eric the car guy here we have a torque converter a torque converter it's only found on an automatic transmission manual transmissions do not use torque converters and a torque converter performs three main functions function number one is it transfers power from the engine to the transmission function number two is it drives the front pump of the transmission in for those of you that saw the transmit the automatic transmission dissection video you know that the the pump of the transmission sends fluid flow throughout the transmission it is basically the heart of the transmission so it's a pretty important function and the last thing that a torque converter does is it doubles the torque output of the engine and we'll get to how it does that in a moment but why don't we start with the anatomy of the torque converter itself this is where the torque converter is bolted to the flexplate of the engine so what that means is when you start the engine up the torque converter is spinning with the engine so as the engine spins this is bolted directly to the flex plate which is to builted to the crankshaft of the engine and it rotates at the same time the engine rotates I have here the front part of the transmission this is the bellhousing in which the torque converter lives so if you were looking at how this is mounted in here the torque converter is in this area in the front of the transmission so if we take this and flip it around we can see a couple of those key components the first of which is going to be that input shaft of the transmission so this part is actually inserted into the torque converter there and that is what transfers power to the transmission this is our front pump assembly and this is actually splined to the stator which we'll get to in a minute but this is the front pump of the transmission and this is what's driven by the torque converter so as the Tour career spins it drives this front pump so as the engine is running the front pump of the of the transmission is running and sending fluid throughout the transmission once again that's covered more in depth in the video about the automatic transmission dissection but this will give you a better visual of how these parts interrelate to one another a torque converter has three major components or in modern torque converters we'll say four major components on the inside of it and we'll start with the the first part which is the impeller which is actually welded to the outside of the torque converter housing so the impeller spins with the engine so as the engine spins the impeller spins and some might look at this and say hey it looks just like a jet engine in a way it does and in a way it sort of works in a similar way in the way of moves fluid through these veins here on the inside so as the engine is rotating it's moving fluid through these veins and as the fluid moves through these veins it goes to a couple of different places it goes through the stator which is what this part here is and to the turbine which is what this part here is we have one more part in this converter because it is a quote unquote modern torque converter and this is the lock-up clutch assembly and this clutch assembly is attached to the the turbine or turbine this is attached to the turbine so these two pieces are sort of locked together and this area here is some friction material that under the right conditions causes that to lock up against the outside of the torque converter housing itself so as the engine is spinning everything is going to spin as one so now that we know what the parts are let's talk a bit about how those parts work okay to simplify things a little bit I've got three major components in front of me I have the impeller which is welded to the inside of the torque converter housing itself and spins with the engine and over here I have the turbine which is splined to the input shaft of the transmission so if you were to look at this this would be the the torque converter on the outside of it and this part would be inside the bell housing of the transmission as I showed you earlier the input shaft passes through the impeller and splines up to the turbine so you can see how these two things can move independently of one another and that's really important and I'm going to show you how this relationship works with this really cool practical that I have here and here is our practical so in front of us we have two just regular old fans one is plugged into the wall and has power going to it we're going to call this one our impeller and we're going to call the power going to it our engine the one on the right is going to be our turbine and this one is not plugged in so this one just does not receive power directly from the engine so when we start our engine we can see that the movement in this case of the air that goes from one fan to the other causes the opposite fandom move now you'll see that it doesn't necessarily rotate it exactly the same speed there is some power loss here but there is power that is transferred from one side to the other just like in the transmission so this this side over here would be our impeller driven by the engine and this side over here would be our turbine that drives the input shaft of the transmission so these two things work together so the fluid that passes through these veins once passed once it does that once it passes through the the impeller or the pump into the turbine it causes the turbine to move and here's the cool part about what a torque converter does like say for instance when you go to a stoplight so you're going to a stoplight and you're slowing down and you stop the vehicle so the engine can still run but it's just not turning the turbine at this point but then when you go to take off there you go it can start again now you you notice that when I when I let go of the the second fan what would be the turbine it took a little while for this to go that's because you really need like a move to overcome the static inertia of vehicle so a car when it's just sitting there has a lot of weight to it and that weight equates to what's called a static inertia so that car now that's at rest does not want to move so you got to get it moving but in order for this to work more effectively and more efficiently we use the stator okay so here we have our three major components again we have our impeller our stator and our turbine the stator is placed in between the impeller and the turbine and what happens is when you take off from a dead stop the vanes in this stator actually cause the fluid that's going from the impeller to the turbine to change direction you can see how these are are placed in one direction and then these fins are placed in the opposite direction so what what happens when that fluid changes direction is it increases its its output in fact that's what doubles the torque but it doesn't do this all the time if it this all the time I mean it would be kind of crazy but so let's talk a little bit about how to state or does that here's our front pump assembly that if you looked at it would would be coming through the bell housing and the stator your spline to it just like that and what you'll notice if you had this is it is it can rotate in one direction but not in the other direction so I can spin it in this direction just fine it will freewheel but whenever I try to turn it in the opposite direction it locks up that's because it has a one-way roller clutch or what's called a sprag clutch inside of here and it's very similar to like your ten-speed bicycle to where you can freewheel and you can just stop pedaling and then when you start to pedal it locks up and causes it to spin well the reason this locks up is because the weight of the vehicle when the impeller is trying to work against it when the impeller is trying to work against the weight of the vehicle it causes the stator to lock up and when it does lock up these fins stop in place and because of that it causes that fluid that's passing from this impeller to the turbine to change direction go like 180 degrees and when it does that it it increases the torque output of the engine so you get that extra oomph to get it off the line if you've ever had to push a car which I'm sure lots of you have you know cars are heavy so in order to come that overcome that static inertia they use the stator to do this now back in the day I know GM had a had a version of a stator that could actually change the output based on the angle of these fins so these fins could could move and it was called a switch pitch torque burger I'm sure they still have something like that today but those things really multiply to work but because this fluid changes direction it multiplies torque I hope that makes a little more clear so let's uh let's put our fans up here and I'll give you an idea okay we're back with our fans again and we have our impeller here on the left and our turbine here on the right impeller or pump and we have our I just put the input shaft into the turbine to basically show you that that's that's the power going into the transmission and here we have our stator so we have impeller here on the Left turbine here on the right and I'm going to place this in between so the engines running you go to take off from a dead stop and this stator causes that fluid to change direction thus multiplying torque but then once it starts moving the second it starts moving the stator starts spinning but then when you come to a stop and you go to take off again the stator locks up doubles torque output but as soon as you start moving the stator starts spinning again so the one way clutch only works at a dead stop so it only multiplies torque from a dead stop to get you going now let's talk a little bit about that fourth component the torque converter clutch now how does this come into play well as you can see behind me the impeller is moving the turbine but the turbine is not moving at the same speed as the impeller and this equates the power loss so you're losing power with this type of system so the way that they've dealt with this situation is they've created the torque converter clutch or lock-up clutch or TCC I've heard it called now this this is this is the the clutch assembly itself and this is the inside of the torque converter housing so what happens when you're when you're driving down the road and this the torque converter clutch is only going to be active like as you're at cruising speed it's never going to be active like if you're at a dead stop or in any of the other gears it's after the last gear has engaged so say you've got a 4-speed transmission you shift one two three four and then the lock-up torque and rode clutch will kick in so it's almost like a fifth shift you could in fact you can feel it many times well it's it's many times barely perceptible as a shift but the way this works is here we have our turbine which over here is driven and it sits inside this torque converter clutch assembly and if you're wondering what these Springs do these Springs are there for when this thing applies you don't want it to be a jarring apply you want it to be like a softer apply so those Springs there help dampen when this when this application happens but in essence what this torque converter clutch does is through fluid pressure that is sent many times through the input shaft of the transmission so there's pressure that passes through here and causes this to lock up against the outside housing of the torque converter and what that means is that instead of you having the power loss that you have back here everything turns as one unit so this way that power loss that you have here with just the fluid passing between the impeller and the turbine that power losses is negated because now the turbine is all part of the torque converter housing they all spin is one so it's locked up so the lock-up torque converter now say for instance this stays locked up and you come to a dead stop both fans stop and the engine stalls so if you have a problem with your torque converter clutch it can actually cause your engine to stall when you come to stops and that does happen sometimes so sometimes stalling at a stoplight may actually be this torque converter clutch not disengaging when I said that fluid would pass through here I believe it passes through that passage right there and goes through the shaft and into the back of the torque converter housing now it also has to release it's like I said if it does not release it can actually cause your engine to stall but that is how the torque converter clutch works and once again it it doesn't do this and any other speed other than a cruising speed so we'll lock up in any of the gears as you're shifting up through it will be after the last gear is shifted into then the torque converter clutch will engage in order to prevent the power loss that happens between the two here okay let's review we have our impeller our impeller is welded to the outside of the case of the torque converter and spins with the engine so as the engine is running the impeller is always spinning in between that we have the stator the stator has the one-way roller clutch or spray clutch on the inside of it and when taking off from a dead stop that spray clutch locks up causes the fluid to change direction and as a result multiplies the torque output in the engine the turbine is driven by the impeller and you saw that there's some power loss in between the two so to deal with that power loss we have the torque converter clutch which is in some way fastened to the turbine of the torque converter and at given conditions and given speeds the torque converter clutch will lock up and cause the turbine to spin at the same speed as the case so it will lock the turbine to the case of the torque converter and everything will spin as one and you will have lockup but those are the four major components of a modern torque converter older torque converters don't necessarily have the torque converter clutch but they do have the stator the turbine and the impeller torque converters I know some of you say that manuals for the wind you want to drive a manual transmission and you don't want to mess with the complicated horsepower robbing slush box and I get it however these things are out there and I hope this video in some small way has helped increase your understanding of how those automatic transmissions work in particular the torque converter and something occurred to me before I did the closing of this video and that is stall speed in reference to torque converters and that that may come up somewhere along the line so what is stall speed well stall speed in loose terms is when that stator locks up and causes that torque multiplication to happen between the impeller and the turbine and usually it's you know in passenger vehicles normal everyday driving vehicles it's somewhere around like the 1500 to 2500 rpm range and what that means is is that's the point like when you step on the gas where you start to move because remember that's work multiplication happens when the resistance of the weight of your vehicle works against the fluid that's passing between the impeller and the turbine and then that stator locks up torque is multiplied you get that little extra kick to get you off the line well like say for instance in performance applications you want you want to stall speed of the converter to match the maximum torque output of the engine you know like when your drag racing so that when you take off from a launch your engine is producing maximum torque so say for instance in a drag racing situation you would want your stall speed to be relatively high you would want it to match the torque output of the maximum torque output of that engine you probably find that with with the cam spec so the cams of the engine is going to tell you when maximum torque output is going to happen find out when that is and get yourself a torque converter - that has a stall speed to match that that torque output whatever RPM that may be it's if you've ever driven one of those cars with a high stall speed converter and they're much smaller the the higher the stall speed the smaller the converter gets so big converters have low stall speeds and smaller converters tend to have higher stall speeds but if you ever driven a car like that and you try to drive it normally like taking off from a dead stop you got to hit the gas and nothing's happening so you have to rev the engine up into that like 4000 rpm range or whatever for that thing to finally take off but when it does takes off like a bullet it just because that's that's the way it's designed so if your drag racing it's fun if you're trying to drive around like a normal person not so much but that's that's one of the philosophies behind it and that's how stall speed relates to torque over soap that little bit of information helps round out this video as far as the information that was in it but I hope that you know that the information found in this video and the practical of these two fans gives you some understanding of how that power is transferred from the engine to the input shaft of the transmission via the impeller and turbine inside there and also a bit about how that torque converter clutch works remember if that torque converter clutch stays stuck and then it could possibly stall your engine when you're coming to a stop or cause some kind of shudder at times there's lots of things that can cause that but a torque converter clutch is one of those things but also remember that the torque converter clutch will not be active until you've shifted through all your gears so you're in your highest gear you've got no place out nowhere else to shift then the torque converter will lock up - to minimize that that power loss that happens between the impeller and the turbine naturally as you can see because the turbine is not going to spin at the same rate as the impeller does just because of the fluid did there it has to move that fluid through there so there's no direct connection until that torque converter clutch locks those two things together but anyway I hope this information was helpful and useful to you I really really do take - so if you have questions or want to discuss this video further there will be a link in the description to a forum discussion about this video in addition you can post comments below and I will answer some of them probably not all them but mostly I'll be over at the website and speaking of the website if you have automotive questions I would ask that you head over to said website Eric Carr guide.com and type in a couple of keywords into the search function that you'll find at the top of the page and there's a very good chance an answer to your query will come up if it does not please sign up for our forum it's absolutely free all you need is an email address make sure you respond to the confirmation email and you can ask your question over its service and repair and we'd be more than happy to help you over there if you're looking to connect with me via social networking I can be found at Google Plus Facebook and Twitter and I will close with be safe have fun and of course stay dirty see you next time

Channel: EricTheCarGuy

Views: 3,188,376

Rating: 4.912919 out of 5

Keywords: torque converter, torque converter operation, how torque converters work, stator, turbine, impeller, torque converter clutch, fluid dynamics, how a TCC works, automatic transmission, automotive education, how to, auto repair, eric the car guy, ericthecarguy, etcg

Id: pTfipsejqS0

Length: 19min 58sec (1198 seconds)

Published: Mon Mar 04 2013

Reddit Comments

[u/xrudeboy420x]

u/freekmagnet you have some great posts man. Thanks for digging up all this great stuff. If you happen to come across a video about an 86 f-body heater wiring, do share ha!

It was a cold ride home tonight.

[u/pixelseverywhere]

im no expert, but at 7:23 and later, he is saying that the stator changes the direction of fluid which goes from impeller to turbine. isn't that actually the exact opposite? it changes the direction of the low energy fluid that comes from the turbines core and makes it curved. so impeller will take better (already swirled) fluid input resulting as higher pressure and greater torque to spin turbine(=transmission input)!

also i don't get how the clutch gets locked. does the transmission box pumps oil through the shaft? if that is true, does that mean transmission oil is the same oil as the oil in the converter?