Super newb question, torque converters

[Oceanside78]

Can someone explain them to me? What do the terms mean? Flashing, locking up, stall, I kinda understand that stuff but how and why is what kind of confuses me. When someone says, "my stall is 2500" but it "flashes" to 3500 what's that about? How can it be different? Thanks for the insight

 

[deadpres]

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[Oceanside78]

[youtube_browser]QIobzoSGhy4[/youtube_browser]

Thank you for that, it actually helped quite a bit. Can you or someone explain a TC in regards to performance?

 

[Mike L.]

Can someone explain them to me? What do the terms mean? Flashing, locking up, stall, I kinda understand that stuff but how and why is what kind of confuses me. When someone says, "my stall is 2500" but it "flashes" to 3500 what's that about? How can it be different? Thanks for the insight

Stall refers to standing still on the brakes and bringing the throttle up till it begins to push through the brakes or starts spinning the tires at standstill. At that point, watch the rpm when that happens and that is your true stall speed. All cars are different so a rated stall speed will change from car to car.
Flash is standing still without the brakes and flooring the throttle. Watching what the rpm is when the car takes off is your converter flash speed.
Flash speed will be lower than stall speed because of the load difference.

Locking up refers to the converter clutch which is electronically applied by the computer. When this occurs the converter becomes nothing more than a shaft. Nothing in the converter is spinning. Converter spins as a direct connection. hope this helps.

 

[Oceanside78]

Ok thanks. So when someone says "my converter isn't locking" does that mean their car is just free revving? Saw a thread about that after installing an aftermarket one

 

[Mike L.]

Ok thanks. So when someone says "my converter isn't locking" does that mean their car is just free revving? Saw a thread about that after installing an aftermarket one

No.
That means the converter clutch never locked and stayed in the torque multiplication mode.

 

[Oceanside78]

No.
That means the converter clutch never locked and stayed in the torque multiplication mode.

So it'll move, just with no power? How do you now what TC you want when it comes to stalls and flashing when upgrading your stock one?

 

[Mike L.]

So it'll move, just with no power? How do you now what TC you want when it comes to stalls and flashing when upgrading your stock one?

You need to talk to a high performance trans expert that is experienced with your model car. You might get a lot of great feedback and knowledge from forum members here that have been through this and possibly made mistakes and corrected them. It would save you a lot of trial and error which costs money.

 

[Oceanside78]

You need to talk to a high performance trans expert that is experienced with your model car. You might get a lot of great feedback and knowledge from forum members here that have been through this and possibly made mistakes and corrected them. It would save you a lot of trial and error which costs money.

Gotcha. I'm wanting to build a street car project with an auto soon and trying to nail down things that have always been a gray area for me. Thanks for your help though!

 

[xblitzkriegx]

Stall refers to standing still on the brakes and bringing the throttle up till it begins to push through the brakes or starts spinning the tires at standstill. At that point, watch the rpm when that happens and that is your true stall speed. All cars are different so a rated stall speed will change from car to car.
Flash is standing still without the brakes and flooring the throttle. Watching what the rpm is when the car takes off is your converter flash speed.
Flash speed will be lower than stall speed because of the load difference.

Locking up refers to the converter clutch which is electronically applied by the computer. When this occurs the converter becomes nothing more than a shaft. Nothing in the converter is spinning. Converter spins as a direct connection. hope this helps.

You have brake stall and flash stall reversed in regards to which one is higher. Look it up.

 

[Stanger00]

you have brake stall and flash stall reversed in regards to which one is higher. Look it up.

+1

 

[STAMPEDE3]

Read this,

What is Torque Converter Stall

 

[Mike L.]

You have brake stall and flash stall reversed in regards to which one is higher. Look it up.

I do this for a living. I don't need to look anything up.
Go test a car before you post.

 

[Stanger00]

I do this for a living. I don't need to look anything up.
Go test a car before you post.

Flash stall speed (RPM) will be higher then foot brake stall speed.

Trans brake will be the best indicator of stall speed.

My 3300 stall starts to over power the brakes at ~2300 with 3.73's and 26" tire.

 

[Oceanside78]

Read this,

What is Torque Converter Stall

Good read, thank you

 

[Oceanside78]

Flash stall speed (RPM) will be higher then foot brake stall speed.

Trans brake will be the best indicator of stall speed.

My 3300 stall starts to over power the brakes at ~2300 with 3.73's and 26" tire.

So "flash" is like, going down the road at X RPM and when you mash it, it "flashes" and locks up in your power band?

If your stall is 3300 why does it over power your brakes 1K rpm less? Is it broke? Not being a smart a$$ btw

 

[Katy TX5.0]

The 3rd part of a TC not mentioned is the stator. It makes the converter more efficient at lower speeds. I've been fascinated with auto transmissions ever since I went to apply for an engine building job and got hired to build Allison autos. Guess it was fate. I've always wondered if I could build performance units on the side. The ones I built were the size of small cars and cost upwards of 100k so I'm not sure how it would translate.

The way the planetary gears and valves work to run the thing is amazing to me.

 

[LS2GTO]

So "flash" is like, going down the road at X RPM and when you mash it, it "flashes" and locks up in your power band?

Yes, flash is the RPM that the engine will be taken to when getting on the gas.

Lockup is completely different. It is usually used in an OD gear to lower the RPMs while cruising, sort of like an extra gear. While locked up, the converter doesn't flash to the RPM it's setup as. It only does that when it's unlocked.

For example, my old car with a 4 speed auto would be around 2500rpm in 4th gear unlocked. At that point, if I got on it it would flash to 3800rpm. But if I locked the converter, the RPMs would drop to around 2000rpm and if I got on it at that point, it would barely go up a few hundred RPM at the most.

Big power guys with expensive triple clutch disks can lockup the converter at full throttle for less power loss through it, but most aftermarket converters do not do that due to price.

 

[Stanger00]

So "flash" is like, going down the road at X RPM and when you mash it, it "flashes" and locks up in your power band?

If your stall is 3300 why does it over power your brakes 1K rpm less? Is it broke? Not being a smart a$$ btw

According to the article posted above a converter will slip if you are in 2nd or 3rd and will get to its stall speed in a rpm higher than its rated. I, personally, confused this with converter lockup. If I go WOT at 3500 rpms in 2nd or 3rd gear my rpms will shoot up to 4500 or so and then drop down all the while the car is still accelerating.



Flashing at idle will most likely spin higher than its rated stall speed due to a light load.

Foot brake stalling will always be lower then its rated stall speed. Mine I not broken. The load starts to become to great and will over power the brakes and the wheels will spin.

The more the converter spins without the clutch locked the more heat it creates. There were times on really hot days my leg would sweat from city driving because the converter doesn't really get a chance to lock up.

 

[Mike L.]

Sorry I made a mistake. I build high performance diesel transmissions and in my case I'm correct. Our engines produce so much tq ( 1,000-2,000 ft lb and higher ) we do stall higher than flash. This is not true with cars. It is the opposite. Sorry.