So I have my transmission out for other reasons but I was going to use the opportunity to get some higher stall and change the converter while its out. The trouble is that Im not getting the stall out of the current converter that i should be able to according to the charts.

its a GM 6 converter for a th400 with two rows of fins. The factory stall on the converter is supposed to be 2400-2800 rpm. The converter was modded by the local shop that has a good reputation for being able to make converters for our kind of use...racing, street performance, etc... So I'm ruling inexperience out for the moment. Plus im seeing a lower stall than even GM says for the converter before it was modified.

I get a 1875rpm stall out of it. It's built to be as high of a stall as possible for the 13" GM 6 converter with 2 rows.

So what can cause a converter to stall so much lower than it should? The engine is a 5.3, stock and turboed. But it obviously stalls way before it makes any boost so its basically a stock engine as far as the stall speed is concerned, 300hp, 330lb torque or so?

 

Unfortunately with current technology and the math formulations that come of it... the science and techniques employed in torque converter construction; are very far and away from being able to generate exact characteristic for a given use case.
The science is relatively good, however outside factors of the torque converter will effect the characteristics of the torque converter.

Essentially a given torque converter (rated 3,000 RPM brake stall) that is used on two different engines... (One with lots or low RPM torque and mild high RPM horse power. The other with very little low RPM torque and massive high RPM horse power)
Will produce two different sets of characteristics from the torque converter... (The first may brake stall higher ...3,800 RPM. The other may only brake stall to 2,200 RPM)

In the real world... your turbo 5.3L engine does not produce as much low RPM torque as the engine model that the torque converter technology is based on.
This causes the stall speed to be lower than intended and is not a defect.
You should explain to the torque converter manufacturer what you are experiencing and see if that GIANT torque converter can have the stall speed increased any. (This may not be possible with a large diameter torque converter).

So... Point being... The engine's characteristics (along with other things... vehicle weight, gearing, among others) will dictate the torque converters characteristics

 

You mean this one? Said 15-1800 on the website, and I'm not sure I'd put that behind a turbo mill.

 

There are more than a couple GM6 converters. Some have 3 rows of fins some have 2. There is nothing in inherently wrong with using it on a turbo. It isn't going to perform like a Yank but it cost about $250 and the Yank is about $900. The converter guy is going to change a couple things inside it and try to get me closer. He said the same thing as above, if i dont have the torque it needs the stall will lower dramatically so you actually lower the stall a bit and it will raise it for that given engine. Ill give it another shot after its changed and if it still isnt close to what i need ill drop the money on a Yank because they have the stalls figured out already.

But honestly I'm not worried about the thing breaking or the turbo being to much. Not ideal for the setup but certainly not weak or anything.

 

LOL Ls1tech never seems to disappoint

 

It's not even worth it anymore.
People are going to do what they want and learn the hard way. This includes the guy screwing with the converter.
Trying get a high efficiency stall speed out of a 13" converter is what inexperienced people were doing in the 70's

 

Maybe if you put a transbrake with your 13 inch converter, maybe then you'll get 2500 worth of stall speed out of it. Do that and report back.

 

Jeez!!! You guys are ruthless! ;-) LMAO!

I think everybody should just have to use a Lenco for a transmission... Problem solved!

 

LOL
There's nothing wrong with using it as a CORE for the correct application...but there are a multitude of issues when using it in a setup like yours.

You go ahead and try what you want...but if you're looking for something proven to perform...at less than 900 bucks...PTC, FTI, and Jakes all have the "stalls figured out already" as you so eloquently put it and they have their budget converters for around 450 ish bucks.

If you want to use a 13" converter for your small block turbo build...be my guest. Let me know how that goes. I hope you don't poop an engine thrust bearing in the process.

 

If i was picking a converter for a turbo setup such as this one i would go no less than a 9.5" billet piece. anything less and you are going to find a weak point somewhere eventually.

-Dalton

 

I agree, the converter is the most important part of a build.
It will make or break the entire car/combo

If you only buy one 'good' part it had better be a 9.5" converter from one of the 'big' names

 

You guys done run this fella off, yall are much like piranhas!

 

lol I'm not thinking im going to get a 3k stall from one of these converters. i would be happy if it came out to 2400 at best. But if you think its stupid to use the 13" converter, say why in a bit more detail than "lol internet people...". I'm not going to use it after they told me it deformed a few thousands of an inch this morning. It was just used as a core, the guts were replaced, it had a fully welded case, they did all the stuff they could. But this is why I ask the damn questions.

It's a budget turbo truck i built for $5k in a few months when i was bored. Most people are not going to budget out an amount that affords them the best listed stuff off the bat. Not to mention have it figured out bumper to bumper without having a career or life of hobby building this stuff already. If you built your first hotrod/turbo car and did it perfect and put the best parts in it the first time around and got to laugh at every idiot that thought better, good for you. You'd be the only person on the planet with that title but good for you. I'm going to keep asking my stupid questions and building my car...

 

After that cheap converter wrecks your bottom end (nevermind the horrid performance), you will be out the money....AND still need to get a good converter. I understand the money part of it, I really do. But there's a reason we all use good converters around here, ESPECIALLY behind a turbo mill.

 

What did the converter cost you when you bought it? What did the modifications cost you?
FTI, PTC, Jakes all have converters that would work properly for this build...in the 400-500 dollar ballpark...I'd consider that very budget friendly.

If you want more explanation than "lol internet people" here you go...

Lets look at 2 converters. Converter A will be a 9.5" core that stalls at 2800. converter B will be a 13" core that stalls at 2800.

The fin angles on these two converters will be DRASTICALLY different. The stator fin count/angle will also be different.

The 9.5" converter will stall to 2800 by virtue of its size. There isn't as much area for the fluid to couple at low rpm...so it can have an efficient fin angle and still stall where desired. Then up top in the rev range...because of that favorable fin angle (and its weight) it will couple more efficiently. It will run cooler...it will show better et/mph...it will just be an all around better unit

the 13" converter will do the opposite...it's so large and has so much coupling at low rpm that it will use a very unfavorable fin angle so that it can produce enough slip to stall to 2800. Then when you get up top...it will still have a **** fin angle and it will be very inefficient and heavy.
It will run hotter (because it is slipping like hell)...it will et/mph worse (because it is inefficient as hell)...and it is just a crappy choice

There are other issues like thrust on the engine, converter cavitation, etc that I won't get into...just know that the larger converter is the worse choice for you.

The times that you need to go to a larger core converter are when the smaller core just does not have the size to couple up top, or when you make too much power and the stall speed becomes to great despite stator/fin angle changes (think of "blowing through" a converter)...with most setups that can be remedied with a fin angle/stator change...but if it cant be, then it is usually time to step up to a larger core.

If you didn't read all that...just take away that a 13" converter is essentially never used in a performance application...unless you're doing sled pulls/diesel stuff

 

I understand that it is never chosen. I dont see any threads around here dealing with them and thats all the evidence you need to see that.

I did call Yank, the conversation ended with him recommending an $855 converter. The shipping on it to where I am at is about $300. If anything ever happens to it, what ever that may be, I have to ship it back to him and ship it back to me...about $300 each way. This is the real reason I don't pull the trigger on these kinds of things as easy as I would if i lived in California or literally any other state save for Hawaii. Same reason a lot of the people up here doing this do not order stuff like converters and transmission from out of state here in Alaska. The shipping is insane and the season to use the stuff is short. If you can't get the work done locally then you might be waiting a month. Like everyone else here, I have to make sacrifices to do anything cool with this kind of stuff. We only have 90 octane gas and not a drop of fuel alcohol in the whole state. We have I think one single shop with a chassis dyno and one other shop with an engine dyno. There are maybe 3 machine shops capable of doing a performance engine. There is one torque converter guy. There isn't even a single mechanics shop up here that will perform a camshaft change job on an LS engine...No tuners save for the one dude with the chassis dyno and he is imports only lol.

My biggest worry with it right now is the thrust on the rear bearing. I've had the guy stop working on it twice now while i was trying to make a reasonable decision what to do. The outside diameter is not changed, so it didn't balloon like that. One of the parts inside was not perfectly straight so that's getting changed out.

I'm $200 total in to the converter. So until it gets new bearings and the stage 2 cam installed this winter you can probably now see why I hesitate on dropping $1200 on a mail order converter. I restricted the feed to the pump with a drilled out set screw when i built the transmission originally to try and prevent thrust. That is my real only concern with it right now. Would the general consensus be that you cannot prevent thrust enough to be safe for the 5.3 main bearing with a 13" Gm converter? Performance abilities aside.

 

So...can you not read...or are you just that dense?
I've listed 3 converter companies...that have budget converter options...not 1200...not 855...
If you don't want help, fine. If you want to stick with your 13" converter that doesn't work...fine
if you want to keep using a local company that likely doesn't have a clue what they're doing...fine

but if you want to keep doing it your way and not listening to advice...and keep making excuses for your reason to run the converter you have...then quit asking for help here and move along.

 

Still costs $300 to ship it, still has proprietary components that cant be serviced here. I explained that.

 

Back ten years ago when I started thinking about my turbo 4l80e build I sorted out the converter first


Because I didn't want to go through what you are going through. The converter is the centerpiece of a build and must be taken to consideration above all other details when using an auto. For myriad reasons (economy, efficiency, drivability, response, etc... everything about the car is affected)

If I lived in a place where getting a proper converter is 'inconvenient' or 'too expensive' then the automatic goes right out the window and in goes a manual transmission... /story

 

When my 72 vette's TH400 need a rebuild and a new torque converter, I went with a Yank 3200. It stalls at 3200 rpm I'd rather do it once and get right than take three tries.