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Author Topic:   Powerglide Torqconverter
Tobyone
Dirt Newbie

Total posts: 1
posted August 17, 2000 11:03 PM
I was wondering what a good low stall converter to run in a powerglide would be.thanx

TCI
Dirt Roller

Total posts: 11
posted August 18, 2000 11:20 AM
A good low stall converter would be an 11" style converter. It weighs a couple of more pounds than a 10" would but it locks up quicker which means less slippage and quicker throttle response. TCI's part number would be 741125.
www.tciauto.com

RickP
Dirt Roller

Total posts: 17
posted August 18, 2000 02:56 PM
I've heard this before. I personally use a smaller diameter one that is lighter. It's my understanding that a Torque Converter is usually "locked up" at anything over 3000 RPM or so anyway. I never drop below 4500 while I'm racing so I think it's locked the whole time and even if it's not (say on restart) I say let it slip it's making torque! Like a internaly gear reduction!
RP-02BB

Limited5
Dirt Maniac

Total posts: 141
posted August 19, 2000 09:18 AM
Did you just fall off the Turnip truck? Remember cheaters always win! Regardless of what your parents may have told ya. You need to gut that torque convertor and use it as a direct drive! Take it to a machine shop and have em take all the internals out and then balance it for ya. Theres tons of powerglides out there that use direct drives. Think this sounds far fetched? I bet if you look at some front runners they've already beat ya to it! Now you've got a direct drive tranny and you got rid of all that rotating m***. If ya dont get caught, it aint cheat'n in my book! Not that I would ever do anything like that! Ha Ha

TCI
Dirt Roller

Total posts: 11
posted August 21, 2000 09:48 AM
RickP is correct a smaller converter does weigh less but a converter is always slipping because you cannot acheive 100% lockup in a fluid coupling component. So basicially the higher the stall the less lockup percentage you will have. If slippage didn't hurt you could put a big cam in the motor and run a hi stall converter.
I have been in the converter business for over 15 years and have put converters in everything from monster trucks to volkswagons and you don't want much stall in a oval track setup. If that were the case a direct drive would hurt a car.

PEDDLER
Dirt Maniac

Total posts: 148
posted August 21, 2000 09:20 PM
TCI,
Just a question. We ran a th350 for 5 years with a stock converter. We had no problem with the exception of it being lazy on a slow start or restart. Thats when the guys with standards killed us.
We thought that with the cam we were running that the slow starts were out of our power range and that a stall conv., would in reality, help us on starts. We never got around to trying it.
A reply would be appreciated.
Thanks Jim

TCI
Dirt Roller

Total posts: 11
posted August 22, 2000 09:04 AM
The biggest problem with using a higher stall converter is that when you get on the throttle the converter will "flash stall" therefore it will slip and instead of the rpms going to the ground at that time they are "lost" in the converter. It will provide better torque multiplication, but only at the stall rpm. Look at a low stall converter like a stick application; less slippage, quicker throttle response and car moves ahead quicker.
quote:
Originally posted by PEDDLER:
TCI,
Just a question. We ran a th350 for 5 years with a stock converter. We had no problem with the exception of it being lazy on a slow start or restart. Thats when the guys with standards killed us.
We thought that with the cam we were running that the slow starts were out of our power range and that a stall conv., would in reality, help us on starts. We never got around to trying it.
A reply would be appreciated.
Thanks Jim

PEDDLER
Dirt Maniac

Total posts: 148
posted August 22, 2000 07:41 PM
TCI,
Thanks for the reply, I'll have to think about that for awhile.

RickP
Dirt Roller

Total posts: 17
posted August 23, 2000 07:51 AM
TCI,
I have to disagree with you, but please don't take it personally, I understand you have much experience with this and want to get to the bottom of this. We keep talking about stall speed when in actuallity this is just a theoretical "means" of comparing TQ's. It's not something we actually use on the track. It is my understanding that converters that are "high stall" rated are simply less efficient at low RPM's. The shape of the fins inside is designed to operate high RPM's. Consequently the converter functios poorly at low RPM. This will acutally shift and increase the efficiency at the top end. Yes all TQ's will slip as it is a fluid coupling, just the more efficent it is the less slippage there is (and heat generated too).

And Limited5, It's not me but our track officials that have fallen off the truck, they force us to run "stock" cars on a race track LOL
RP-02BB

TCI
Dirt Roller

Total posts: 11
posted August 24, 2000 08:43 AM
If slippage, stall etc does not matter then everyone would be running a converter instead of direct drives or even dummy converte, at least in my opinion. But some things work better for some than others. and the more slippage the less efficiant through the entire rpm range. Good luck Tobyone and I didn't take anything personal Rickp.

RickP
Dirt Roller

Total posts: 17
posted August 24, 2000 11:04 AM
Well I didn't mean to say that stall speed dosn't matter (or slip for that even, it sure does and that's my point) but it's my impression that the stall speed is simply a "theoretical" value to which we can compare two TQ's. We never buy a converter to watch it stall at the advertised RPM.

It's just that from what I've read that the higer the Stall speed rating the more slip it has at lower RPM and this is a direct consiquence of the internal fins being designed to work more efficiently at higher RPM.

Guys who race Jet skis know this, the blades on the impellers are designed to generate the most thrust at racing speeds, consequently they are dogs off the line.
RP-02BB

PEDDLER
Dirt Maniac

Total posts: 148
posted September 05, 2000 06:50 PM
TCI,
If I use say a 2500 stall TQ and could start a race at 2500 to 3000 rpms instead of 1500, that would put me more in my power range. It is nothing more than what the guys with standards are doing by slipping their clutch or bringing their engine to their RPM's then dumping the clutch.
Right or wrong?

Limited5
Dirt Maniac

Total posts: 141
posted September 05, 2000 09:48 PM
Basicly how stall speed works: If you took 2 identical fans and placed them facing each other, and they ran at the same speed and had the same blade pitch, they would eventualy both lock when achieving a certain speed. A torque converter does the same thing only using fluid instead of air. Now, if we change the pitch of the blades, a higher or lower "lock" effect takes place. Desired stall speed however depends on engine size and torque. Advertised stall speed is achieved on a stall test machine, and is a uniform test inorder to control uniformity and baselines.
Now enter the into the equation, the converters diameter and weight, along with the flywheel weight and so forth. All these weights will affect the actual stall of the converter and its performance. I've seen guys go through 4 or 5 units till they got it right! Good luck.

24ksi Racing
Dirt Roller

Total posts: 13
posted September 07, 2000 04:21 PM
On dirt it is beneficial to have rear braking bias. One of the things that a manual will do is force the motor to wind down when you lift through drag on the rear wheels. Similarly, a tight converter on an automatic is a lot better on dirt than otherwise.

If you have to run a fully operational converter, have one built out of a small diameter with the blades pitched for towing. In a TH350, an 11" conveter built tight will act better than stock and a LOT better than any small diameter "stall" conveter.

For what it's worth...

Bill
24ksi

[This message has been edited by 24ksi Racing (edited September 07, 2000).]

PEDDLER
Dirt Maniac

Total posts: 148
posted September 07, 2000 06:49 PM
Thanks Bill

V6
Dirt Newbie

Total posts: 1
posted September 14, 2000 12:01 AM
Gentlemen,

I have read this thread with great interest. I have had some of the same questions also.

I am running a V6 in an IMCA stock. I currently run through a stock converter and a powerglide, first gear with 4.11 rear gears. I pretty much have the power to weight thing handled. I have a couple of heat wins and some second and third place features. I'm thinking about going to a direct drive coupler to reduce the rotating weight.
I know that converter stall speed is determined by available horsepower, converter design and load factors, but does a converter ever turn one to one under a load? I don't think so. If it does not, then am I right to believe that I will need to put more rear gear in when I go to a direct drive to keep the overall gearing (crank shaft RPM to drive axle RPM)similar?
Thanks

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