Foundational question regarding Torque Converters.

MikeKanterakis

SCCoA Member
Can someone please help me decifer this e-mail from Art Carr transmissions? thanks. Specifically, what is flash? and why won't that use the car as well?

The "Mileage Maker" converter is designed for offroad, 4WD,
pulling, &
highway use. It will give you better fuel mileage by lowering
the stall
slightly below stock. You gain fuel mileage but the stall is
lower.
When you accelerate, the converter won't flash as high so it
won't be
utilizing your cam's power range as well.




Edit: Given this setup, wouldn't a 3.73 rear-end help satisfy this problem? At ultimate cost of top speed, but none the less...
 
Flash is how many rpms the converter allows the engine to jump to.
Do this get in your car put your foot firmly on the brake and then put it in gear.
Snap the throttle to the floor and the rpms will rise fast. Lets say you have a 2200 stall converter. It will generally flash to about 2400 and settle in about 2200 provided the wheels don't start moving. Bringing up the rpms slowly will not get the flash out of the converter. I hope that made sense, it is much easier to show somenone.
Alan
 
Thanks for the reply. So you're saying that it's that "slack" you see on the tach. when bouncing in and out of gear as you're cruizing along on the highway?

Bouncing in and out of gear by either pressing on enough gas pedal to cruize along, or to pull your foot off the pedal and let the rmp's drop. ???
 
now, i'm not sure... what did you mean when you said : Bringing up the rpms slowly will not get the flash out of the converter.
 
MikeKanterakis said:
now, i'm not sure... what did you mean when you said : Bringing up the rpms slowly will not get the flash out of the converter.

Easing the throttle down instead of shoving it to the floor
 
so, the more flash you have, i.e. the higher the stall, the more engine rpm you'll have towards your launch. But, this lessens fuel economy because you're revving the engine higher and using more engine power to take off faster. where by a lower stall, would give you less take-off / launch power, but would keep the rpm's nice and low, there by saving on gas?

Then, a change in the rear gears would keep those rpm's low, but now, you wouldn't need such a high stall b/c the engine doesn't have to work as hard in order to cruize down the street.

?
 
Smaller converter flash considerably high than larger converter. It all has to do with pressure building up in the turbine. For example if you have a 2200 stall 12 inch converter it will flash to about 2400. If you have a 2400 stall 9.5 inch converter it will flash to about 2800. The 10 inch units I build stall about 2500 and flash to about 2600, but that is because i close up all the leak points and trap the fluid in.
Alan
 
ok, i've read some more about torque converters, and came up with this. Basically, you need to match the torque converter to the engine's peak torque rmp, as well, as the gearing in the differential. This way, you use the converter's torque multiplying properties up the the point where the engine takes over in terms of peak power.

I'm rebuilding my wife's SC as a stock + car. By that I mean, that I want to run it in it's stock configuration, but if I can ease some stresses inherent in the system, then that's the plus part. I.e. add a tranny cooler, install a different power steering cooler (yes, i've been meaning to post that for ever, but I'm slow.), replace the air dam with the pontiac air dam, etc.

So, when I saw the listing for this Mileage saving torque converter, I got all excited. But, it seems that, really, all I can do is match the torque converter to the system, and that's about it. Therefore, do you, Dirtyd0g, or anyone else, have a recommendation for a good light-weight torque converter with a stall matched to the stock setup? Howabout a match for 3.73 gears?

Damn, I thought I was done with these messy automatics when I got my 5-spd. Oh well. Wish they made a clutch light enough to satisfy the wife.

Thanks for the replies Dirtyd0g. I appreciate your making me more informed. Between the advice I get here on SCCOA, and this rebuild project with my wife's AOD, I'm on the road to SC enlightenment! Pretty soon, I'll get to the mountain were all the people wear robes and talk about that silly little puzzle called the internal combustion engine. he he he he he
 
For a stock engine go with a 2200 stall non lockup converter.You just missed it I sold a couple of those. Bill Evanhoff @ SCP sells the ones I build very reasonably.
Alan
 
ok, thanks for the recommendation. Have you done a write-up regarding the "better" quality of your rebuilt torque converters? If not, I think it would be a great idea.
 
MikeKanterakis said:
ok, thanks for the recommendation. Have you done a write-up regarding the "better" quality of your rebuilt torque converters? If not, I think it would be a great idea.

I have done several writeups on tccoa about my 4r70w converters. I will be building a few of these aod converters here in a couple weeks and I'll get some pictures. Words mean nothing without pictures. :)
Alan
 
Wow, that made for some interesting reading. Would you answer a few questions for me?

1. What is/are single / tripple plates?
2. you recommended me a 2200 stall non-lockup converter. are any of the ones you will be building in a few weeks available for purchase?
3. How streetable are the TC's you build? Or is that just a matter of the stall?
 
MikeKanterakis said:
Wow, that made for some interesting reading. Would you answer a few questions for me?

1. What is/are single / tripple plates?
2. you recommended me a 2200 stall non-lockup converter. are any of the ones you will be building in a few weeks available for purchase?
3. How streetable are the TC's you build? Or is that just a matter of the stall?

Single and triple plates refer to 4r70w transmissions. Aod transmissions do not have a lockup clutch.
All of the converters I build are for sale, see Bill@supercoupe performance
streetability is determined mostly by stall speed. Yes the 2200 is completely streetable. You will need to run an external cooler to run the converter unlocked.
Alan
 
My brother gave me the one from his old auto tranny. it's a stacked plate design, and it's like 8 X 11 inches. I was thinking of attaching a 9'' fan to that with a temp. switch. Do you think the fan would be over kill?
 
I am running a 8.5'' convertor 2400 stall,non-lock.I had to install a
26000 GVW 10'' wide x 12'' long cooler.Still ran warm,so I install in
a series a 9'' wide x 13.5'' x3.5 thick cooler with a 10''fan with
160 degree thermostat.And the trans fuild runs though the radiator.

And my SC still runs warm when it is 32 degrees out.So I do not think the car
will be drivable in the summer.So I am going to delete the radiator as
part of the transmission cooling system.And hope that the motor and
trans will start running cooler.

And I lost over 4 miles per gallon of gas.This is with a stock motor.

I think I may have to pull the lentech trans out.And install a locking convertor.And I have a one peice shaft in the trans.So I need to
know what type convertor I can run now to cool the car down.
I don't think that a stock convertor will work now.I may need to get
another trans.This will be 5th trans in less than 6000 miles.

Randy

Randy
 
Last edited:
I got dibs on the lentech trans if you dont want it. Ever thought of a fuller 10 speed lots of gears and really heavy duty!!
 
Randy N Connie said:
I am running a 8.5'' convertor 2400 stall,non-lock.I had to install a
26000 GVW 10'' wide x 12'' long cooler.Still ran warm,so I install in
a series a 9'' wide x 13.5'' x3.5 thick cooler with a 10''fan with
160 degree thermostat.And the trans fuild runs though the radiator.

And my SC still runs warm when it is 32 degrees out.So I do not think the car
will be drivable in the summer.So I am going to delete the radiator as
part of the transmission cooling system.And hope that the motor and
trans will start running cooler.

And I lost over 4 miles per gallon of gas.This is with a stock motor.

I think I may have to pull the lentech trans out.And install a locking convertor.And I have a one peice shaft in the trans.So I need to
know what type convertor I can run now to cool the car down.
I don't think that a stock convertor will work now.I may need to get
another trans.This will be 5th trans in less than 6000 miles.

Randy

Randy


It isn't the lack of lockup killing your gas mileage and creating all that heat. Your converter is too small for street operation. I have actually had customers tell me they got better gas mileage by installing a 2000 stall non lockup converter. Any non lockup will generate slightly more heat ,but one that small will generate too much. Small converters like that are generally race only. Anything less than 10 inch without lockup is too small for the street.
Alan
 
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