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SBF, turbo car powerglide/ converter problems. Any ideas?

28K views 65 replies 16 participants last post by  ChuckDirt 
#1 ·
First off let me say that PTC and Dusty have been nothing but good to me and I firmly believe that they build superior products and I will always use their products. My purpose for posting this is in hopes that someone else might have had a similar problem. Okay here we go, I have a 347" SBF with a GT47-88 and a powerglide and PTC 9.5" converter. The problem is that the converter has a 20 blade stator in it and still has 1400-1500 rpm drop at the gear change. I took the trans to PTC and they took it apart hoping to find something wrong inside but unfortunately they didn't. It looked like brand new inside and has a BTE front pump that has a bushing for a ringless shaft but I am running a ringed vasco shaft. We put the trans with my converter on their dyno and ran it. It had 250-270 lbs of line pressure and 90 lbs on the cooler circuit under loaded rpm. I took the trans back home and installed it. I wanted to check the pressure on both sides of my Chiseled water trans cooler to make sure that I didn't have any restrictions causing the fluid to get backed up into the converter in essence "tightening the converter up" I had 80-95 lbs on both side of the cooler with the car on jackstands and running the car in gear. So I still do not know why I am having this problem. The car is making 26 lbs of boost on the run and has been a 5.12@142 with the out of the box 47-88. I cannot help but think that we are leaving some on the table. We shift the car at 8100 and it will drop to 6650 and then gain 500 rpm in high gear. Anyone got any ideas? Thanks.
 
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#2 ·
Converter sounds like its to tight, loosen up just a tick!!!!!!!
What's the percentage slip @ the end of your run...
 
#5 ·
Does your 347 use the smaller bore and the 3.40" stroke? or the larger bore and the 3.20" stroke? Engine tune and turbo back pressure at the gear change also has a lot to do with rpm drop.. Don't know about most but I have seen improvements in converter performance by reducing my charge pressure to 20-40 psi range during a pass..
 
#6 ·
Does your 347 use the smaller bore and the 3.40" stroke? or the larger bore and the 3.20" stroke? Engine tune and turbo back pressure at the gear change also has a lot to do with rpm drop.. Don't know about most but I have seen improvements in converter performance by reducing my charge pressure to 20-40 psi range during a pass..
That's where we are most likely heading. Converter has been loosened twice but has not responded on the 1-2 gear change. The initial flash stall of the converter has changed. I'm leaning towards putting in a ringless shaft to reduce converter pressure. This should get him back to needing the tighter converter yet still be dropping 1000 rather than the 1500.
 
#8 ·
This last restall was a pump and stator change. It obviously effected initial flash but rpm drop on the gear change was still the same. I was suspecting an issue with the cooler circuit causing backpressure in the converter but I think he looped the lines and nothing changed. It's as if the fluid isn't getting out of the converter down track making it tight.

Back when I swapped to a ringless shaft and cooler circuit pressure dropped, the converter got looser. That's the next step. I expect it to loosen the converter enough that he can try a converter I have for a combo similar to his.
 
#19 ·
We have not yet but we will.

I did this on my own car. Lowered charge pressure from 85psi to 40psi and the converter had to be tightened to compensate. Actually went all the way down to 20psi by running a ringless input shaft without a bushing in the stator tube and could not make the converter tight enough. We found 40psi was as low as I wanted to run it.
 
#20 · (Edited)
With the 2 speed T-400 my charge pressure is the most consistent it has ever been, varied 25 psi from the highest to the lowest throughout the run. I'm using a .100 orifice on the discharge line set to pop open at 55 psi.. Don't know what Dave has done to restrict the charge side...This is with my aggressive fin angle 8 inch converter,, the much less aggressive angle 9 inch converter operates about 8-10 psi lower for some reason..
Anyway this helped my gear change rpm drop {and the back half times improved}but I would like to get closer to 750-800 drop.. The car is a F-1 pro-charger car so rpm drop at the gear change effects boost... Charge pressure is in yellow
 
#21 ·
Looks good. It's always interesting to see what the pressure does as the converter flashes then couples. You can see when the converter flashes it's blowing the fluid out of it causing the cooler circuit pressure to rise. It's very clear at the gear change also.
 
#24 ·
So as the converter flashes it pushes the fluid out the cooler circuit causing the higher reading.. I never understood why the pressure changes so dramatically during the run,, I was beginning to think the trans pump was cavitation under acceleration do to the fluid uncovering the filter during certain points of a pass??... Also makes sense why my flat fin angel 9 inch converter operates at less pressure than the tight eight inch...
 
#40 ·
Now I know I can put a ringless shaft in it that will allow more fluid flow out of the converter.
How can that be? There is no difference on the way out unless the shaft to tube clearance is offering restriction or there is a stator tube bushing and path that is offering restriction.

If you reference is a ring to ringless (with cooler) I don't see the difference in out flow.


Hutch
 
#43 ·
How can that be? There is no difference on the way out unless the shaft to tube clearance is offering restriction or there is a stator tube bushing and path that is offering restriction.

If you reference is a ring to ringless (with cooler) I don't see the difference in out flow.


Hutch
It's the clearance between the shaft and tube that changes with some ringless shafts. I have dropped cooler line pressure from 80 psi to 20 just by swapping from a ring shaft to a ringless vasco. Putting a bushing in the pump was enough of a restriction to raise the cooler line pressure from 20 to 40. In the end dropping the cooler line pressure from 80-40 loosened the converter.
 
#23 ·
Im sure that is true,, I have had the charge pressure go as low as 4 psi briefly and run down the track never exceeding 38 with no ill effects to the converter or gear-bushing assemblies {lube circuit} or burning the fluid. Need to keep in mind my car isn't very powerful comparatively speaking {SBF with F-1, runs 5.00 range at 3170lbs}
On the more powerful cars I we haven't tried running the charge pressure down below 40 psi....
I have seen some turbo cars with charge pressures exceeding 120 psi,, usually these are the same turbo cars that kill the thrust bearing in the engine
Stock PG from the sixties vehicles operated charge pressures from 25-55 depending on application, load, rpm..
Wish there was a way we could have more volume with out an increase in charge pressure and have the ability to manipulate charge pressure during a pass,, I think Hutch and Dave are working on something as we speak..
At one time there was a company that produced a valve body that would allow the operator to turn off or dump all charge pressure for easy spool-up and or better recovery at the gear change, that system seemed to cause the fluid to burn rather quickly..
 
#27 ·
You restrict the circuit. But, you are playing with a critical amount of fluid. It needs to keep the converter full of fluid to work properly. The variable stall stuff (I did my own years ago) pretty much just restricts fluid to the converter to up the stall speed. It's a fine line though. Keep the converter full but hold down the pressure so it won't hurt the thrust, and still keep it flowing as lube oil downstream.
 
#29 ·
Yes, it could be,, but worth the return if you are willing to use this as a tuning tool,,
anytime you give a pg more line pressure you will increase charge pressure, the restriction just bring it back down to a pressure it would have been with the stock line pressure valve and spring?
 
#32 ·
I realize that... that's how I would do it as well and always do with the TH-400's. But what I'm getting at is even if you have a popoff valve set to 55 psi... what is the pressure upline from that? It still may be excessive. I'd rather watch the pressure and tune the charge to maintain it. IMO the passages are smallish between the exit path from the converter and the cooler line and in reality bleeding it there may not really be doing anything back upstream. It'd be nice to have a pressure transducer in the converter to see what's really going on.
 
#41 ·
I need to remember the pressure my RP transducer is reading is actually cooler line pressure,, not necessarily actual converter charge pressure... What i have learned from this thread is charge pressure is a product of fluid exhaust efficiency and converter design and inlet pressure-volume. Restricting the converter inlet can effect converter pressure only because the volume of fluid pumped into the converter is less..
Wonder if I can fit a pressure transducer to the converter inlet conduits somewhere down stream of the restrict and-or, or fit a pressure regulator valve that can control converter inlet pressure independent of line pressure..
 
#39 ·
I'm not much of a trans guy either,{more of a suspension guy} but I do spend a lot of time test ideas,reviewing the results, listing and learning.. In the past I worked with clutch cars and learned how critical clutch set-up is to the performance and drivability {call it "winablity"} of the car .. A working knowledge of the torque converter and having the ability to tune the converter is of vital important.. Manipulating charge pressure is one more tool a tuner has at his disposal..
I am very interested in the results you find on Cory's car...
 
#42 ·
I'm sure you can. Years ago I built an external charge system with solenoids and an rpm switch to gain around 300 rpm of stall with my little small block. When the car left and the rpm switch closed it flooded the converter to tighten it up. But, I'd like to know what the actual pressure in the converter really is at. I always monitored cooler circuit pressure and then dealt with the charge restriction to control that. Someone needs to make an affordable and smallish pressure transducer system!
 
#47 ·
The ringless shaft I'm referring to does require a bushing in the pump. Otherwise there isn't enough restriction to keep fluid in the converter when the power comes in.
 
#48 ·
Ok , that is a ringless that uses no cooler. Now you can figure out what the last restriction is by measuring the total area of the flutes on the shaft then calculating the feed orifice required to keep the converter charged. The only problem with that system is you can't check the pressure. The other side to it was a problem with the clearance between the tube and shaft in the original ring land area. It was too tight there and the oil was being forced to go out the lower cooler line (by accident). Someone figured a band aid repair was to run an external line to the pan instead of fixing the problem in the shaft design. Its a good shaft if a cooler is not required but the design needs attention in my opinion.


Hutch
 
#49 ·
With this shaft we do not run a restrictor in the feed and we do run the bottom port back to the pan. I've ran this set up for years without the cooler but Lane has a mod for this design to force cooler flow.
 
#50 ·
I've had good results with the newest generation BTE ringless Vasco shaft. It uses dual bushings near the back of the stator tube to feed lube oil. It has spiral flutes and allows use of a "normal" TH stator tube bushing at the front with no flow restriction. Fluid is pushed out in front of the bushings at the rear of the tube to the cooler and then returns between them as lube oil. Gear life has been good as well as bushing life. I also prefer to use fluid that has good lubricity characteristics to help things out.
 
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