Don what does "something is missing in the trace that I would expect to see "mean?If I knew the mods done to the pump, I would have a better reference to use in my attempt in understanding it all. Allan made some good points, but then something is missing in the trace that I would expect to see.
At this point, all I can say is, "very interesting".
turbo 400's, flywheels, and Thrust bearings
- Thread starter karolko
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turbobitt
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- Feb 14, 2002
I wonder if the converter itself is creating the pressure spike. In other words, the converter itself is pumping fluid around internaly. On the gear shifts, the sprag becomes active and changes the dynamic of the fluid flow. So I ask myself if this would look different with a spragless converter.
Allan G.
Allan G.
At the initiation of the two shifts I would have expected to see a short dip in pressure as the PR moves to meet the added volume demand. If there is a full time lube mod, then that would explain why no dip.
Notice how the pressure drops with rpm at the end of first and after the other shifts. And, the pressure drop is different in different gears. I wonder if when the clutch drums rotating at increasing speeds, if the lube oil is being flung out at the various exit points around the drums with enough force to cause an increasing pressure drop in the lube circuit which travels back to the cooler system and plumbing?
The pressure drop seems to follow the speed of the two drums in the different speed ranges. Less pressure with more drum speed.
The most pressure drop in first gear. Forward drum at near engine rpm and the direct drum at 2 times that.
Second gear, the least pressure drop by the end of second. Forward drum at near engine rpm and the direct drum stopped.
Third gear, both drums rotating near engine rpm.
Good argument for keeping endplays on the tight side. Or, maybe you want this pressure drop to some extent.
I wonder if this pressure drop travels back to the T/C? If the oil pathways are good sized, I would imagine so.
The pressure drop seems to follow the speed of the two drums in the different speed ranges. Less pressure with more drum speed.
The most pressure drop in first gear. Forward drum at near engine rpm and the direct drum at 2 times that.
Second gear, the least pressure drop by the end of second. Forward drum at near engine rpm and the direct drum stopped.
Third gear, both drums rotating near engine rpm.
Good argument for keeping endplays on the tight side. Or, maybe you want this pressure drop to some extent.
I wonder if this pressure drop travels back to the T/C? If the oil pathways are good sized, I would imagine so.
Another thought. Notice how the pressure fluctuates while on the 2 step. Then, as engine boost and rpm builds, so does the pressure, until soon after transbrake release and the drums start turning.
Like Allen, I also wonder about how the internal flow pattern and the T/C rotating speed affect cooler line pressure, if at all.
Like Allen, I also wonder about how the internal flow pattern and the T/C rotating speed affect cooler line pressure, if at all.
turbobitt
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- Feb 14, 2002
I wonder if the spike occurs after the clutches engage and the PR valve not acting fast enough. Also, kinda like a water hammer effect maybe.
After looking at this data, I would think that it would be a good idea to have an accumulator in the line pressure circuit with a spring tuned to give max accumulator travel somewhere above max line, to compensate for pressure spikes. Without having a VB in front of me, I wonder if it is possible to use the existing acumulator circuit for this purpose ? Could make for a good A/B test. I don't really think that it would supply enough volume to do the task succesfully though.
Allan G.
After looking at this data, I would think that it would be a good idea to have an accumulator in the line pressure circuit with a spring tuned to give max accumulator travel somewhere above max line, to compensate for pressure spikes. Without having a VB in front of me, I wonder if it is possible to use the existing acumulator circuit for this purpose ? Could make for a good A/B test. I don't really think that it would supply enough volume to do the task succesfully though.
Allan G.
Suppose the graph you are looking at which shows the spikes has a restrictor right off the regulator AND has another restrictor in the lower cooler line port in the pump. You see the spike but not to the extent you should and the pressure seems quite low? Maybe someone is just trying to show you what you want to see and not whats really happening.I have seen this many times during teardowns and im not sure what someone was trying to accomplish.
The regulator won't close on the gear change because the regulator is fluid balanced. Spikes happen , I said that on page 1 and its not from some full time lube mod either. The converter is a pump, we can't forget that.
Hutch
The regulator won't close on the gear change because the regulator is fluid balanced. Spikes happen , I said that on page 1 and its not from some full time lube mod either. The converter is a pump, we can't forget that.
Hutch
I understand the different flow patterns that go on in a T/C and I'm not totally convinced that either type of flow has an affect on the in and out feed locations in the T/C.
I also believe that a pressure spike of such short duration is not anything to worry about. It would be a much different story if a high pressure was maintained for the duration of the running time.
That being said, if this transmission pump has an appropriately sized T/C feed restrictor off the PR, I'm am at a loss in understanding where such a large spike in the cooler line is coming from.
turbobitt
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- Feb 14, 2002
I'm not convinced it's a problem. We see these spikes but with no documented side effects.
Allan G.
turbobitt
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- Feb 14, 2002
Ya, what he said...
The effects are documented. I had a turbo car that would eat a thrust in 1 pass. I mean chew it right off to the effect of .030" after a pass. I made adjustments and we went to the track to test. The static cooler pressure was intact and we were ready to test.
We made 3 passes which consisted of spoolup , stage , launch but no gear change just ran it to the shift point and let off.
Checked the thrust every attempt and it was fine. There were some spikes on the launch but it seemed ok.
The next pass was a full pass and it was all over. Crank was done .017"
thrust from .008" Better than .030" but not fixed.This was a glide and the time spent on stall after the gear change is greater than a 3 spd.
Hutch
turbobitt
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- Feb 14, 2002
The effects are documented. I had a turbo car that would eat a thrust in 1 pass. I mean chew it right off to the effect of .030" after a pass. I made adjustments and we went to the track to test. The static cooler pressure was intact and we were ready to test.
We made 3 passes which consisted of spoolup , stage , launch but no gear change just ran it to the shift point and let off.
Checked the thrust every attempt and it was fine. There were some spikes on the launch but it seemed ok.
The next pass was a full pass and it was all over. Crank was done .017"
This was a glide and the time spent on stall after the gear change is greater than a 3 spd.
Hutch
just as you said, the results are documented. The poster with the trace said he never had an issue. Based on the trace and there reported success, why would I ot anyone else add extra clapp-trapp to the transmission ?
turbobitt
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- Joined
- Feb 14, 2002
The effects are documented. I had a turbo car that would eat a thrust in 1 pass. I mean chew it right off to the effect of .030" after a pass. I made adjustments and we went to the track to test. The static cooler pressure was intact and we were ready to test.
We made 3 passes which consisted of spoolup , stage , launch but no gear change just ran it to the shift point and let off.
Checked the thrust every attempt and it was fine. There were some spikes on the launch but it seemed ok.
The next pass was a full pass and it was all over. Crank was done .017"
This was a glide and the time spent on stall after the gear change is greater than a 3 spd.
Hutch
I would also much rather understand what is happening in the circuit before throwing another fix at it.
Back in my dyno days, we were developing overhead engine brakes and variable valve technology that actuated from hydraulic pressure. We would use strain gages to measure load on certain engine components and transducers to measure circuit pressures. Most often we would see very high spikes in pressure but they happened to fast and never materialized into any real reading on the force gages. There are many reasons for this but the message here is that a small duration spike with a high magnetude doesn't really affect anything. In this case, If I read the graph correctly, the spike doesn't get over 100 psi. This spike wouldn't worry me at all.
Allan G.
Do you have a similar pressure trace like the one that was posted already, that you could share of that particular run you're referring too? I'd be interested in knowing how long in time and how high in pressure.The effects are documented. I had a turbo car that would eat a thrust in 1 pass. I mean chew it right off to the effect of .030" after a pass. I made adjustments and we went to the track to test. The static cooler pressure was intact and we were ready to test.
We made 3 passes which consisted of spoolup , stage , launch but no gear change just ran it to the shift point and let off.
Checked the thrust every attempt and it was fine. There were some spikes on the launch but it seemed ok.
The next pass was a full pass and it was all over. Crank was done .017"
This was a glide and the time spent on stall after the gear change is greater than a 3 spd.
Hutch
Very interesting stuff, guys.
OT / clap trap . English , speak english. I am dumb farmer , can you rephrase this for me.
Hutch
The pressures don't get over 100 psi in THAT graph. That doesn't mean they will all be like that one even with the same system pressure and restrictor size. There are too many variables and with that said you guys can theorize until you puke blood but the fix will still be a regulator controlled cooler system. This is not some new stuff either , remember back in 1964? Its already been done but was discontinued because GM saved 2 cents per pump.
Hutch
