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torque converter - Q
Can some body take the time to explain to me exactly how the TC is supposed to function. I'm not really sure if I should be playing with my custom setting for the locking and unlocking of the TC but I'm not totally happy with how easy my truck seems to want to downshift.
I usually run my 87 performance tune and it seems like the truck is more willing to downshift from 4th to 3rd then when it is in stock form??? Is this normal? I just have to breath on the pedal and it downshifts to 3rd. The power is great but not always necessary. When cruising and pulling out to pass just one car.......I would like to be able to just nicely lean on the peddle to go by him without the downshift if it's not really required. I can understand it if I really come on to it, or even moderately...........but should it gear down when slightly shoved?:shrug: Or is this even a TC unlocking issue at all? thanks, Chris |
Probably not a torque converter issue at all. Sounds like a transmission shifting strategy issue. Bill can change this fairly easily, you just need to get into contact with him. When the torque converter unlocks it should only change your r.p.m by about 300 r.p.m, whereas a downshift will change by about a 1000 r.p.m. When the torque converter locks it no longer has a fluid coupling between engine and transmission, but now has a more mechanical connection, kind of like a clutch on a 5 speed. Well I hope this helps.
Ty |
Chris,
Change one of your display PIDs to "GEAR". This will display the current gear and also indicate if the converter is locked or unlocked by a little "lock" symbol on the display. This will help you determine if the problem is downshifting or converter unlocking. Once the problem is identified, we can modify the offending parameters to resolve the issues. :2thumbs: Take care. |
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okay, thanks guys!
I'll do that and get back to you Bill. I hope it doesn't involve re-tuning........you just made some adjustments to my tunes :doh: |
Hey... gotta keep things interesting, right?
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Chris, you might try reducing your 4-3 downshift and 4-3 TC unlock speeds. I tried this and it seemed to help that overly eager desire to downshift or unlock. But, I haven't really been where I could test it properly yet. This is the same problem Twintips was talking about too. It's almost as if Ford engineers thought we wanted to hear our engines rev. (Like you, I'd just as soon it didn't unless I REALLY wanted it).
- Jack |
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I was able to do what Bill said and have determined that is definitely my TQC coming unlocked........it's not a down shift! Engine revs higher and rpm's climb about 3-400 or so. So now what?............do I just reduce the TQC unlock setting or increase it? How much should I start with. Like I said, I want to be able to gently pass a car without it unlocking!:help: |
Great! I BELIEVE, you reduce the TC unlock settings on 4-3, 3-2, etc. I think this inhibits unlocking until the speed is lower and the engine is under more load.
If I'm wrong, the Mad Doctor will jump right in here and set me straight! But this seems like the way it works to me. Note: I've also decreased the TC lock speeds on upshifts. I changed them all to the max. I really haven't been in a situation to properly test them, but my limited driving over some hills seems to feel right. - Jack |
You've got it right, Jack. Drop the 4-3 TC downshift a couple MPH at a time and give that a shot. If it helps, then we can make similar changes to the strategies in your custom files so you don't have to reload them every time you change a level.
Let me know how it works and where you end up. |
Okay will do........Bill did you get my email about me having that lean miss back again? I made an error in judgement and got greedy thinking we could cheat a little more on the lean side.........but not gonna work pal. We gotta get rich again:'(
It's hard to believe an adjustment that minor can produce such a noticeable increase in power and fuel economy.......too bad the engine didn't like it :confused: |
Yep... working on it tomorrow and will get it resolved. :thumbsup:
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Cool.......my apologies again for the mistake!
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I haven't tried this either, but I think it should lock in 3rd with OD off, or in 2nd or 1st if you put the shifter in one of those two slots. To keep it locked though, you have to have a pretty constant throttle deflection. Increasing it or letting up on it is going to unlock it.
- Jack |
I had something happen today I hadn't noticed before. I was experimenting and advanced shift firmness to 5,8, and 8. After this all was smooth until I went up a small rise. The gear PID showed the TC stayed locked until I came over the top to a slight decline, then it jumped in and out of lock a few times until it settled down. This happened again a couple of other times even after I set the firmness back down. I had the cruise set at 65mph and when I increased it a couple of mph it seemed to help. Would changing the TC lock or unlock points correct this or do I just need to pay attention to the cruise setting.
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I don't think it has anything to do with shift firmness, Dfish. I bet it's because you had the cruise control set, which lets up on the throttle as you start down the incline. If the converter is locked and you release the throttle, it will unlock and, Bill explained that was a feature Ford put in to increase your fuel economy. (The engine/transmission doesn't drag in coast). Now, I'm guessing that the small decline wasn't really enough to keep the throttle at the "let off" point that caused the unlock, so, it locked back up again. But that wasn't stable either, so it unlocked/locked....
Possibly, if you reduced the lock and unlock speeds for each upshift/downshift, it might "tame" this behavior a bit. - Jack |
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It's not a degree in these settings, it's speed, in mph. Which, is kind of misleading too, since shift and torque lock/unlock depend on not only speed, but throttle position too. I suspect you're going to have to move the setting quite a bit more to notice much of a difference.
- Jack |
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Likewise, I've wondered about the definition of WOT. Does the PCM go into WOT map at a specific percentage of throttle pedal position, a specific amount or rate of change in TP position, or does WOT kick in when the pedal really hits the metal... |
I think, but again I could be wrong, that the balance between speed and throttle position determine the "load". If you are say, cruising at 40 mph, there is little load, but if you advance the pedal (try to accelerate the vehicle), then the load increases. It's controlled by a valve, I believe which "floats" back and forth in response to both speed and pedal position, but, below a certain speed, regardless of pedal position, a downshift is commanded and, above a certain speed, regardless of pedal an upshift is commanded.
But, as I understand it also, a WOT throttle overrides everything and shifting becomes controlled totally by RPM. As far as what constitutes WOT, I don't know. It seems to be awfully close to the max deflection point though. I know if I let up just slightly in a WOT situation, the transmission downshifts. I'm sure someone on this forum can enlighten us (and probably tell us that all my earlier statements were wrong too). :hehe: - Jack |
WOT throttle is usually anything over 80%, regardless of load or how fast the "pedal hits the metal" (I like that...LOL!!). This is the point that the ECU goes into "open-loop" and reverts to the basic programming...start-up, cold-running, and WOT. Basically the stuff you can adjust on any handheld tuner. Once the ECU senses that the engine is warm (closed-loop), it uses all the emissions sensors to adjust long and short fuel trims and to maintain efficeint operation. You are right that WOT overrides everything, because it "locks out" the sensor information and looks specifically at the predetermined tune values. That's why if you were to say, adjust your spark advance when it is 30* ambient and dry and it works great, at 70* with high humidity, it will not run the same at WOT, possibly to the point of causing damage. The ECU no longer cares about what the air conditions are, it goes to the basic programming (for 30* and dry in this example). Part-throttle, it affects nothing because the ECU is in closed-loop, using the info it's getting from the MAF, O2s, etc.
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Good information Grabber, thanks! This also makes me think it's not a good idea to "continuously" run in WOT (even though I know you really can't). But, people who continuously like to drop the hammer are going to be in that open loop mode probably more than is good for the engine.
- Jack |
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Here's a couple thoughts...
1) Open Loop only affects fuel delivery calculations, not spark timing or shifting. Quote:
3) WOT mode occurs at a predetermined point in the calibration and is based on a calculated voltage value from the APP (accelerator pedal position) sensor. This value can be changed to meet the performance need of the vehicle and/or driver. 4) During Open Loop at WOT, there are two things happening: First, the PCM goes into Open Loop fuel mode and runs based off the Open Loop fuel table and MAF. Second, the PCM goes into WOT Fuel Enrichment which provides an extra shot of fuel to help maximize torque output as well as reduce combustion temps. This is the WOT Fuel Multiplier found in the custom options. Since the target fuel ratios are richer at WOT than at cruise, you are often actually safer running at WOT than you are at cruise. Of course, fuel economy is going to be severely affected. 5) At WOT, shifting will revert to an RPM based strategy instead of the normal MPH vs. APP strategies. What the PCM tries to do is anticipate when to shift based on the target shift RPM and the current rate of acceleration of the engine. Based on calculated factors, the PCM determines how long the upcoming shift will take to complete and generate an RPM value at which to begin the shift procedure. This is MUCH trickier than it sounds and more involved than I'd care to get into at this moment. 6) Spark Timing is based on Load and Engine Speed, but is also heavily influenced by AFR, Engine Temp, Air Temp, Knock Sensor input, and other factors. This is not directly affected by WOT or even Open Loop, but can be indirectly affected by changes in AFR as a result of going into WOT or Open Loop modes. There is a tremendous amount of data being processed inside the average vehicle's PCM. In fact, the 04-08 uses a derivative of the Power PC processors to handle meet these needs. Feedback (Closed Loop) systems try to maintain a zero control error, but that is only if the values from the sensors are accurate and why many CAI kits cause problems. Without changing the appropriate tables, the MAF data being returned to the PCM no longer has any direct relationship to the actual amount of air entering the engine. From that point, all other calculations based on MAF value are going to be incorrect - both Closed Loop and Open Loop. I hope this makes sense. It did to me at 1:00 in the morning. :D |
[B]3) WOT mode occurs at a predetermined point in the calibration and is based on a calculated voltage value from the APP (accelerator pedal position) sensor. This value can be changed to meet the performance need of the vehicle and/or driver.
Bill, About where does this occur (APP) in your standard tunes and custom tunes. I am not an automotive engineer so have only a rudimentary understanding of all the values used and how it changes WOT. I guess what I'm asking is as a rule of thumb is it at 80%, 90%, 100% APP? etc. |
One of the things I love about these forums, and this one in particular, is all the nifty knowledge you can pick up by reading them and asking questions.
Thanks, Bill - that was a super contribution! - Jack |
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I love his long winded posts :) |
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