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Thread: 6R80 6F55 - Over-revving / commanded shift points??

  1. #21
    Tuner JaegerWrenching's Avatar
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    Quote Originally Posted by metroplex View Post
    So, OSS= (Turbine Speed * ISS ) / Gear Ratio?
    No he's saying your input into the transmission is the Turbine speed. The turbine is driven by the Impeller which is bolted to the flex plate and always the same as engine RPM. Turbine speed is what the transmission is actually seeing for input speed but it's not physically connected to the engine unless the torque converter is 100% locked, thus your OSS or output shaft speed is going to be calculated by taking Turbine or "input" divided by the current gear ratio. Of course you can have clutches slipping which change this. But The ratio is determined by any combination of planetary gears selected, thus giving you your final OSS drive ratio. The formula is INPUT/Gear ratio = output, or turbine/current gears ratio=OSS. If the converter is 100% locked you can use engine RPM, otherwise you must know the slip amount in RPM or the turbine's RPM to target a specific shift point. This is why you're commanding a "lower" RPM and it shifts where you want. This means your converter is still slipping which is why veefour said to lock it up faster and sooner. I can't log my turbine speed so i am tossing rocks in the wind if my converter is unlocked or slipping during the shift. This video helps illustrate what's going on. https://www.youtube.com/watch?v=bRcDvCj_JPs
    Last edited by JaegerWrenching; 6 Days Ago at 06:38 PM.

  2. #22
    Advanced Tuner metroplex's Avatar
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    that's what I thought but his use of parenthesis confused me. Well most Ford autos can't lock the TCC in 1st gear and 2nd gear can be iffy. That explains why 3rd and above work better. But again that WOT table didn't have any effect on the newer transmissions and the factory had it set wrong from the start!

  3. #23
    Tuner JaegerWrenching's Avatar
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    Quote Originally Posted by metroplex View Post
    that's what I thought but his use of parenthesis confused me. Well most Ford autos can't lock the TCC in 1st gear and 2nd gear can be iffy. That explains why 3rd and above work better. But again that WOT table didn't have any effect on the newer transmissions and the factory had it set wrong from the start!
    Try playing with clutch fill time after setting your OSS slightly higher or get the converter to lock 100% before the shift and see how clutch fill affects it. Remember if the clutch fill is set to a longer time and the clutch fill actually completes quicker the shift will occur.

  4. #24
    Advanced Tuner veeefour's Avatar
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    Quote Originally Posted by metroplex View Post
    that's what I thought but his use of parenthesis confused me. Well most Ford autos can't lock the TCC in 1st gear and 2nd gear can be iffy. That explains why 3rd and above work better. But again that WOT table didn't have any effect on the newer transmissions and the factory had it set wrong from the start!
    Yeah I use lyrics...

  5. #25
    Advanced Tuner metroplex's Avatar
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    After looking at my old logs (6F55 all seem to have the OSS pid), the OSS in 1st and 2nd takes into account the delta between engine RPM and input shaft speed, which can be between 200 and 400 RPM. So basically I had to lower the OSS tables at WOT for the 1-2 and 2-3 to match the data from the logs and now the 2-3 is happening at the right engine RPM. Bottom line is that the WOT tables weren't being used. My Fusion Sport factory OSS tables commanded 6500 RPM shifts while the WOT tables were 6250. This resulted in banging against a limiter at 6500 plus RPM most of the time, with the occasion short shifting no rhyme or reason. Definitely not the same as the 2014 6F55 tuning