Slimy38
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| posted on 16/4/17 at 07:12 PM |
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Using TorqueApp logs to diagnose a slipping clutch
I have an automatic 9-3 Aero, and I want to try and see if the clutch slipping is normal or whether I have an issue. I am aware that in first and
second the clutch intentionally slips to smooth out the drive before locking, then in third and fourth it locks immediately to put drive power
through.
What I had planned to do was log RPM against speed via TorquePro Android app. My theory was that when the car is locked into a gear, the speed and RPM
would increase at a fixed ratio (the gear ratio). If the clutch is slipping, the ratio would be ever changing.
So plotting speed divided by RPM I expected to see a series of five horizontal lines, each one corresponding with each gear but changing maybe half a
dozen times in the journey (it was a fairly steady drive in a 30, then a 40, then NSL, then back to 30). Instead it goes up and down like a yoyo. As
far as I know it's not changing gear that often, so does that mean I do actually have a slipping clutch, or is my test method flawed?
I can't watch this happen in realtime as I need to be driving, I also can't tell what's happening by ear as I can't tell
whether it's an intentional shift or the clutch is slipping.
(By the way, I am aware that it's a torque converter rather than a clutch, but there's more letters to be typed in clutch converter!).
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gremlin1234
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| posted on 17/4/17 at 12:15 PM |
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the method of testing seems sound to me.
when you are monitoring speed, is this from the obd, or gps?
I tried logging both gps and obd speeds, and gps ones seem to lag.
also note the odb mph is calculated from the kmh value. so goes in steps of about 0.6mph
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Slimy38
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| posted on 17/4/17 at 02:10 PM |
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It was OBD, I did notice it was kmh although that should just change the numbers rather than the graph itself.
I'll have to take it for more of a run and see if the graph makes more sense.
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MikeRJ
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| posted on 17/4/17 at 02:18 PM |
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Are you referring to the lock up clutch within the torque converter? They are normally only engaged under cruise conditions.
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Slimy38
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| posted on 17/4/17 at 03:11 PM |
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I thought it would lock during hard acceleration as well? Or does it just rely on friction to transfer torque?
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scudderfish
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| posted on 17/4/17 at 07:27 PM |
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I created a website mainly for my own amusement that can draw graphs from Torque (and MSDroid/TunerStudio) along with a map. Give it a go, and if it
doesn't work send me the log file so I can debug it 
https://scudderfish.github.io/LogViewer
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