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Thread: Lightweight Button Clutch Stalling Help - 20 lb rotating assembly

  1. #1
    Lifetime Member Kevin Doe's Avatar
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    Default Lightweight Button Clutch Stalling Help - 20 lb rotating assembly

    I just switched clutch setups from an already light setup using a Fidanza aluminum flywheel and Spec 3+ clutch (40 lb assembly), to a Quartermaster 7.25" twin plate on a button flywheel and flex plate (20 lb assembly). I'm having a lot of stalling issues that I've been unsuccessful in resolving on my own.

    Background: My car is a 1993 Mazda RX-7 with a 2004 GTO engine/trans/PCM. The car is more or less a race car at this point. I've been racing it now for 10 years with more or less the same tune. The tune felt very dialed in, and had great manners (while racing, driving in the paddocks, and the occasional street cruise if the event called for it). Between the old and now, here is a list of everything that changed on the car: Clutch assembly (-20 lbs), ATI Super Damper (-2 lbs), Faceplated transmission.

    I've been playing with the throttle cracker, throttle follower, idle underspeed error timing, desired airflow, desired idle speed, etc with no success. My primary issues are stalling in two scenarios. Comparing the two attached tune files will show a complete list of things I've changed.

    1. When coming to a stop while driving. Sometimes, but not all the time, when I push in the clutch while coming to a stop (~20 mph and under) it just goes to 0 rpm. Doesn't even seem like it tries to catch itself.
    2. While stopped, and reving it up. This often results in a stall when I'm attempting to get the car rolling to back out of the garage. I give it some gas, and when the RPM comes back down it undershoots. Sometimes it recovers, sometimes not.


    I've attached a few things:
    1. FD_190509_FidanzaSpec.ctz - This is tune for the old clutch, which was my baseline.
    2. FD_190713_0010_QuarterMaster.ctz - This is the most recent tune I've tried with the lightweight clutch.
    3. 190714_0001_cruise.efi - The log file goes with FD_190713_0010_QuarterMaster.ctz tune file. It is a ~15-20 minute drive.

    In the log there are several stalls in each of the categories I'm having issues with. Any help would be appreciated.

  2. #2
    Joe (Moderator) joecar's Avatar
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    I'm looking at your files...

  3. #3
    Lifetime Member Kevin Doe's Avatar
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    I've made some really good progress the last few days. Here are the things I've changed:
    1. Decreased the direct airflow correction a touch for low rpm.
    2. Increased throttle cracker at 1000 rpm.
    3. Decreased throttle cracker decay rate, and increased the decay delay.
    4. I added ~1 degree of timing around idle.
    5. Raised the DFCO enable and activate for 1st, 2nd and 3rd gear.


    Probably the most beneficial thing I did was move out the DFCO. With the reduced moment of inertia of the clutch, it was really dropping fast when I pushed in the clutch. By the time the timing was back to normal the rpm was already below idle. Moving DFCO up and out of the way really eliminated the stalls while pushing the clutch coming to a stop. The end result was no stalls but still a few issues. The main issue is overshooting correcting the return to idle, causing oscillations, mostly above idle speed. I also had an issue when the engine was cold, and I was rolling down my driveway. The idle corrections were not yet active and the engine nearly stalled.

    FD_190716_0001.ctz - This is the latest tune I've logged data on
    190718_0001_cruise.efi - This log goes withe FD_190716_0001.ctz tune

    FD_190718_0001.ctz - This attempt, which has not yet been driven, has:
    1. Removed some throttle cracker at 400 rpm.
    2. Pushed out DFCO enable and activate speeds in 1st 2nd and 3rd.
    3. Added 1 more degree of timing at idle.
    4. Decreased min idle learning temp from 160 to 140F.

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