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Thread: 2015 Coyote: "Piston Rattle" table

  1. #1

    2015 Coyote: "Piston Rattle" table

    I'm still new at this for please forgive me asking perhaps a stupid question. I was going through my stock tune and comparing it to FRPP 3 and noticed that the "Piston Rattle" tables were zeroed out in the FRPP tune. The stock tables have quite a bit of retard built into them. If it's just to eliminate piston rattle noise, then I'd prefer more power over noise

    Is this something I can safely zero out? Or would the FRPP (For whatever reason) compensate by adding retard somewhere else?

    I should add that the FRPP 3 is a poor tune for me to compare to because I am still running the stock manifold and stock throttle body (But with a steeda cold air intake). I can't find a FRPP 1 or FRPP 2 tune in the repository. (If anybody has one to share, I would greatly appreciate it).

    Thank you for your thoughts!

  2. #2
    Advanced Tuner
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    Its safe to zero out. Piston rattle is when the piston bounces off the cylinder walls instead of going straight up and down..

  3. #3
    Thank you, I just saw the reply.
    Sorry for asking a lot of probably stupid questions, I'm trying to learn. Thank you in advance for any information you have provided me

  4. #4
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    Quote Originally Posted by Thatwhite5.0 View Post
    Its safe to zero out. Piston rattle is when the piston bounces off the cylinder walls instead of going straight up and down..
    Sorry for my ignorance but isn't that going to hurt the engine?

  5. #5
    Senior Tuner veeefour's Avatar
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    Quote Originally Posted by mudar View Post
    Sorry for my ignorance but isn't that going to hurt the engine?
    Tuning will hurt your engine in general.

  6. #6
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    Quote Originally Posted by mudar View Post
    Sorry for my ignorance but isn't that going to hurt the engine?
    Its normal for pistons to rattle to one degree or another, it mostly goes undetected, and causes very minimal wear, but engines need proper clearances, and things tend to take the path of least resistance when pressure in the cylinder isn't consistent.
    Piston rattle to a degree that it registers as detonation usually only happens when something is already worn out. Usually only high mileage engines are prone to it. With hypereutectic (hypoeutectic) pistons, low temperature can cause it as well. They use a lower silicon ratio than normal hypereutectic pistons, making the high compression pistons less brittle, and more resistant to detonation. The low silicon ratio requires higher clearances at lower temperatures because they expand more when warm. That can lead to rattle when the engine is cold. I'd take a slightly noise prone engine to "glass pistons" any day.

    This table is not a limit to spark advance, nor is it to prevent a physical phenomenon of the piston. More of a limit to spark retard.
    Because piston rattle and detonation both will trigger the knock sensors, as they make the same noise, this table just defines an area prone to the piston rattle, and sets a minimum advance the knock retard can go below the MBT/ borderline values. Its kinda right where the transition from MBT to detonation limited is defined. Zeroing it out basically makes every noise in the range show up as detonation even if it could just be piston rattle from the high clearance tolerances. You could end up with less advance from the "false knock" thats actually just piston rattle. Very safe, but not very good for performance. It wont damage the engine in any way making the values lower. Making them higher it could mistake detonation for piston rattle, and that could damage the pistons.

  7. #7
    Thank you murfie, I've been reading a lot of threads that you have contributed to and I'm always learning from them. I know the LS engines a while back had pretty bad piston slap, I think some of it has to do with the rod to stroke ratio or how high the piston pin is compared to the skirt below it, at least that is what I seemed to remember because of the piston's rocking tendency.

    Maybe FRPP zeroed them out because they were running a pretty aggressive calibration from the get go, and didn't want to filter out any possibilities? I do notice that they use a cylinder based knock instead of the global that my stock GT has.
    Sorry for asking a lot of probably stupid questions, I'm trying to learn. Thank you in advance for any information you have provided me