Knock readings on low load

Discussion in '2007+ Mustang GT500 Tech' started by luillo, Jan 18, 2021.

  1. luillo

    luillo forum member

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    S197 team i have been monitoring my 2013 GT500 for some time and noticed that the nGauge reads knock very often but only in 4th and 5th gear at a very low load. Anything from .25 to 5 degrees specially in 4th gear at 2K rpm. While cruising is all fine, it starts reading once i slowly press the gas pedal and start climbing up in revolutions. All very light and slow climb until it hits 2,500 or 2,600 rpms and stops reading any knock.

    Some times it also reads in 5th gear around the same 2K rpm. If I am in 4th gear and start gassing up the car and reads knock i let off a little then back on it and it wont read any more knock then i can gas it harder past 50% throttle and is mostly fine.

    I use boostane in every fill of 93 octane to up it to around 97 octane. Change the plugs on every oil change TR6 gapped first at .032 and now to .035. I will next do a full exhaust check and anything else that could be touching or tapping around but doubt ill find anything, i have been under the car many times and it all looks good.

    Anybody has experience anything similar? I just want to see if i have to baby this car to ensure the engine last until i can finish current upgrades before any build.
     
  2. eighty6gt

    eighty6gt forum member

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    This sounds normal to me, at low rpm and high load, the car will want to knock, the sensors tell the ECM and it takes out timing.

    I do not apply much throttle at all to my blower motor below 2500 rpm. Launching in 1st I slip the clutch/tires to make sure the load isn't excessive. Acceleration is still limited by traction.
     
  3. luillo

    luillo forum member

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    Thanks for the info. I was thinking it was normal because it always happens under the same conditions and no other so sounded like it was some type of mechanical situation. I am not very informed about what is normal or not so I figure I'll ask.

    I can hammer the gas above 3K rpm and the knock reads negative and have no issues so i figure is fine if the ECM is giving me timing otherwise.

    Why did you say at low RPM and high load the car wants to knock? why would that be? is it that the engine cause resonation or vibrations under those conditions?
     
  4. eighty6gt

    eighty6gt forum member

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    Low rpm, everything is moving more slowly, a lot easier for the flame front to catch up to the piston. You don't want to light things off early. Load is comparatively high at low rpm, cylinder filling is incredible with a positive displacement blower, you can have a heavy duty charge in there, lots of fuel.

    N/A engines are still affected by "lugging" but not as much.
     
  5. Juice

    Juice forum member

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    Yes, low rpm and light load is the most knock inducing operating range. As it has been said, everything is moving slower, and the pcm adjusts timing based on knock. Sounds about right as to what you are seeing. It also sounds like the pcm is adding timing on high rpm/load situation. Also a good thing. Theretically, some timing could be removed where you are seeing knock, and some timing could be added up top. But IMO, let the pcm do it for ya and keep things safe.

    This is NOT the same as high load detonation due to low octane fuel or an overly aggressive tune.

    Ps: I actually saw timing on mine go to 2* ATDC on light loads and high gear. But that has been fixed since I got Pro Racer/Advantage software.
     
    Aerofinz likes this.
  6. luillo

    luillo forum member

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    Thanks for all this information. It’s been very helpful as I thought it felt normal and yes I agree at a low rpm felt as if things could be kind of loose in my opinion but I thought that was my bro-science.

    Good so I should mostly worry about any knock on top, at higher rpm if any correct? My car does great with Lund tune on that side.

    Thanks again guys!!


    Sent from my iPhone using Tapatalk
     
  7. Juice

    Juice forum member

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    Keep running good fuel, and and if it runs good, don't worry about it. Sounds like the tune is working like it should.
    Get used to how your car feels/runs/behaves. Worry if you notice a change.
     
    Aerofinz, jewc75 and crjackson2134 like this.
  8. luillo

    luillo forum member

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    Got it, thanks for the advice, it gives me big piece of mind.


    Sent from my iPhone using Tapatalk
     
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