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Thread: 5.7 Hemi Eagle rev limit

  1. #1
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    5.7 Hemi Eagle rev limit

    I have a 5.7 hemi 2013 that ive retrofitted ina 1972 car using a MP crate PCM.

    It is a std 5.7 with an Inertia 209/2016 .556" cam and 6.4 intake manifold and injectors.

    Initially i left the std 6000 rpm rev limit and at 5800 rpm the car would lean out massively on the dyno.

    We raised the rev limit progressively as the car made max power around 6600 rpm.

    However every time anything up to the rev limit in the tune sometimes 200 rpm before sometimes 600 rpm before it reduces pulse width to act as a rev limit.

    Do these not have a hard cut ignition rev limit or do we rely on a fuel cut leaning us out while its still ramping up in rpm?

    Ive attached a log
    Attached Files Attached Files
    Last edited by L4staero; 1 Week Ago at 05:42 AM.

  2. #2
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    There are tables for fuel cut and several tables for torque reduction (retard and/or throttle). Are you logging throttle position and spark advance? What happens when it starts limiting?

    Also log throttle torque source. See if it shows rev limit or pedal or something else.

  3. #3
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    Quote Originally Posted by spoolboy View Post
    There are tables for fuel cut and several tables for torque reduction (retard and/or throttle). Are you logging throttle position and spark advance? What happens when it starts limiting?

    Also log throttle torque source. See if it shows rev limit or pedal or something else.
    I have been logging throttle torque source. You can see in the log as it nears 7000 rpm it changes from pedal to LV2 (torque monitor) then shortly after it changes to RPM limit and it cuts the inj ms time down while the motor is still ramping up on the dyno and causes a big lean spike. At that point i lift off the throttle when i see the AFR's go lean.

  4. #4
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    I was more hoping there was a traditional hard rev limit i can set as this fuel rev limit is not very safe in my opinion in a race car where you need to turn the motor to 7000rpm.

    Ive been setting the "Cut off" a few hundred rpm higher than maximum table. Maybe i should try doing them at the same value?
    Last edited by L4staero; 1 Week Ago at 05:10 PM.

  5. #5
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    So setting fuel cutoff higher than max RPM still gives you a lean condition near max RPM?

    Limit.JPG

  6. #6
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    Thanks for the reply Homer.
    I set all the cut offs to 8000 rpm and the max RPM at 7500 rpm and it still went lean at 7300 as it ramped up.

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    That's a lot of rpm. Are you still seeing rpm limit for torque source? What is injector DC?

  8. #8
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    What do you have your WOT FA set to at the high end? Your commanded fueling goes from 0.862 to 0.923 just before 7000rpm and just before throttle torque source switches.

  9. #9
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    Quote Originally Posted by spoolboy View Post
    That's a lot of rpm. Are you still seeing rpm limit for torque source? What is injector DC?
    Yes it doesnt even start to roll over til around 6600rpm and has a very flat power/torque curve.

    Yes still seeing RPM limit as torque source and i havent logged Inj DC.

  10. #10
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    Take a look at the torque reduction table that's near the rev limit tables. It should show reduction vs rpm error.