Why does the sound of a 5.7L HEMI change when ~ 3500RPM

Discussion in 'General Off-Topic Chat' started by Dominator211, Sep 8, 2019.

  1. Dominator211
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    Dominator211 JFK's Jelly Donut

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    I thought I would put it in General off-topic chat sine EOF seems like its more of a general meme than a serious question. Well, anywho I've asked life questions along with hundreds of other questions on here so here is an automotive one. I have seen many videos about my favorite Chrystler engine the 5.7L HEMI V8 and I have one question in several videos I have seen once the engine reaches anywhere from 3000 - 4000 RPM it seems like the engine changes pitch, it seems like the range is really 3500 to 4000 with older vehicles changing pitch earlier and newer ones closer to 4000RPM. Why does this noise change happen?



     
  2. ThoD

    ThoD GBATemp Addict (apparently), but more like "bored"

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    All rotary car engines change pitch at higher RPMs, more pistons are used (low RPMs don't use all the pistons), higher torque means more rotations and more rotations means different sound because of change in airpressure (rotation speed is higher than speed the air is pushed out from the chamber causing buildup) so pitch changes, plus exhaust also plays a role in it (more airpressure means more thick exhaust fume so deeper sound).
     
  3. The Real Jdbye

    The Real Jdbye Always Remember 30/07/08

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    You can literally hear the RPM on any sort of motor, you might have noticed that with computer fans, where the small ones have a higher pitched/more annoying sound because they need to spin faster. Or even just when you start doing a heavy task and you hear the pitch change as the fans spin up, that's especially noticeable on laptops.
     
  4. Dominator211
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    Dominator211 JFK's Jelly Donut

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    well its the coolest shit to me, its kinda like "MAXIMUM OVERDRIVE!"
     
  5. raystriker

    raystriker The powers that be

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    lmao what drugs are you on. Rotary engines are different from piston engines. Damn I don't even want to bother correcting the rest.

    Any difference in exhaust you see is due to the different tuning.
    Cars and SUVs/Trucks have differing needs in power delivery. The heavier you are, having more torque will do you good. Hence, SUV applications of engines in popular cars usually have different power/torque outputs. (eg, the Ford F150 and Mustang.)
    One simple way for having different power/torque bands is by having a different exhaust design. Another way that could lead to having a different sound is by having different cams and air intake, head design etc.

    Edit: The Charger video literally has an aftermarket catback exhaust.
     
    Last edited by raystriker, Sep 9, 2019
  6. Dominator211
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    Dominator211 JFK's Jelly Donut

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    yes yes I charger has aftermarket exhaust, my dads old 2012 RAM 1500 had aftermarket as well and I heard it do the pitch thing before he got rid of it
     
  7. raystriker

    raystriker The powers that be

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    You like higher pitched sounds? Usually americans love the V8 because of the "rumble", but I see most of them try to emulate the higher pitched sounds of a flat plane crank euro/japanese V8/V10 or V12.

    Here is what happens when you destroke and let the best american V8 ever, the LS7, rev to 8500rpm
     
  8. Dominator211
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    Dominator211 JFK's Jelly Donut

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    I love the rumble too, the pitch change really makes it sound like its getting ready for buisness
     
  9. raystriker

    raystriker The powers that be

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    Then you might appreciate this
    I assume you've heard the LFA V10?


    Still pick the 5.7 Hemi over that?
     
    Last edited by raystriker, Sep 9, 2019
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