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

Dominator211

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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?



 

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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).
 

The Real Jdbye

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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?




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.
 

Dominator211

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

raystriker

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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).
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,

Dominator211

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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.
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
 

raystriker

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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
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
 

Dominator211

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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

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

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