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Discussion Starter · #1 ·
(Challenger scatpack 2017 manual with stainless works long tube headers, borla atak exhaust, comp cam, Diablo tune.)
Hey everyone,
I’m turning to the forums for help on this as I’ve been to three different mechanics all who can’t figure out what’s going on with my car. The issue started a month ago, I noticed that during slow acceleration and deceleration as the Rpms passed just under 2k a “vvvvvrrrrrooooommmppp” sound would come from what seems to be the engine bay and could be heard inside the cabin as well as slight vibration felt in the gas peddle. This isn’t a change in the exhaust note but seems to be a sound generated by something independent of the exhaust. The sound is usually loud and very noticeable when I first fire the car up and then almost goes away the more I drive it through out the day but can still be slightly heard. I’ve been told it may be clearance issues with my long tube headers rubbing something but that’s been checked several times and they are clear. I have stressed concern that it may be the new comp cam I recently installed along side hellcat lifters but I’m being told that if it was those things there would be way bigger issues going on. The only other recent event would be a bad bottoming out leaving a parking lot. Any insight would be helpful!
 

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2015 RT 5.7 M6
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9,785 Posts
Welcome to the forum. I wonder if maybe one of your high flow cats is damaged and the catalyst is possibly shifting? If your tune is on the lean side it is possible the catalyst could have been overheated and the bottoming out of the headers knocked it loose. Just a wild guess.
 

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The Bacon Hauler (‘12 Cop Charger)
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Record the sound and share that out so we can hear it for ourselves
 
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2014 Shaker Boosted 392 Stroker M6
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How can there be a vibration in a drive by wire throttle?
 

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2016 SXT Plus Blacktop
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In the throttle pedal...it's attached to the car, no?

A Guy
 
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2014 Shaker Boosted 392 Stroker M6
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2015 RT 5.7 M6
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Actually, what I am wondering is how were the headers installed? Did the shop remove any brackets, mounts that they might have forgotten to tighten? Also I too run SW headers (2" primary version but on a 5.7) and there is not much space between the floor board and header collector so I wonder if you have worn engine mounts if they might be touching the during accel/decel? Checking the exhaust stationary sometimes makes it hard to find any contact. In fact, my catback (AWE 3") appears to clear everywhere but under the right condition (off idle with a little load) the passenger side pipe just kisses the spare tire well.
 

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Too many variables until we hear the sound. It is tough to diagnose sounds from reading posts as one man's "thud" is another man "bang" or a "squeak" becomes a "creak."
 

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2015 RT 5.7 M6
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Although even if we were to hear the sound (like the SXT thump at start-up or the beep sound after washing their car people have posted on this forum) it still might not be enough to pin point the problem. Hopefully whatever advice you do get from us not hearing the sound does help in your troubleshooting.
 

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Discussion Starter · #10 ·
Although even if we were to hear the sound (like the SXT thump at start-up or the beep sound after washing their car people have posted on this forum) it still might not be enough to pin point the problem. Hopefully whatever advice you do get from us not hearing the sound does help in your troubleshooting.
the comment about a worn engine mount is something I haven’t looked into yet and sounds like it might be a good direction to investigate. I’ll try to get a clip of the sound in the next few days but I appreciate everyone who already commented.I just really hope it is nothing to do with my cam. I’ll post an update soon!
 

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The Bacon Hauler (‘12 Cop Charger)
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the comment about a worn engine mount is something I haven’t looked into yet and sounds like it might be a good direction to investigate. I’ll try to get a clip of the sound in the next few days but I appreciate everyone who already commented.I just really hope it is nothing to do with my cam. I’ll post an update soon!
If there were a problem with the cam, there would be drivability issues which would force a diagnosis and require a resolution with continued driving.

If the NVH was not there before all the mods but is now with all the mods, it's a safe bet either one or a combination of the mods (or their installation) is the root cause. Without more detailed info or a sound clip, the best you can hope for is a bunch of guesses from members here.

My guess is it's a resonance/harmonics problem with the new exhaust hardware. It doesn't have to be the exhaust that's making the noise, but the exhaust could be causing whatever is making the noise to vibrate at just the right frequency to make the noise.
 

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My guess is it's a resonance/harmonics problem with the new exhaust hardware. It doesn't have to be the exhaust that's making the noise, but the exhaust could be causing whatever is making the noise to vibrate at just the right frequency to make the noise.
Well around 1500-2000 rpm is usually the drone sweet spot on a manual...if the catback has no resos and no provision for exhaust flaps.
 

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2020 Dodge Challenger Hellraisin Scat Pack
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What ChallyTatum said. Another car of mine had some road debris -- piece of cinder block -- bounce up and just so happen strike the converter housing. Hard enough to leave a pretty substantial gouge in the stainless steel housing.

This impact caused the converter "brick" to come loose. The converter worked ok most of the time but once in a while would shift position and then generate a P0430 error code. Upon cool down the brick would return to the correct position and the error code when cleared would stay away. (If I didn't clear the code it took a good number of warm up cycles before it would be cleared by the engine controller.)

Lived with this for a some years.

But at some point I noticed a dull deep knocking sound upon cold start. When warm the brick would buzz. Sounded like a piece of sheet metal was loose. Finally broke down and sourced two used converters and had these installed. Ahhh, peace and quiet once again.
 
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