Diesel Bombers - 12 valve with a terrible fluttering paper bag sound from exhaust. HELP!!!

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- 12 Valve 2nd Gen Dodge Cummins 94-98 (https://www.dieselbombers.com/12-valve-2nd-gen-dodge-cummins-94-98/)

- - 12 valve with a terrible fluttering paper bag sound from exhaust. HELP!!! (https://www.dieselbombers.com/12-valve-2nd-gen-dodge-cummins-94-98/135603-12-valve-terrible-fluttering-paper-bag-sound-exhaust-help.html)

It does flutter with a load but becomes less noticeable in higher gears at higher rpm, It’s most noticeable at idle for sure. As far as a resonator goes I feel like the flutter would still be there just masked more, I’m trying to eliminate the flutter all together even with it straight piped. I’ve heard plenty of 12 valves straight piped without any type of fluttering I’m encountering, there has to be an underlying issue.

You said you've had this noise from day 1, then you said you've had it since the HX35. Has it had the HX35 since day 1? Just trying to get this straight.

Yes I’ve had this problem since day one with the HX and the problem persists even with the he351, both turbos same issue.

Oh, I see. I misunderstood. Hopefully someone else comes through, because this makes no sense to me at all.

That sound clip would help. Because I , like many others that have read your post, don't know what sound you're chasing. Could be something simple. Could be something huge.

Considering all of the changes that you have made to the tuck and it still has the sound. I would start with a compression and a leak down test. Just to eliminate a base engine issue. Its also possible that you have an injection pump issue. But there's no way to tell without hearing it ourselves.

While I don't see this being it, have you ever verified the timing on the truck? I've seen timing do funky things.

Thanks for the response Crawler. Yes I need to figure out how to upload a video, I know it would make this a lot easier if it could be heard rather than just what I’m trying to explain. And yes I did the timing myself shortly after the injector and delivery valve install, I bumped up to 18 degrees from 14 and the truck was at factory timing before I did the bump and the flutter was there before and continues to be so.

Still no luck yet!!!

anybody out there maybe have any new clues on what the issue can possibly be. I can better explain the sound as like an exhaust leak inside the exhaust and out the stacks. Very strange exhaust tone. Would incorrect valve adjustment cause such an issue. I’ve lashed the valves twice now since I installed a new head so I can’t imagine that’s it but just a thought.https://share.icloud.com/photos/0ac6...#Las_Vegas,_NV

Here’s another video with the down pipe on out the back to just before the Y pipe to the stacks. I know this is not how a 12 valve is suppose to sound. I hope you all can hear what I’m talking about.

https://share.icloud.com/photos/0QWG...#Las_Vegas,_NV

Mine sounds like that until it warms up, Are you still on stock governor springs? if so changing to 3k springs will help.
What do you idle at?

I did some thinking, that fluttering sound is the interaction of your exhaust gas with the turbine wheel, at cold start my truck idles at 400 rpm, exhaust flow is not great enough to accelerate the turbo to a sufficient speed where it doesn't disturb exhaust flow, but as the engine warm up the exhaust drive pressure increases speeding up the turbo to a point where it doesn't impede exhaust flow and just sounds smooth with a nice whistle.. Thats why no matter what turbo you put on there that 12 valve will do that. Mine did it with a HX35 and does it with a Cheetah.

Try jamming something in the turbo to prevent it from spinning and see if the sound is still there. No amount of drive pressure will over come a piece of metal holding it static.

TL:DR

nothings wrong with your truck, its a completely mechanical turbo diesel and its normal with no temperature or barometric pressure compensation. stop worrying and drive it.

Just so you dont think I'm bullshitting, I'm a jet engine mechanic, turbo's are my life, knowing how this stuff works and interacts is my job(I made an account just to type in this thread)... I thought about this for awhile before posting. The other trucks you hear are probably have a high idle, my Idle is set to 750 RPM AC off.