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Discussion Starter · #1 ·
Does anyone make a downpipe for the Dmax that has a vibration damper built into it?
 

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This is an up pipe, but you can see the vibration damper in it. It's the accordion looking section in the pipe.



Just wondering if anyone builds these into down pipes. With all the harmonic humming that occurs in the exhaust of these trucks it would seem lile a simple solution.
 

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I don't think the bellows are build into the up pipes for vibration reduction. I thought the bellows were for dealing with exhaust pressures?

also the stock downpipe is bolted to the turbo and bolted to the exhaust manifold, it cant really vibrate. the rest of the exhaust system is rubber mounted.
 

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The bellows are for heat expansion, contraction and exhaust pressure, these short pipes take a lot of heat/stress under load when towing, Profab make a set of uppipes.
 

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The bellows are designed exactly like a vibration damper. They both allow flex of the pipe.

I believe the down pipe is bolted from the turbo to the rest of the exhaust system, not the manifold.

They are too stiff to expand just from exhaust pressure, I believe, and if for heat, why is there only one shown with the bellows on them whenever you see a set advertised?

It could be for all of the above. Trust me there is less vibration being transmitted from the exhaust manifold to the turbo, than there would be from the turbo to the rest of the exhaust system. The up pipes do not need to move since they are bolted from solid point (manifold), to solid point (turbo) but the down pipe is bolted from a sold point (turbo) to a moving point (main exhaust system) so engine vibrations would be transmitted through the down pipes. GM even had TSB's on this issue and not just for diesels.

I turned in a 2006 GMC 1500 (CA lemon law) for this very same issue that they could not resolve. That truck had other issues as well, but the vibration on it at 55 mph was incredibly annoying.
 

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The bellows are designed exactly like a vibration damper. They both allow flex of the pipe.

I believe the down pipe is bolted from the turbo to the rest of the exhaust system, not the manifold.

They are too stiff to expand just from exhaust pressure, I believe, and if for heat, why is there only one shown with the bellows on them whenever you see a set advertised?

It could be for all of the above. Trust me there is less vibration being transmitted from the exhaust manifold to the turbo, than there would be from the turbo to the rest of the exhaust system. The up pipes do not need to move since they are bolted from solid point (manifold), to solid point (turbo) but the down pipe is bolted from a sold point (turbo) to a moving point (main exhaust system) so engine vibrations would be transmitted through the down pipes. GM even had TSB's on this issue and not just for diesels.

I turned in a 2006 GMC 1500 (CA lemon law) for this very same issue that they could not resolve. That truck had other issues as well, but the vibration on it at 55 mph was incredibly annoying.

the down pipe has a flange on it that bolts it (albeit with one bolt) to the manifold.

everything on the motor properly fastened, the up pipes and downpipes are not moving.
 

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Here are all three of the heat expansion bellows on a LBZ motor.....
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Down pipe connection on a stock truck disconnected
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After market down pipe
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The bellows on the up-pipes are to allow for metal expansion when the engine warms up. Since the pipes are all hard mounted to the block, the heads, block and manifolds all expand. If there were no bellows, those pipes would crack due to the expansion of the heads/block/manifolds. They're not for vibration. Theres no bellows on the DP since it's mounted solidly on one end and the rest of the exhaust is able to move.
 

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This is an exaggerated example of pipe expansion, watch the pipe after the turbo going to the outside of the building/dyno room starting around 12 seconds in the video...

https://www.youtube.com/watch?v=_pn4Q-s3Sas

Most of the vibration you have is inherent in a 90° V8 design engine. 90° does not divide equally into 360° degrees so the end result you will have an inherent vibration. In a horizontally opposed engine it does not exist as much when you have two opposing cylinders.

https://www.google.com/search?num=1...jcoATMnYLoBQ&ved=0CBwQvwUoAA&biw=684&bih=1146
 
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