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Why Exhaust Pipe "expansion Joint"

spikesputnik

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spikesputnik Enthusiast

spikesputnik

Posted
Posted

So I'm under the truck this week sizing up the install of my new system/removal of the OEM, and the flexable section of exhaust pipe between the cats and muffler catches my attention. I noticed that as I rock and wiggle the cat-back, this section flexes and gives quite a bit, allowing the entire catback to move indepentantly of cat-foreward.

So I can understand why GM does it. Why does the aftermarket not, other than expense?? ( it is a impressively designed and crafted peice, IMO)

Has anyone ever left this section there and had their aftermarket exhaust system grafted on to it?? Seems that would be the best of both worlds? Otherwise (and how the aftermarket does it,Magnaflow in my case) from the engine/headers to the tail pipe tips is one ridgid tube with no designed flex sections. Of course the engine and system are both isolated from the frame via various dampers and hangers, but still it is one loooong bolted together peice with no designed releif.

 

Comments?

 

Oh yea, and did I mention that mysystem has arrived :thumbs: It's purrty, seems too much so to put on the underside of the truck! Can't wait till saturday!!!

66nova Senior Enthusiast

66nova

Posted
Posted

I'm guessing your new system doesn't have just due to length. Since it comes out before the rear wheel.

 

I know the Corsa system do come with it.

spikesputnik Enthusiast

spikesputnik

Posted
  • Author
Posted

Well, there is about a 4' section of more or less straight pipe into which an expansion/isolator could have been inserted.

I guess I'm starting to see some of the "economy" of the Magnaflow already...while it's still sitting on the living room floor.

 

Questions are- How necessary is such a isolator or whatever it's called?? Is it overkill? Worth the hastle of grafting?

 

 

 

Watch this vid Kluge provided. When he leaves the concrete pad it looks like there is a downward bounce to the system, maybe even a clockwise torsion(as viewed from behind). While the hangers can take care of the up and down motion, if there is torsion ,too, that force will be applied to the clamped junctions...hmmmm. But then again, if there were a flex joint, it would not provide any rotational stability as the straight pipe does. Just something to chew on.

66nova Senior Enthusiast

66nova

Posted
Posted

I really can't see it being that big of deal for your system. I don't have any flex joints on my nova, and I am quite certain it has a lot more vibration/rotation then our trucks.

 

Magnaflow may not be the price of Corsa, but they are still a very high quality company/system. I would not be concerned in the least. Plus, the system has a lifetime warranty on it.

 

I'm not worried :thumbs:

spikesputnik Enthusiast

spikesputnik

Posted
  • Author
Posted

Eureka!! :thumbs: That's where the muffler bearings are, or should be, in order to relieve that torsional stress on the pipe section! :wtf:

66nova- yea your Nova shakes more for sure. I watched/listened that vid you posted-nice!

Darkanion Senior Enthusiast

Darkanion

Posted
Posted

If we're talking about the same flex-piece, they can disconnect the front portion of the exhaust from the back portion to assist in easier access to the transmission, during repairs. I doubt that is its only purpose. But, that is one I was informed of a few months ago..... :thumbs:

brims Senior Enthusiast

brims

Posted
Posted

Vehicles didn't have that flex joint in the exhaust before, not sure when that started, but there were never any issues without that piece so I wouldn't worry about it.

ajcain79 Enthusiast

ajcain79

Posted
Posted

My guess is that it is there to reduce noise and rattles from vibrations. When a louder exhaust is installed the sound of it will cover any rattles/vibrations. Therefore the piece is not needed.

Sounds feasable, right.

502chevy Enthusiast

502chevy

Posted
Posted

my theory is that the flex pipe allows pressure to be taken off of welded parts of the exhaust and where it has a flange bolted together. i have had welds crack on high end headers and the only reason i could find that it happened was because when the exhaust would "bounce" then there would be nowhere for the pressure to go and it would stress these joints and caused the crack in my situation. my situation is a very rare one but it did happen and i believe it to be from the solid piece of pipe going from the engine to the tailpipe. now did i add a flex pipe, no. and i probably would by an exhaust that didn't have one because the likely hood of that happening is very rare. plus i don't plan on putting headers on the truck because of maintenance involved in keeping them tight. and i don't believe it will hurt the stock y pipe or manifolds. so i wouldn't worry about it, i just thought i would share my experience for what its worth.

Mr_Rooney Enthusiast

Mr_Rooney

Posted
Posted

The flex section is used to separate the powertrain vibration modes (roll in particular) from the exhaust system vibration modes (lateral modes.) If the two systems couple up, you feel it and complain to the dealer.

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