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Discussion Starter · #1 ·
I did a couple searches but didn't come up with answers, and I think my questions would be pretty common. I started doing the downpipe for my Durango and found myself doubting if I chose the location right.

-Just how close can the downpipe be to the firewall of a typical modern vehicle (with carpet, insulation, and heater boxes inside the firewall) without any protection (such as header wrap, insulation, etc.)? How close can I get with header wrap? How about header wrap and some sort of heat insulation? I did my best to get the downpipe to clear the firewall, but the best I could do is about 1/2" of clearance about 5" down from the turbo. The heater box is just inside the firewall at that point, so dimpling the firewall is out of the question, and I don't want the heater box melted!

The next question has to do with flex pipes. I see them on diesel exhausts all the time, but not all of them. My Ram came without any type of flex pipe, so I know they aren't absolutely necessary. I'm just wondering if having a flex pipe between the downpipe and exhaust pipe would help isolate engine vibrations? I have a 2.5" Mac exhaust on the Durango already, I'll be replacing the cat with a piece of straight pipe, and I'm considering putting 12" or 18" of flex pipe between the downpipe and exhaust. If its not necessary I won't bother, but I do want the least amount of vibration and noise I can get.

Jim
 

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but the best I could do is about 1/2" of clearance about 5" down from the turbo.

That is enough if wrapped. use 2" wide wrap and overlap 1" each turn so it is always double thick.

The flex is an excellent thing to have, these 4BT's will REALLY shake a solid exhaust system.
 

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The exhaust can be close as 1'' before heat starts to melt but some material may melt sooner.

The flex pipe isn't needed as long as your exhaust is mounted on rubber hangers .

Scott
 

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Discussion Starter · #4 ·
Thanks. I have header wrap already (2") because I was sure I would be using it. I'm also planning to get some of the reflective heat insulation to put on that section of the firewall. Hopefully the combination will ensure there are no problems. I hope to get the downpipe finished up today.

Jim
 

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The flex pipe isn't needed as long as your exhaust is mounted on rubber hangers
Hmmmm......I dunno. I basically took the stock 92 Dodge Cummins systems and chopped it up and re-welded to make it fit my F250. No flex pipe.

At idle, the exhaust tip REALLY shakes a lot. Kind of like how you can hold a willow branch and jiggle it a little, the tip moves a lot. I guess I would have to keep an eye out for cracks, but I think I'll just add one of the $30 braided flex joints into the system.

 

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I wish I had a photo but I chopped my exhaust and put a really tight little bend in there to get more room. Seemed to work well and no performance loss. I also used heat tape. This was with about 1" of room. My second vote is swapping manifolds and this moves the turbo around. This is the best, but most PITA route. That GM manifold sure puts it in an annoying location...
 

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Discussion Starter · #9 ·
Or Napa, for about the same price. Roughly $35 IIRC. I will most likely add one of these in after I get it up and running (and tested).

Jim
 

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The ones I have used at work come from Walker. They are accordianed(?)/ribbed metal on the inside and braided steel on the outside.
 

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I wrapped my down pipe it was melting the Fatmat that I put on the firewall for noise. I also just installed a Flex-joint in my exhaust system right after my down pipe. Before the flex-pipe the exhaust would rattle on my Jeep and also it was ripping the pipe where I welded a hanger to the pipe. I purchase all the piping and flex-pipe from the following place.. http://www.verociousmotorsports.com/
 
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