Flex Pipe

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Howdy gang;
Last week I was in a parking lot and saw a peterbuilt sitting there, I looked over and saw that it's stacks were connected to the rest of the system ala what looked like stainless flex pipe. I am thinking about putting some stacks on my truck and I was thinking that instead of fooling around with a good dozen 4" pipe bends, how about Flex pipe for the curves?
What do yall think? Any pros vs. cons of using flex pipe vs. curves? Most of the curves to set up the stacks will be pretty much out of sight in the bed, so looks aren't really a concern, but $$$ is, any idea of how much this stuff costs?
Thanks guys, Josiah

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Y2K 2500, 4X4, Auto, Quad Cab, SWB, 4. 10, Black. VA Box, Line-X, PE Roll top bed cover, Stainless add-ons.

 

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The con would be the turbulence the ripples in the flex pipe would create. The pros are that the system should last longer with the flex, if you are not looking to cool down your EGT's then the turbulence does not matter. My system with all 4" mandrels was in the low $700's. This is stacks and all. Good luck, Eric

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'98 ext cab 4x4. Skyjacker 4. 5" lift w/ 36" swampers. 370 injectors, pump done right, psychotty air, HX40 18. 5 housing, JRE stage III fuel plate, McLeod dual disc street clutch-"Mitchellized", ISSPRO gauges, 4" black smoke puffin'-hear me CUMMIN chrome stacks. A member of the best brotherhood around-GLTDR.
**Skyjacker raised**
**Cummins praised**

 

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The following is quoted from the Donaldson Heavy-Duty Exhaust catalog. "Flexible tubing's function is to prevent excessive stress on exhaust system components by absorbing vibration and thermal expansion that would otherwise cause system components to shake loose and break. To provide adequate flexibility, flex tubing should be installed in a half extended state... . Do not use flexible tubing to form an exhaust pipe bend. Use elbows instead. "

I once thought flex tubing was to make bends, until a heavy truck mechanic informed me that it should be used straight only and I later read the above in the Donaldson catalog I just got.


[This message has been edited by Koa Man (edited 07-07-2000). ]

 

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I use it on my stock exhaust to reduce the vibration drone in the exhaust. It works. But get the good stainless flex pipe from Napa or another good source with stainless band clamps.

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Steve McDaniel, IUEC local 74
98 2500 "Buckwheat" CC 4X2 12v 5spd 4. 10, Comanche 245/75R16Es, Monroe LT Plus shocks, Silencer ring removed, Stainless exhaust flex coupling. VDO boost and pyro gauges. AFC tweeked just alittle.
97 Dodge Stratus 150HP
92 Harley Fatboy, Dynojet fuel management, Supertrapp 2-1

 

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Thanks guys.
Eric, I really like your system and I guess I'll just bite the BOMB and use solids.
Hey KOA man, did your mechanic or the Donaldson catalog say why you shouldn't use them for bends? I can't rally think of any reason not to, but I'm not an expert on exhaust so my opinion might only be worth $. 01 lol.
Again, thanks guys. Josiah

 

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Big U, no, the Donaldson catalog did not say why and the mechanic I talked to said turbulence and prone to breakage on bends. I just looked in the Nelson Exhaust Products catalog and it says the following about flex hose (pipe): "The minimum bend radius refers to the amount of deflection that the hose can structurally tolerate, however, flex should be installed in straight position and not be used as an elbow. "

Since that is two different manufacturers and a heavy truck mechanic telling me the same thing, I WILL use elbows when I make my stack exhaust and use a short length (18 in. should be sufficient) of STRAIGHT flex pipe to absorb the vibration and thermal expansion.

 

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The problem I have had with flex pipe is that it sometime leaks around connections. The stuff will lose its integrity if you weld it so it should be clamped. I had 4" stacks run down the side like sidepipes. I used flex pipe to run from the down pipe out to each side. It leked real bad around the connections. You can see the leaks easily. Just look for soot.

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98. 5 3500 QC 4x4, Driftwood/Mist Grey, 5 spd, 3. 54, 19. 5 Alcoa's, 245/70-19. 5 Michelin's, Ranchhand front bumper, Ranchhand rear bumper, Ranchhand toolbox, "Scotty Air", TST PowerMax2, Autometer Gauges, Centerforce clutch, Upgraded fuel lines (JRE and Aeroquip), MagHytec Diff Cover, PacBrake

 

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Jeff, using seal clamps,(wide band) instead of the regular guillotine (round band) clamps should help quite a bit in closing off the leaks. Flex with the fitted ends so you can go ID to OD should stop any leaks.

 

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Koa Man, you are right about the band clamps. That is what I should have used and I would have changed them, but I removed the system because it was too loud in the cab.

 

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Jeff, where did you come across the frame with the drivers side exhaust? I would like to map that system, I saw it before and loved it. I also know someone that likes the vibration of the exhaust due to his hearing impairment. Also, do you have any pics?

[This message has been edited by Stack'd-n-Jack'd (edited 07-11-2000). ]

 

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Stack'd, I came across right behind the links for the front suspension. If you look from the side, you will see a void that looks made for a pipe to run thru there. I built the system from sractch. I had a 4' down pipe with a Y on the end. The flex pipe hooked to that to allow the system to flex when the motor torqued up. I had chrome 90 degree elbows and chrome stacks down the side. I used angle iron welded to the underside of the body as a mounting place for hangers. Being as close to the cab as it was, it was very loud. To much for me. I still have the entire setup in my garage. I also just bought a digital camera. As soon as I figure out how to use it, I will e-mail you some pictures.