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Old 05-21-2006, 01:34 PM
FiLkY tha FELON's Avatar
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3" exhaust

Well I went to an exhaust shop out here in the carolinas and tried to get an 3" exhaust installed and the shop owner said it would defeat the pupose and I would lose power is this true?He also said I have to have an engine built for 3" exhaust?I'm not well versed in the specifics so I need some help!

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Old 05-21-2006, 01:46 PM
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It depends on the engine. 2 3" pipes are large enough for a 700HP big block assuming the headers, mufflers and bends are correct.

What's your application?


Larry
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Old 05-21-2006, 02:09 PM
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First off knowing the engine size is a must. I know lots of people that run two 2 1/2 or two 2 1/4 inch pipes into one 3inch pipe. Mainly because of limited space further back on the car. There has been a few articles posted here very recently about exhaust effecting the engine. Super Chevy has a great talk about headers and it includes pipes length and size. Hope that helps.

Chris
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Old 05-21-2006, 03:37 PM
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3 inch pipes

Iv'e allways heard that going to big on pipe size will kill the bottom end power.
My wife and I got a new Chevy Silverado with the standard 6 liter v8 and you should see the pipes on it.
The exhaust comes out of 2 1/2 inch manifolds into dual 3 inch pipes in and out of dual cats to a dual 3 in. inlet muffler dual 3 in. out of the muffler and then the two 3 in pipes out of the muff merge into a 3 1/2 in tailpipe.
??????????? go figure ??????????
Gene
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Old 05-21-2006, 05:49 PM
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your exhaust is like a river, a narrow river flows faster, wider flows slower and obstacles will accelerate the flow, such as baffles in the muffler. if you have too big of a pipe the exhaust gasses will sit in the tube kind of like a pond, and the newley excaped gasses will get backed up and so on and so on, so yes you will hurt the low end power because of this.
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Old 05-22-2006, 12:06 AM
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Quote:
Originally Posted by strikingthematch
I know lots of people that run two 2 1/2 or two 2 1/4 inch pipes into one 3inch pipe.

Chris
That's what I run on my motorhome and I love it. Headers into 2 1/2" headpipes, a Y pipe turns the two headpipes into a single 3" pipe, and I run two 3" Flowmasters, one after the other. Works awesome!

Some people are adamant that smaller pipes will produce more torque, some are adamant that after the collector free flowing exhaust is THE most important thing.

Maybe try the Dr. Gas website Filky? He's pretty good with the technical side of exhaust.
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Old 05-22-2006, 06:38 AM
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It's an 350 rebuilt no extras so it's basic but I was getting another motor built and hoping to put 3" inch pipes on it cuz this man I know has it on his roadrunner and it so sounds sick!And I want my camaro to sound like that when I get it to that stage it has an 400 in it.
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Old 05-22-2006, 10:21 AM
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If you design the primary and secondary tubes correctly with the junctions in the right place, the tertiary pipes have little effect on the system.
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Old 05-22-2006, 02:42 PM
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You must rejet the carb to see the full effect of power. All lot forget this. So yes, sometimes when going to a bigger exhaust without rejetting, will hurt power. If you rejet, power will probably increase.


My daily driven trucks looses 3 MPG with a collector leak. I kid you not.
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Old 05-23-2006, 02:51 PM
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Bigger ain't always better

Filky
This is absolutely the most committed mistake seen in exhaust systems - people buying headers/exhaust TOO big - much bigger than what is necessary for the engine to produce maximum performance and, because of that, reducing bottom and mid-range power in the process. Depending how much oversize the header is, peak power can even be reduced!

I have been running a 5.0 or 351 Fords for years and @ 5 to 5500 RPM, you only need a 2 1/4 to 2 5/8 header exhaust tube then to a pair of 2 1/4 to 2 1/2 exhaust and tail pipes. Remember also, 99% of the time you will be at 2-3000 rpm putting around town. With 3" pipes you will have NO scavanging effect pulling the burned charge out of the cylinders and in turn bringing the new charge in. Like johnsongass1 says, you will be losing gas mileage and at $3/gallon....
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Old 05-23-2006, 05:26 PM
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I think it's worth mentioning that the headers basically do the scavanging and the exhaust pipes basically gets the junk out. If you want 3" exhaust go for it. It's what you like and that's what's important. Will you have to rejet the carb? Depends on if your current system has back pressure or not. As long as your doing it have him weld in an X or H pipe as well.
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Old 05-23-2006, 06:36 PM
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Quote:
Originally Posted by Rick WI
I think it's worth mentioning that the headers basically do the scavanging and the exhaust pipes basically gets the junk out. If you want 3" exhaust go for it. It's what you like and that's what's important. Will you have to rejet the carb? Depends on if your current system has back pressure or not. As long as your doing it have him weld in an X or H pipe as well.
the pipes will fill up in 1 spot faster b4 it goes through the rest of the pipe so it could actully clog up on itself in a sense, a smaller pipe will fill up quicker/ less and flow faster.
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Old 05-23-2006, 06:45 PM
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3 inch exhaust

Hi, 3 inch pipes will not do much for you,performance or sound.I assume you want a mellow sound at idle and want at to talk when you hammer it.A 2.5 inch system will do everything you want and cost less than a 3 inch system.I make custom systems. Check with your guy about a 2.5" system with an X or H pipe.Also check on Vortex V baffle mufflers,they flow great and sound great.You can check them out at www.supremeperformance.com.I like these better than Flowmasters,they sound better and flow better,also they last longer than the Flows.If you check the design of Vortex verses Flowmaster you will see the diff.As far as carb jetting I find most guys are already using more carb than they need,oh yeah bigger is better.Most likely with out a lot of mods to your engine 2.25 or 2.5 pipes are plenty.Good luck
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Old 05-23-2006, 06:50 PM
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Quote:
Originally Posted by matt167
the pipes will fill up in 1 spot faster b4 it goes through the rest of the pipe so it could actully clog up on itself in a sense, a smaller pipe will fill up quicker/ less and flow faster.
MMMMM, I don't think so.
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Old 05-23-2006, 07:16 PM
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Quote:
Originally Posted by Rick WI
MMMMM, I don't think so.
I don't know the truth to it but. my autoshop teacher who used to own a engine shop ( owned several repair shops also, then decided to teach auto ) told me this. in a sense it does seem very logical because the exhaust gasses will flow faster through a smaller diamater and slower through a larger diamater unless the exhaust gas volume emmited by the engine was enough to permit the larger pipe, I'm not talking putting a 2" exhaust on a 454 the only way to tell is to use some kind of flow bench and compare. the volume of the pipes is diffrent obviously but, the real part that can't be prooven without a flow bench is if the gasses expelled into the larger diamater would take up enough of the volume or not, even if it flows slower than a smaller diamater. I know there is a lot of contraversey on exhaust sizing, some say bigger is always better, some say that the way a long tube headder is set up, each primary makes a little vacume to pull the gasses out of the next, some say a little backpreassure will aid the low end due to cylinder scavenging. some of these I can see how these could relate to the smaller/ faster bigger/slower theory ex, running a smaller pipe thinking it will aid in gaining a little backpreassure, it could be the smaller/faster theory actully working.
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