Re: exhaust size
[Re: onebad340]
#1761953
02/24/15 02:53 PM
02/24/15 02:53 PM
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Joined: Jun 2006
Posts: 5,166 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,166
CT
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You're on the border there, I think 2.5 would be sufficient with good mufflers though.
What is the collector diameter?
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: exhaust size
[Re: onebad340]
#1761954
02/24/15 03:22 PM
02/24/15 03:22 PM
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Joined: Jan 2003
Posts: 5,444 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,444
Indiana
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I too agree with 2.5" and good flowing mufflers. 2.5" is good for apx 463hp (521cfm). What about 3" x-pipe/mufflers, then 2.5" over axle/tail pipes since you are close to the 463hp mark?
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: exhaust size
[Re: onebad340]
#1761955
02/24/15 03:30 PM
02/24/15 03:30 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I would suggest 3". Std hooker BB headers have 1&7/8 pri tubes (TTI's might be 1&3/4 iirc) but to me, pushing 1&7/8 times (4) into 2&1/2 is restricting the flow. A 3" setup is gonna require regular muffs plus in addition glasspacks along side the rear leafs to get the noise down to an acceptable level & yes X pipes do work to quiet it. Make sure the glasspacks you pick do not neck down where the end nipples are welded to the case. The BEST killer setup (IMNHO) is an electronic (cable might suffice but I like the touch of a button/switch) is 3" open cutouts right at the collectors (no reduction) plus a restricted system rearward (even if 2&1/2) for noise compliance then when the time comes open em up & before they figure out what hit em the 10 second race will be over & the money will be in your (or a third parties') hands . No need for constant racous noise until needed (we ain't in high school).
live every 24 hour block of time like it's your last day on earth
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Re: exhaust size
[Re: onebad340]
#1761956
02/24/15 04:08 PM
02/24/15 04:08 PM
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Joined: Apr 2005
Posts: 15,134 Kelowna, B.C. Canada
DPelletier
I Live Here
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I Live Here
Joined: Apr 2005
Posts: 15,134
Kelowna, B.C. Canada
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All you need is 2.5" mandrel bent....if you go with compression bent exhaust you may want to use 3" to make up for the restriction. The best pipe in the world won't help much if you use crappy mufflers so chose wisely... Dave
1970 Super Bee 440 Six Pack
1974 'Cuda
2008 Ram 3500 Diesel
2006 Ram 3500 Diesel
2004.5 Ram 2500 Diesel
2003 Ram 3500 Diesel
2006 Durango Limited
[url] http://1970superbee.piczo.com [/url]
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Re: exhaust size
[Re: Mattax]
#1761961
02/26/15 12:06 AM
02/26/15 12:06 AM
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Joined: May 2011
Posts: 220 Aurora, CO
jbeintherockies
enthusiast
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enthusiast
Joined: May 2011
Posts: 220
Aurora, CO
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Quote:
I agree with both of Dave's posts. Those are 3" collector exits and with that Hp, keeping the 3" collector to the next interuption makes some sense. I'd take it back to an H pipe. From the H to mufflers could be 2.5. Getting good flowing mufflers will be the critical item. If this is an issue, and high rpm is important, then an X could be better than an H. In theory it allows more sharing. In theory 'cause the best way to know is test on your engine. Even with a program like Pipemax it is recommended to test. The easiest way to test is bolt on open collectors of different lenght. When that is established, the H pipe can be placed there or an X at the next harmonic.
The exhaust gas is cooling and therefore takes up less volume as it moves along. So even if a 3" is needed at the collector, it won't be needed for the entire system.
A long time ago I read a Hot Rod magazine article on a white Chevy Nova. The owner of the car was going to school for some automotive degree. In the article he explained he ran collector-size pipe into the mufflers and stepped it down coming out of the mufflers. If I recall correctly, I think he said when the exhaust gases enter the muffler they ionize and cool. So, as the gases leave the muffler, they have less volume and thus don't need as large of a pipe diameter. Based on that, I would go collector-size into the mufflers and step it down 1/4" or 1/2" coming out of the mufflers.
Dynomax has a new muffler out that they claim eliminates the annoying drone that performance mufflers typically emanate. They also offer different input and output sizes to customize your exhaust system.
http://www.dynomax.com/mufflers/dynomax-vt-mufflers
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Re: exhaust size
[Re: jbeintherockies]
#1761963
02/26/15 11:04 AM
02/26/15 11:04 AM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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As far as as volume goes, its pretty straightforward physics. As a given amount of gas molecules are cooled, density increases. Wherever there is a temperature differential, there is heat energy flow. So as soon as the combustion is done, heat starts flowing out to the cooler surrounding environment - the heads - then the exhaust system it passes through etc. The sound reduction adds a level of complexity, but as far as heat goes the principle is straightforward. Sound is also energy and in reducing sound amplitude some portion is converted to heat. The real complexity comes in with the sound versus pressure waves and how that impacts the gas flow. Calvin Elston has been posting his thoughts (and questions!) on headers. One of his conclusions has been that the most important thing is to get the gases far enough away from the exhaust valve so they don't get sucked back in. The OP's TTI step headers will do that as well as anything non-custom on the market. So I think everything else is about not stuffing it up with a major restriction in the mufflers, and how every much time and effort he wants to invest in tuning the placement of the first major change in pipe flow after the primaries. The latter is gravy unless ringing out max performance is the goal.
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Re: exhaust size
[Re: onebad340]
#1761966
02/27/15 07:47 PM
02/27/15 07:47 PM
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Joined: Jan 2003
Posts: 8,403 Highland, MI.
Sunroofcuda
master
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master
Joined: Jan 2003
Posts: 8,403
Highland, MI.
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2.5" syatem & good-flowing mufflers. What's the downside if you go with 3" system? I think it's too large a diameter for that HP range, & you'll lose flow velocity which will affect bottom-end & midrange performance that you could probably feel. Also, a 3" system will be a LOT louder than a 2.5". 3" is simply overkill unless you are going to be running the car at the dragstrip all the time & never seeing RPM's under 4,000.
No Man With A Good Car Needs To Be Justified
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