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Jay
Dodge Dakota
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4/09/2003
20:47:36
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 Subject: 2.50 vs 3.00 exhaust
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Hi all, well time to get a new exhaust. I've searched the boards and didn't find an answer to this. I want to get a Gibson 3.00" system and someone said to watch out for the 3.00 as it will reduce power. Anyone have any thoughts on this sibject? How about Gibson?
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goon1
Dodge Dakota
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4/10/2003
00:39:13
|  RE: 2.50 vs 3.00 exhaust
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i got a gibson on my 02, 4.7. It runs good but i also have an airaid intake, if you are gunna get exhaust you will want to get an intake to cuz u gotta be able to suck in what u spit out.
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goon1
Dodge Dakota
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4/10/2003
00:39:57
| RE: 2.50 vs 3.00 exhaust
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I.E. an intake generally should help with whatever lower end power losses you may get with the 3 inch
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brianman
Dodge Dakota
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4/10/2003
16:51:37
| RE: 2.50 vs 3.00 exhaust
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dual 2.5 should give you good power and still keep low end. do the math and the single 3 inch is less restrictive, less surface area and such but this kills the exhausts gas velocity which kills low end. but either way you should also upgrade the intake. the more you get in the more you have to get out.
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Mithrac
Dodge Dakota
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4/10/2003
20:06:21
| RE: 2.50 vs 3.00 exhaust
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brianman I am confused. Dual 2.5" pipes move more air than one 3" pipe. Where are you getting your info from? Anyway here is how is would break down.
area= pi*(the radius sqaured)
A 2.5 inch diameter would net a 1.25 inch radius
1.25 squared is 1.563 multiply that by pi and you get 4.91 multiply that by two pipes and you have a net area of 9.81 inches.
A 3 inch diameter would net a 1.5 inch radius
1.5 squared is 2.25 multiply that by pi and you get a net area of 7.07 inches.
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al
Dodge Dakota
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4/10/2003
20:15:41
| RE: 2.50 vs 3.00 exhaust
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Dual 2.5 are the way to go.5.9 or nothing
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brianman
Dodge Dakota
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4/10/2003
23:06:36
| RE: 2.50 vs 3.00 exhaust
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so i did a little more math and compared total surface area to circumference and i came to the conclusion that with all things being equal the 3inch is more efficient. it offers less pipe surface area or exhaust contact area which aids in efficiency through drag reduction of the spent gases. but one 3 inch in the end cant move as much exhaust gas as dual 2.5. the total given surface area for the gas to be moved through is still greater in the true duals than the single 3. but i think the ratios between total surface area given and total surface area of the exhaust pipe walls is better in the 3 inch. but the 3 inch does a better job of balancing out the uneven exhaust pulses, more than any h pipe could do. but screw the math go with duals they sound so much better and look cooler to.
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MikeD
*R/T*
4/10/2003
23:31:24
| RE: 2.50 vs 3.00 exhaust
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Think of it like this...forget that math sh!t lol....ever put your finger over a water hose? Well the smaller the hole the faster it shoots out...you take your finger off it yeah more is coming out because of the bigger area but its slower because its lost its velocity. I've been told if you don't have over 400-450HP then stick w/ 2.5"
~Mike~
Get In...Sit Down...Shutup...& Hangon
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mjhipp
Dodge Dakota
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4/11/2003
02:05:59
| RE: 2.50 vs 3.00 exhaust
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I have the same Question about my 4.7 L sport..
What is the absolute best exhaust setup for power and flow, considering the addition of HI flo cold air intake, HO CAMS, and INTAKE MANIFOLD, along with a 70 mm TB + a PCM flash?
My thought was to run 2.5" duals from the manifolds through a pair of 2.5" CATCO CATS, and then combining them EITHER into an X-PIPE , splitting back into 2 , and through dynomax 2.5" mufflers, OR , run from the CATS into a single 3" pipe to a 3" inlet , pair of 2.5" outlets DYNOMAX muffler (2 in 1 out muffler).
what is the best for this setup?
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brianman
Dodge Dakota
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4/11/2003
02:06:37
| RE: 2.50 vs 3.00 exhaust
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thats all i am saying, just go with dual 2.5 inch.
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Jay
Dodge Dakota
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4/11/2003
07:02:50
| DYNOMAX responds
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This is the answer I just got from Dynomax concerning their system for the 3.9L
Thank you for your inquiry for Dynomax Exhaust. We appreciate your
interest in our products. In regards to your 2003 Dodge Dakota with a
3.9L, our system does use the 3" pipe diameter, however with using the
Super Turbo muffler with it's 3 tubed internal design, it will have enough
back pressure so you will not loose low end torque, and will have a power
gain.
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TurboGuy
Dodge Dakota
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4/11/2003
08:49:50
| RE: 2.50 vs 3.00 exhaust
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You sh_itbags that say dual 2.5" is the way to go are morons. First off..lets not even discuss the wieght issue.
I have 4" pipe after the collector on my headers.
No loss in low end power and I can pull 2.03 60fts on a stock motor/trans/convertor and stock RSAs.
3" Single is the max I would go on your puny machines. 3" pipe can flow ALOT of air. (it was good enough for my 450hp V6 turbo)
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al
Dodge Dakota
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4/11/2003
16:19:45
|  RE: 2.50 vs 3.00 exhaust
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Didnt you read my previous post turbo guy!5.9 or NOTHINGGGGGGGGGGGGGGGGGGGGGGGGGGGGG!
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mjhipp
Dodge Dakota
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4/11/2003
17:38:50
| RE: 2.50 vs 3.00 exhaust
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Don't start that s_hit again
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Danny
Dodge Dakota
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4/12/2003
13:24:50
| RE: 2.50 vs 3.00 exhaust
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I notice a lot of people use Gibson exhaust. Is there any advantage to using a Gibson or other high dollar exhaust rather then just slapping on a cheapo glass pack from the local muffler shop?
Also, I have noticed a lot of guys have gone with cat back systems rather then just changing the muffler. Why is that? That just seemse wasteful to me considering that the factory exhaust is a 2.5" Mandrel bent system. the only really restrictive is the super big factory muffler. Or at least that's all I observed from the quick exam I did under my truck.
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mjhipp
Dodge Dakota
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4/12/2003
13:31:38
|  RE: 2.50 vs 3.00 exhaust
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Good point, I read an article about the exhaust on these trucks in Truckin or a magazine like that one that added a cat-back system and barely gained anything - like 3 or 4 hp.
the real exhaust gains will be made with aftermarket headers, HI flo cats, and like a single 3" through a Flo Master or Dyno max.
It seems that true duals dont gain anything but looks.
An H pipe b/t true duals will even out the pressure but it has to be done properly. You dont just put duals on it and weld in an H pipe b/t em.
Theres some sort of formula that I would love to know.
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