looking to put a hooker aero-chamber exhaust for my 3.1 bird and have one question. 2.5 or 2.25 inch. the guys at hooker say i can keep my bottom end of i should use the stock 2.25 inch size, however, i have heard many talk about 2.5.

if 2.5 is better, hooker only makes a 2.25 replacement, would there be negative effect of running 2.5's in and out of the 2.25" muffler?

 

im running all 3 in pipe if it matters, and 3" in and out flows

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1989 Firebird
2.8 v6, t5 swapped in

Ram Hi-po clutch, Cold Air, 1.6 rockers (ready to install), Lakewood LCA's, Lakewood Lift bars, Wonder Bar, 3" y-pipe, Random Tech Cat, 3" I-pipe, Flowmasters, MSd 6a, MSD Coil (Fireball in future) Accel 8.8 wires, MSD Ignition Module, 4th Gen Seats (not front yet)

" I'd rather run last in a full out race, than to NOT run at all ".

 

just bumping this back to the top because i was really hoping to get some replies and advice....i know you all have your own opinons, they would be appreciated.

 

I run 2.25 with a random cat and flowmasters

 

Well, if you run a 2.5 inch intermediate (and tailpipes) into a 2.25 inch muffler, you're negating the effect of the 2.5 inch pipes. The 2.25" muffler will become the kind of restriction you're trying to avoid!

Odd how Hooker (Holley) makes that 2.25 in/2.5 out muffler! I did notice one thing at their website, though. Check out this link. It appears that the muffler for the 93-00 f-bodies has the same external dimensions as the 82-92 muffler, BUT it has a 2.5 in and 2.25 out. In "theory" (hopefully this theory post won't start another long-winded argument), two pipes of smaller diameter will out-flow one pipe of larger. So the 93-00 muffler of 2.5 in/dual 2.25 out could be thought of as a 2.5 in/single 3.0 out. Then you could run your 2.5 inch intermediate pipe. Odd. Anyway here's the link for the muffler specs. I'd think that since both mufflers have the same dimensions, the 93-00 can fit, especially since there are no exhaust hangers welded to the mufflers. http://www.holley.com/HiOctn/ProdLin...ero.html#Chevy

Let us know what you decide on!

[edit] Oh, since we're listing our systems, my Dynomax has 2.5" all around, piping & muffler.

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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

[This message has been edited by TomP (edited April 23, 2001).]

 

makes sense....in theory...hehe. so i guess my only question is what do you think would be the best size for me....i will list the mods at the end...just want some help making the right decision from people who have been there before...i am thinking the exhaust will help open my engine and get the most out of my other mods...what do you all think?

1990 Firebird - 3.1l
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ASP pulleys
Home-Made C.I.A.
MSD 8.5mm superconducter wires (custom)
MSD GM Blaster coil
Rapid Fire plugs

 

Hey guys, not trying to start an argument just wondering what theory states that 2 pipes flow better than one. I have been under the understanding that one pipe (with the same cross sectional area as two) will flow better because there is a smaller surface area of pipe, creating less friction. Just curious because I like to know as many theories as I can.

 

Hey guys, not trying to start an argument just wondering what theory states that 2 pipes flow better than one. I have been under the understanding that one pipe (with the same cross sectional area as two) will flow better because there is a smaller surface area of pipe, creating less friction. Just curious because I like to know as many theories as I can.

It's not so much friction that matters. It's volume. Two 3in pipes have a greater volume than one 3in pipe, therefore more flow potential. However if you have alotta blockages in your two pipe system, you'd be better off with one clear pipe... That whole bit about the same cross-sectional area and friction is intrigueing though, however you would need one hella big pipe to obtain the same area as a two'r and the friction would restrict flow in such a minuite way that it wouldn't really matter. So you'd be better off with 2 anyway.

(Hope you understand all that, feels like I blabbed on when I was typing this)

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1985 Camaro SC - 2.8L, auto. Stock.

[This message has been edited by Xenodrgn (edited April 24, 2001).]

 

You are right, the area or actually the cross sectional area is by far the most important factor. I work for G.E. manufactoring jet engines and if I remmember correctly they always try to run the least number of pipes possible for cooling because the frictional factor does add up. I am not sure how significant this would be on a car engine. However, a single exaust would allow less weight with less actual material to be in the exaust system. On the plus side for dual exausts, if the exaust pulses are not timed exactly right the exaust can cost a little power. On the other side if you time them correctly you could theroretically get additional scavenging, like running an h-pipe. Kinda like running equal length headers vs. unequal. All in all it probably doesn't really matter on a street driven car. Put your time and money somewhere else. It is the area that is important. Just something for the tech heads to ponder.