2.75" or 2.5" that is the question
Thread Starter
Intermediate
Joined: Oct 2007
Posts: 42
Likes: 0
From: Cumming GA
2.75" or 2.5" that is the question
ok i am about to install my hooker long tube headers. im not worried abuot any visual or emissions testing so i am eliminating the cats. i will also be cutting out the stock resinator and running an x-pipe in its place. other mods include custom ECM, GM Hotcam, stage two clutch, 52MM throttle body, and the never go wrong K&N air filter. With my current mods i am at an estimated 340-350 WHP.
So my question is this, what size piping should i run? my plan was to go with 2.75" piping and a 3" X-pipe (seeing as how they do not make a 2.75 X-pipe that i can find) what i am afraid of is since im eliminating the cats and will have nothing but the X-pipe and mufflers to create back presure that a 2.75" system might be to big therfor causing me to loose torque. but at the same time 2.5" seems like it would be tosmall from my personal expieriance with other vehicles.
Please all personal expieriance and knowledge on this matter would be greatly appreciated.
So my question is this, what size piping should i run? my plan was to go with 2.75" piping and a 3" X-pipe (seeing as how they do not make a 2.75 X-pipe that i can find) what i am afraid of is since im eliminating the cats and will have nothing but the X-pipe and mufflers to create back presure that a 2.75" system might be to big therfor causing me to loose torque. but at the same time 2.5" seems like it would be tosmall from my personal expieriance with other vehicles.
Please all personal expieriance and knowledge on this matter would be greatly appreciated.
Burning Brakes
Joined: Aug 2007
Posts: 915
Likes: 0
From: salinas ca
ok i am about to install my hooker long tube headers. im not worried abuot any visual or emissions testing so i am eliminating the cats. i will also be cutting out the stock resinator and running an x-pipe in its place. other mods include custom ECM, GM Hotcam, stage two clutch, 52MM throttle body, and the never go wrong K&N air filter. With my current mods i am at an estimated 340-350 WHP.
So my question is this, what size piping should i run? my plan was to go with 2.75" piping and a 3" X-pipe (seeing as how they do not make a 2.75 X-pipe that i can find) what i am afraid of is since im eliminating the cats and will have nothing but the X-pipe and mufflers to create back presure that a 2.75" system might be to big therfor causing me to loose torque. but at the same time 2.5" seems like it would be tosmall from my personal expieriance with other vehicles.
Please all personal expieriance and knowledge on this matter would be greatly appreciated.
So my question is this, what size piping should i run? my plan was to go with 2.75" piping and a 3" X-pipe (seeing as how they do not make a 2.75 X-pipe that i can find) what i am afraid of is since im eliminating the cats and will have nothing but the X-pipe and mufflers to create back presure that a 2.75" system might be to big therfor causing me to loose torque. but at the same time 2.5" seems like it would be tosmall from my personal expieriance with other vehicles.
Please all personal expieriance and knowledge on this matter would be greatly appreciated.
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
The stock :LTX exhaust uses 2 3/4" pipe.
Are you still using the stock cat back?
If your are you should be fine, many are running the stock pipes without cats, resonator, or mufflers!
Are you still using the stock cat back?
If your are you should be fine, many are running the stock pipes without cats, resonator, or mufflers!
Racer
Joined: Oct 2007
Posts: 478
Likes: 1
A few things you should know in helping you make your decision.
One: You need a minimum of 2.2cfm of exhaust capacity per motor horsepower for 1% or less back pressure.
Two: One square inch of exhaust pipe(o.d.) will move 115 cfm of exhaust.
A 2.50" pipe will move 560cfm.
A 2.75" pipe will move 682cfm.
A 3.00" pipe will move 812cfm.
A 3.50" pipe will move 1105cfm.
A 4.00" pipe will move 1444cfm.
A 400 horsepower motor will require 880 cfm.
A 450 horsepower motor will require 990 cfm.
A 500 horsepower motor will require 1100 cfm.
One: You need a minimum of 2.2cfm of exhaust capacity per motor horsepower for 1% or less back pressure.
Two: One square inch of exhaust pipe(o.d.) will move 115 cfm of exhaust.
A 2.50" pipe will move 560cfm.
A 2.75" pipe will move 682cfm.
A 3.00" pipe will move 812cfm.
A 3.50" pipe will move 1105cfm.
A 4.00" pipe will move 1444cfm.
A 400 horsepower motor will require 880 cfm.
A 450 horsepower motor will require 990 cfm.
A 500 horsepower motor will require 1100 cfm.
Pro
Joined: May 2002
Posts: 635
Likes: 6
From: New Jersey
I had true dual (3" pipe) and X pipe with 2 3/4 Magnaflo LT1 mufflers pull on my car last thursday and pick up .3 and 3 mph but my car is a L98 and it had headers and a cat back with (flo)slowmaster mufflers
Randy
Randy
