2.5 VS 3 inch power gain/loss
01-09-2006, 06:51 PM
#1
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2.5 VS 3 inch power gain/loss how much power will I lose if I go 2.5 as opposed to 3inch on a bolt on car..
true duals with an X pipe and purple hornys..
my only problem with it is.. the collectors on the headers are 3inch.. am I suppose to reduce it down to 2.5? and then run the X and then dump it?
am I losing any more then 2-3rwhp?
true duals with an X pipe and purple hornys..
my only problem with it is.. the collectors on the headers are 3inch.. am I suppose to reduce it down to 2.5? and then run the X and then dump it?
am I losing any more then 2-3rwhp?
01-09-2006, 07:10 PM
#2
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Use something like the Flowmaster 3" to 2 1/2" cone reducer on your collectors, I think summit calls them venturi cones. IMO you wont loose any power on a bolt on car.
01-09-2006, 07:32 PM
#3
The reducer's mentioned ^^^ are pretty sweet, seen 'em the other day. 2.5" system wouldnt cost you any noticable amount of power untill you made 500rwhp. I wish i had gone with a 2.5" system when i got my 3" duals now due to the clearance problems.
Think about all the mustangs running 2.5" systems.... wait nevermind they suck
Think about all the mustangs running 2.5" systems.... wait nevermind they suck
01-10-2006, 07:52 AM
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so the cone reducers it is..
if somebody does a good job fabbing up and everything I heard there is zero loss till 574 hp.. that being the mufflers flow as well as an open pipe.
okay well 574hp is where it starts to limit but it doesnt answer that if you had the same exact setup.. same size bends same person fabbed it up.. all factors equal.. except the muffler and piping is 3inch.. is there power gained? or is it exactly equal because the 2.5 is not limiting it?
this may seem like a far out question but I've been pondering this for a while and want to get a good answer from somebody who is knowledgeable'
ttt
if somebody does a good job fabbing up and everything I heard there is zero loss till 574 hp.. that being the mufflers flow as well as an open pipe.
okay well 574hp is where it starts to limit but it doesnt answer that if you had the same exact setup.. same size bends same person fabbed it up.. all factors equal.. except the muffler and piping is 3inch.. is there power gained? or is it exactly equal because the 2.5 is not limiting it?
this may seem like a far out question but I've been pondering this for a while and want to get a good answer from somebody who is knowledgeable'
ttt
01-10-2006, 10:47 PM
#6
I actually asked the same question to one of the tech's from burns stainless just yesterday. He told me basically that if you needed to reduce the exhaust size to keep torque, that you have the wrong size collector on the headers.
But being that most of us have "commercially built" headers and not custom ones we all have 3" collectors. What he told me was to run the same size x-pipe as the collector size and if it needed to be reduced to do it after the x-pipe.
I know that doesn't really answer the 3" vs 2.5" question, but I really don't think you want to reduce it at the collectors. I really think that after talking with him, both the primary size and collector size most of us use is to big. Probably should be more like 1 5/8 and 2 1/2 till you get over 500 hp. But thats just my opinion.
But being that most of us have "commercially built" headers and not custom ones we all have 3" collectors. What he told me was to run the same size x-pipe as the collector size and if it needed to be reduced to do it after the x-pipe.
I know that doesn't really answer the 3" vs 2.5" question, but I really don't think you want to reduce it at the collectors. I really think that after talking with him, both the primary size and collector size most of us use is to big. Probably should be more like 1 5/8 and 2 1/2 till you get over 500 hp. But thats just my opinion.
01-11-2006, 06:58 AM
#7
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Originally Posted by SOM98TA
how much power will I lose if I go 2.5 as opposed to 3inch on a bolt on car..
2.5" is good for 500bhp zero loss.
Originally Posted by SOM98TA
my only problem with it is.. the collectors on the headers are 3inch.. am I suppose to reduce it down to 2.5? and then run the X and then dump it?
Yes you'll need to reduce, anypoint after the collectors will do, or if not after the X.
Yes you'll need to reduce, anypoint after the collectors will do, or if not after the X.
Originally Posted by SOM98TA
am I losing any more then 2-3rwhp?
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01-11-2006, 07:18 AM
#8
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Originally Posted by 25thhawk
I actually asked the same question to one of the tech's from burns stainless just yesterday. He told me basically that if you needed to reduce the exhaust size to keep torque, that you have the wrong size collector on the headers.
But being that most of us have "commercially built" headers and not custom ones we all have 3" collectors. What he told me was to run the same size x-pipe as the collector size and if it needed to be reduced to do it after the x-pipe.
I know that doesn't really answer the 3" vs 2.5" question, but I really don't think you want to reduce it at the collectors. I really think that after talking with him, both the primary size and collector size most of us use is to big. Probably should be more like 1 5/8 and 2 1/2 till you get over 500 hp. But thats just my opinion.
But being that most of us have "commercially built" headers and not custom ones we all have 3" collectors. What he told me was to run the same size x-pipe as the collector size and if it needed to be reduced to do it after the x-pipe.
I know that doesn't really answer the 3" vs 2.5" question, but I really don't think you want to reduce it at the collectors. I really think that after talking with him, both the primary size and collector size most of us use is to big. Probably should be more like 1 5/8 and 2 1/2 till you get over 500 hp. But thats just my opinion.
Originally Posted by 25thhawk
I actually asked the same question to one of the tech's from burns stainless just yesterday. He told me basically that if you needed to reduce the exhaust size to keep torque, that you have the wrong size collector on the headers.
But being that most of us have "commercially built" headers and not custom ones we all have 3" collectors. What he told me was to run the same size x-pipe as the collector size and if it needed to be reduced to do it after the x-pipe.
I know that doesn't really answer the 3" vs 2.5" question, but I really don't think you want to reduce it at the collectors. I really think that after talking with him, both the primary size and collector size most of us use is to big. Probably should be more like 1 5/8 and 2 1/2 till you get over 500 hp. But thats just my opinion.
But being that most of us have "commercially built" headers and not custom ones we all have 3" collectors. What he told me was to run the same size x-pipe as the collector size and if it needed to be reduced to do it after the x-pipe.
I know that doesn't really answer the 3" vs 2.5" question, but I really don't think you want to reduce it at the collectors. I really think that after talking with him, both the primary size and collector size most of us use is to big. Probably should be more like 1 5/8 and 2 1/2 till you get over 500 hp. But thats just my opinion.
Flat plane crank V8's such as Ferrari's, Lotus and TVR's dont have this problem, but that's why they sound different. These engines are basically two straight 4 cylinder engines using a common crank. They would not need as big collectors because at any one time there would only be one pulse per bank.
A traditional V8 like the LS1 is really two V4 engines. And because of the uneven firing order at some points there is double the exhuast gas/pulse per bank. So the collectors have to be large or else severly limit output.
Check out the sticky about mods/exhausts. Look for the info from David Vizard, I think post 6 and 13 onwards are worth reading.
01-11-2006, 07:32 AM
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Originally Posted by SOM98TA
so the cone reducers it is..
if somebody does a good job fabbing up and everything I heard there is zero loss till 574 hp.. that being the mufflers flow as well as an open pipe.
okay well 574hp is where it starts to limit but it doesnt answer that if you had the same exact setup.. same size bends same person fabbed it up.. all factors equal.. except the muffler and piping is 3inch.. is there power gained? or is it exactly equal because the 2.5 is not limiting it?
this may seem like a far out question but I've been pondering this for a while and want to get a good answer from somebody who is knowledgeable'
ttt
if somebody does a good job fabbing up and everything I heard there is zero loss till 574 hp.. that being the mufflers flow as well as an open pipe.
okay well 574hp is where it starts to limit but it doesnt answer that if you had the same exact setup.. same size bends same person fabbed it up.. all factors equal.. except the muffler and piping is 3inch.. is there power gained? or is it exactly equal because the 2.5 is not limiting it?
this may seem like a far out question but I've been pondering this for a while and want to get a good answer from somebody who is knowledgeable'
ttt
LT's for them are 3" and 3" setups are then used.
01-11-2006, 07:32 AM
#10
I agree that you want to use 3" up to the X then after that 2.5 should be fine. Thats how my setup is and I gained over 10rwhp over a 2.5 Y with an open 2.5 cutout in the I pipe. I think down sizing right off the collectors can restrict the system a little.
01-11-2006, 09:10 PM
#11
I was actually speaking with a tech at burns stainless and they custom make alot of headers for race teams in stock eliminator, nascar, probably annyone that knows anything about racing knows who they are. I don't know about the whole firing order/ collector size thing, I don't think that two cylinders fire at once so I don't believe that has anything to do with collector size. I think that if that was an issue, merge collectors would also hurt horsepower and I haven't heard anyone complain about that either.
Ryan
Ryan
01-11-2006, 09:13 PM
#12
Back to the topic though I would run 3" if you can, if not reduce to 2.5 after the x-pipe. Some companies offer x-pipes that reduce the pipe size at the junction, but I don't know if that would choke off the x-pipe or not. I am personally buying a 3" in/out x-pipe, and then reducers for after the junction.
Ryan
Ryan
01-12-2006, 04:31 AM
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Not being a smartass but read the stickys. They have some good stuff in em.
"In the case of V-8 firing order, the five pulses fire alternately back and forth from left to right collector, giving the ideal 180 degree firing cycle. Then it fires two in succession into the left collector, then two in succession into the right collector. If the proper collector outlet diameter is being used (two sizes larger than primaries) the two pulses in succession load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine to "sign off" early, not reaching its potential peek R.P.M. The improper firing order on a V-8 engine results in the need to use large diameter collectors so the engine will perform well at high R.P.M.s."
"In the case of V-8 firing order, the five pulses fire alternately back and forth from left to right collector, giving the ideal 180 degree firing cycle. Then it fires two in succession into the left collector, then two in succession into the right collector. If the proper collector outlet diameter is being used (two sizes larger than primaries) the two pulses in succession load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine to "sign off" early, not reaching its potential peek R.P.M. The improper firing order on a V-8 engine results in the need to use large diameter collectors so the engine will perform well at high R.P.M.s."
