true duals - 2.5" or 3" 
true duals - 2.5" or 3"
Originally Posted by DVST8OR
which is better?
Originally Posted by Cal
Get three-inch duals. 2.5 duals only flow a little better than a single three inch.
Duals dont really show any big gains over y-pipes until you get into the big cube motors. mabe 5-10rwhp on a h/c car over a 3" y pipe with a decent catback.
2.5 in duals can easily support 400-450rwhp, ground clearence is the big issue. i have 3" duals and i would not recommend it for daily driving. my 2c
I have 2.5" and would not have anything bigger. With subframes and a lowered car, there is just not enough room under there to go any bigger. On top of that, 2.5" is good for 475-500 rwhp.
Someone posted a dyno comparison a while back that showed an 18 rwhp gain with 3" duals on a relatively stock motor. I'm not sure what this was in comparison to, but I know the stock fbody exhaust is very restrictive. Do a search on this section, you should find that thread.
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Originally Posted by 2001CamaroGuy
I have 2.5" and would not have anything bigger. With subframes and a lowered car, there is just not enough room under there to go any bigger. On top of that, 2.5" is good for 475-500 rwhp.
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Originally Posted by Cal
Someone posted a dyno comparison a while back that showed an 18 rwhp gain with 3" duals on a relatively stock motor. I'm not sure what this was in comparison to, but I know the stock fbody exhaust is very restrictive. Do a search on this section, you should find that thread.
"choking".......LOTS 
About 475-500 rwhp would be the max I would want to run through 2.5" and still be looking for MAX hp. I want to build a 388 all bore and would LIKE to see 550rwhp (still through my 2.5" duel) but realize at that hp level I will be leaving a good 25+ hp on the table (compared to 3" or a cut out).
About 475-500 rwhp would be the max I would want to run through 2.5" and still be looking for MAX hp. I want to build a 388 all bore and would LIKE to see 550rwhp (still through my 2.5" duel) but realize at that hp level I will be leaving a good 25+ hp on the table (compared to 3" or a cut out).
Launching!
Joined: Jun 2003
Posts: 249
Likes: 0
From: texas unfortunately for now
just got my hooker lt's on last week and 3 inch all the way out. i felt a loss of power down low but gained it up top. then i put the cam in and everything is all good now. i was thinking about 2.5 but im planning on doing heads in the near future so i chose the 3 inch.
TECH Junkie
Joined: Jan 2002
Posts: 3,015
Likes: 0
From: At the office
I went 3" all the way for a few reasons. My header collectors are 3", the 3" does sound deeper than the 2.5", and I did it for the increased flow.
My car lost nothing down low and held its power peak longer than when I had a ypipe and catback.
My car is not lowered, and if yours is, don't even both with 3" true duals; you'll bang the crap out of them.
My car lost nothing down low and held its power peak longer than when I had a ypipe and catback.
My car is not lowered, and if yours is, don't even both with 3" true duals; you'll bang the crap out of them.
