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Ill be doing 1 7/8 SE headers over winter so ill be looking to upgrade the exhaust system and would like some input on what would be ideal for 400+ LS1 with 243s and probably stage 4 BTR cam and Fast 92. It has to be over the axle, NO DUMPS. Ill build my own 3" Y pipe into a flowmaster merg and build my own single (i think 3" will be to small) which would be the easiest or 3" off the headers into a X pipe and duals all the way back, might use the factory 2 3/4" piping and get a new 2 3/4 replacement exhaust system and build a dual 2 3/4, or get a pair of 3" I pipe and over the axle pipes from Dynomax and build a dual 3" system(likely the most expensive and time consuming).
I understand im gonna need a relocated PH bar brace.
I have the same cam and I couldn't be happier with my duals. I swapped from 1 3/4 headers and a y pipe set up to 1 7/8 headers and true duals and picked up a good bit of power.
Im going with single 4" on my heads/cam iron block 6.2 build. Do i NEED 4"? Probably not...but I didnt want to have to mess with trying to get duals over the axle or listen to all the noise by dumping them under the car. Plus I had single 4" on my Silverado SS and it was the best sounding exhaust I ever had on there. Only makes sense to try and replicate it with the camaro.
Anyway, for power, dumped 3" duals would be my vote. They aren't obnoxious and won't drone if you clock the tips right...
2nd would be the 4" I-Pipe with a cutour before it goes up and over the rear axle.
Single 3" is not a restriction up to 450hp at the crank. Afterword it will work but begins to restrict and thus cost some power. At 500 crank hp I doubt it's costing you much but a few ponies. But you get the added velocity at low/ medium engine speeds so more hp/Tq down low where you need it on the street. Going to 3.5" is good for like 500-525hp before becoming a restriction and single 4 is good for 600hp or about what dual 3" is good for.
im at about 525-550hp through a aftermarket summit catback and CME tips on my 87ta with a supercharged 5.3 and I actually picked up low end down grading from a single 4" on the same combo. Single 3" is working great for me and it's livable on the street. I couldn't take the single 4" with dual mufflers driving on the street... just too loud. Exhaust must be tuned for the engine Hp/rpm/ driving habits. I spend 90% of my time at less than 3500-4000rpms so I'd rather the 20-30hp/Tq with the 3" down low vs going with the 4" and losing low end but gaining the 5-10hp I might be losing at 5500-6000 bs the 3"
Duals are unnecessary for up to 700-750hp. It's easier to run a single 4" vs dual 3" and cheaper. Both flow the same and support the same hp.
My car picked up quite a bit going from a single 4inch cat back to true duals dumped with an x pipe
Apples and Oranges. Your adding a Xpipe (equalizer) which are the most efficent of all the designs and known to add power throughout the curve (more up top over Hpipe) then your shortening the length of the exhaust which is the distance it must travel thus decreasing flow restriction. However your setup now is illegal and can be given a ticket on visual inspection alone. Been there and done that. I ran 3 different 3" dual dump setups with Xpipe and it was the best performing, however the noise and the tickets made it a definite change. Ive also run dual 3" all the way back to the bumper, single 3" and single 4". Gotta remember there is a frictional loss every inch the exhaust has to pass through the exhaust tube, a single 4" has less frictional loss than dual 3" due to mess material the exhaust contacts (larger open area in single tube vs contact of two tubes), so technically a exhaust of the same length of both 3" and 4" the exhaust has to overcome more friction on the dual 3" vs the 4". Shortening the length of the exhaust dramatically reduces the friction compared to full length. this is great for higher RPM spinning but a full exhaust will always make more low end/mid tq/hp vs a shorter dumped exhaust.
I picked 2 tenths and 2mph going from hooker 1 3/4 with catback to kooks 1 7/8 with TD's and no tune changes on a bolt on car. The cat back did have the shitty merge though. The main reason why I changed was for the stall. Y piped LS cars have that raspy cackle sound around 2500 rpms which is right where a good stall operates when cruising. With a good TD setup that is eliminated...perhaps a better Y helps too.
I will bet a free exhaust to anyone that can make more power with 3" duals over this setup. Not gonna happen. This is one of my systems I built over the years. I have made a bunch of different exhaust and I can promise you that the merge on what you see here and the scavenging effect it has by running the pipes side by side and not into each other at a 45* angle as well as the area of the merge being a full 4" as opposed to maybe 3.5" section of an x merge.
Im comparing the system in this picture against a 3" dual thats dumped. I have run both and the 2 into 1 just pulls harder. I cant comment on a single 4" all the way out the back.
I've had various exhausts on my car. From the oe slp dual dual with mac headers to mac headers with a 3.5" catback i made out the back to kooks on that same catback to kooks with a 4" dump to now kooks with a td 3" x.
I can say it liked the 3.5" i made vs the dd set up to the tune of .2 and 1mph.
When i went to the kooks vs the macs it picked up huge.....i mean yuge! midrange.
From that to the 4" dump it didn't like. Sounded like a dump truck and felt flat. It did run the sig times like that tho.
Now it has the 3"td x and i haven't drove it. But just starting it and whacking the throttle it seems happier and more responsive.
Last edited by HioSSilver; 11-11-2016 at 03:20 PM.
when i put 1 7/8" headers on my car and a 4" exhaust with a magnaflow look alike muffler in factory location i made 525 rwhp. dropped my exhaust and immediately made a dyno pull with open headers.... 525 rwhp.
I will bet a free exhaust to anyone that can make more power with 3" duals over this setup. Not gonna happen. This is one of my systems I built over the years. I have made a bunch of different exhaust and I can promise you that the merge on what you see here and the scavenging effect it has by running the pipes side by side and not into each other at a 45* angle as well as the area of the merge being a full 4" as opposed to maybe 3.5" section of an x merge.
Im comparing the system in this picture against a 3" dual thats dumped. I have run both and the 2 into 1 just pulls harder. I cant comment on a single 4" all the way out the back.
Then throw it on the dyno and test it. Take them both to the track and test it. SHOW ME.
I don't really need to see it though, bc I already know what the outcome will be.
From a monetary / sales standpoint, I'd think if that's the case then all the vendors would be selling THAT, as it's less material, cheaper to produce, and makes more power... right?
We're splitting hairs here to begin with. A dumped dual setup is going to support whatever you throw at it, as will the single dumped 4".
Sound being subjective or not, I know which one will sound better. About 75% of the folks on here still driving an F-Body actually DRIVE them, not just take them to the track. That has to be taken into consideration as well.
Then throw it on the dyno and test it. Take them both to the track and test it. SHOW ME.
I don't really need to see it though, bc I already know what the outcome will be.
From a monetary / sales standpoint, I'd think if that's the case then all the vendors would be selling THAT, as it's less material, cheaper to produce, and makes more power... right?
We're splitting hairs here to begin with. A dumped dual setup is going to support whatever you throw at it, as will the single dumped 4".
Sound being subjective or not, I know which one will sound better. About 75% of the folks on here still driving an F-Body actually DRIVE them, not just take them to the track. That has to be taken into consideration as well.
I have built many of both types. What you see pictured here and the TSP style dual 3" x pipe. You cant tell the difference between the two in sound when they are both dumped.
11-01-2016, 12:56 PM
True duals, single 3",3.5",4" exhaust for 400+whp 
midrange.
