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true duel xpipe required??

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Old 05-01-2012, 03:05 AM   #1
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Default true duel xpipe required??

i have been searching google and this site and others all night. i just need to know if the xpipe is required in a true duel setup.

some people online say it helps scavenging, some say it helps cancel out bad exhaust notes. others say true duel (no x or h pipe) is bad for the car and the exhuast note sounds uneven? i cant seem to find a straight answer.

here is what im doing, i have an ls1 swapped 240sx. This is my daily fun car. it has a huge cam with all supporting mods.

my headers are fueled racing 1 7/8 lt, with 3" collectors, to magnaflow ory to 3.5 to hushpower muffler.

I HATE the rasp that happens at 2200rpm. i love the sound at idle and wot. its just right around 2200 rpm it goes from a deep vrrooooomm to mmmmvrapvrapvrap sounds like a honda civic with *****.

So what im doing is dropping in a fuel cell and running 3" true duels all teh way back. do i need an xpipe to make the exhaust sound good? i want it to sound like a muscle car with none of the rasp. im not running any cats and dont plan to. i have not dynoed yet but am estimating 450hp.

so would you recomend me using the x, or h, or just true duel and why???

i need concrete info, and take into account my hp, my engine is far from stock.
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Old 05-01-2012, 03:13 AM   #2
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also i dont want drone on the highway. i do drive this car a lot!!! so if the x and h are better at tuning the sound thats fine! just lemme know why i should get either. i want no rasp and little drone as possible. just want it to sound deep


and from everything im seeing on google, x pipe may sometimes flow a little better depending on design.. but will have higher pitched tone. the h pipe will kill all the rasp and have a deep tone. it says hp figures between the two is nill. looks like ill prob go H pipe.

and no crossover pipe pretty much everyone says gives mad drone at highway speeds

Last edited by dm79; 05-01-2012 at 03:41 AM.
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Old 05-01-2012, 04:05 AM   #3
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Cross overs of any design are far better than just straight pipes. They help scavenge and smooth out the tone, like you have already mentioned. I highly doubt anyone on this board will disagree with that. However, if space is at a premium, running without a cross over will not make or break you.

In your setup, I would go with an h pipe as they tend to take up less room and imo, give you a smoother tone.
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Old 05-01-2012, 04:28 AM   #4
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Make sure you run them all the way back as well,dumped duals will drone alot
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Old 05-01-2012, 07:14 AM   #5
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Originally Posted by BOBS99SS View Post
Make sure you run them all the way back as well,dumped duals will drone alot
not if it's done right...
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Old 05-01-2012, 09:13 AM   #6
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i would run the h pipe and run exhaust out the back. i had true 3 inch duels on my mustang with x pipe n magnaflows turned down behind the rear end.. it will drone, but kinda gotta expect a little out of a 450hp street car... turn the radio up!!
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Old 05-01-2012, 09:19 AM   #7
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An X-pipe will get you a get more hp from the scavenging and in some cases reduces rasp.
for the drone, measure the peak frequency of the drone in your car and add a 1/4 wave resonator to the exhaust.
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Old 05-01-2012, 09:57 AM   #8
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a rule of thumb I've always been told is H-pipe helps with torque and gives up a little up top, X-pipe helps HP across the band and picks up more on the top end (depending on your cam this may be the ticket for you). sound-wise.. H-pipe is more muscle car sound X-pipe is a smoother more exotic sound. My current setup is in my sig.. but H-pipe with dynomax ultra-flo mufflers. 2.5" all the way out the back. I do not have any drone that I notice anywhere. I also have about a foot more of piping than you will have on that 240 lol.

sidenote, I have a friend with a s13 240sx (SR20DET conversion) that has 4" all the way out and I don't see how it clears the ground any bumps or animals in the road and yet my exhaust drags on more crap than his -.-

Going to the exhaust shop Friday
Here's a back to back of sorts for a sound comparison for you. I dug FOREVER trying to find a sound comparison on the same car with no other changes when I was debating it, so I hope it helps you out lol.
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Old 05-01-2012, 01:02 PM   #9
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Quote:
Originally Posted by dm79 View Post
some people online say it helps scavenging, some say it helps cancel out bad exhaust notes. others say true duel (no x or h pipe) is bad for the car and the exhuast note sounds uneven? i cant seem to find a straight answer.
It is not "bad" for the car to have no cross over. Many GM cars came stock this way in the '60s/early '70s, and the muscle car burble that these cars had even when stock comes from a straight true dual system with no cross over in many cases.

Having said that, you'll likely pick up a bit of power/torque with an H or X pipe, but it's not required by any means, and you won't "hurt" anything by not having it. The truth is, the better your header collectors are, the less gains you'll see from a cross over. There are race cars that run only open headers and they do just fine.

As for sound, that kazoo type rasp that you hear and hate right now is the product of a Y-pipe design. You won't get that sound with any sort of true duals, whether it be H, X, or straight pipe.
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Old 05-03-2012, 05:10 PM   #10
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thanks for all the help guys. i have listend to lots of exhuast sounds and i really like the h pipe design. when i take it back to the exhaust shop ill ask the guy to fab up an hpipe. i plan to run another hushpower muffler out back but i will be turning both down just before the rear bumper and have them tucked up. 240's look a little funny with dual mufflers out the rear to me.

edging every last bit of hp is not my concern right now. its already a crazy car. i just want that sound im looking for.

also my exhaust guy has been doing it for 30+ years, but just incase is there a rule of thumb about the h pipe size? ill be running 2 3" all way back. im guessingi the crossover needs to be smaller diameter. and i saw a spread sheet online to guestimate how far back it needs to be. does this kinda stuff really matter? or should i put the crossover where its convenient? pics coming soon
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Old 05-03-2012, 06:19 PM   #11
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Duel:

Click the image to open in full size.


Dual (exhaust):

Click the image to open in full size.
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Last edited by sepsis; 05-05-2012 at 10:32 PM.
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Old 12-19-2015, 06:55 PM   #12
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I know this is a bit of an older thread but it's similar to a question I've had for a while
I have a '71 Nova with a 350 in it (for now...) that has nice Doug's headers with 3" collectors that step down to 2.5" all the way to Flowmaster 44's dumped before the axle, NO crossover. I like the guttural sound from no crossover, especially at high RPM, but I have had a pretty hard time finding cars with similar setups with an LS. I'm super curious as to how the different firing order (Gen 1 vs LS/Gen 3+) would affect not only sound but also power and torque. I know GM changed it so it was "smoother" (cross-plane crank v8's only get so smooth haha) and to pick up some power also, does it also mean I might be able to get away with a bit less of a deficit when I swap an LS into my car?
I plan on eventually having a totally built 7.0+ liter LSX block with nice heads etc, likely n/a but not sure on EFI vs carb yet, but a similar exhaust setup to what I have with the 350, albeit with 3" all the way back and Spintech mufflers with 3" in and dual 2.5" out on both sides (yes 4 exits total, going for something a little different)
I don't care much about drone since this isn't a daily driver at all, more of a street legal (barely haha) track type car (drag and road course/auto-x)
Anyone have any sort of a similar setup on a car with NO crossover at all and longtubes? And preferably not glasspacks since that's not the sound I'm shooting for...
Videos would be cool, but at least an idea of how it sounds and maybe feels power wise vs a crossover
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Old 12-19-2015, 07:00 PM   #13
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I should also mention it will be a mid-range/flat torque band build, 500ft-lbs from 2000rpm+, not necessarily a stump puller but I'm shooting for near big block torque if I can, how much would o crossover affect the low end?
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