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2.5 in exhaust verses 3 in exhaust?

This is a discussion on 2.5 in exhaust verses 3 in exhaust? within the External Engine forums, part of the LSx Technical Help Section category; I've been wanting to go true duals. And I want to go over the axle out the back. 2.5 will ...

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    2.5 in exhaust verses 3 in exhaust?

    I've been wanting to go true duals. And I want to go over the axle out the back. 2.5 will be easier to go over the axle then 3 in and I've read that 2.5 in sounds better then 3 in. And that H sounds better then an X pipe. What is everyones thoughts on this.

    Thanks

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    Member AB'sLs1's Avatar
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    red
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    Quote Originally Posted by Goblin View Post
    I've been wanting to go true duals. And I want to go over the axle out the back. 2.5 will be easier to go over the axle then 3 in and I've read that 2.5 in sounds better then 3 in. And that H sounds better then an X pipe. What is everyones thoughts on this.

    Thanks
    if u want to run some kinda cross section in the pipe run an X ive heard they give u more low end torque. as far as the size of the pipe goes i know u will get a deeper sound if u go 3in but 2.5 is easier to go over the axle. what i know alot of guys r doing is running a 3in pipe till they get to the axle then going to 2.5 over the axle and back over at 3in. idk if that answer ur question or not tho

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    Senior Member camarojunky74's Avatar
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    unless your running big ci, and spraying 2.5 will be sufficient enough by far, think about it, you will be running almost 1.5 bigger than a single 3, thats huge, and x pipe is the way to go, less resonance and a little rasp. go to ls1sounds.com and look around, im sure you can find a similar setup,

    good luck.

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    Member AB'sLs1's Avatar
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    red
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    one more thing if u run an X pipe it will also quiet down ur exhaust a bit in comparison to u having just duals with no cross section. but an X creates low end torque and will give ur exhaust a different tune. just something to think about

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    Not much to add to the previous replies except, if you got TD's, make sure they are mandrel bent. If they are compression bent, you are wasting your time and money and you are not going to see any gains!

    How much are you willing to spend on TD's ?

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    Member AB'sLs1's Avatar
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    also keep in mind what kinda tubing u want (stainless and mild steel) thats a cost factor but its a nessicary factor to think about. and also if u want to be runnin cats yet?

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    As of right now I have LT ORY and Magnaflow exhaust. I was mainly curious about the sound. It's not going to be a high horse power car and I was going to build it myself. I know going out the back is going to cost more and up until yesterday I was willing to pay around a grand for it. But I just found out last night that my wife is pregnant. So, any plans I have for the car are now on hold. So never mind anyways. Thanks.

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    Quote Originally Posted by Goblin View Post
    But I just found out last night that my wife is pregnant.
    Congratulations

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    no problem. congrads.

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    cutting and welding mark21742's Avatar
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    Quote Originally Posted by Goblin View Post
    As of right now I have LT ORY and Magnaflow exhaust. I was mainly curious about the sound. It's not going to be a high horse power car and I was going to build it myself. I know going out the back is going to cost more and up until yesterday I was willing to pay around a grand for it. But I just found out last night that my wife is pregnant. So, any plans I have for the car are now on hold. So never mind anyways. Thanks.
    congrads man!.......that means you have maybe 7 months of free time and money to do all your modding and partying so youd better start now lol
    just think after a few years your kid can talk smack to the other kids (my daddy's car is faster than your daddy's car) lol

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    Still The Junior Member RedVertTA's Avatar
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    Exhaust: 3 in vs. 2.5 in

    It depends on how big your engine is. Is it bored out, super or turbocharged? In that case you might want the bigger exhaust.

    If its a stock + bolt on or mild cam engine you'll want the smaller exhaust.

    You may have a lot of trouble getting the exhaust to clear the panhard bar, a buddy of mine has the true x pipe setup and he ended up giving up and letting the muffler end just before the axle. He also used the 3 in setup and told me he had lost low end torque, he was running a stock engine with bolt ons, no tuning.

    If you are planning to really mod the hell out of the car in the near future, I would go with the bigger exhaust setup even if you experience lower torque for a short period, this will be much easier than having to install a completely new exhaust setup for a bigger motor later on, and save you money. $$$$

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    Im trying to decide which route to go. Im getting a ford 9" since my 10 bolt broke and Im gettin a lid, ls6 intake, throttle body, Pacesetter longtubes, then when i get the cash Im throwin in a cam. I would like to do true dual over catback. 2.5" with xpipe over the axle with no cats and the car is not lowered. Would the true duals be the way to go? I want a deep, throaty and loud exhaust note. And I cant really tell the sounds apart on ls1sounds because my computer speakers suck.

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    umi has a panhard relocation kit to fit 3s over the axle

  14. #14
    Still The Junior Member RedVertTA's Avatar
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    Exhaust: 3 in vs. 2.5 in

    If you're not going to be pushing 400 rwhp or more, I would not go with 3 inch, I would go with 2.5. It sounds like you're going to make this a bolt on motor, if so, you may lose low end torque, and consequently gas mileage with the 3 inch system. More exhaust flow is good, but there is a point in which its too much.
    FAST 90/90, SLP Lid, Kooks JetHot Coated LT's, American Racing Y-Pipe+Magnaflow Cats, DHM Electric Cutout, Flowmaster American Thunder Catback, HP Tuners Software, 343 rwhp.

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