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How much HP will Long tubes make with or w/o Cats?

This is a discussion on How much HP will Long tubes make with or w/o Cats? within the External Engine forums, part of the LSx Technical Help Section category; Here's where I am stuck. Picked up a great deal on a Corsa exhaust which was the only option for ...

  1. #1
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    How much HP will Long tubes make with or w/o Cats?

    Here's where I am stuck. Picked up a great deal on a Corsa exhaust which was the only option for me since On the vette they are phenomenal and have no drone on the highway.

    As for headers i want the LPP with the merge collectors but 60 day back order. like wtf...

    May consider pacesetters now but am wondering about wether or not to go with high flow cats or no cats at all. How loud will it be without cats ?? I don't care how loud under wot just when I'm putting around town I want it as quiet as possible.

    Also what gains are we looking at with longtubes and a cat back vs stock manifolds and cats w/catback ? If it's not noticeable or huge I may just bolt on the corsa and call it a day and be emissions friendly too.

  2. #2
    cutting and welding mark21742's Avatar
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    I'd give a guess of around 20 true rwhp, but the gains get greater and greater if and when you do bigger mods (heads, cam).
    a good set of functional hi-flow cats won't lose any power for you, they will look good for emmissions and quiet the car down some.....but I'd still get the codes deleted and tune (sometime hi-flow cats read as bad cats) plus the tune will gain some more hp.....plus free flowing exhaust and headers can gain up to 5 mpg

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    That guy thearborbarber's Avatar
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    I gained 25rwhp with longtubes and off road y pipe. 287hp to 312hp.

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    Senior Member karpetcm's Avatar
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    20-25 rwhp with a good tune, ive seen a few on the dyno that pull about that. Youll have a few that will pull higher. If you have emissions id go with high flow cats and with good Highflow cats youll hardly lose power if any, it wont be as loud either. For me im gonna just put one highflow on or a resonator to kill some of the sound, dont care to much for emissions.

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    Just me Y2KPewterSS's Avatar
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    20 RWHP is a good average.

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    member since may 2000 nhraformula's Avatar
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    I gained 30 with a tune
    2000 nhra edition formula
    a few bolt ons, 379 rwhp
    11.96 @113.25

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    Senior Member karpetcm's Avatar
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    Man i wish i will gain that much after my install, im at 336 now and im hoping for 355-360 but who knows.

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    Hmm. I'ts a tough decision for me . I want cats just for the noise reduction. I'm going to remove the air/egr and go with headers without the hookups for a cleaner look and less clutter in the engine compartment. it will also make changing plugs a snap. What's hard is that the headers/Y from Lpp will be about $650 shipped + 650 labor (to install everything incl catback) + $300 or so for high flow cats. I'm looking at just under $2000 cdn for 25 rwhp

    Maybe I Wont rush it and go with the cat back for now and when i have the extra cash I'll blow it on the headers etc. The Lpp are 60 days away anyways so maybe I should wait.

  9. #9
    Senior Member karpetcm's Avatar
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    If you want to compare HP to dallors then nitrous would be an easy choice, atleast for me. I have the tune for nitrous as we speak. If you want to make that HP to dallor gap closer get Pacesetter LT's which are very good headers and get a better pricing for labor. Even the most expensive shop in my area is charging 400 for the install including plugs. The catback should not cost an additional 250 to install at all. Ive had both done in the past and not a hook up price at all and paid 500.00 for headers, plugs and catback install. So you can find someone that should be able to install it for cheaper just look around more and see what happens.

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    Member 2K2SLPSS's Avatar
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    i just recently installed pacesetter ceramic and Ory to my cme. i think the noise if fine. it only gets loud when you get on it. i would not be scared to go with out the cats. cats just cost you money...and so does taking it some where to get it put in. if ya got the tools and the jack stands for it go ahead and do it yourself. i did mine in about 8 hours. (two days after work) just make sure you W-D everything for a couple of days, remove plugs and wires and the stock system should come off in a breeze. i didnt have to sawzall mine. passenger side fits perfectly, but driver side you have to take the nut off you engine mount and pull the bolt out about half way. jack up on the pan and with a little more clearance you should be able to get it in there. then the rest is piecing up the y pipe. loosen up you cat back hanger and you should be able to bang her together.

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    Senior Member Z28_Driver's Avatar
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    did you weld or use clamps?

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    Senior Member Z28_Driver's Avatar
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    Quote Originally Posted by mark21742 View Post
    I'd give a guess of around 20 true rwhp, but the gains get greater and greater if and when you do bigger mods (heads, cam).
    a good set of functional hi-flow cats won't lose any power for you, they will look good for emmissions and quiet the car down some.....but I'd still get the codes deleted and tune (sometime hi-flow cats read as bad cats) plus the tune will gain some more hp.....plus free flowing exhaust and headers can gain up to 5 mpg
    you actually improved your gas mileage by adding headers and high-flow cats.
    Did anyone else experience increased mileage?

  13. #13
    cutting and welding mark21742's Avatar
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    Quote Originally Posted by Z28_Driver View Post
    you actually improved your gas mileage by adding headers and high-flow cats.
    Did anyone else experience increased mileage?
    I have headers and trye duals, but no cats. free flowing exhaust will give you better gas mileage IF you can keep your foot out of the throttle to hear the new exhaust so expect low mpg when you first put new exhaust on it, but then it will get better lol

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    NY Representative basballny2's Avatar
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    sell me your corsa and buy a magnaflow.....headers and magnaflow is VERY quiet at idle and low RPM but at WOT sounds great

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    Quote Originally Posted by mark21742 View Post
    I have headers and trye duals, but no cats. free flowing exhaust will give you better gas mileage IF you can keep your foot out of the throttle to hear the new exhaust so expect low mpg when you first put new exhaust on it, but then it will get better lol
    Since my headers, ORY and a tune, I'm getting 19.64 MPG highway and that is with quite a few WOT passes. Long range economy, I'm suspecting somewhere around 24-26 on cruise. No CATS of course but, the tune def helped.

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    Senior Member Too Fast's Avatar
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    Quote Originally Posted by Z28_Driver View Post
    you actually improved your gas mileage by adding headers and high-flow cats.
    Did anyone else experience increased mileage?
    My gas MPG went from 25-27 to 26-28.2. Definite improvement on my car. Hooker LTs and ORY. I still have not had a tune, it's been almost 3 years.

    The car is LOUD under WOT, no drone and almost as quiet as stock just cruizin'. I also gained 2 MPH on average at the 1/4 mile, I've never had this car on the dyno.

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    Senior Member Z28_Driver's Avatar
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    sounds like 1 or 2 mpg improve from headers, y and no cats.
    not worth it for that alone.
    the sound and the power gains are good!
    just don't want to hurt mpg (daily driver)

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    War Machine BIG GUNS's Avatar
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    The only way you will hurt your MPG is if you don't get a tune afterward. The headers and ORY without the CATS will require a tune. Especially if you remove the EGR which is a vast improvement.

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    Senior Member Too Fast's Avatar
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    Quote Originally Posted by BIG GUNS View Post
    The only way you will hurt your MPG is if you don't get a tune afterward. The headers and ORY without the CATS will require a tune. Especially if you remove the EGR which is a vast improvement.
    I have not had a tune, these cars with MAF are self tuning to an extent. Tuning is a great idea, but not a requirment.

    On second thought, if you want your SES light off, then for sure a tune is required! I sure like that glow at night on my dash.....

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    Senior Member Z28_Driver's Avatar
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    Quote Originally Posted by BIG GUNS View Post
    The only way you will hurt your MPG is if you don't get a tune afterward. The headers and ORY without the CATS will require a tune. Especially if you remove the EGR which is a vast improvement.
    what is the EGR, and how do you remove it?
    i see pacesetter offers race and headers with pollutin fittings.
    if i remove the egr would i need race headers? i haven't done much on pollution controlled cars.
    Last edited by Z28_Driver; 06-19-2009 at 10:09 AM.

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