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Exhaust cutout

This is a discussion on Exhaust cutout within the External Engine forums, part of the LSx Technical Help Section category; would there be any sound difference if i put a cut out before my muffler. i already have a slp ...

  1. #1
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    1998 camaro z28

    Exhaust cutout

    would there be any sound difference if i put a cut out before my muffler. i already have a slp exhaust. and yeah i still have my cats.

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    Member fast enough Z28's Avatar
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    Quote Originally Posted by newcomer View Post
    would there be any sound difference if i put a cut out before my muffler. i already have a slp exhaust. and yeah i still have my cats.
    yes it would be louder and a little faster.

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    Senior Member 35thAnniZ28's Avatar
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    decrease in mpg....get a screw on..or electric.....don't mess with gaskets

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    98 T/A WS6

    no power gain

    it will be louder but you will lose power on a stock system. you need the proper amount of backpressure from your muffler which you will not have with the cutout. but it will be louder

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    louder and fun to rev at people

  6. #6
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    I disagree that you will loose power. We put a cut out on our '98 and '00 Formula's, with each one we picked up at least 20rwhp. The cars before hand just hand flowmaster muffler, and once we put the cut out on each car we picked up power. Plus when we had lid and cut out we were still getting @ 30mpg on the highway with M6's.

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    Exalted Cyclops 67CamaroRSSS's Avatar
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    2002 Z28 A4 NBM
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    2nd mod to my Z was an electric cutout (1st was a CAI). Still had stock exhaust manifolds and cats. It picked up 19rwhp and 16rwt on a Dynojet.

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    Exalted Cyclops 67CamaroRSSS's Avatar
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    Quote Originally Posted by Semperfiws6 View Post
    it will be louder but you will lose power on a stock system. you need the proper amount of backpressure from your muffler which you will not have with the cutout. but it will be louder
    Where did you get this info from? I mean about the lost power. If this was the case then why do open headers make the most power? Also, everyone I know that runs in the "stock" class on dirt oval tracks has to run cast iron exhaust but has straight pipes that dump out the side. This is more of a safety issue than a requirement. Can't have all that CO going into the passenger area.

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    Senior Member 440 rwhp trans am's Avatar
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    Quote Originally Posted by Semperfiws6 View Post
    it will be louder but you will lose power on a stock system. you need the proper amount of backpressure from your muffler which you will not have with the cutout. but it will be louder
    not true! i have headers into a electronic cut out! great mod!

  10. #10
    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by 67CamaroRSSS View Post
    If this was the case then why do open headers make the most power?
    Open headers don't make the most power on a near stock car.
    Might have a slight gain at the very top of the RPM range, but you will lose tenths at the track.

    A properly located cutout will gain power over MOST systems. 20RWHP is a stretch, but I guess I can see it over the terrible flow of a blowmaster.

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    Slow'er'Ass Mr. Luos's Avatar
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    Lower RPM's will see a drop in power. On a stock set-up, you probably lose tenths....but might gain a couple extra horsepower at the peak. It will most likely lose horses under said peak.

    But you are down on power anyways if you have a flowmaster.

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    why did i lose power?

    Quote Originally Posted by Mr. Luos View Post
    Open headers don't make the most power on a near stock car.
    Might have a slight gain at the very top of the RPM range, but you will lose tenths at the track.

    A properly located cutout will gain power over MOST systems. 20RWHP is a stretch, but I guess I can see it over the terrible flow of a blowmaster.
    ok, what did i do wrong then? ive got a stock exhaust before the muffler (flowmaster), i put the exhaust cutout in and i can feel the loss of power. is it just me? why did i lose power if everyone else is gaining?

  13. #13
    Slow'er'Ass Mr. Luos's Avatar
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    What happened to your post?
    Somehow I replied and ended up above you.

    Check the second post I made. See if that helps.


    Just because you gain a couple horses at the very top of the powerband doesn't mean you are faster if you lost lower RPM power. Which a cutout can cause.

  14. #14
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    ok

    Quote Originally Posted by Mr. Luos View Post
    Lower RPM's will see a drop in power. On a stock set-up, you probably lose tenths....but might gain a couple extra horsepower at the peak. It will most likely lose horses under said peak.

    But you are down on power anyways if you have a flowmaster.
    that makes sense, but shouldnt it gain over the flowmaster at low and high rpm's?

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    Slow'er'Ass Mr. Luos's Avatar
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    No.
    I would say it would be better just above maybe 4500 RPM's.
    With the stock mainfolds in place, I honestly don't know exactly how it would act. Best bet....dyno it, once open, once closed.


    I did.
    Click for full size

    Red is open, blue is capped duals with Magnaflow mufflers.
    Notice at 4200 RPM's mine picks up strong, but under that, I am down on power when the cutouts are open.

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    alright

    Quote Originally Posted by Mr. Luos View Post
    No.
    I would say it would be better just above maybe 4500 RPM's.
    With the stock mainfolds in place, I honestly don't know exactly how it would act. Best bet....dyno it, once open, once closed.


    I did.
    Click for full size

    Red is open, blue is capped duals with Magnaflow mufflers.
    Notice at 4200 RPM's mine picks up strong, but under that, I am down on power when the cutouts are open.
    thanks for the input. i guess i just need to replace my stock manifolds.

  17. #17
    Slow'er'Ass Mr. Luos's Avatar
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    Remember, I am also nowhere near stock with my set-up.
    Might be much later that a cutout would pick up power for a near stock LS1.

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    suggestions?

    Quote Originally Posted by Mr. Luos View Post
    Remember, I am also nowhere near stock with my set-up.
    Might be much later that a cutout would pick up power for a near stock LS1.
    how much do you think i can modify my exhaust if i still have to take it to emissions? and what is a good set of headers to get that wont sacrifice ground clearance?

  19. #19
    Slow'er'Ass Mr. Luos's Avatar
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    Emissions. Tough call. Do they do a sniffer test or just a visual?
    Here they do the Cali shit. Everything. Sniffer, visual, etc...
    Most states a cutout won't pass emissions, even capped. I know mine are coming down for cats soon to get past.

  20. #20
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    i dont have to do emissions right now, but when i get out of the military and go back home i will. im not sure how in depth they go. i guess i will have to wait and see.

    you change yours back to the stock system every time you gotta get a smog check?

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