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Flowmaster question

This is a discussion on Flowmaster question within the External Engine forums, part of the LSx Technical Help Section category; I had my stock muffler replaced with a flowmaster on my 99 WS6. I also had the flat portion of ...

  1. #1
    Member Tony180a's Avatar
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    Question Flowmaster question

    I had my stock muffler replaced with a flowmaster on my 99 WS6. I also had the flat portion of the Y pipe replaced with a round less restrictive pipe. I love the sound but I noticed that when I take off in 1st gear I hear a popping noise that stops as I accelarate and it only does it in 1st gear. It seems to be coming from under the driver side any suggestions ?

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    Tech Junkie hammertime's Avatar
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    Well, drivers side is the pipe that you had cut and replaced. First guesses:
    1) is the new pipe contacting the floor or anything else under load?
    2) is there a pinhole leaking exhaust and letting air in under decel?

    If the Y was not removed for finish welding, I would recommend that.

    Good Luck & Let us know what you find.
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    2001 Light Pewter Metallic Camaro SS, 6 speed
    K&N, SLP Lid, SLP y-pipe, GMMG cat-back, Lou's Short Stick - more to come!

  3. #3
    Member Tony180a's Avatar
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    Hammer I took my car back to the muffler shop that did the work and it has plenty of clearance all the welds are good. I had to replace my egr valve last month and I'm wondering if this could be the problem. As I said it makes this popping noise when I take off in first gear and it also makes the noise in 2nd and 3rd if I get down on it. I am not getting any ses codes and I'm wondering if the new egr is malfunctioning or could it be a cat failure ? What puzzles me is it does not make this noise if I rev the engine while stationary only when I take off.
    Last edited by Tony180a; 02-05-2006 at 10:51 AM.

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    I Love My Bong easyericvan's Avatar
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    Your y-pipe is probably hitting the heat shield. There will probably be a shiny spot on the y-pipe where it is hitting. You can completely remove it or hit the shit out of it with a hammer until it quits rattling.

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    used and abused at wot ibanez7's Avatar
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    first off, if you want big horse power after adding more mods, the flowmaster was a bad choice.

    flowmasters just dont flow but they do sound get until you get headers installed.
    I replaced my flowmaster because of losing 10+rwhp from it.

    Also are you sure the popping noise is the y-pipe hitting part of the chasis. It may look like you have the clearence but once the engine is under load, it torques to the right pulling the y-pipe with it, slamming into the frame!\

    i had that problem after installing my hooker LTs and ofy, so I bought this.

    scroll down to mufflex bumpstop

    http://www.thunderracing.com/catalog...&vid=3&pcid=54

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    Don't Listen to Me NE98LS1's Avatar
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    you think you lost 10rwhp from stock by going with flowmaster? or lost 10rwhp compared to say borla or loudmouth?

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    Senior Member SeVeReDiStOrTiOn's Avatar
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    Quote Originally Posted by NE98LS1
    you think you lost 10rwhp from stock by going with flowmaster? or lost 10rwhp compared to say borla or loudmouth?
    He probably gained 10 rwhp when he took the flowmaster off...so the flows were causing him to lose 10hp

  8. #8
    Don't Listen to Me NE98LS1's Avatar
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    yeah, i've heard that borla will give about 7 more hp gains over flowmaster, but for the price, i think a set of flowmasters with cut outs gives an incredible sound, and real decent gains.

  9. #9
    Junior Member Schantin's Avatar
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    Quote Originally Posted by ibanez7
    first off, if you want big horse power after adding more mods, the flowmaster was a bad choice.

    flowmasters just dont flow but they do sound get until you get headers installed.
    I replaced my flowmaster because of losing 10+rwhp from it.

    Also are you sure the popping noise is the y-pipe hitting part of the chasis. It may look like you have the clearence but once the engine is under load, it torques to the right pulling the y-pipe with it, slamming into the frame!\

    i had that problem after installing my hooker LTs and ofy, so I bought this.

    scroll down to mufflex bumpstop
    I agree that the popping sound you're hearing is probably the Y-pipe tapping the frame. You said it happens during WOT. Classic symptom. I've also had the tailpipes tapping the heat shield by the fuel tank....causes a similiar sound.

    As for the Flowmaster....I doubt it loses 10RWHP over stock. Unless you put it on in addition to the stock muffler The Flowmaster isn't a good power producer, but it sure sounds nice. I have the "Blowmaster" 3" American Thunder catback on my car.....and added a QTP electric cutout when more power is needed. Sure is cheaper to add a cutout than change the entire rear exhaust.....and nothing flows better than bypassing the muffler altogether.

  10. #10
    Don't Listen to Me NE98LS1's Avatar
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    isn't it possible to have too LITTLE back pressure though? i've heard people say yes and no

  11. #11
    Senior Member SeVeReDiStOrTiOn's Avatar
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    Quote Originally Posted by NE98LS1
    isn't it possible to have too LITTLE back pressure though? i've heard people say yes and no
    Yea...usually with low back pressure you'll lose some low-end torque

  12. #12
    Junior Member Schantin's Avatar
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    Quote Originally Posted by NE98LS1
    isn't it possible to have too LITTLE back pressure though? i've heard people say yes and no
    Guess it depends on what you're driving style is. You will lose a little low-end torque with a cutout. But, the high RPM HP gain will outweigh this (especially if you're running an aftermarket cam.) For street driving...might ot want tolose any low-end. But, at the track I was gaining a consistent 1mph in the trap speed with the cutout open (roughly a 10HP gain.)
    Running high-flow cats (vs none) helps keep the low-end torque too. I have LT headers w/ cats on my system.

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