1998 Cadillac Exhaust Questions
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 1998 Cadillac Exhaust Questions in Past Cadillac Vehicle Discussion; Hey guys I got a 1998 Cadillac Seville STS and I was wondering about the exhaust. I noticed it has ...
  1. #1
    jdpetersdoc is offline Cadillac Owners Member
    Automobile(s): 1998 Seville STS, 2000 Eldorado ESC
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    1998 Cadillac Exhaust Questions

    Hey guys I got a 1998 Cadillac Seville STS and I was wondering about the exhaust. I noticed it has a Cat (obviously) and behind that a resonator? then a y-pipe then 2 huge 3+ chamber exhausts. I want to keep the stock exhaust but what size is the main pipe is it 3inchs? Its alot bigger then the pipes that come after the y-pipe the y-pipe looks like 2.5 inch. Also what about removing the resonator? I don't want a really loud car I just want it to have a cool muscle car sound. My buddy talked me into putting cut outs on it electronic cutouts from QTP. Itd be easier and I wouldn't be chopping the hell out of the nice stock stainless exhaust. I was just wondering about sound and performance if I did this. Also there's a large body stiffener thats part of the exhaust heat shield it. The body stiffener is rotted out and I want two replace it with a junkyard one......is this easy to change?

    Thanks
    -James

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  3. #2
    N*Caddy's Avatar
    N*Caddy is offline Cadillac Owners Master
    Automobile(s): 1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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    Re: 1998 Cadillac Exhaust Questions

    If you don't want a loud exhaust system then leave the system alone.
    Performances, I would like to see a paper that proves the aftermarket system gives you 0.1HP gain. Noise is NOT power! Larger pipes will actually decrease the mid range torque, you may gain what you lose at mid range (where you need it) at WOT (where you don't need it).
    Pipes dimensions, is 2.5 all the way from the "Y" pipe - cat - silencer up to where it splits for for the mufflers, then for mufflers is 2.25 or 2? not sure.
    Don't butcher the car, that's my 2c, on the other hand is your car...

  4. #3
    johnny kannapo's Avatar
    johnny kannapo is offline Cadillac Owners Connoisseur
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    Re: 1998 Cadillac Exhaust Questions

    All though small improvements could be made beginning with an extensive Y-pipe rework the car wants the back pressure for low end torque & MPG.

    Appreciate that it's a Cadillac.

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
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    Re: 1998 Cadillac Exhaust Questions

    Early or late 1998 - look at the door sticker for the build date. The exhaust systems are different - if yours has a pretty straight pipe from the resonator to the Y, then it's the later design - all the way to the end of 2003.

    The main pipe is anywhere from 2 1/4" to 2 1/2", depending on the roll bends. The Y and muffler stubs get down to 1 3/4" in places. The cat is already a honeycomb high-flow unit. There are NO substitutes.

    Take a look at www.corsaperformance.com

    Cutout(s) will do absolutely nothing for you, and as posted, mufflers will also do nothing.

    Here's what the mufflers and Y looks like out in the light. I did the CORSA in 2006. Happy camper. The free-flowing (no baffles, anywhere) CORSA will NOT affect low-end torque and has not changed my gas mileage one iota.

  6. #5
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 1998 Cadillac Exhaust Questions

    This is an Eldorado system, but it's very similar to the early 1998 and earlier Seville systems............

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