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Will a Flowmaster/K&N hekp with stock cat?

Discussion in 'GM Powertrain' started by omnisi, Mar 11, 2009.

  1. omnisi

    omnisi Rockstar 100 Posts

    Vehicle is a'96 burb 2500/4x4 454... Ive read if I emiminate the cat, then mpg will suffer (due to O2 sensor)...??

    I did that on a Jeep, and it didnt hurt mpg. Dont want to spend a lot, just wondering if I should:

    1) add Flowmaster & K&N

    2) Get rid of cat and do #1

    3) Add aftermarket cat, Flowmaster, and K&N

    Im looking to increase HIGHWAY mpg, not concerned with town or torgue...I think the 454 has it . Dont want to spend a lot or get into heavy mods...this is probably all I will do.

    Suggestions??

    Thanks
    Last edited: Mar 11, 2009
  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Will a Flowmaster/K&N help with stocl cat

    What year Suburban? If its 96 and newer it has before and after o2s. Keep your cat if its good (96 up will show code if bad). I would add K&N with the Flowmaster.If your cat is bad replace with high flow cat. If your truck is 95 and older it will not show a bad cat code. Have exhaust shop check the cat.If it has over 100,000 miles on it, than I would change the cat.
  3. trailshredder

    trailshredder Member

  4. Chris Miller

    Chris Miller Rockstar 100 Posts

    If it's 95 or older, you can always take the cat off and knock the guts out of it, then reinstall it. Keeps the inspectors happy. ;)
  5. trackbird

    trackbird New Member

    I'd leave the cat, too. I think the cai & flowmaster are good choices, but don't count on much of a difference in MPG. You might take out the back seats and eliminate as much weight as possible. A fresh coat of wax might help w/ wind resistance :money: (just kidding w/ that one)
  6. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    I personally like #3 if the stock cat is bad. If it isn't, I would have to think about whether I want to replace a perfectly good cat or not.

    As far as MPG goes, I'm not sure. If it's an OBD II vehicle, than it will have before and after cat O2 sensors which will throw a code. I have heard that some vehicles will add more fuel just because of a code in the ECU, not sure if the GM's do it or not. I could also see the ECU adding fuel to the motor because it won't know whether it's running too lean, or too rich or what.
  7. omnisi

    omnisi Rockstar 100 Posts

    Its a '96 with 132K miles. I used the terms "K&N" and "flowmaster" in a generic sense.

    How much are the high flow cats now?....

    Most importantly, I guess i need to know if eliminating the cat will make fuel usage worse...I can stand the dash light for the O2 sensor...just dont want to burn more fuel..

    Thanks
  8. mjalstad

    mjalstad Rockstar 100 Posts

    No, the second O2 sensor is only there to monitor catalyst efficiency, it in no way will change your fueling, that is what the 1st O2 sensor is for. The cat is a restriction in your exhaust so removing a restriction will free up your exhaust and should only result in better fuel efficiency and power. You will probably notice a little louder of an exhaust and stinkier exhaust. I have had a couple of cars without cats and they ran great, my Buick Regal 3800 with 250K got 27 mpg.
  9. heavy chevy

    heavy chevy Epic Member 5+ Years 500 Posts ROTM Winner

    Man be nice to the enviroment put high flow cats on and you will get the same reasults as cutting them off. Plus they make it sound nice to.
  10. trailshredder

    trailshredder Member

    Can get a Dynatech from summit for $170.
    http://store.summitracing.com/egnsearch.asp?N=700 115 309216&D=309216

    Can also get an O2 sensor fooler. No personal experience with them, but have heard they work.

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