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  1. #1
    Jr. Mechanic
    Join Date
    Mar 2009
    Location
    Florida Gulf Coast
    Posts
    120

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

    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 by omnisi; 03-11-2009 at 07:35 PM.
    Semper Fi :fighting0037:

    1990 1500 Suburban 6.2L Diesel 4x4


  2. #2

    Smile 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. #3

    Default

    I would do #2 and anything but a K&N filter. I would go with a AirRaid, AFE or S&B. 10 times better filter. Here is a good read on air filters. http://duramax-diesel.com/spicer/index.htm
    02 Chevy Suburban 1500, 4:10 Difs, Stock for now.

    02, CC, LB, 4x4, LB7, 145K Miles, EFI Live Tuned by Nick at Duramaxtuner, Banks Ram-Air w/ superscoop (Plate Removed), Banks Big Head, AirDog 100, Pillar Gauges, 16x8 Eagle wheels, 285 BFGs, Bilstein 5100's, Ride Rite Air Bags 5" Exhaust, 4" downpipe, Prodigy Brake Controller, Goose Neck.

    02 Grand Prix GT.

  4. #4

    Default

    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. #5

    Default

    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 (just kidding w/ that one)

  6. #6

    Default

    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.
    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
    CFM Technologies TB spacer
    CB w/ 44" whip antenna


  7. #7
    Jr. Mechanic
    Join Date
    Mar 2009
    Location
    Florida Gulf Coast
    Posts
    120

    Default

    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
    Semper Fi :fighting0037:

    1990 1500 Suburban 6.2L Diesel 4x4


  8. #8
    Jr. Engineer
    Join Date
    Jan 2009
    Location
    Rochester, MN
    Posts
    231

    Default

    Quote Originally Posted by omnisi View Post
    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
    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.
    99 Silverado Z71 4.8
    2" Suspension lift (Add-a-leafs and leveling keys)
    Long tube headers with 3" offroad Y-Pipe
    Volant Cold Air Intake with Ram Air Intake Tube
    Jet Mass Air Flow Sensor
    Diablosport Predator Tuner

    Previous Truck:
    97 Suburban K1500
    3" Body lift
    2" Suspension Lift (Add-a-leafs and cranked up torsion bars)
    35" Yokohama M/T's
    K&N Intake
    Airraid Throttle Body Spacer
    Hypertech Programmer
    Dual Flowmasters

  9. #9

    Default

    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. #10

    Default

    Quote Originally Posted by omnisi View Post
    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
    Can get a Dynatech from summit for $170.
    http://store.summitracing.com/egnsea...09216&D=309216

    Can also get an O2 sensor fooler. No personal experience with them, but have heard they work.
    02 Chevy Suburban 1500, 4:10 Difs, Stock for now.

    02, CC, LB, 4x4, LB7, 145K Miles, EFI Live Tuned by Nick at Duramaxtuner, Banks Ram-Air w/ superscoop (Plate Removed), Banks Big Head, AirDog 100, Pillar Gauges, 16x8 Eagle wheels, 285 BFGs, Bilstein 5100's, Ride Rite Air Bags 5" Exhaust, 4" downpipe, Prodigy Brake Controller, Goose Neck.

    02 Grand Prix GT.

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