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

[omnisi]

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

[silveradotrailblazer]

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.

[trailshredder]

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

[Chris Miller]

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. ;)

[trackbird]

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)

[ct9a]

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.

[omnisi]

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

[mjalstad]

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.

[heavy chevy]

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.

[trailshredder]

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/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.

[mjalstad]

If you are only looking to increase MPG, I would get an intake and a programmer. From personal experience, I have noticed those two things to be the best MPG gainers. I gained 1.5 MPG with those two mods on my 99 Silverado and on my 97 Suburban. Removing the cat really isn't going to give you anything and as long as it functions well, I would just leave it alone. It's not worth polluting or the chance of getting caught without a cat for the tiny increase in MPG and power you would see. Also, the programmer and intake are very easy to install and pretty cheap. If you bought them used and/or on ebay, you could get both for under $500 and it would take only about an hour to install the two. Also, when modding for gas mileage, you need to realize that it is going to take a long time to see a return on your investment, so if you are only doing it for MPG you may want to rethink it. If you spend $400 and your mileage increases from 14 to 15.5 mpg, it's going to take 30,000 miles of driving just to break even with gas at $2/gallon.

[omnisi]

If you are only looking to increase MPG, I would get an intake and a programmer. From personal experience, I have noticed those two things to be the best MPG gainers. I gained 1.5 MPG with those two mods on my 99 Silverado and on my 97 Suburban. Removing the cat really isn't going to give you anything and as long as it functions well, I would just leave it alone. It's not worth polluting or the chance of getting caught without a cat for the tiny increase in MPG and power you would see. Also, the programmer and intake are very easy to install and pretty cheap. If you bought them used and/or on ebay, you could get both for under $500 and it would take only about an hour to install the two. Also, when modding for gas mileage, you need to realize that it is going to take a long time to see a return on your investment, so if you are only doing it for MPG you may want to rethink it. If you spend $400 and your mileage increases from 14 to 15.5 mpg, it's going to take 30,000 miles of driving just to break even with gas at $2/gallon.

Roger that...what specifically are you referring to as an "intake" ?

As far as saving mpg, thats why I was wondering specifically what a higher flow air filter and exhaust would do because thats probably all Im willing to spend on the 454. I want to PEAK it, no chance of a dramatic gain....

Maybe I should have asked...For best mpg on a '96 454 how do you get peak mpg with the least $$ ?

Thanks

[silveradotrailblazer]

Jegs has Magnaflow highflow cats for around $90.00, depending on truck. I have two on my Silerado.