Cat size?

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1badgmc

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I'd go with 2" diameter, I'd rather be 1/8th to large than 1/8th to small, most people will tell you "ahh hell, just cut them off" but if it's not intended to be loud, then I'd put some magnaflow high flow cats on, although I heard even them can throw a code.

Yeah, eliminating the cats is not an option. We have inspections. Though I'm not in an emissions testing area, they do visually check sometimes. Even without the inspections, I wouldn't lose the cats. This is the family hauler and I do appreciate the quiet exhaust.

Also did you scan the codes to see if it was just a bad o2?

Ok, it had been a bit since I scanned it and I just glanced when I did that. I've got a friggin' laundry list of codes right now. :(

Here are the O2 codes:

P0131: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
P0141: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
P0151: O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
P0161: O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)

Reading up on the codes, it seems like the cats may not necessarily be bad. I may just need a shopping cart full of sensors.
 

RHamill

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How's the gas mileage, I know on the 5.7 vortec you have 4 o2 sensors, 1 on each pipe before the cats and 1 on each pipe after the cats, the front 2 are in charge of the A/F (Air to fuel) Ratio. If those o2s are bad, I'd recommend replacing them as soon as possible, otherwise you will be running super rich because your truck thinks you are running lean.

The rear 2 o2s are basically there to tell you whether or not your cats are bad, from what I've heard/read you can run without them and it wouldn't change anything, you would just have that annoying idiot light on forever. Nothing a decent PCM tune can't take care of.
 

DRAGGIN95

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I have done this one other way one time and it does work, I removed both cat's and put a nice flowing y in it's place and then a single 3 in. high flow convertor right behind the y, and then put the rear o2 sensor's side by side behind the convertor they don't know the difference of being behind the same convertor. This saved me some money, and still sounded the same and I like the 3in. high flow convertor.
 

dusterbd13

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yea thats what i figured thats why i didnt do it, would have liked to though. how about some hi flow thunderbolts $35 a piece worked great for me. just get 2" ones.


or you could leave them alone and get some spark plug defoulers to stop the codes.
http://www.msprotege.com/forum/show...ure-Cel-Mil-from-removing-cat-with-Non-Fouler

can you give a link to the high flow thunderbolts for 35? i need to put a cat on my 89 when i do the exhaust next month, and i like that price.

Michael
 
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