I'm just about ready to have exhaust put on my 4.6L. I think I'm going with true duals, running up to a couple Flowmaster Super 40's and then straight out the back..The question is whether to fork out some cashfor some high-flow cats or to not have any cats at all and save myself some $160.. I would like to know if not having cats and then running some O2 simulators will affect the way my engine runs.. Or will the truck never know what hit it and run fine.. If I need the cats, I'll get em but I was looking for a way to save some cash...
Any help would be apreciated...

 

While I can't tell you what your final results will be without the cats in place; I do want to tell that the way the computer uses the front and rear sensors is quite complex.
The front sensors controls the fuel injection corrections on a continous basis but also does some very fancy calculations by looking at the rears sensor switching rates and compairs to the fronts switching rates.
This then becomes the basis of telling how efficient the cats are operating and determines the thresholds to set an engine code for service.
So what this means is that in some cases, even a cat change may take the system out of normal operation according to the engine PCM.
Trying to fool the PCM may keep the CEL out, but still change the operation of the fueling system such that milage may be greatly affected as well as power.
It's your call besides any state inspecion requirements.

 

i was thinking about how you said the front sensors regulate the fuel flow and got an idea.. Since there's quite a few people i know running around here without cats and not having trouble with the authorities...I really want to save some money..I thought that I could put new front sensors to start with, that way the engine would have something to read and run by.. Then plumb without cats. You mentioned that the readings and how they differed between the two sensors set off the bad cat code....Well If I had O2 simulators on the back 2 sensors, as far as the computer knows, I have great working cats...
As far as I know this would be a great setup, but If you or anybody else finds a problem or something I overlooked, please tell me..Thanks again

 

Keep in mind that the "Check Engine" light comes on only when emissions exceed 1 & 1/2 times the federal standard for that year of vehicle. "That's a pretty big cushion in my opinion!"

Read all the post I was afraid it would be to long and get messed up! Sorry...

 

So just because anyone is not throughing a code whether they are with or with out cats. That does not mean that it is running at peak perfromance and effeciency!

 

So if you put a voltage generator on it and it's not throughing a code then that just means that your generating with in 1 & 1/2 times the federal standard for that production year.

 

Generating +/- (.01 mv) can change a lot of parameters on the engines overall parameters. (AKA Performance) Including but not limited to Fuel/ Air Intake, and timing.