OK...converters are finally starting to show signs of going bad. I've already got a good muffler back set-up that'll stay in place; SIDO muffler with 3" in. I want to replace everything forward except I think I'm gonna leave the stock exhaust manifold. I'll leave them for low end torque, but mainly for budget as I've got other priorities and don't want to budget for headders and a tuner right now. So, considering leaving stock manifolds, I want to get the Magnaflow high flow converter and new O2's. My main question would be which converters to go with and where to place them in the system, along with where to place the O2's in relation. With lack of a tuner, I'd really like to avoid a CEL. So what tips and suggestions you guys got?

 

Highly recommend that you re tune after upgrade. Truck will run too LEAN. Lot of people don't want to reflash after parts install. Also cats should be right after manifolds. You can also get a multiple tune kit to keep mpgs or a performance map as well.

Also being that you live in Cali, it will be a nightmare trying to find someone to smog your truck. All new STAR smog facilities require physical inspection prior to test. You should know that there currently is no "legal" performance cats here in Cali so you won't be able to get sniffed. Judging by your profile you are about at your max limit as far as exhaust mods unless you want to swap parts every other year.

 

Nope, I'm not in Cali. From the homework I've done, I thought I'd be pretty safe in the A/F ratio department keeping stock manifold and stock exhaust design.

 

Thought you had Cali plates, my bad. Once you change cats you will need to re tune....period. The band in which your truck operates on is pretty narrow. It's only designed to change a/f ratios to a certain extent. When going with a smaller cat the ecu thinks the car is too rich so it will lean itself out to the lowest setting it can in order to fire the cylinders. Then you end up with a cel, had that experience on my sports car. The tune is well worth it. This is all solid info that I would know still not look past.

 

Replace the 4 cats with 2 high flows that have the bung in them for the rear O2's. Keep the front O2's in the stock location.

 

Still won't change the fact that the truck will be running lean.

 

I don't understand why - as long as the FRONT O2's are working properly. Those are before the cats and control the mixture. The rear O2's only monitor cat efficiency.

 

Front sensors are for air and fuel rationing. Secondary sensors monitor the expelled gases from vehicle. If cats are smaller there isn't as much being burnt off from catalytic converter. Hence the reason why you get a cel.

 

The mixture will be correct as long as the front O2's are in the right place and functioning correctly. True, you might get a cat efficiency code but they don't affect the way it runs. They can either be turned off in a tune or you can use the Gotts O2 mod.

 

you turn them off in a tune because the catalytic converter is shorter and the ecu cannot compensate for the loss of catalytic converter. In the tune you have to re adjust the afr rate. My car when I tuned was at 13.9 which was too low, due to less catalytic converter. Final adjustment was at 14.7What you just stated is incorrect.

 

Anywhere that has a dyno jet would be sufficient, otherwise a handheld wouldn't be a bad option. Your better off doing it right the first time.

 

I don't see how that's possible. The FRONT O2's control the AFR, not the rears. The front O2's are before the cats.

 

The rears monitor the expelled gases. If too rich it sends signal to ecu to rich or lean engine.

 

No, it trips a CEL for low cat efficiency on THESE engines.

 

http://www.easterncatalytic.com/educ...he-po42o-code/

Knowledge is power. Smaller catalytic converter will give same symptoms as a bad catalytic converter. It is not "a check engine light"