Catalytic converters

Second this any cat other than stock and you will still need a URD O2 simulator.

 

Must be a 2nd gen thing, I have aftermarket cats on my 04 (Magnaflow) and they work just fine. They are CARB
compliant though.

 

If you don't care about emissions equipment just do yourself a favor and de-solder the LED. I went with full URD exhaust. Long tube headers (no cats), Y pipe (no cats), then the magnaflow muffler. It sounds a little raspy between 2.5-3.5k. Originally I had the URD rear O2 sensor emulator, but the ABS and EVAP bypasses lit up my dash so I just removed the simulator and got rid of the CEL, ABS, and TC lights.

Anyone who tells you that your vehicle will run like crap without the cats or down stream O2 sensors is an idiot. As long as the upstream O2 sensors are in place it won't be stuck in open loop. If you're concerned with loss of back pressure, I suggest you read up on how engines function. Maximizing the amount of exhaust gas that can evacuate the cylinder is not going to hurt your engine.

 

Well that's the thing...I have read numerous accounts of where the 4 cyl engines need the back pressure in order to keep the low end where you want it as well as keep the valves doing their jobs the right way.

Not trying to debate you...but rather I am looking for some more information on why this may or may not be the case. Like I said, Im ready to bite that bullet and go free flow....so long as it will still deliver on low end and not hurt the valves.

 

@eppy i had code referring to cat efficiency.
It happened shortly after a motor swap and the guy is telling me i need cats when all i needed was the donut gaskets for the y pipe after scoping things out. That was at around 238k. I'm over 275k now...
It may be worth your time to have a look-see.

 

This^ An exhaust leak will cause the PO420 code to pop up.

 

Sorry if this sounds harsh, but really aren’t many exceptions to the rule that modernish naturally aspirated japanese engines do not make noticeable power gains with only intake/exhaust. If you really don’t care that much about the environment, just get o2 simulator for the rear sensor and be done with it. (Unless it’s physically broken).

 

Not how it works buddy. The front sensor output is used for fuel trims. The rear sensor’s sole job is to check catalytic converter function, zero impact on how the engine runs. This is the sensor he would put the simulator on.

 

Fellas, thanks for all the feedback and much appreciated. I will report back after I get the scan performed and address the issue. Gaget from URD informed that most likely the element in the rear cat is wearing out causing the code to be thrown. If that's the case, I will most likely go with the URD 02 simulator, gut the Cat if needed and see how it goes. My only concern is if the rear cat is wore out, the other might be getting ready to go also. So we'll see what shakes out.

 

That may be true in some cases due to improper tuning, or poor exhaust velocity. All I'm saying is allowing more exhaust to evacuate will not damage or reduce the life of an engine. It seemed like the damage factor was your concern in the post I was responding to. Good luck with whatever route you take. I have a rear O2 sim for the 4.0L sitting in my garage, but I won't be back until June. If they're compatible & you still need one when I get home you can have it for the price of shipping.

 

My bad. Didn't have my coffee yet. That said, a pretty much totally open exhaust does little for increased performance on a stock motor since the intake side will become the bottleneck. The ability to piss off the neighbors does go up exponetially though. For reliability, I'd just go with an aftermarket cat and whatever you want behind it.

 

@kidthatsirish
I've been running ice headers & injen intake w/ stock cat/exhaust for over 30k & pushing 55k now & never lost mpg or threw any codes. The 4cyl runs @ 35krpms torque band w/ these 2 things mine runs bout 27krpms torqueso any thing you do to it lower this so it's definitely gonna be more responsive after these tyhings your talking bout. I say go for it & see how fun tthe truck becomes.
Quik question.... manual or auto? Cuz autos don't react power wise the same as a manual w/ these mods by what I gathered from here

 

Real quick here is a legal issues to think about it is technically a federal offense to take a catalytic converter off and not replace it. Secondly desoldering the chk engine light isn't wise for future reference if you have an issue with something else that is your warning system. Plus if you have a desoldered light then resale someone could catch that if you do ever sell it.

Now if you go long tubes the front O2 sensor is monitored to regulate the air fuel ratio.
The O2 simulators are only for the rear O2s which are cat monitors so no problem there.
If you are dead set with not fixing the cat and you go with headers the y-pipe and catback I would suggest getting the simulators and go that route that is the smartest route to go.

The rear cat is not monitored at all so that is incorrect information!!!! Only the cats built into the manifolds are monitored.

The question about not enough back pressure kills low end torque the best answer for you is go dyno before and after and see. There is a science to exhaust and it really isn't as big of a deal with a stock car to do this the torque loss will be negligible at best. Those headers are I would hope better at scavenging than the stock manifolds so you'll get some torque gain there.

 

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