I have a set of stainless works catted headers to install on my 08. They are used and came with 02 extensions for the front, but not the rear. The rear bungs are plugged at the moment. I know you can have a tuner turn this reading off, but are there any adverse affects to doing this when it comes to passing inspection? Should I just go ahead and order rears, or should I just leave them plugged and turn off via tune? I'm dealing with a MD state inspection for what it's worth.



Thanks in advance,


Daniel

 

Previous owner most likely turned the rear o2 sensors off. If you want to use them, you will need extensions. Either way, you will need a tune.

 

I believe he just got the headers and is deciding if he wants to extend for the rear o2's or not. So previous tuning probably doesn't apply here.

As timd38 mentioned, you're going to need a tune either way. But with your build (heads, cam, etc) you already knew that. If you're concerned about passing a visual inspection I'd go ahead and extend the downstream sensors. If not, I would just bung them... which is what I did for my long tubes.

 

So this would only be for the visual? Would not affect sniffer or anything like that?

 

Without rear o2's, you may not pass a sniffer.

 

The rear O2 sensor only monitor the cats, and have nothing to do with the tune.

As for passing a sniffer test, all depends on the tune once the header with high flow cats have been installed. Hence the headers will have the motor running leaner (due to the way the headers scavenge exhaust gases better), so to get all the power from the headers , this requires the engine to be re-tuned.

Also, depending on the high flow cats and if they are still good or not, this will play a big part in passing the sniffer test as well. So if the high flow cats are still good, and your tuner is aware that you need to get the car through a sniffer test/how he tunes the car, should have no problems passing the sniffer test.
Note, if you are in CA, or some other location that will do a visual test of the exhaust system, may or not pass the visual part of the test due to the header and high flow cats isntead.


As for back to the rear O2's, since the header system is using High flow cats, and the high flow cats have been moved down father away from the heads, they are not as effective as the stock cats. So this means, even with the high flow cats in play, installing the rear O2 sensors (with them in play monitoring the differential readings of the cat's pre and post stream) the car is going to throw codes. You can install anti foulers on the rear O2 to pull them out of the exhaust streams enough lower their readings, but as stated, since the Rear 02 sensor only monitor the cats, and have nothing to do with the cars tune, they are just tuned off in the tune/not installed in the system instead.

anti-foulers


Since I bring up open loop, and closed loop. When the car is Wot, it runs in open loop, and does not use the input of the front o2 sensors (it running on all tune, about a AFR of 12.5~12.9). When not wide open throttle (WOT), the motor is using the front O2 sensors input to control the motor, to tries to hold the AFR to 14.7 isntead.


So really, its the WOT part where the car is running in open loop that the tuner has to play very close attention during the tune mostly, so the car in not running too rich in open loop when it running on all tune without the input of the front o2 sensor to cause you to fail the sniffer test isntead. Also, adjustment are made for closed loop as well, so the tune is not having to deviate much from it base lines to hold the motor at 14.7 aft as well.

 

I don't even know why I said sniffer. I just checked (first year living here in MD) and there is no sniffer. so I'm just going to stick with the front 2 and have the tuner turn them off. thanks for the input guys.



Daniel

 

They do a quick visual inspection using a mirror they slide under the car, primarily to verify there are cats (which I have). I have my rear O2's turned off. I ran the wires back toward's the wiring harness and tucked them up and out of sight with a zip tie. All looks intact and I've never had an issue passing.

 

Thanks man. Now to figure out what i need to do to get a md registration and tag

 

 

It's not legal to defeat them for a vehicle running on US roads... but since your car is never driven on public roads, you don't need the rear 02 sensors connected at all. They can and should be disabled (or rather ignored) when tuned.

 

 

probably just a gear head appreciating the ride.

 

I wasn't sure and I wasn't going to invite him to take a second look at the car.

 

I got the "what kind of tires are those"? one time... it ended up being appreciation, not the guy trying to fail me.. but you never know