What did you do to your NBS GMT800 Tahoe/Yukon Today?

[Tonyrodz]

If you don't need cats to pass visual inspection, just get a catless Y-pipe and have your tuner turn off the rear O2s when they tune for the cam.

That's what I did, but my state does a visual. #OUTLAW

 

[Rocket Man]

That's what I did, but my state does a visual. #OUTLAW

Effin Jersey....

 

[Tonyrodz]

Effin Jersey....

Agreed!

 

[Keviebear86]

You can get y pipes with cats or without cats from most of the bigger name header manufacturers. The pre cat (upstream) O2 sensors are what your ecm uses for tuning purposes and those stay regardless if you have cats or not. The post cat (downstream) sensors are what the ecm uses to monitor cat performance and you can eliminate them physically and then have them tuned out or use spoofs like antifoulers. If you end up with cats it’s best to have the downstream sensors. On a side note some emissions places have visual inspections that look for cats and will fail you if they’re not there but some people install things that look like cats. My state doesn’t do a visual, they just hook up to the obd port and since my O2 sensors are tuned out everything passes.

There are not inspection required in Illinois (at least in my county) so I think I'd be ok without them, but I worry that removing the cats will give me a raspier tone and make it considerably louder.

If you don't need cats to pass visual inspection, just get a catless Y-pipe and have your tuner turn off the rear O2s when they tune for the cam.

I had intended on removing rear O2 sensors since they won't be needed after the tune is done. I guess I'm just second guessing myself at this point and making sure I'm doing the correct thing for my project.

 

[Tonyrodz]

There are not inspection required in Illinois (at least in my county) so I think I'd be ok without them, but I worry that removing the cats will give me a raspier tone and make it considerably louder.



I had intended on removing rear O2 sensors since they won't be needed after the tune is done. I guess I'm just second guessing myself at this point and making sure I'm doing the correct thing for my project.

@Bombsquad85 just posted a video of his Denali running without cats. His is a 6.0, but you should listen to it, just to get an idea.

 

[Rocket Man]

@Bombsquad85 just posted a video of his Denali running without cats. His is a 6.0, but you should listen to it, just to get an idea.

Oh yeah I forgot about that. He has a stock exhaust though but you get the idea. You can always quiet things down with a muffler when running headers if it's too loud.

 

[Tonyrodz]

Oh yeah I forgot about that. He has a stock exhaust though but you get the idea. You can always quiet things down with a muffler when running headers if it's too loud.

Yeah, just like mine

 

[Bombsquad85]

you have a air leak on the intake manifold(seals can go bad)..
( you can hear it more in the center, then when the camera is on the pass side area )

or connection to the intake I would inspect every hose .. use something flammable like Axe just only use tiny squirts that stuff has Propane ..you can find the vacuum leak with that just do it on a cold engine

have a ABC rated fire extinguisher on hand just in case..


o

Thanks. It makes sense. I just did the knock sensors so maybe something isn't sitting right. I'll loosen the intake manifold bolts and check to make sure it's seated properly. There shouldn't be any leaks. The manifold gaskets are newish (about a year) and the bolts are torqued properly but I'll give it a once over tomorrow. I appreciate it

 

[Bombsquad85]

Oh yeah I forgot about that. He has a stock exhaust though but you get the idea. You can always quiet things down with a muffler when running headers if it's too loud.

Yup stock exhaust with just the cats removed sounds pretty great. Not raspy at all

 

[Bombsquad85]

you have a air leak on the intake manifold(seals can go bad)..
( you can hear it more in the center, then when the camera is on the pass side area )

or connection to the intake I would inspect every hose .. use something flammable like Axe just only use tiny squirts that stuff has Propane ..you can find the vacuum leak with that just do it on a cold engine

have a ABC rated fire extinguisher on hand just in case..


o

You think I could use a spray bottle with soapy water and spray that to see if I see air bubbles like a leak from a tire?