Upstream and downstream?

Wide197

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thanks for your input, guys and gals......here's my first post with the recent arrival of an '06 S197 GT!

(Upstream and downstream refers to oxygen sensors)

Purchased a few months ago, it was only a matter of time before the first, ominous check engine light arrived. What else can one expect from a 200k daily/HPDE car owned by a twenty-something kid from downtown (Phoenix). Talked him down to 11k for it. Pictures to come.

6

No, not the race car number or what I did to the kid not the kid (86'd him) I purchased it from, but the cylinder number. Coils looked good. MSD, newish......but a bad coil and a few decent looking plugs meant americanmuscle.com is a few days out. Seems to be a lot of #6 cylinders with bad COP's based off the forums I've been reading.....any input to this particular engine?


Fast forward to today. Car is up on blocks. Figured it would be a good time to give it a tune while I wait for the plugs and coils. Fluids checked out. I've done the brakes already. How about new oxygen sensors? Turns out, after the addition of Pacesetter long-tube headers, it appears the upper 02 sensors have been deleted (or are not able to be used on this particular set of headers) in favor of a cat-less exhaust. Only the downstream monitoring sensors for the engine are active. How would this effect the engine? Does this need to be compensated for when tuning the car professionally? It currently has a LITO 91 tune.

Either way, take a look at this pic and see if I got it right. Green is downstream and blue (the plugs with no 02 sensors) are the upstream. Update the plugs with new ones or test first, then decide?

Sure hope it passes emissions......

Oxygen Sensors.jpg
 

MrBhp

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FYI, factory coils are the go-to. MSD unfortunately are not what they once were.
I'm catless. I installed the O2 sensor simulator from Big Daddies Garage. No codes.
 

AHaze

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I can't remember connection colors but hopefully the upstream O2 sensors are the ones that are still there. The downstream sensors can be turned off in the tune as all they really do is monitor catalyst efficiency. The upstream sensors are what the PCM uses to adjust fuelling.
 

07 Boss

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You want your upstream or front sensors on. The rear or downstream are for monitoring catalyst efficiency only and do not have any bearing on how your engine runs. I can't remember the color of the connectors but I think I have extensions on there anyways. I also have the pacesetter LTs and catless mid-pipe. I too run the big daddies O2 sims with 90* extensions.

 

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