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Discussion Starter #1
Ok I am getting a header and am looking my car and it has 2 o2 sensors. The header has 1 bung in it. Can I eliminate the 2nd sensor or should I ad the 2nd bung?

Also I noticed that the upper o2 in the new header is in the #1 cylinder tube. Shouldn't be somewhere near the point where they all come together?
 

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1997 Civic Hatch D18Y8 M62 S/C
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2,663 Posts
You can get rid of the second O2 sensor but then you'll throw a CEL assuming you're running the stock P2E ECU. You might also end up running lean because the ECU uses both reading to determine how much fuel to run. To get around this you could run a shipped OBDI ECU which to me isn't worth it just so you can bolt on a header.

IMO it's better to have the O2 bung at a collection point in the header so that all the exhaust gases are sampled not just one.
 

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1995 Civic EX Coupe
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579 Posts
they have headers all over ebay that have 2 O2 bungs. my buddy just picked one up but we had to extend the wires from the front of the motor all the way down by the cat.
 

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99 civic hatch
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for my car, 99 cx hatch, you do not have to extend wires, just strip the plastic around it and you can pull it back. if you want to keep the stock obd2 ecu, you will have to run a bypass on the os sensor that makes it read a lower signal so you won't throw a CEL. Get a obd1 conversion harness and run an obd1 ecu and chip it and tune.
 

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The second O2 sensor has to be after the cat. OBD2 requires monitoring the cat, and that's what the second O2 sensor is for. When I swapped to a normal header on my Y7, I simply had an O2 bung welded in after the cat, then extended the wires for the secondary O2. You'll need to solder the wires when you extend the harness, as these are very low resistance sensors, and simply crimping may still throw a code.
 

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Discussion Starter #9
No no emissions here eithere, and I am eliminating the cat by installing the new header. Breakin the law breakin the law!!!!

LOL!!!

I am not installing the header yet till I get the rest of the exhaust done and a muffler.

I was thinking something liek a twin loop, and 2.25 pipe.
 

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No no emissions here eithere, and I am eliminating the cat by installing the new header. Breakin the law breakin the law!!!!

LOL!!!

I am not installing the header yet till I get the rest of the exhaust done and a muffler.

I was thinking something liek a twin loop, and 2.25 pipe.
Yeah, that's almost what I'm running... Y7, DC4-2-1, no cat anymore, 2.25" pipe, Pro-Flo Twister race muffler as a resonator and a R-active twin-loop muffler. Sounds really deep, with no fart pipe sound.
 
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