I just ordered a 4-2-1 header for my 93 LX. 2 reasons... 1, the prevouse owner that put in the z6, reused the exhaust manifold from the d15 that was in it... and 2, that manifold has a crack and is leaking where it meets the down pipe.

Looking at the pic of the header, there are 2 places for the O2 sensor, almost right of the engine, only reading one of the cylinders and one back at the end, near the joint to the cat. does it make any difference rather its reading just one or all four. If it does, would it be a good idea to order an O2 extention to be able to reach the back bung?

 

ok so i am assuming u ordered a chepo ebay header one of the o2 sensors goes in the fist bung u cap off the 2nd bung and u run ur 2nd o2 sensor behind the cat unless u dont have a cat which means you will need to get one because because if im not wrong the b15 has the cat on the manifold

 

96 and newer have the cat with the manifold, mine is more or less under the shifter (that general location anyway)

Actually, it is like a $50 ebay header but even the megan racing 4-2-1 headers have the same 2 bungs. Only reason i went cheap like this is i didnt see the point of getting a "good" one when im planning on turboing is in the next 12 months or so... i just need this to fix the exhaust leak

 

Use the bung at the end of the collector.

 

Use the bung that the wire length dictates, those 2 wire o2 sensors aren't that picky.

 

I'm assuming you got something similar to this (ignore the test pipe in the middle):



If so use the bung location at the end. If you are only monitoring 1 cylinder by using the other bung it's not going to give your ECU the most accurate reading and could throw off your mileage and hinder performance. You may have to extend the O2 wiring depending on how much length you have. It's a 4 wire O2 not a two wire.

 

Yes that looks exactly like what i ordered, sans the test pipe

Thats what i was thinking.... now should i order and extension cable for the sensor, or just break out the soldering iron and extend them my self

 

some will tell you to use an extension for me i used a soldering iron and heatshrink and some wire wrap and i extended it after the cat

and my bad you are right about the exhaust manifold forgot that they changed that