Y7 header on y8 block bad idea?
 

Hello Honda people. My catalytic converter is worn out (or so my Ho2s says) the inefficiency code seems to come and go with the weather, so I think it's a temperature issue with the cat, not retaining heat, whatever. But:
I have a new-ish manifold/cat laying around that I bought for my old Civic, bolts up to the d16y7. I'd like to know if the y7 manifold is any more restrictive than the y8? I understand the cats are in a different place and it would take some exhaust fabricating to take the old cat out and make everything fit up. Can I still use the 2 - 1 pipe (or b pipe I think it's called) from the y8 setup? Should everything hook up nice and easy? Also, I will need to lengthen the O2 sensor wires, are there any dos and donts about this? Good idea? Bad idea? Thanks everyone!
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Re: Y7 header on y8 block bad idea?
 

You could try the spark plug defouler method first. Google it, it'll only cost around $8

Re: Y7 header on y8 block bad idea?
 

I've thought about it, but it seems a little greasy to me. Doesn't the PCM determine air/fuel ratio by the Ho2s outputs? I'd rather have everything work properly and not cause other issues. My commute is currently 110km one way, so fuel economy is important to me! Will the fouler mess up anything else?

Re: Y7 header on y8 block bad idea?
 

The secondary 02 basically only lets the ECU know the cat is working so it won't mess with fuel trims

Re: Y7 header on y8 block bad idea?
 

But then won't it not know what the fuel trim is actually like? Sorry, I'm having a hard time understanding. Is it the upstream O2 sensor that tells the PCM weather or not the fuel trim is okay? And the downstream just monitors weather or not the cat is working properly?

Re: Y7 header on y8 block bad idea?
 

Yeah the defouler goes on the post cat sensor. The one before is what monitors air/fuel