ALittleTooHigh

Hello HT

So I have a y7 hatch and the header goes straight into a cat. I want to get an aftermarket header in place of that. My plain is to install the 4-2-1 header, go straight into a magnaflow high-flow cat, and run straight pipe to a magnaflow muffler. Is this going to work on this car? I am pretty much ditching the whole stock exhaust and having the shop run new pipe and everything.

My question is - will the fitment be right for the header, cat, and piping? the header is a 2" outlet, haven't picked a cat yet, but I had a magnaflow highflow cat on my ex coupe that worked great, so I was going to pick up another one of those.

Also will there be any CELs involved in this? I know the header I can plug the primary o2 in, but the secondary o2 was going to the cat after the header, so I guess I would either have to do an o2 simulator or run it to the cat?

Help is appreciated, I searched and found a few things but didn't really see anyone trying to do what I am.

koolhut

The cat size does not have to be the same diameter as the header, my gf has a 2" header outlet going into a 2.5" test pipe/cat. If you mean length wise, if the shop is doing the work, they will make the length fit to the cat. Your o2 sensor/r's can be disabled with a simple chip in your ECU.

HondaPartsHero

Just get a cat that has the 02 bung in it. The extend your secondary 02 to run to it.

B20DelSol

Is there any reason for going to a header? Cracks in the exhaust manifold maybe?

I only ask this because I did the same thing on my old Y7 and as many will tell you, it won't make too much of a difference.

My manifold had a crack in it though and I did not want to weld it up so that was my stupid way to rationalize the header. lol!


HondaPartsHero has the correct way of doing things for the secondary O2 sensor

You can also buy a spark plug non-fouler that has the same threads of the sensor, drill out the non-fouler to fit the sensor, and place that into the exhaust if you use a test pipe or are worried about codes. This is a tried and true method that works great for $2.

A Magnaflow muffler will be great with the combo if you want it to be quiet with a bit of tone. I just switch to a magnaflow (2.25 in/out center/offset 4x9x14 oval) and I absolutely love it compared to the LOUD N1 Ebay muffler I used to have.

ALittleTooHigh

No real reason, just wanted to get them. Probably going to try the foulder. I had a magnaflow muffler on my coupe and it sounded really nice

ceresia

Is there anything wrong with the stock cat?

I just installed my DC headers last night and used the stock cat, bought a new o2 sensor for the upstream on the headers and spliced it in to factory connector, plus full tsudo cat-back, sounds great and no worries about CEL coming on.

B20DelSol

Hahaha...okay...good answer...don't we all just want something for these damn cars!

I only recommended the fouler idea because the OP stated he wanted to use a high flow cat which may/may not cause a code thrown. But depending on the header, the OP may be able to use the stock cat...well, do they even make the longer tube tri-y headers for d-series engines? In any case, most headers will work with the stock cat too.

HondaPartsHero

The problem is the stock cat is part of the header (exhaust manifold) so he'll have to get another cat welded in

ALittleTooHigh

Okay so heres a little update what I did

So first off the manifold was cracked hella bad when I took the heat shield off, so good thing I got the header.

I took out the mani and cat (those bolts were a bitch with my little 3/8" set hahaha) but I bolted the 4-2-1 header straight to the piping (for now). I wasnt able to make it to the exhaust shop in time so i'll go friday. But I ended up getting a regular magnaflow universal cat instead of the high-flow. There is no bung hole on it though, so I may get the shop to drill a bung hole or i'll just run a fouler.

Also to those who are interested, yes it did bolt up to the stock exhaust. The header does touch the bottom of the transmission though, and rattles a bit. I think I am going to get the shop to fix that.

B20DelSol

Haha..I forgot about that too

ceresia

Dang, too bad you don't live around IL, I could just give you my EX header that I took off.

HondaPartsHero

the EX header doesn't have the cat built in