96-00 LX/DX/CX/HX to EX Exhaust Conversion
 

This thread is designed to help you understand the reason for and concept of converting your 1996-2000 Civic CX, DX, LX, or HX's full exhaust layout to that of the 1996-2000 Civic EX.
Start here to get the basic idea.

Then, read the DIY to see exactly what you will be doing.
Here's a link to a detailed thread that shows the exact process of the conversion and everything you need to know about how to do it: https://www.hondacivicforum.com/foru...ad.php?t=73504

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So you have a 1996-2000 Honda Civic DX, LX, CX, or HX with either a D16Y7 or a D16Y5, and you want to install a header.
Well, unfortunately, the design of exhaust manifold (a.k.a. header) on your car is different from the design of the aftermarket headers available for your car. Your exhaust manifold has the catalytic converter integrated into it.

DX/LX/CX/HX Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)
http://i75.photobucket.com/albums/i3...austlayout.jpg


The headers available for 96-00 Civics are only made for Civic EX’s (except for one made by Magnaflow, but I am not going to talk about that because it is not as good as an EX header). Civic EX’s have a regular exhaust manifold, with the catalytic converter located directly after the exhaust manifold.

If you have an aftermarket catback exhaust on your DX/LX/CX/HX, then chances are, your catback looks like the one in the first diagram, but has a short removable ~16" section of piping, located where the catalytic converter is on the EX layout. In this case, when you get the EX catalytic converter, you just replace that short ~16" pipe with the catalytic converter. This ~16" section of piping is essentially a test pipe.

EX Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)
http://i75.photobucket.com/albums/i3...austlayout.jpg


There’s two things you can do - a wrong way and a right way.

The wrong way:
Install the EX header onto your car, and leave the catalytic converter completely out of the equation.

This is a bad idea for a few reasons:
1. It is illegal, and if caught, you will be penalized.
2. You will throw a CEL (check engine light) and the car will run in limp mode (limited power, bad gas mileage lower rev limiter, etc.) because the secondary O2 sensor will think that the catalytic converter isn’t working, or you may not be able to hook up the secondary O2 sensor at all.
3. Instead of CO2, NOx, and H2O, your exhaust will spew out hydrocarbons and poisonous carbon monoxide gas.
4. You will fail emissions/smog/inspection/etc.
5. A test pipe gives you only ~1WHP over a high flow catalytic converter. 1WHP isn't worth breaking the law and/or failing smog.
6. You will be polluting our air even worse than it is already being polluted.

The right way:
Convert to the EX exhaust layout by installing the EX header, installing an EX catalytic converter located directly after the header, and using an O2 sensor wire harness extension to relocate the O2 sensor to it’s new location on the EX catalytic converter.
You can convert using bolt on parts designed for an EX, or you can cut and weld the exhaust parts together as needed. You can have your original catalytic converter cut off and welded directly after the header if you want. The advantage to bolt on parts is that anyone can do it themselves with simple hand tools, and different pieces can be taken apart in the future if necessary.
Any method will work, as long as the finished product has this layout:

Converted Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)
http://i75.photobucket.com/albums/i3...tedexhaust.jpg


Items needed:
-EX catalytic converter
-EX header (a.k.a. exhaust manifold)
-O2 sensor extension wire harness
-EX aftermarket or stock catback exhaust (aftermarket DX, LX, CX, HX catback exhaust will work if it has the removable ~16" section that I mentioned earlier. If it doesn't have that section, the only thing you can do is cut the piping and weld the catalytic converter to the mid-pipe of the catback exhaust.)

Items I recommend:
-Magnaflow 22628 Catalytic converter (direct bolt on, high flow)
-Megan Racing 4-2-1 Header (best bang for the buck, although any brand will work)
-PasswordJDM O2 sensor extension wire harness
-Apex-i WS2 Exhaust or other oval-canister style muffler


BEWARE: eBay "high flow cats" aren't catalytic converters! They are resonated test pipes!