Ok, here's the deal. First, the O2 sensor: I know my CRX needs one; the CEL comes on intermittently, the ECU flashes code 1, and it failed its smog test MISERABLY. So, here's my question:

I just bought a used DCsports header, and the O2 sensor hole is waaaaay down by the cat flange. Stock CRX O2 sensor is located right up on top. Is the O2 sensor just a single wire that can be extended with a splice? Or is there a special piece that I'll need to extend the wire?

And secondly, along with needing a new O2 sensor, it needs a new catalytic converter also. Here's my question:

Should I buy a factory Honda cat? Or should I use an aftermarket high-flow unit? My CRX is autocrossed as well as daily driven. Only bolt-ons for the engine are allowed, so I'm wondering if a high-flow cat will improve anything at all. What say you? Stock size? Or go with a high-flow unit in combination with the allowed cold-air-intake, header and aftermarket exhaust (no larger than 2.25 inches)? Also, which brands of aftermarket catalytic converter (if i should use one) are good? thanks!!

 

The oxygen sensor should have more than one wire if it's a newer car. Ask if there's an extension cable available for your header; they sometimes sell them together. I'd get an aftermarket cat if you're autocrossing. You'll want it bigger if you spend a lot of time at WOT. Stock cats can clog, and you'll lose performance with them, but more surface area will clog less.

 

You can extend the O2. Just use a similar guage wire and solder the connections. As for the cat, a stock cat will cost a couple hundred dollars, most likely. I would run a high-flow 2.5" cat. You can get a universal 2.5" Carsound for like $50-60 and have flanges put on it at a muffler shop.

His CRX is OBD-, I believe, and they use single-wire unheated O2's.

 

yea, it's OBD. As far as I can tell (without cutting open the wire), it's just a single wire. I'll look into the 2.5 inch cat, thanks for the advice

 

That is correct. Although the header didn't come with an O2 extension wire, it would be best to track down some shielded stuff. The O2 sensor readings are of the low voltage type, which makes it increasingly easy for interference to limit what the ECU sees correctly.

 

AwwwsChwa -- I'm having about the same problem you are, my stock O2 is shot, hell my car won't even idle. My O2 is way back where the cat would be on my setup and it fouls every time I drive the car. The reason is that it just can't stay heated that far back in the exhaust track........So here's the best thing I can recommend that you do. Convert to a 4-wire O2 sensor, they're self-heated and work just like the 1-wire versions.

Goto your local parts house and grab a 4-wire O2, just ask for one from any of the ODB-1/2 Honda's. I intend on using a 4-wire pigtail and splicing it into my stock harness. That way I can just swap 4-wire O2 sensors like it would be stock.

Here is where you can find a nice write up on the process.

 

:shocked: splice all 4 together??? holy ish batman! talk about messin your stuff up!! 2 wires are the heater and the other two go the the comp

 

Re-read the post... he's not talking about wiring all 4 together, he's talking about adding in a 4 wire plug into his existing wiring harness. If you read the link you'd know that too...

 

Neat trick, Speed Phreak! :bowdown: I'll have to remember that one...

 

:werd: that's a great way of beating the system, that's exactly what I'm gonna do. Thanks!!