Oh... you have a CX. LOL. I think I know what your problem is.

The o2 sensor on a CX, VX, HX is really really close to the head. It's not a heated o2 sensor. It's a 1-wire sensor. On your aftermarket header, the o2 sensor bung is much farther away, thus, receives less heat. You'll notice the location of your catalytic converter is different for a header than it was on your stock manifold, too.

On other Hondas that have the 02 bung on the lower part of the car and the catalytic converter underneath the engine, you'll find that they're all 3 and 4 wire o2 sensors. This is because they have a heater circuit that warms up the o2 sensor so it can work. They're called "heated oxygen sensors".

What you need to do if you've moved your o2 sensor is to get one for a DX, and tap your engine harness in 3 locations to get 2 grounds and a + feed from the ECU. I don't think the CX ECU even has a powered 02 heater circuit, so the easier solution would be to move the o2 sensor to a closer location to the head, or return your car back to stock. Aftermarket headerS (meaning multiple brands) aren't intended to be used on models that have converters mounted at the front of the car. You can work around it, but it's a hack.

I had to sort this out on my CX because I DX'ed everything... motor/intake/exhaust/ecu/injectors ...and kept the CX engine wiring harness. It didn't have wires for the different o2 sensor that I needed to use.

 

I know this is a no-brainer, but since no one else has said it... DO NOT waste money trying to get power out of a D15B8. It's a lame-ass motor. For the $300 you'd probably spend on a decent header, you could pick up an Si motor. Of course, there are cooler swaps you can do if you have deeper pockets, but for the money, buy a Z6.

 

^ i agree. you could hassle with putting on a vtec head and crap, but i personally dont see the point.

 

Too easy and 1/3 the cost of a head swap to just replace the engine/ecu/injectors/exhaust than it is to do a head swap because you're probably going to have to rebuild the whole motor to do a head swap. In order to do a head swap, you'd need everything on the top half of the motor, plus an intake, plus a new exhaust system from manifold to tailpoop, a new ECU and the injectors from whatever car the head came from.

I swapped a D15B7, and while it made a huge difference above 4000 RPMs, I didn't change the CX gearbox and it's still a pretty miserable performer. I can downshift to 1st gear at 40mph, but at least I can still get 40 mpg on the highway.

 

im just going to put on my stock headers for now then i guess and when i do the head swap im going to put the headers on... wat if i got a ex ecu... i wouldnt need the second sensor right because ex only has one by the headers...

 

header. i would just save for a full swap, either a z6 or a y8.

 

yea it drives me nuts when people say headers :a:

 

i am going to do a swap... im jus buying piece by piece right now...

 

Tailpoop!! HAHAHAHA!!!
::ahem:: Sorry..It just made me giggle.

I've actually gotten 45mpg out of my Si motor/DX tranny combination. Only once though. Usually average about 34-36 city+highway. 2nd gear is really the only one that is any fun.