Honda CRX Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
276 Posts
Discussion Starter · #1 ·
From what I've found, the stock manifold has one O2 for each pair of cylinders. Has anyone had any problems adding both sensors next to one another downstream (single pipe). The DC header that came with my car only has one O2 bung, and I'm trying to figure out where to weld the other.
 

·
Premium Member
Joined
·
4,512 Posts
Not that you probably already know,but in a 2 sensor O2 system the usual is one upstream(pre-cat) and a downstream(after-cat).
Now if you run sans catalytic converter I don't see the need for a second O2 sensor.
 

·
Registered
Joined
·
276 Posts
Discussion Starter · #3 ·
ollie said:
Not that you probably already know,but in a 2 sensor O2 system the usual is one upstream(pre-cat) and a downstream(after-cat).
Now if you run sans catalytic converter I don't see the need for a second O2 sensor.
Thats what I've always seen in the past, but I was under the impression that the OBD-0 B16s ran the O2's right next to one another.
 

·
Registered
Joined
·
276 Posts
Discussion Starter · #6 ·
Will one-wire O2 sensors get/keep enough heat in them if mounting near the exit end of the header, such as where your typical 4-wire would go? I need to mount another O2, and I'm wondering whether I should weld another bung next to the O2 at the end of the header, or whether I should weld two bungs on two different runners of the manifold, closer to the head.
 

·
Premium Member
Joined
·
4,512 Posts
lessonsinspeed said:
Will one-wire O2 sensors get/keep enough heat in them if mounting near the exit end of the header, such as where your typical 4-wire would go? I need to mount another O2, and I'm wondering whether I should weld another bung next to the O2 at the end of the header, or whether I should weld two bungs on two different runners of the manifold, closer to the head.
First question-No a 1 wire o2 sensor will not get enough heat to run properly.Thats why you don't see 1 wire o2 sensors that far downline.

Second-If your wanting to get a little more accurate with fuel ratios you can run 2 seperate o2's on different runners.It will be a little more accurate,but probably not THAT much more.
GL on your install.
 

·
Registered
Joined
·
3,255 Posts
If its a 4-2-1 DC header I would just set it up like the OEM OBD0 manifold:



Just weld in 2 O2 bungs at the 2-1 section.

Are you also using a PR3 ecu?
 

·
Registered
Joined
·
4,384 Posts
OK, I have to step in here.

There are 2 distinctly different 02 setups for the obd-0 (pre-obd) crx and civic platforms using the B16A or the B16A1 engine.

The PM3 and PW0-000 (JDM) and PW0-X00 (EDM) respectably use different designs.
The JDM versions of both ECU's which have a different ID codes to tell them apart.

The JDM versions of the ECU's use the in-line consecutive design, using dual 02 sensors. One sensor is positioned before, and one after the catalytic converter.
Each sensor will measure at all 4 firing instances, measuring a certain resistance between them. An algorithm connected to an in-dash warning light will tell if the catalytic converter is faulty.
Removing the catalytic converter will prompt an CEL and engine error code respective to that sensor.

The EDM versions work different entirely.
The 02 sensors are paired up along side, dividing the runners of the headers in pairs as well.
The runners are seperated as the inner, and outer pairs, placing the sensors either in cilinder pairs 1+4 and 2+3.
The ECU readings will alternate between each pair, reading only the relevant sensor.
So swapping them around will cause both sensors to get false readings, throw a CEL and the corresponding error codes.

The most common causes for faulty readings, besides faulty sensors is placement.
Most header designs on B-series engines, make use of a single 02 sensor location. Reading only 2 outlets.

Most common is that the only placement is on the runners 1+4.
While in the best case, this means you are only measuring half of your cilinders, this also means the EDM ecu will throw a code, because it's only getting half of it's required readings.
A simple fix is tapping a hole in header tube merger 2+3.

Another is placement.
While exhaust gasses travel down the exhaust line, they cool down.
The 02 sensor readings are temperature dependant. Thus getting a faulty reading.
While some of the JDM ecu's use a heated core to resolve this issue. No OBD0 EDM ecu's are available with this feature.
A simple solution to this would be to manually hook up a heated sensor to a switchable power source.
 

·
Registered
Joined
·
276 Posts
Discussion Starter · #12 ·
Thanks for the great info. I was completely unaware of the two versions of the PW0, so I will be checking into that before determining where to weld on my new bungs. I unfortunately am running a 4-1 design, making this slightly more difficult, so a heated O2 may be in order.
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top