O2 Sensor Question

[Voltaire]

I am building a B & B cobra and will be running a fuel injected 5.0. The headers that came with the car are long tube multiply pipes terminating where they connect to the side pipe. The pipes do not run together before they enter the side pipe. The question is has anyone else had pipes like this and how did they manage to add the 02 sensor. I was thinking of taping one pipe on each side of the motor.

[olddog]

That is the way my pipes are. The O2 bungs are welded in about (estimated not measured) 14" from the head in a single pipe. I have read many sources who claim it is better to use a single pipe and stay within 18" of the head, than to use a collector 30" from the head. Obviously it is best to have all pipes merged together closer to the head, but that isn't going to work with Cobra side pipes.

Using a single tube means you need a very ballanced air flow on both intake and exhaust side to keep all cylinders equally rich/lean. A bad injector on the cylinder with the O2 will mess up your day too.

Now I saw quite a few Cobra with the O2 in the collector on the side pipe. A couple of the guys I questioned are using a system that has a wide band O2, not the narrow band O2 used in the OEM applications.

I'm far from an expert, and I have pretty much told you all I know. Hope it helps.

[DonC]

If the original engine had wide band sensors you might be able to get away with them mounted in the collector. Most of the good quality wide bands have very capable heaters. A good number of after market wide bands will work in a tail pipe mount and that's a lot farther away from the exhaust ports than a collector. If the original engine had narrow band sensors keep them within about 18" of the exhaust port. Primary difference between the two is that a narrow band sensor is just that, narrow. It only reads from about 14.0 to 15.0 AFR. A wide band sensor will read from about 10 to 20.
What kind of EEC does the system have? If it's and earlier Ford A9L then you're restricted to narrow band sensors as far as the system goes. You can add a wide band to the narrows but all it will do is report AFR in a data log. It won't interact with the EEC for tuning or operating the engine.
DonC

[Voltaire]

Thanks for the information. The ECU that I have is a A9S. It appears either way I have only 2 choices pick one of the single header pipes or punch a hole in the side pipe. I am leaning toward one of the header pipes as the side pipes are ceramic coated.

[DonC]

I'm pretty sure the A9S uses narrow band 02's so putting them in the collector wouldn't work.
DonC