Where to mount fuel ratio sensor

[ward00]

I'm planning to use a fuel ratio sensor to try to performance tune my 75 Spider. The car has headers with a bung on one of the 4 exhaust pipes where the sensor could be mounted, but that location would provide info about only one cylinder. If your car has headers with a single bung and you are using a fuel ratio meter, is this where you mounted it? If not, what's the purpose of the bung?

[rebar1111]

O2 gage suppliers say to install the sensor a minimum of 18in downstream of the exhaust valve. I have twin IDF's and wanted to be able to tune each carb (one venture per cylinder) using a 421 exhaust pipe. I installed the bung in the '2" area of the pipe as low as I could and still have access from the engine compartment. The best I co due on the tuning ratio was a variation pulse from 12 to 1 to 14 to 1. Two cylinder measurement on a 4 cylinder engine just varies too much. I have asked the supplier (Innovative) if there is a damper or orifice that can be installed to level out the pulse but to date there has been no response.

[redcars]

I have mine 4" after the collector.

[ward00]

Sounds good. What the heck was the single bung on one of the header pipes provided for?

[rebar1111]

I finally got Innovative Motorsports to give me a response to my exhaust pulsing affecting the readings on my analog O2 meter. They said to essentially use a spark plug anti-fouling standoff Their 'specialty' standoff cost $87.00. I don't believe that the standoff will affect the pulsing but it may reduce the temperature the sensor sees.

[AndyVAS]

Fiat ran the stock sensor in the upper section as it wasn't a fancy heated unit. The headers are made with the bung up close to help heat it.

I've run a wideband O2 sensor in the collector and the upper section and found it reads the same.