Got long tube headers with dual exhaust what do people do to hook up an AFR gauge? Do they just use one O2 senser and messure the ratio of one bank of cylinders or can you put a heated sensor far back from the headers were the exhaust joins?

 

You can wire the O2 signal wires from both OEM O2 sensors to a single pole-double throw switch, then to the A/F ratio gauge. That way you can monitor either side of the engine. Its not likely a new, single sensor at the point where the two banks of the exhaust join together would get hot enough to provide a good reading. Wiring up a heated sensor might help a little, but it still might not run hot enough.

Even using the stock O2 sensor locations, the A/F ratio gauge is not going to give you much in the way of useable info, since the narrow-band sensors are simply not very accurate at anything other than the 14.7:1 stoichiometric A/F ratio. At the richer A/F ratios you need for max power/torque, the narrow-bands are way too sensitive to operating temperature changes, and that reduces their accuracy.

 

An AFR gauge in an injected car just jumps all over anyway complete waste of time money and effort. The pcm varies AFR making the O2 MV cross 450mv this constant switching is why it would be pointless it will just flash around till you go into hard throttle then it will display a solid but inaccurate number below 14.7.