A/F Meter

[veeten]

How far down from Primary Exhaust should A/F sensor be placed on a Carbureted car .
It is a 4 into 2 into 1 system. I assume on the collector somewhere.
Thanks

[mikey]

You'll probably get a bunch of different answers on this one. I'd suggest putting it in the collector after 2 to 1 come together or within 6" of that behind it. Stay at least 18" forward of the end of the tail pipe.

[veeten]

Thanks
I expect to hear several Ideas, I just want to get a general recommendation .

[Hardingfv32]

1) If this is for a FV then your are going to have a problem getting far enough from the end of the exhaust system if it is a 4-2-1.

2) If you have hopes of tuning your engine with a wide band sensor forget about it. You tune engines on a dyno. Carburated engines in general and a FV for certain have highly cyclic variation in the combustion event. This makes the reading of the O2 sensor extremely variable. I dyno using an O2 & EGT sensor in each primary and when the engine is held at a constant load/rpm there is as much as .50 to .75 of a point variation in the O2 sensor readings. Takes multiple runs/pulls and statistical analysis to get useful data.

3) A FV carburetor is very crude in operation even in steady state operating conditions. Small changes are very hard to see without a dyno. Except for EXTREME altitude (Denver) or weather (thunder storms)… you never change the jets on a FV carb that has been setup on a dyno.

Brian