I’d like to install a bung to hold an A/F ratio sender in my 2 1/2 in H pipe. Is that an OK place for accurate readings or is there a better location?
You want it 6 to 8 inches past the collector on one side and have at least 18-20 inches before the exhaust hits atmosphere if your exhaust is short/open. Do not put in an "H" or "X" crossover, as the sampling is too screwy (subject to screwing). One side near the optimal area of reading is going to provide a stable and truer reading. At the point mentioned, gasses are stable, consultant and not "muddied" (skewed) by the added variables that occur "downstream" farther away and/or dealing with mixed "sampling" from the other bank. Consistency is the goal.
Couple things- AFR readings will drive you nuts. It's a single data point. Use it in conjunction with your plug readings. Remember also that it's an average of the cylinders tested. Some may be richer, some may be leaner. You want to get it around 12.9ish... 13.0-1. Maybe a little richer for wot. You want to get a reading for your idle, cruise and wot. Once you have it in the ballpark, take it out and put the plug in the bung.
No. The mixture as it gets to the sensor, will be consistent, as the manifold and/or headers are fixed. The only thing that changes are things affecting the gasses sampled over the dynamic conditions encountered. Those things being RPM, timing and related burn of fuel/air, temp, load and what not. The sensor "reads/samples" all of those events as the variables. but the physical conditions, like exhaust manifolds/intake, heads/valves, cam events, and other "hard" physical parameters are not as relevant until you start changing those components. But dealing with air/fuel, timing events, quality of fuel, density altitude, (temps/humidity etc) and anything that changes the "softer" variables have greater degrees of effect on the AFR readings. Those things that are stable/static have less variable affect and after baseline numbers are noted, you can somewhat ignore those things and focus on the effects of the things that can swing/affect your numbers. ,
