Best Location for AF Sensor Bung, UPDATE: I got a SS muffler, what you all say now... Options

[913B]

I got a new to me muffler.
I believe it was originally purchased from 914rubber.
@Mikey914 @mb911
What do you all recommend for the placement of the AF sensor ??
I am trying to avoid hitting into into any baffles.
Thank you

[technicalninja]

I would need to figure out where all primaries came together inside that muffler before I could really say.

You don't have to actually sniff all 4 cylinders to be reasonably accurate.

The difference between cylinders is less as your equipment improves.

Using L-jet is far less precise than a digital modern unit.

Modern injectors (Bosch EV14s) are more precise than the early injectors.

FI (any) is far more precise than carburetors and so on.

I prefer to have either a single O2 sensor sniffing all cylinders or have individual O2 sensors in each primary for the ultimate in precision.
I am a picky bastard that prefers to have more data than I need to do a job and tend to "over-kill" far too often.

Most of the modern digital ECUs allow individual injector adjustability. You can change the pulse width on individual injectors. I'm not sure how you would know when or which way to adjust this without individual O2 sensors OR individual EGT thermocouples to gather data from. So, if you're planning for a perfectly tuned car, you will need 4.


@VaccaRabite is right however...

For the average enthusiast much less precision is required.

Most likely, with the modern stuff you are using, a O2 sensor in a single primary before the nice SS muffler you have would work just fine.

I'd try it in two spots. In #3 primary pre-muffler and just past the muffler.
The primary location will give you really good data on a single cylinder and the post muffler will give good data on all cylinders EXCEPT for use at idle and over-run.
I would expect idle/over-run to be lean on the post muffler sensor.
I'd make sure the data from the primary location matched the data from the post muffler location except at idle and most likely live with a single sensor in one of the primaries.

I chose #3 as it is the cylinder that is most crippled by design in the engine and if I have to only live with one set of data, I want the data from the most troublesome cylinder.
And once again VR beat me to it. He's got his in the spot I'd most likely end up with.

That center "tube" that is shown in the non-exit end might also be a good spot.
It all depends on the internal structure of the muffler.

[mb911]

I have absolutely ZERO to do with 914 rubber. That said I also have nothing to do with any exhaust products anymore.

The best location for the bung would be just to inside of the muffler as it transitions from 2.5 tail pipe material to 6”. You want to get it in that last mixing chamber.