MSefi.com read only forum (Jan.15,2018)

Hello,

I have done and engine conversion using a 1995 4.3l TBI v6. For the first several years (while I was young and knew everything in the world, ha ha ha) I ran the motor with no oxygen sensor. A buddy of my dad's makes radios and he made me a circuit to give the computer the feedback it wanted. I am not looking to run an O2 sensor and was looking for advice.

1) How many O2 sensors should I have (pre and post catalytic converter?)?
2) What type of O2 sensor should I run narrow band or wide band (I and building an MS II, and just trying to get the motor to run)
3) Where should the O2 sensor go (before or after the catalytic converter.
4) Has anyone tried using those "No-weld bungs"? Do they get a good seal and hold it. I do have a mig welder and I am moderately ok with it.

As always I would appreciate any information you can give me and thank you for your time.

Will

If you are keeping the cat., I'd say all you need is a narrow band sensor. As a mixture well outside stoichiometric for any length of time will damage the cat.

With no cat, most engines will run best with a richer mixture for power, and a weaker one for economy. Which is were a wideband comes in as it shows the actual AFR with no guessing.

MS can use a narrowband sensor directly.

Widebands need their own electronics, and produce a control signal that MS can read and use.

Thank you for the information. I was just at the parts store looking to pick up an oxygen sensor as I have never had one before. I was wondering;

1) I don't know if my motor came originally with the 3 wire or 4 wire version. I am assuming that the wiring diagram for megasquirt has three wires coming off the oxygen sensor, I will need the 3 wire version. Is this correct?

2) The ground for the oxygen sensor should go back to one of the pins?

3) I have been under the impression that the o2 sensor should be before the cat, so I should buy the upstream (pre-cat) oxygen sensor?

Will