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I agree with Graham that with two O2 sensors, it probably is a I4 engine. V6 and V8 engines for a long time, have three, one for each bank and one after the catalytic converter,. In either case, the one after the cat is just for checking the cat. The engine actually runs via the front sensor.

It is your choice as to what to do. If you run closed loop, then you will need the upstream one. at a minimum. But you don't have to run closed loop. You can run open loop in which case, none are required. I believe that you are in Mex? I don't know what your requirements are. Maybe you won't even need to run a cat converter. If so, then there is your answer. I don't know if the recent MS firmware now has the option to check the downstream sensor and output or log the result. (probably does)

It has been a while since I dabbled with MS. If you decide to run both, and run a wideband, you will need a wideband controller and just feed the analog output to the MS. I can't imagine needing a wideband downstream of the cat ust to check the cat's . A narrow band should do just fine I think.

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Chuck.

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Sorry;
Info on my build Log, but "my" build log appears a someone´s else due to a change in user name.
It is a 1995 5.0 V8 Mustang.
The second O2 Sensor would be on the other side collector



Well, I´m inclining myself to keep both available sensors wired in, but only one connected to the Megasquirt.
Lter on I may consider fitting a Wideband.
As per Mexico requirements, there´s no regulations regarding self build cars, so I can pretty much run whatever I want.
Thanks all for your help.
Angel Acevedo

Don't run a narrowband; while it may be able to tell a stock ECU if your mixture is at stoich or not, it tells you basically nothing when it comes to tuning.

Do not leave an unpowered O2 sensor installed in the exhaust. The wideband controller provides power to the O2 sensor to keep it at the proper temperature for accurate readings and to prevent excessive carbon buildup for maximum sensor life. O2 sensors are kind of fragile, and letting one sit cold in the exhaust is a great way to throw away $50.

I initially ran my 5.0 on a Megasquirt with a single O2 sensor in the right bank. This was enough to get the car tuned and running well. However, when I had an ignition coil die on the bank that the O2 sensor wasn't monitoring, the engine began running poorly and I had no indication as to why. I ended up installing a second wideband in the other bank, so now I can monitor both banks simultaneously.

If you are running a standalone ECU, you NEED a wideband. You can get away with one, but two is better to make sure all of your plugs, wires, coils, and injectors are doing their job.

Check out the Spartan for a simple wideband controller that's easily integrated with the Megasquirt.

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Ford 5.0 into an M3
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