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  • 2 Post By eschaider
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  #1 (permalink)  
Old 11-16-2022, 02:18 PM
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Default I've been running FI without 02 sensors

Hello everyone, I just wanted to share a positive experience with running a Fuel Injected engine without 02 sensors. I currently have a Factory Five MK4 with a rebuilt donor motor from a 2003 Mach 1 mustang. I bought the car 80% done and I noticed the builder had no provisions for 02 sensors. After completion of the build I was worried about the missing 02 sensors.

After searching various Mustang forums I noticed most of the guys deleted the 02 sensors due to modifying the exhaust to long tubes and cat delete.

So I asked a local tune shop (Premier Performance) and they stated that it can be done tuning without 02's.

The simple answer is the EEC-IV and EEC-V ECU can run without 02 sensors. It uses the mass airflow sensor, intake air temp sensor, and baro sensors to adjust for atmospheric and temperature changes. The stock EEC-IV and EEC-V will go into closed loop above 140F coolant temp and go into open loop above a 70% engine load. To run without 02's the tune starts with the combination of closed loop and the adaptive learning which allows the ECU to maximize fuel economy and maximize emissions.

When tuning turn off the adaptive and forced the computer to stay in open loop then adjusted the fuel tables and MAF function. Once the AFR match the ECU command AFR they turned the adaptive and closed loop ability back on. I understand the computer will try to cut timing to richen up the fuel. When I used my SCT X4 scanner I noticed the spark advance was set to 10. I'm assuming this was set to compensate for the computer wanting to cut timing.

I've accumulated over 4k miles without any ill effects. The cobra idles great and traversing the canyons without any issues.



Last edited by Leecbr; 11-16-2022 at 02:28 PM..
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Old 11-16-2022, 08:16 PM
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That OEM computer can be run in open loop or closed loop (if you have working O2 sensors). If you do not have working O2 sensors then the ECU must always operate in open loop. The learning logic, actual vs commanded AFR or lambda (whichever you use) will either not be available or will not be accurate without the presence of the O2 sensor to read exhaust oxygen.

It is to your decided advantage to use O2 sensors and even more so to use Wideband O2 sensors. The engine will operate without them but you will give up stunning tuning capabilities.
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Old 11-19-2022, 09:38 AM
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I agree eschaider running with 02 sensors is the ideal way. Sometimes people buy cars that are built and the previous owner has decided to omit or cut out options. In my situation the 02 connectors have been removed and trying to run wiring back to the ECU wasn't optimal. I was writing this as a helpful tip incase someone else decides to go in this direction.

The previous 3 cobras I've owned had 02 sensors or a wideband 02 sensor in place. So I was worried about this build but all is good. I'm pretty much running a Fuel Injected motor set up similar to a well tuned carburetor.
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Old 11-19-2022, 11:40 AM
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It is more than the proper way. It is the way the engineers who designed the EFI system intended it to be implemented and used. Can it be run w/o sensors - yes. Do you loose significant EFI benefits that accrue from the ability to measure exhaust gas oxygen content - yes again.

It is not hard to run O2 sensors. If the ECU is an OEM unit you simply run the sensor lead back to the wiring harness wire or plug. If it is an aftermarket ECU you just run the sensor lead back to the O2 sensor input on the ECU.

This stuff is easier than wiring a headlight.
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Old 11-21-2022, 09:27 AM
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That's awesome.
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