jn2630

I've been pondering the possiblity of having my 4.6 stroker cherokee run on ethonal. We all know the main problem with that is overcoming the air fuel ratio problem that the computer has set. Ethonal runs at a higher fuel ratio than regular gas. I had a few ideas to trick the computer into changing the ratio:

The first thing to do is put more fuel into the cylinders. This can be done by adding a voltage regulator to the MAP sensor. They can be made for around $15 and are adjustable. This tricks the computer into reading a lean mixture and keeps the injectors open longer, making it a richer mixture.

Another is to add bigger fuel injectors, thus putting more fuel in. This can be done in combination with the voltage regulator.

There is a drawback, when not in open loop mode, the computer reads the o2 sensors and detects a rich mixture, and try to lean it back out. The engine only goes to open loop mode when at Wide open throttle, and when the engine is cold. I'm not sure, but it could be possible to trick the computer run at open loop all the time, therefor making the fuel mixture rich enough for ethonal at both wide open throttle, idol, and everywhere in between.

Could this type of computer modification be possible?

JrRifleCoach

Yes. Except the O2 sensor has the final say. It will detect the change and bump the fuel injector pulse width to make the proper A/F ratio in its memory. I have used the device you mention (MAP) and also an EFIE device that adds voltage to the O2 signal indicating a rich condition.

In both cases I found that the ECM will relearn the condition and compensate. Clearing the ECM by disconnecting the battery creates a new learning condition. But over time the ECM rolls back to its original AFR.

I'm installing the AFR gauge this weekend to monitor what the ECM is actually producing.