June 17th, 2020 we unlocked the PCM in our Jeep Wrangler JL. Since then we have made some changes to the tune trying to unlock more performance. This is our first update in that progress.

What have we done so far?

All of the changes so far are to unlock the performance the motor came with from the factory. (At this time we have not changed the fuel or spark advance.) To do this I focused on changing limits and removing barriers to maximum performance.

One example was removing torque limits. In lower RPM the maximum torque was limited to under 177 lb/ft. In our previous testing peak torque occurred at over 3,500 RPM. The testing I did over the weekend resulted in the same peak coming in 1000 RPM lower and maintaining a flatter curve over a larger RPM range. Horsepower remained largely unchanged. (Peak torque was 224 lb-ft.)

In order to properly data log and not try to fight the system, I temporarily eliminated some of the PCM learning features. Right now consistent issues won’t get saved into the memory with their auto-compensated changes. This allows me to tune the Jeep without the computer also trying to make changes.

The next two initial changes are probably my favorites. Change one eliminated the Jeep’s anti-stall technology. Combined with changing the pedal parameters so maximum voltage is always available the overall driveability has been completely revamped. Instead of the pedal feeling completely disconnected from engine response it works in unison with operating the engine opening.

I am now able to feather the throttle without the Jeep thinking something is wrong or lagging behind my input and causing the occasional stall.

What’s next?

The next step is to finish data logging and begin to make changes to the fuel and spark advance tables. There are some significant dips in the spark advance at 55 MPH and a few other spots.

The goal is to get maximum power without needing to run Premium fuel. I have a slim hope that I can improve fuel efficiency by giving the engine more of what it wants to run better.

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William Connor

As the Editor, William is responsible for all the good, the bad, the ugly and the indifferent that happens at 4WAAM. William brings a wide range of experience to this role. He also wields a freely shared...

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