Logging Port Injector Duty Cycle on 2018 Mustang GT

[WesDuenkel]

Need help/clarification on logging injector duty cycle in VCM Scanner on a 2018 Mustang GT. The standard layout for 2018 Mustangs has a "guage" and a graph for Injector Duty Cycle, but it doesn't have any data.

I added "Injector Pulse Width Cyl 1" to the channels...and now it works.

My quesiton: is simply adding one cylinder to the channels list going to give accurate duty cyce information for logging? If not, what is the proper way to monitor port injector duty cycle?

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[engineermike]

Look in your cylinder fuel trims and pick the highest one to log. If they are the same, then #1 will work. But on the gen3, you dont really go by duty cycle. The pcm is always measuring fuel pressure and adjusting the pulsewidth, and calculating maximum pulsewidth based on rpm and cylinder trim. It also calculates what the maximum torque achievable based on maximum pulsewidth and injector flow at actual pressure. Driver demand torque starts falling when the fuel system cant support the driver demanded torque, and if the fuel flow-limited torque falls below brake torque, it will cut throttle. If everything is calibrated accurately, this happens when pulsewidth meets maximum pulsewidth. Its a fascinating system and works well but the torque tables, injector data, and maf curve have to be pretty accurate for it to work.

[WesDuenkel]

Look in your cylinder fuel trims and pick the highest one to log. If they are the same, then #1 will work. But on the gen3, you dont really go by duty cycle. The pcm is always measuring fuel pressure and adjusting the pulsewidth, and calculating maximum pulsewidth based on rpm and cylinder trim. It also calculates what the maximum torque achievable based on maximum pulsewidth and injector flow at actual pressure. Driver demand torque starts falling when the fuel system cant support the driver demanded torque, and if the fuel flow-limited torque falls below brake torque, it will cut throttle. If everything is calibrated accurately, this happens when pulsewidth meets maximum pulsewidth. Its a fascinating system and works well but the torque tables, injector data, and maf curve have to be pretty accurate for it to work.

Noted with thanks. I wasn't sure if I needed to adjust the "math" if it was one cylinder or an average of four or eight. Noted also the way it can pull throttle if it's approaching maximum pulse width. Which is smart. I'll keep an eye on throttle angle during my dyno pulls. If it pulls throttle, I'll look into it more.

[engineermike]

You can easily plot pulsewidth, maximum pulsewidth, driver demand torque, driver demand torque source, and brake torque and the fueling limitations become very obvious. FYI if your engine can only makes 500 ftlb, you demand 750, but only have enough fuel for 600, the driver demand will be 600 and driver demand limit source will be insufficient fuel flow but it will not reduce throttle at that time. It will disable wot start/end though.