Injector duty cycle 110%

Hi guys using a links ecu on a evo injector duty cycle is above 100% and when richen the engine . enigne does go rich . was wondering how is this possible as at 100% injector duty cycle isnt the injectors maxed out?

This may be due to a decrease in air mass rather than an increase in fuel delivered.

Ultimately the solution is reduce airflow or increase fuel system potential, in order to keep the injectors operating within their capacity, so that engine operation is under control and can be more consistent.

hi mike what I'm not understanding is when the duty cycle is at 100% isn't the injectors maxxed out? with the links ecu I had injectors running at 110 % injector duty cycle and just to test I richened the engine and yes the afr indicated the engine richened . so how is it possible to deliver more fuel. injectors max out at 100%.

Often times the duty cycle is calculated as desired open time, not actual open time. You are correct it's not possible to open the injectors more than 100 %.

That's a very good and interesting question. I also tried to figure it out once. Had a debate with one reputable tuner about situation when he stated 110 percent duty cycle but his only explanation was it's because of universal formula that's used in every ECU. To me it didn't make much sense as the theory should go together with reality in this case so I started looking for more information. Haven't been too successful to be honest. The only reasonable theory I found says that's because of mismatch in measurement between real AFR and RPM. The suggestion was to measure IPW at the engine slowest acceleration rate on the dyno to make duty cycle as accurate as possible...

I understand your original question and I've seen the behavior before. Many injectors have non linear behavior at their upper limit which can make 97% flow more than 100% for example. Then you have discrepancies in ECU reported IDC based on whether they count dead time in the calculation for potential on time or not. You can perform your own on time to duty cycle calculation if you want to investigate further. Just make sure you know if the on time you're seeing is with or without dead time.

Ultimately, getting away from 100% duty is desired to get back in a region of safe and consistent operation.