Understanding injector Duty cycle
Posted: Mon Jan 24, 2022 3:12 pm
I don't completely understand the duty cycle table and injection time used in SManager.
Attached a log file and a fuel map.
So in the log file I run with 0.32 bar boost at 5000 rpm, the AFR is 14.23 so I like to increase the amount of fuel.
The injector timing is 16.65ms and Duty is 70%, so I expect that I'm able to increase the injection time.
I understand that with the same injection duration of ~16ms at higher rpm's the duty cycle will go to around 100% at 7000rpm.
But I don't completely understand why I'm not able to have longer injection duration at lower rpms (for example 5000rpm).
As you can see at the 7200 rpms my AFR is going to 11.88, which is great, therefore I like to increase the injection duration at 5000rpm because this seems to solve my problem.
In the Fuel map I see that in that operating point my injector duty is above 100% so it makes sense that this is the limiting factor.
But I don't see where this limitation comes from, which calculation/parameters are behind the duty cycles in the fuel map?
Is this a setting that cannot be changed by the user?
Obviously I understand that I can buy larger injectors but for my own understanding I like to understand where the duty cycles in the fuel table come from.
Attached a log file and a fuel map.
So in the log file I run with 0.32 bar boost at 5000 rpm, the AFR is 14.23 so I like to increase the amount of fuel.
The injector timing is 16.65ms and Duty is 70%, so I expect that I'm able to increase the injection time.
I understand that with the same injection duration of ~16ms at higher rpm's the duty cycle will go to around 100% at 7000rpm.
But I don't completely understand why I'm not able to have longer injection duration at lower rpms (for example 5000rpm).
As you can see at the 7200 rpms my AFR is going to 11.88, which is great, therefore I like to increase the injection duration at 5000rpm because this seems to solve my problem.
In the Fuel map I see that in that operating point my injector duty is above 100% so it makes sense that this is the limiting factor.
But I don't see where this limitation comes from, which calculation/parameters are behind the duty cycles in the fuel map?
Is this a setting that cannot be changed by the user?
Obviously I understand that I can buy larger injectors but for my own understanding I like to understand where the duty cycles in the fuel table come from.