Static flow (shown as “Design Flow” in green below on our Data Match Technology sheet) is based on industry standards. This standard has traditionally come from companies only testing injectors in a static, or “always open”, state. Consumers have become accustomed to these numbers and talk about them in casual terms.
Dynamic flow (shown as "Slope Flow" in blue below on our Data Match Technology sheet) is the more accurate way of rating an injector flow value. This is the value that the ECU uses to calculate the pulse width length to provide an accurate amount of fuel as it attempts to hit the target air fuel ratio (AFR). This is more evident in a closed loop scenario, but will affect the tune in open loop if the settings are incorrect.
An injector’s dynamic flow is always less than its static flow since there is a loss due to the inertia of getting the fuel to flow once the valve opens. This is evident even after you compensate for the delay or “loss of open time” in the process of opening and closing the valve with the battery offset or deadtime corrections entered into the ECU.
This is a sample graph that shows data points from a flow test. The line drawn that connects the output data points is the slope flow. The data found in this line is used in the ECU. To find the slope of that line, we calculate rise over run where rise is flow rate and run is pulse width.
On the far right side of the graph, you can see the line spike up and the level off. The spike you’re seeing is the transition period from true dynamic flow to static flow. Eventually the line levels off and you’re left with the static flow of the injector, which is when the injector valve is held open.
Tuners may change deadtime and flow values from what is provided on our Data Match Technology sheet to correct issues they see in a log. This is more commonly seen on cars being tuned with flashable ECU’s (mainly DSM/Evo on stock ECU and piggyback/open source software). This allows the tuner to make one change to the injector settings and not have to flash or change various cells/tables.