injector times and tables help

In the module titled "fuel models" you talked about injector time tables. You said we must input the correct time for the injector to be open in relation to the load the engine is under in order to get the appropriate AFR we desire. But my question is: how do we find out what the injector opening time needs to be at all the different load points? Is it inputting opening times into our table and seeing if the engine is meeting the desired AFR and, if not, adjust accordingly. A kind of guess and check system? Or is it some other calculation I am not aware of?

If you could advise me on the process used to calculate correct injector opening time tables that would be greatly appreciated and is precisely the kind of information and help that I was looking for when I enrolled in HP Academy.

I appreciate it and look forward to hearing from you!

Neil

I suppose the module "Calculating Injector Pulse Width" answers this question. . . . But, if you have any additional information on this subject you would like to share, I would love to hear it. Thanks!

While it's possible to calculate the required injector opening time in order to achieve your desired target AFR, this calculation requires us to accurately know the the engine's volumetric efficiency and this is information we are unlikely to have. Since we don't know the engine's VE, the process of finding how long the injector needs to be open for is really a trail and error method. We test, measure the AFR and then adjust the injector opening to suit.

The process isn't as scary as it sounds though since if you follow the HPA 10 step process, we start from low rpm and load and gradually build up from there. We quickly see trends emerging which allows us to guess ahead to the untuned parts of the map, and this means that we're normally very close as we increase load and rpm into the untuned areas.