DIYAutotune: Sequential vs Batch Fuel Injection Timing

Batch Game 2023

DIYAutotune just ran an excellent story by Greg Banish on sequential versus batch fuel injection timing. Here’s a quick excerpt to give you started.

Before we ever begin tuning our delivered air to fuel ratio in the engine, we have to make some decisions about fuel delivery and calibration. I will preface this with the usual requirement that we also have complete injector characterization data (flow rate, offsets vs voltage, short pulse nonlinearity compensation) before programming the controller. But, assuming that we have that, we also need to decide how we will time the fuel delivery to the cylinder events. Sequential vs Batch Injection — what is better?

In a carburetor, we have a more or less constant stream of fuel being mixed with a more or less constant stream of airflow through the venturis. Fuel droplets mix with the airflow and either evaporate on their way to the inlet valves or they impact the walls of intake manifold to be evaporated (and mixed with the airflow) later. During steady state or WOT operation this works surprisingly well. The cylinders, pistons, and spark plugs don’t know that the engine is carbureted. They just see a well-mixed charge that is available for combustion.

When we step from carburetion to fuel injection, we gain the ability to more precisely dose the delivery of fuel to each cylinder. Done properly, it allows us to ensure that each cylinder gets the same amount of fuel in the same relative state of evaporation and mixing. However, if we deliver a chunk of fuel to a cylinder that isn’t completely evaporated or mixed with the air charge, we can get poor combustion quality. You can read the rest of this great story here.