Fuel Injector Balancing mean the fuel injector both in spray pattern and in quantity of fuel delivered are even.
Fuel injector manufacturers in general send their fuel injectors as balanced sets to the end users such as auto, motorcycle, marine engine etc. manufacturers.
Due to dirt and contamination buildup over time fuel injector spray pattern and quantity delivery will change and become uneven. This in turn can cause many drivability or engine performance issues. To correct this all that needs to happen is for the fuel injector set to be ultrasonically cleaned.
Occasionally a fuel injector set just does not perform evenly and it requires to be “balanced”, but here is the catch in the phraseology being used on the internet. “We flow test and balance fuel injectors”
The flow testing part is correct but the balancing part is a myth. To our knowledge there does not exist a company that can precision drill or re-drill the fuel injector outlet holes or regrind the pintle shape to such exacting specs that will allow for precision balancing in both spray pattern and flow. Yes there are companies that can re drill the outlet holes of the fuel injector nozzle by means of laser but they cannot guarantee that the injector set you send them will be balanced.
So how do they balance fuel injectors both in manufacturing and in the aftermarket?
In manufacturing the new injectors are flow tested and then sorted in groups consistent in spray pattern and volume. Balanced set in the aftermarket is a whole different ballgame. Injectors are sourced from junk yards, cleaned and then flow tested. Fuel injector styles with the same volume are put together as flow matched sets. The same happens when fuel injectors are modified to make them deliver more fuel. Injectors are modified in bulk. They are then matched in volume but not in spray pattern.
It is highly unlikely that the same set of unbalanced fuel injectors sent to one of the companies claiming that they do fuel injector balancing service will return that original set of fuel injectors as a balanced set.
There is nothing wrong with doing this … just a misunderstanding of the terminology.