We are contacted on a regular basis with a request to flow match fuel injectors. Unfortunately we always have to explain to the customer that flow matching his specific set of fuel injectors is something we cannot do nor is it something any other fuel injector cleaning shop can do. The comeback from just about everyone is most always the same “Well such and such at this or that place advertise that they flow match fuel injector”

Flow match fuel injectors.

In most cases injectors are purchased in bulk. Ether new or from junk yards and various other facilities. Injectors are grouped together by part number. The injectors are tested for resistance and then put through an injector cleaning process. The cleaned injectors are now statically flow tested and those that flows the same amount are grouped together and sold as a flow matched fuel injector set.

Having a set of flow matched injectors just mean that they flow the same when they are fully open, it does not meant that the injector set is balanced.

What is static fuel injector flow testing?

Static fuel injector flow testing measures the amount of fuel that will flow through a fuel injector when that injector is fully open.  It is done at a determined fuel pressure and over a specific period of time.

Static fuel injector flow testing will only indicate if a fuel injector set flow the same and not how healthy the injector or fuel injector set is. Dynamic flow testing is a much better test but unfortunately a more time consuming and thus  more expensive way to test fuel injector health.

Dynamic Injector Flow Testing.

Dynamic flow testing does not tell you how much fuel an injector or a set of injector delivers, but rather how healthy you injector set is.

The injectors are tested under a determined pressure from 200 rpm to 10 000 rpm’s at various injector duty cycles. The injector set should be able to deliver the same amount of fuel for each RPM range and each duty cycle set it is tested at. This type of testing not only indicates if the injectors flow the same at each testing point but it also indicates if injector latency is the same.

If an injector set delivers the same amount of fuel under static flow testing but not under dynamic flow testing it normally is an indication that the injector set’s latency values are not the same. This condition might not have serious consequences under normal engine conditions. For a high performance or race engine this might have disastrous consequences.

Fuel injector balancing and blueprinting.

For fuel injectors to be balanced or blueprinted the following must be true:

1.    The amount of fuel each fuel injector delivers must be exactly the same throughout the entire injector duty cycle range.
2.    Atomization and distribution of each injector should be exactly the same.
3.    Resistance and reluctance of the injector set must be the same
4.    Fuel injector latency values should be exactly the same

What is fuel injector latency

Injector latency is also know as injector dead time or injector lag time.

Fuel Injector latency is the amount of time it takes for the injector to fully open once it is energized and on the back end it is the amount of time the injector takes to close after current has been switched off.

Fuel injector latency testing is time consuming and expensive. The injector is tested at a predetermined fuel pressure in increments of 0.1 volt from 6 volts to 14.5 volt. The time the injector takes to open and close is notated. When fuel pressure change latency values change

To truly be able to balance a specific set of fuel injectors will require expensive and very specialized tools and equipment that I believe only large manufacturers such as Bosch, Denso and the likes can afford or have.