Thesis 1: injection valves are maintenance parts.

 Although injectors for fuel injection are not subject to significant wear, they lose performance due to sediments clogging the internal mechanics and paths.

To determine whether this effect  is substantial, a large amount of used injectors from the BMW K-Series, and BMW cars were to tested by measuring the amount of Fuel supplied, before and after inside cleaning.
From 70 surveyed sets, each with 3-4 injectors, only 8 sets had no significant  difference regarding spray pattern or flow rates at low and high speeds after cleaning.

These 8 sets came exclusively from motorcycles with extremely low mileage or were professionally cleaned elsewhere shortly before this procedure.


At this point a big thank you to the participants of the Forum for BMW K-bikes www.flyingbrick.de for loaning the injectors!

Since this finding hundreds of sets have been subjected to this procedure, confirming the results stated  above.


Result: Thesis confirmed.


Observation :

 After cleaning the Injectors the Bikes were often running much calmer with less vibes, and could be better adjusted (synchronization).

As a conclusion we formed the next Thesis:

Thesis 2: engines do run better whith injectors installed that have been synchronized in Flow  

So we developed a method of testing, and installed optimized Sets of injectors into our Bikes.


(now it is getting a little unscientific)  :-)


4 Cylinder: JEP!


3 Cylinder: JEP !!!


2 Cylinders: JEP !!!!!!!


So quite clearly...Our Bikes do run much better when the valves are dynamically synchronized.

Typically the effects where...easier to achieve synchronization (Airside), improved cold starting, better acceptance of gas, during acceleration even from lower RPMs, less Vibes.


Result: Thesis confirmed.


As a result of our ongoing discussions the question came up: Do new Injectors have the same effect without further sorting? EG are manufacturing tolerances small enough?

Various batches of brand new Injectors where tested...and ...

Result: NO, without sorting even brand new injector are not delivered within our observed need for best engine run.


 Effects of suboptimal injectors:

Uneven flow rates in one set:


Engine Runs Rough, cannot be synchronized (airside) to a perfectly clean run.

A considerable amount of engine power is converted into meaningless vibrations.


Effect: for example, vibration while driving


For engines with Lambda driven ecu (with one probe only), all cylinders and thus the fuel injectors to be treated equally.
The cylinder with the lowest fuel injection running potentially lean and therefore too hot, leading to engine failures most likely.


Poor atomization of the injected gasoline: 

poor, uneven burning,

-> Power loss

-> Engine Runs Rough



 non-uniform spray pattern:

As a result, uneven running again because the combustion in the cylinders runs differently.


Increased opening time by clogged injectors


Injectors opening times are known and taken into consideration when ecu mapping is created, clogged injectors do show difference in opening behaviors, so fuel injected differs from manufacturers Spec.

As a result, in those most likely cases or reduction in supplied petrol... lean and therefore too hot combustion with the risk of a potential engine problem.

For example, to cylinder engines with different color exhaust pipes..




The best Set of injectors in multi-cylinder engines shows the following properties:

1. flow rate within manufacturer specifications.


2. Flow rates, measured dynamically, not statically, are the same on all cylinders as close as possible.


3. flow rates equal also in the upper RPM range

Most offered injectors are statically measured, ie valve on, wait a minute, close valve.
Some are measured with volume measuring tubes with accuracies that are not good enough as they are greater in tolerances than we found to be needed.
Others measuer only once, at a a single RPM setting.

We measure the valves with simulated engine speeds up to 10,000 u / min, with a series of measurements the valves switches 80,000 times and more, the only way to determine what actual impact the inertia of valves has on the delivered amount of fuel, we measure weight, not volume, with high precision instruments.

4. For optimum ignition of air/fuel mixture, the spray should be as fine as possible and focused on the intake valves. Terefore some injectors (with split spray pattern) are to be installed in a specific position to fit the given Intake arrangenment. 


Injectors old design (single beam 1975-1990) are typically giving a straight line of injection.

An optimum atomization is not given with those older style injectors, this can be achieved by upgrades to modern injection valves.

A finer spray pattern alone has some positive effect but, but the best engines run can only be achieved with an identical amount of fuel per cylinder. Therefore, valves should only be installed with the same flow rates.

Installing Injectors with matched flowcharacteristics is recommended and beneficial.
The upgrade from 1-hole valves on modern 4-hole valves finer spray pattern almost always gives a noticeable improvement of engine operation.


Less cylinders, the greater the effect by optimal injection valves. (of course only for multi-cylinder engines)

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