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Since our inception, we have offered various remanufactured parts to our customers, helping you save even more on all of your car projects. We're excited to announce that with our recent partnership with GB Remanufacturing, we'll now be able to offer remanufactured Index 12 Fuel Injectors for the BMW N54 engine.

If the word "remanufactured" scares you, don't let it. Fuel injectors have been undergoing remanufacturing processes for as long as they have been on the market; however, this process has mainly been used in diesel applications. For over thirty years, GB Remanufacturing has been rebuilding fuel injectors, and are now the first company to remanufacture BMW's Index 12 injectors for the N54, and we are the only company to make these available to you

Update: 4/14/2022

Due to the current supply of cores, remanufactured BMW Index 12 Fuel Injectors are backordered with no ETA on additional supply. Additionally, if you are looking for new, Genuine BMW injectors, those are also backordered due to current supply chain issues. You can however be notified when stock becomes available by visiting the product page and clicking the "Email Me When Available" button. 


Remanufactured vs. New Fuel Injectors

Remanufactured BMW Index 12 Fuel Injector
New Genuine BMW Index 12 Fuel Injector

If you don't feel like reading everything below, I'll just make it clear nowfor all intents and purposes, there is no difference mechanically/physically between a remanufactured piezoelectric fuel injector and a brand new one. The only difference is the price. To understand why this is, it helps to understand how a piezoelectric fuel injector works. 

How a piezoelectric fuel injector works:

"Piezoelectricity" is the effect in which a material generates an electrical charge in response to a force (mechanical stress) applied to it. This mechanical stress can be anything from pressure to heat. However, piezoelectricity works conversely, so when applying an electrical current to a material, this results in a change such as pressure or movement in that material; this is how a piezoelectric fuel injector fundamentally works. 


Image courtesy of: International Journal of Engine Research

When electricity is applied to the "slice" of piezo material inside your fuel injector, this material moves around two-hundred-thousandths (.00002) of an inch. This alone isn't enough to move the nozzle in which controls the flow of fuel. So, engineers layer the "slices" of piezo material into a stack. When electricity is applied to this stack, the total movement is increased to four-thousandths (.004) of an inch. This is enough movement to open and close the nozzle of the fuel injector, controlling the flow of fuel. 

Now that you understand the fundamentals of how a fuel injector works, you can understand how the rebuild process works. 


BMW Index 12 N54 Fuel Injector Remanufacturing Process:

The piezoelectric fuel injector remanufacturing process completed by GB Remanufacturing is comprised of five main steps:


Visual Inspection

Injectors are visually inspected for damage. Nozzles are inspected under a digital microscope to detect combustion damage or erosion.

Exterior Ultrasonic Cleaning

The exterior of the injector is ultrasonically cleaned, which removes grease, grime, grit, and other

Interior Ultrasonic Cleaning and Backflush

Injector internals are ultrasonically cleaned at high temperature while being pulsed. This step removes carbon and fuel contaminate build-up from the precision internal components. Once cleaned, the injector is backflushed to ensure all contaminants have been removed.

Piezo Stack Regeneration

A critical step in the remanufacturing process includes piezo stack regeneration. Over time, the piezo crystal stack used in GDI injectors can expand from continued operation at low engine
speed. This causes slower injector response time and reduced injector flow rates under high fuel demands. This condition results in poor idle quality and poor performance under higher engine
loads. The regeneration process is accomplished by operating the injector under specific operating conditions and voltages using an automated piece of test equipment. The process restores the crystal stack to its original dimensions and performance.

New Components

All GDI injectors receive new components. Tin the case of the 855-12101 injectors, a new and improved internal filter is installed with a new fitting sealing washer. The combustion seal is replaced with upgraded material, and a new body decoupling ring is installed. 


Remanufactured BMW Index 12 N54 Fuel Injector Testing Process:

Once the injectors are rebuilt, GB Remanufacturing puts each one through a stringent testing process to ensure each one meets or exceeds OE testing parameters. The injectors are tested for leakage, injection quantity, response time, and injector spray pattern.

Leak Test


Leaking injectors can cause long crank times, excessive emissions on start-up, oil dilution, and in some cases, engine damage. GB's test equipment conducts an automated high-pressure leak test of the injector at rated pressure to ensure all of the injectors are leak-free.

Electronic Flow Measurement



The injector's flow is electronically measured and monitored during each injection event. Multiple tests are conducted at different operating speeds, pressures, and injection pulse widths. Injectors are tested to OE specifications to ensure quality and longevity. 

Response Time and Spray Pattern Analysis


Injector response time and spray pattern geometry on GDI injectors are critical to ensure injection timing and proper fuel atomization. Improper fuel atomization can result in cylinder hot-spots, high emissions, and poor engine performance. GB's test equipment allows full 360-degree inspection of the spray pattern. Injector response time is measured electronically and is tested to OE specifications. 


How do I know which BMW fuel injectors I need?

It used to be a bit more complex to figure out which injectors you need depending on the model and year of your car (BMW offered injectors with the part #13538648937 & #13538616079). However, a service update from BMW has changed this. You can read all about the injector choices and the update here. 

If you have your injectors, rebuilt or brand new, and are looking for how to replace them, we have a DIY video where Gareth walks you through all of the steps. 


So you might now be wondering why you would ever buy Genuine BMW or OE fuel injectors and not just remanufactured ones. Well, there really isn't a reason. Save yourself the money and put that back into one of the other systems of your car instead. 

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Written by :
Evan Madore

Writer/Editor at FCP Euro and owner of a daily R53 MINI Cooper, a track-built R53 MINI, and a 1997 Dakar Yellow E36 M3 Sedan. ••• Instagram: @evan.madore

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