EJK Gen 3 fuel controller for Ducati ST4S (1997-2003)

More control over the fuelling of your Ducati ST4S (1997-2003)

• Focus on usable performance: fine-tune throttle response, acceleration and drive through the usable rev range, rather than focusing solely on a peak power figure.
• Load-based tuning: EJK uses engine load as an important part of its control strategy, looking beyond engine speed and throttle position alone.
• Adjust directly: normal adjustments are made using MODE, PLUS and MINUS on the controller; no laptop is needed.
• Model-specific application: this GEN 3 controller is intended for the application shown above and uses the connectors and programming developed for it.
• Technical support: GeGShop supplies the module together with access to the appropriate baseline data, instructions and help understanding the settings.

A different exhaust, a modified intake or simply a desire to match the fuelling more closely to your vehicle does not necessarily call for a complex tuning platform. The EJK – Electronic Jet Kit was developed as a practical piggyback solution: the original ECU remains active while the EJK can adjust injector control within its programmed operating zones.

For the rider, the main benefit is usability. Clean throttle response and strong, predictable drive through the relevant rev range usually matter more in everyday riding than a small increase in peak power. That is why we do not present EJK as a box that promises a fixed horsepower gain. The outcome depends on the original tune, the condition of the vehicle and any modifications. EJK gives you an accessible way to make targeted fuelling adjustments.

Why EJK works differently from a simple fixed map

Many EFI tuning solutions are described in terms of engine speed and throttle position. EJK uses its Load Based Technology, which also takes engine load into account. The same RPM and throttle position can occur both on level ground and while accelerating uphill, even though the load differs. This is the technical principle behind EJK: the correction relates to what is being demanded of the engine at that moment.

Operation is deliberately straightforward. The controller uses coloured zones and transition settings. The functions of Green/Blue, Yellow/Blue and Red/Blue vary by EJK part number. This page therefore uses the functions and values for this specific controller rather than a single generic EJK table for the entire range.

A less familiar brand, not a new tuning experiment

EJK grew out of the Dobeck/Techlusion line of aftermarket EFI controllers; current production and ongoing support are handled by MT Pockets Performance in the United States. Its philosophy has remained consistent across generations: make meaningful fuelling adjustments accessible without requiring every rider to use a laptop, extensive mapping software or a full dyno session. To learn more about its background, development and technology, read all about EJK.

GEN 3 for this application

Always use the correct EJK part number for your application. A controller that looks similar may have different functions, transition points or baseline values. The values below therefore relate specifically to EJK 9120299. Treat a factory map as a controlled starting point: exhaust, air filter, O2 configuration and other changes may call for further fine-tuning.

Baseline settings published by EJK

Adjustment: simple, but controlled

Normal use does not require software on a laptop. Use the EJK buttons to select a zone and change its value in steps. This makes fine-tuning accessible, but do not change several parameters at once without understanding their effects. Always record the original values and first check that the vehicle is mechanically sound. A tuning module cannot resolve a mechanical, ignition or fuel-system fault.

For detailed explanations of the LED zones, changing and saving settings, transition points and systematic troubleshooting, see our main guide: EJK operation, adjustment & troubleshooting.

When does EJK make sense?

For many older and intermediate-generation EFI vehicles, EJK is worth considering if you mainly want practical, directly adjustable fuelling correction . If your engine is heavily modified, you want to optimise the final few percent on a dyno, or you have a modern system with very strict ECU monitoring of injection, a different tuning method may be more suitable. We recommend EJK for the right application, rather than as a universal cure-all.

Frequently asked questions

Do I need a laptop to adjust this EJK?

No. Normal user settings are changed directly using the controller’s buttons and LED display. For most riders, this is one of the strengths of the EJK concept.

Is this the same as an ECU remap?

No. EJK is a piggyback controller. The original ECU keeps working, while EJK influences injector control within the functions programmed for this controller. An ECU flash changes the software inside the ECU itself.

Must I always change the baseline settings?

No. When EJK publishes a model-specific baseline, it is intended as a starting point for the stated configuration. Only make a targeted adjustment if your setup differs or the way the vehicle runs calls for fine-tuning.

Does EJK guarantee extra horsepower?

No, and we do not promise that either. Results depend on the vehicle, modifications and starting condition. The main reason to choose EJK is control over fuelling correction and the ability to match running behaviour more closely to your actual application.

Where can I find fitting instructions and troubleshooting help?

Where the manufacturer provides a model-specific PDF for an EJK product, we link it to the product page. For explanations of settings and diagnosis, also use our EJK operation and troubleshooting page. If you need more help, we can review the EJK part number, vehicle and configuration with you.