Splug: Dongle for Bosch Smart System (BES3)

Splug: Tuning dongle for Bosch Smart System

The Splug from the team MountainTuning is a new E-Bike tuning product in the form of a weatherproof dongle for Bosch E-MTBs with the Bosch Smart System (BES3). In this version, it unlocks the new Bosch motor very effectively, consistently—and, above all, flawlessly. 

The Splug Unlike conventional tuning chips and modules, it contains the complete hardware and software in the dongle and leaves only a wiring harness behind when disconnected. Thus, after removing the dongle, there is no longer any active component in the form of hardware or software on the e-bike.

Important: The Splug is one of the solutions that has the fewest errors on the new Bosch Smart The system works. Therefore, we highly recommend it!

At the Splug This is the modern version of the classic tuning dongle. The dongle is even "programmable," meaning its features can be changed and adjusted externally.

Since the dongle is in "tuning permanently activated" mode upon delivery, programming isn't necessary. You can easily turn the tuning on and off by plugging or unplugging the dongle. (Dongle inserted = tuning active / dongle removed = tuning deactivated, normal speed behavior).

The key difference to well-known tuning chips and modules is that the entire tuning hardware and software is located in the removable dongle itself. 

In other words: Once the dongle is removed from the bike, there are no longer any components (hardware and software) on the bike that can be manipulated. The e-bike's behavior then complies with the requirements of the German Road Traffic Act (StVO), with the maximum assistance limited to 25 km/h.

Weatherproof magnetic connector

Both the holder and the dongle have practical, robust and weather-resistant magnetic connectors (Splug4). This distinguishes the Splug from the team Mountain Tuning from previous dongles on the market (previously 3,5mm jack or USB Type A). Neither moisture nor dirt can enter the Splug penetration.

The dongle

The dongle can be easily removed and stored in a pocket, backpack, etc. It's completely waterproof and holds reliably, even on trails, downhills, etc. – as our testers confirmed. To attach it, simply guide it toward the mount, and the dongle is drawn to it almost by itself thanks to a strong magnetic force. The tuning is then activated immediately.

The magnetic connector (Splug4) has a connecting cable for easy connection in the engine compartment. Here, too, only a plug-in connection to the speed sensor cable is required. No additional power supply or other additional connection to the connectors is required. The cable is thin and sturdy, allowing it to be routed from the engine compartment to the frame, where it is then secured with cable ties. This means that no further intervention is made in the engine electronics; access is only granted to the intercepted sensor signal. This information is then processed in the dongle's smart and proven software.

The tuning principle

The tuning principle corresponds to the well-known Mountain Tuning (MTT SmartSensor and MTT SmartChip) Solutions that have proven to be very reliable so far – especially in comparison to other tuning alternatives for the Bosch Smart System Motor currently on the market.

Splug Settings

You can Splug Make dongle settings and work with the dongle in 3 operating modes.

The maximum supported speed (VMax) is adjustable.

At the Splug Three different operating modes can be assigned by means of specific wheel movements when starting up the e-bike (the spoke magnet is moved past the sensor). This allows the tuning to be switched on and off as required. However, "programming" an operating mode is optional and by no means mandatory. The factory default setting is Splug After installation, the dongle is always in “tuning permanently active” mode, with the highest km/h support.

The following operating modes are available:

• Tuning permanently activated (Factory setting): Speed ​​limit is lifted, correct speed display only up to just under 25 km/h.
• Tuning permanently deactivated: Motor support up to 25 km/h, correct speed display.
• Tuning according to switch-on condition: Here you can spontaneously decide whether tuning should be activated or not when turning on the bike. To activate tuning, the magnet must be in front of the sensor for at least 4 seconds when turning on the e-bike (sensor active); otherwise, tuning remains deactivated.
  

Correct speed up to just before 25 km/h

The time until which the correct speed is displayed on the display can also be "programmed." This is possible up to just under 25 km/h – as a result, the displayed speed is always "frozen" just before 25 km/h. This means that the same value is always displayed at higher speeds.

So far, no tuning solution for Bosch Smart System motors above 25 km/h show the correct speed in the display. Due to the new technology in the Bosch Smart System Motoren also doesn't expect this to be possible. The development team has therefore decided to focus on flawless tuning and rapid legality of the e-bike—two aspects that have been more or less neglected to date.

You can even individually adjust the maximum assisted speed using specific wheel movements. You can find out more in the manual.

Note: In the delivery state the Splug basically in “Tuning permanently activated” mode (with maximum speed support).

Splug Functionality

After installation, the Splug analyze and process the current speed profile, and—if tuning is enabled—output manipulated values. This outsmarts the preset 25 km/h speed limit, allowing you to drive much faster with motor assistance.

Please note: Since the Splug When tuning is active, the motor firmware limits speeds above 25 km/h, so the displayed speed always remains just below 25 km/h. This means that the correct speed is only displayed up to just below 25 km/h. The programmed value will appear on the display as the maximum value for rides above 25 km/h and will "freeze" at ± (at approximately 22 km/h in the factory state). This parameter does not need to be changed and is primarily used for adjustment on bikes with smaller tires.

Therefore, the system's total mileage display will no longer correspond to the actual distance traveled.

Installation

For installation, the wiring harness must be Splug in the engine compartment between the sensor signal. To do this, the wiring harness must be installed once and the magnetic connector (Splug4) to the frame using cable ties. Then the Splug be put on it. 

The connector end is plugged into the motor compartment, which is usually protected by a plastic cover. To access the connectors, the motor's plastic cover (and sometimes a crank handle) must be temporarily removed. The wiring harness must be routed out of the motor compartment and attached to the e-bike frame (see product images).

Splug4 magnetic connectors (left) and Splug Dongle (right)

Splug: MTT for Bosch Smart System Compatibility

This tuning tool is compatible with E-MTBs with the “Bosch Smart System" drive, sometimes referred to as "Bosch Gen4 2022" or "BES3" ("Bosch Development Stage 3"). The system uses mid-engines.

Also compatible with Bosch Smart System Gen5 (from 2024), sometimes referred to as “Bosch CX Gen5” (assuming the e-bike does not have a rim magnet or ABS Pro).

As far as the software version of the e-bike is concerned, no restrictions are known so far, the Splug should also be compatible with the newer Bosch updates (Motor Software: 12.13.0, Kiox 300 Software Display: 12.9.0. Software LED Remote12.10.0).

Also compatible with Bosch Smart System Upgrade April 2025

To our knowledge, this tuning tool is also compatible with the Bosch Smart System upgrade from April 2025 (sometimes referred to as version "15.10.1" or "15.13.1"). You can identify the upgrade by the following software versions:

-Drive Unit Performance Line CX: 15.24.2

-LED Remote: 15.12.3

-Kiox 300: 15.10.0

-PowerTube 750: 15.10.1

Generally the Splug regardless of the display used and its firmware.

Attention: Nevertheless, we recommend not to install Bosch updates after installing and using a Splugs! Compatibility may no longer be guaranteed after this. In particular, do not perform updates with connected Splug by!

Delivery

-Splug Dongle
-Splug4 bracket with cable harness (length approx. 100 cm)
-1 Splug-Lid
-6 cable ties (2 long cable ties, 4 short cable ties)
-Instructions

Important: Not compatible with e-bikes that have a magnet on the valve. These sensors are installed deep in the motor and cannot be Splug be optimized. For this purpose, the RimBoost into consideration.

-Not compatible with Bosch e-bikes with ABS system.

Step-by-step instructions for breastfeeding with the emeibaby carrier: Operating instructions and tips!

Warnings: Please note our warnings. The use of the Splug is not permitted under the Road Traffic Regulations (StVO).

Tip: Simply use GPS-enabled devices like your smartphone if you want to see your real speed while on the go. brackets can be found directly in our shop.

This tuning product is made in Germany.

Tip: Bosch Smart System E-Bikes (BES3) can be easily identified by the plug on the charging cable.

SQUARE plug = Bosch Smart System BES3 (Gen4) + Bosch Gen5:

ROUND plug = Bosch Gen2, Gen3 & Gen4:

Does your Bosch E-Bike charging cable have a square plug (as shown above), you have the correct Tuning module selected (if the bike does not have ABS and a rim magnet). If your Bosch e-bike does not have either of these connectors, you either do NOT have a Bosch e-bike, or you have an e-bike with the old Gen1 drive (Classic Line).