Dethrottling

As dethrottling , particularly small and light motorcycles is called a technical manipulation to increase speed. Measures to restrict performance are circumvented or canceled.

Types of throttling

The performance restrictions can be implemented through various technical measures. Common methods include:

• Throttling via the engine control ;
• modified carburetor nozzles / injection times and throttle valve stop ;
• Reduction of the intake cross-section between engine and carburetor
• modified variator for continuously variable automatic transmissions (shorter translation);
• Interference pipe on the exhaust or
• Reducing sleeve in the exhaust / exhaust tract.

Reasons for the throttling

The legal requirements regarding the driving license provide for speed and power limits for small motorcycles . In addition to design, good driving performance is the most important selling point in this market segment. An unthrottled 49 cm³ two-stroke engine easily accelerates a scooter to 70 km / h . The legally prescribed maximum speed for mopeds (mopeds), however, is 45 km / h (previously 50 km / h) or 25 km / h (moped, light moped only 20 km / h). It is therefore necessary to reduce the maximum speed of the vehicle to the desired value. The installation of a smaller motor is not recommended, as the scooter should accelerate quickly and keep the speed on the hill.

The same motors are used for the moped and moped, because in mass production it is much more cost-effective to limit existing motors by making small technical changes than to operate two different production lines with different motors. A later dethrottling is so much cheaper to realize. In practice, the seller of a small or light motorcycle usually gives advice on dethrottling the vehicle when asked. This behavior, which cannot be punished by law, can be viewed as a type of sales promotion, since the mostly young buyers of z. B. Scooters acquire these already with the intention of removing the throttling.

Legal consequences in Germany

→ see main article: Scootertuning

The operating license expires ( Section 19 (2) No. 1 StVZO) in the event of such manipulations and the vehicle is no longer included in the previous driving license . Driving a manipulated vehicle in traffic is both driving without a license ( § 21 StVG) and the expiry of the operating license . The former is a criminal offense and the latter is an administrative offense .

Legal dethrottling is possible if the dethrottled vehicle is presented to the TÜV or another testing organization (with regard to the legal restrictions on the journey to the test, see § 29 StVZO) and the change in performance is entered there in the papers or when a new operating license is issued ( § 21 StVZO). If the driver has the necessary driving license and has appropriately insured and registered the vehicle, he is allowed to participate in road traffic.

Environmental aspects

Depending on the technical implementation, the exhaust gas behavior of the throttled engine can seriously deteriorate. In particular, motors throttled via the control unit or via speed limiters are problematic here. A simple method of throttling is to switch off the ignition spark via the rev limiter or the control unit when the maximum speed is reached. In this case, a further mixture is sucked in and discharged unburned. The hydrocarbons in the exhaust gas are poisonous and pollute the environment. The petrol is released into the environment unused and consumption is unnecessarily high.

A “throttling” via a shorter gear ratio leads to unnecessarily high fuel consumption, as the engine runs at an unnecessarily high speed.

The throttling via the exhaust (interference pipe, reducing sleeve) does not usually lead to higher fuel consumption with an adapted carburettor nozzle. If the carburettor is not adjusted, the mixture is too rich (too much gasoline in the mixture) because of the obstructed air flow and the consumption is too high.

Technically more complex throttling methods (e.g. carburetor jetting and throttle valve stop) do not have a negative impact on fuel consumption. Comparative drives of throttled and unthrottled motorcycles did not reveal any differences in terms of exhaust gas behavior or consumption.

literature

• Hans-Hermann Braess, Ulrich Seiffert: Vieweg manual automotive technology. 2nd edition, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden, 2001, ISBN 3-528-13114-4