Restrictor plate

Through the air restrictor (also Luftmassenbegrenzer or English air restrictor or restrictor plate ), the amount of air that is supplied to an internal combustion engine can be reduced, so as to limit the power to a predetermined limit in the regulations.

Technology

The cross-section of the intake tract is technically narrowed, whereby less air enters the combustion chamber. In order to maintain the optimum air-fuel ratio, the fuel supply must be reduced accordingly. Thus the converted energy drops per time, that is the performance.

Application

In road traffic, mopeds and motorcycles are sometimes throttled to keep the power within the respective license category or to achieve a more favorable insurance premium. While customary in two-stroke engines exhaust side chokes, four-stroke engines are usually on the intake, reduced with air restrictors in performance.

Frequently encountered are air restrictor on racing cars, so the rules a corresponding performance is achieved. For example, in the turbochargers of the so-called World Rally Cars an air restrictor is used with a diameter of 33 mm, which should lead to a limitation of the nominal power to 220 kW ( 300 hp). If we take as a comparison, a largely corresponding peak engine from the European Rallycross approach, in which an air restrictor 45 mm diameter the engine to 400 kW helps (550 hp), it is easy to see how a relatively simple measure, the maximum power a motor can be limited.

Prominent examples are the cars of the DTM. Also, the vehicles of the American NASCAR Sprint Cup, where it is driven on the there usual high-speed oval courses, the motors by means of the restrictor plates of more than 590 kW ( 802 hp) to approximately 330 kW ( 449 hp ), ie by almost half throttled. In sports car racing as the GT3 group or the 24 -hour race at the Nürburgring air restrictors are used as part of the balance of performance to every year ensure a comparable performance of the top teams.

Since 1971, all engines of Formula 3 must be provided with an air restrictor, which has a diameter of 26 mm. This causes the engine performance of data originating from different manufacturers units, in 2012, at about 158-184 kW ( 215-250 hp) was.