When the throttle valve closes at high engine speed, a strong vacuum is generated inside the intake manifold. Some of the fuel adhering to the internal walls of the manifold evaporates, causing the air- fuel mixture to become too rich temporarily. At the same time, since the intake air volume decreases, the incomplete combustion or misfiring occurs, and a great amount of incombustible gas is emitted in the exhaust. To prevent the incomplete combustion or misfiring, the dash pot is used to keep the throttle valve from closing too suddenly.
During deceleration, the link of throttle valve touches the dash pot. Therefore the throttle valve closes slowly according to the resistance of air passing through. When the throttle valve is opened, the dash pot returns to its original position.
Deceleration Fuel Cut-off System
This system stops the fuel injection during the deceleration part of driving, and decreases the amounts of CO and HC.
Also it prevents after-burning in the exhaust pipe, and effectively decreases the amount of the fuel consumed during deceleration.
The engine ECU stops the fuel injection of the injector according to the engine speed and throttle valve opening.
Wakati valve throttle kufungwa katika kasi ya juu ya injini, utupu nguvu ni yanayotokana ndani ya intake manifold. Baadhi ya mafuta yanayoshikamana na kuta za ndani za manifold huyeyuka, na kusababisha mchanganyiko wa hewa na mafuta kuwa tajiri sana kwa muda. Wakati huo huo, kwa kuwa kiasi cha hewa ya kuingia hupungua, kuchoma kutokamilika au kutokamilika hutokea, na kiasi kikubwa cha gesi isiyoweza kuchomwa hutolewa katika kutolea nje. Ili kuzuia mwako usio kamili au kutoweka, chungu cha dash hutumiwa kuzuia valve ya throttle isifungue ghafla sana. Wakati wa deceleration, kiungo cha valve throttle kugusa dash pot. Kwa hiyo valve throttle kufungwa polepole kulingana na upinzani wa hewa kupita kupitia. Wakati valve throttle ni kufunguliwa, dash pot anarudi katika nafasi yake ya awali. Mfumo wa kukatisha mafuta ya kuharakisha: Mfumo huu unasimamisha sindano ya mafuta wakati wa sehemu ya kuharakisha ya kuendesha gari na kupunguza kiasi cha CO na HC. Pia inazuia baada ya kuchoma katika bomba la kutolea nje, na kwa ufanisi hupunguza kiasi cha mafuta inayotumiwa wakati wa kupunguza kasi. ECU inasimamisha sindano ya mafuta ya injector kulingana na mzunguko wa injini na kufungua kwa valve ya throttle.