The deceleration control system on manual transmission models consists of the anti-afterburn valve (two used on 1981 and later models), the dashpot and its delay valve, and the coasting valve. On automatic transmission models, only the anti-afterburn valve is used.
The single (or primary) anti-afterburn valve is part of the air control valve. Please refer to the preceding Air Injection System coverage for additional information.
On 1981 and later models, the second anti-afterburn valve is located to the rear of the carburetor. It controls air intake to the rear rotor, while the anti-afterburn valve (in the air control valve) controls air intake to the front rotor.
The dashpot acts to slow down the closing speed of the throttle valve in the carburetor when the accelerator pedal is released. This helps prevent engine misfire. The dashpot also acts as an emission control device.
The coasting valve allows additional air into the intake manifold to prevent engine misfire during deceleration at engine speeds over 1,150 rpm. It is regulated by the control unit and the idle switch on the carburetor.
The deceleration control system on fuel injected RX-7s consists of a fuel cut-off circuit, throttle sensor, anti-afterburn valve and dashpot.
The fuel cut-off circuit stops flow to the fuel injectors while decelerating during certain engine speed ranges.
The throttle sensor measures the opening angle of the primary throttle valve; it sends this information to the control unit, which determines the proper air/fuel mixture needed by the engine during deceleration.
The anti-afterburn valve is an integral component of the air control valve. The valve feeds fresh air into the rear port during deceleration.
The dashpot gradually shuts the throttle valve during deceleration.