Because the 142-horsepower in-line four (despite its new variable-valve intake cylinder head) is hardly a tour-de-force motor, and with the Miata now weighing close to 2,500 pounds, the desire for more low-end grunt is nearly constant.
Valves, intake and exhaust ducts, spark plug and crevices were neglected due to the fact that only the closed valves phase is essential for heat release calculations.
Often, dual valve arrangements two intake and two exhaust valves are employed.
The car was notable for its Knight engine, with sleeve valves, rather than poppet valves, controlling intake and exhaust.
The acceleration transducer was installed between the intake valve and exhaust valve.
Minimizing the pumping work penalty, and consequently improving the fuel economy, was shown as an advantage of using the non-typical intake-valve-timing with the timing of the early intake valve coupled with a symmetric degree of exhaust-valve-closing timing.
Two injection timings were fixed in order to inject the fuel at closed intake valve and open intake valve, respectively.
As in the BMW engine, airflow is controlled by regulating the intake valve rather than a throttle valve.
The engine head design provides asymmetrical intake valve timing without the use of poppet valves and the associated valve-train.
In a port-fuel-injected engine, the fuel is generally injected at the backside of a closed intake valve to take advantage of the warm valve and port surfaces for vaporization [22, 23, 24].
A non-typical intake valve strategy was examined; whereby the intake valves were assumed to be independently actuated with the same valve-lift profile but at different timings.
