Development of a New Multi-Mode Variable Valve Timing Engine

<div class="htmlview paragraph">The 4-stroke SI engine offers better performance if its valve events can be varied depending on the operating conditions. Some engines in production are therefore incorporated with variable valve timing (VVT) mechanisms. All of such mechanisms available today however are for two-mode change-over between low-and high-speed operations.</div> <div class="htmlview paragraph">To achieve even better output and fuel economy, a new multi-mode VVT mechanism has been developed, featured by a unique hydraulic device for three-mode change-over as follows:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Deactivate both intake and exhaust valves</div> </li> <li class="list-item"><div class="htmlview paragraph">Select low-speed cam with moderate lifts and short durations</div> </li> <li class="list-item"><div class="htmlview paragraph">Select high-speed cam with high lifts and long durations</div> </li> </ul> </div> <div class="htmlview paragraph">This mechanism enables shutting off unnecessary cylinders during low-speed cruise, or select optimum valve events during WOT acceleration over the entire engine speed range. The engine with this VVT demonstrates a fuel economy improvement up 16% during the Japanese test driving cycle and a power increase by 20% from its predecessor.</div>