2012年9月25日星期二

Fiat variable valve control system Multiair





Variable valve control system, such as the Valvematic Honda VTEC, Toyota, Nissan the VVEL and BMW Valvetronic and needed continuous transformation valve lift. Addition to the continuously variable cam phase, they seem to have very advanced. But the distance of the word "perfect" there is a very long distance. The ideal variable technology should be unrestricted and flexible transform valve lift, in other words, that is, at any time, there should be corresponding to the valve lift so as to achieve the desired combustion. Nowadays any mechanical system is not able to achieve this level of function. Some developers try to develop electromagnetic valve structure, but also facing some technical problems, such as the size and weight of the institutional problems, cost, reliability, and fuel consumption.

But entered the 1990s as a VVT pioneer Fiat sees traditional mechanical structure VVT lack of mobility and responsiveness, the research focus to a more flexible and accurate control of electro-hydraulic control system. After overcoming many difficulties, the 2009 Geneva Motor Show, Fiat officially released its variable valve technology research: Multiair electro-hydraulic intake system. Their assembly the 1.4 FIRE series engine and the subsequent occurrence the 900CC-cylinder engine.




There is no doubt, MultiAir is the most flexible and accurate VVT system. Multiair electrically controlled hydraulic intake system structure corresponding to the different load state design for the five kinds of conditions, in addition to the length of the basic open time, the head outside the low transition, it can in the intake stroke in the valve opening time adjustment.

Analysis of traditional DOHC Engine Valve DOHC VVT diagram we all know, the ordinary engine valve train driven by a cam on the camshaft, valve to open and close the mechanical rhythm, the accelerator pedal by the intake manifold a throttle valve to adjust the flow rate of air. For engine valve timing and lift technology, the size of the valve opening (stroke), the timing (timing) can be determined by the camshaft and control mechanism.

MultiAir the biggest feature is pioneering the use of electronically controlled hydraulic control system to drive the valve timing and lift, it is driven by the camshaft through a set of electromagnetic hydraulic valve, stepless adjustable intake valve lift and timing , though still is a structure of four valves per cylinder, but abolished the side of the intake valve camshaft, and retain only the side of the exhaust valve camshaft to drive intake and exhaust valves. Since the valve opening degree and opening time are arbitrary adjustable, so the system and BMW Valvetronic can be directly closed by the valve opening size to control the flow rate of air therefore also canceled throttle. Exhaust valve camshaft directly promote the intake valve through a set of solenoid hydraulic system for precise control.

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