The efficiency of the internal combustion engine depends on the gas exchange process, that is filling the air-fuel mixture and exhaust already exhaust. As we already know, this is a timing (timing mechanism), if it is correct and "subtly" customize it under certain rpm, it is possible to achieve very bad results in efficiency. Engineers have long been struggling with this problem, it can be solved in various ways, for example by impact of the valve or by turning the camshaft.
THE CONTENT OF THE ARTICLE:
• Why do you need shifters?
• The principle of operation
• VVT (Variable Valve Timing), KIA-Hyundai (CVVT), Toyota (VVT-i), Honda (VTC)
• Honda (VTEC), Toyota (VVTL-i), Mitsubishi (MIVEC), Kia (CVVL)
• A slow start up or Fiat (MultiAir), BMW (Valvetronic), Nissan (VVEL), Toyota (Valvematic)
• FreeValve
To valve the engine always worked correctly and was not prone to wear, in the beginning there was just "pushers", then the lifters, but that was not enough, so manufacturers started implementing the so-called "shifters" on the camshafts.
Why do you need shifters?
To understand what shifters and what they do, beginning to read useful information. The thing is that the engine is running is not the same at different speeds. For idle and high revs ideal will be the "narrow phase", and for high – "wide."
Narrow phase – if the crankshaft is rotating slow (idle), the volume and velocity of flue gases is also small. It is ideally to apply the "narrow" phase, and minimum "overlap" (the time of simultaneous opening of intake and exhaust valves) – new mixture is pushed into the exhaust manifold through the open exhaust valve, and consequently the exhaust gases are (almost) do not pass into the intake. It is a perfect combination. If you do a "phasing" is broader, at low crankshaft rotations, the "testing" can mix with new incoming gases, thus reducing its quality indicators, which will definitely reduce the power (the motor will become unstable work or even stall).
Broad phase – when the revs are rising, respectively, and the growing volume and velocity of the pumped gases. Here it is important faster to bleed the system (from testing), and quickly drive them to the incoming mixture, the phases must be "wide".
Of course supervises the discoveries of the usual camshaft, and it "Cams" (kind of eccentric), it has two ends – one as it is sharp, it stands out, the other just made a semi-circle. If the end is sharp — that is the maximum opening, if the round (the other side) – the maximum closure.
BUT from a regular camshaft – NO adjustment of the phases, that is, they can't expand or do already, all the engineers are asking averages somewhere between power and efficiency. If you fill up the shafts to one side, the effectiveness or efficiency of the engine drops. The "narrow" phase will not let the engine develop maximum power, but "broad" — will not work normally at low speed.
That would be adjusted depending on the momentum! It was invented – in fact this is the system of regulation of phases, JUST — SHIFTERS.