When should the intake valve close?

When should the intake valve close?

The valves are timed so the intake valve opens slightly before the piston reaches top dead center (TDC) on the exhaust stroke. Likewise, the exhaust valve is timed to close just after the piston starts down on the intake stroke.

Why inlet valve closes some degrees after BDC?

It closes after quite a few degrees of piston reaching the BDC, i.e. when the piston starts to move up the cylinder in the compression stroke. This is because the downward movement of the piston creates the vacuum (or negative pressure) in the cylinder and the air-fuel mixture gets filled in the empty space.

Why intake valve opens before TDC?

Prior to the piston reaching TDC, the intake valve starts to open. The previously created vacuum in the combustion chamber will draw fresh air/fuel mixture into the combustion chamber and some will even escape into the exhaust port. This will ensure that all of the spent gasses are removed from the combustion chamber.

What would happen if the intake valve opened too late?

If the intake valve opens too late in the cycle, the initial amount of fuel/air mixture draw into the combustion chamber is reduced and spent gasses will not be effectively flushed from the chamber. If the exhaust valve closes too late in the cycle, the combustion chamber will be “over-scavenged”.

Why does the exhaust valve open before BDC and close after TDC?

The gases inside the cylinder posses a higher pressure even after the expansion stroke. Thus the exhaust valve is made to open before the piston reaches the BDC thus enabling the gases to escape outside on its own and the remaining gases are pushed out by the upward motion of the piston.

What is the importance of valve timing?

For a proper four stroke cycle, valve timing helps to operate the valves precisely to enable the valve opening of inlet, closing of exhaust, and opening of exhaust valves during each cycle.

Should all valves be closed at TDC?

It’s up to you. Both valves should be closed if it’s TDC at the end of the compression stroke. If it’s TDC at the end of the exhaust stroke, you should be in the valve overlap zone, with the intake valve partially open and on its way to opening fully, and the exhaust valve partially open on its way to closing.

How do I know if valves need adjusting?

You should have your valve lash inspected at manufacturers recommended intervals. A sure sign that it’s time for a valve lash adjustment is if your engine is making a loud clicking or tapping noise when starting up or if you experience a loss in engine power.

What happens to the air when the intake valve is closed?

The intake valve remains open during the beginning of the compression stroke however, allowing some of the trapped air to flow back out of the cylinder into the intake manifold. Once the intake valve has closed, the air remaining in the cylinder is compressed in the conventional way.

What is an early intake valve closing strategy?

Early intake valve closing strategy. An ideal early IVC strategy allows air to be drawn into the cylinder as close as possible to atmospheric pressure at the beginning of the induction stroke. The intake valve closes part of the way through the induction stroke to prevent any further air from entering the cylinder,…

Why does the inlet valve of an engine open before hand?

But that is not the real reason that the inlet valve opens before hand. The real reason is scavenging In order to get a rapid combustion and low levels of pollution resulting from incomplete combustion, all modern engines induce turbulence into the fuel air mix.

What is late intake valve closing (LIVC)?

A “late intake valve closing” (LIVC) is the valve train and induction system that mimics, to some degree, what the Atkinson system was doing. LIVC is used in many, but not all, hybrid and plug-in hybrid models. LIVC is also used in conventional cars and trucks as well, but only recently.