Gas distribution mechanism — device (Hyundai Elantra J1)

It takes a short time for a variable valve internal combustion engine to suck in the fuel mixture and expel the exhaust gases. The camshaft cannot open the valves instantly, nor can the valve springs close them instantly. Therefore, the cams are shaped in such a way that the intake valve opens already at the end of the intake stroke and closes only when the piston, after the end of the intake stroke, rushes upward again for compression. The exhaust valve opens before the end of the working stroke and closes when the working mixture begins to be sucked in during the piston stroke. Both valves open simultaneously for a split second when the piston is at top dead center (TDC) and transitions from the exhaust stroke to the intake stroke. This period of time is called valve overlap.

Cylinder head and camshaft

The cylinder head is, to a certain extent, the engine cover. It contains valves and also has channels for the working mixture and exhaust gases. The head is cast from an aluminum-based alloy and, like the cylinder block, is cooled internally by circulating coolant.

At the very top of the cylinder head are the camshafts. With the help of cams, the valves open and close at certain positions of the piston in the engine cylinder.

The intermediate element between the camshaft and the valves are the rocker arms or tappets. Each tappet or rocker arm is located above a valve and two valve springs. The cams do not touch the tappets exactly in the middle, but slightly offset, causing the valves to rotate slightly around their axis with each downward press. This ensures that the valve is sealed in the cylinder head seat.

Hydraulic pusher

With hydraulic valve clearance adjustment, there is no need to monitor these clearances, but it is necessary that the closed valves fit tightly against the valve seats, and at the same time the necessary tightness is ensured.



The article is borrowed from an online resource [HyundaiBook.ru]

Note: Knocking sounds, similar to those caused by damaged bearings, may be produced by an engine with hydraulic tappets when first started after a long period of inactivity. This effect occurs when oil leaks from the hydraulic tappets and this causes a gap in the valve train to form again. But there is no reason to worry: the noise disappears after a while and the valve drive works silently again. If the hydraulic tappet knocks for a long time or even when the engine is warm, it needs to be checked.