Geely EC718 2009 Workshop Manual page 388

2-306 Engine Mechanical System JL4G18-D Engine
2.6.2 Description and Operation
2.6.2.1 Description and Operation
1. Cylinder Head
Cylinder head is made from aluminum alloy casting process.
cylinder valve stem is a mechanical system. valve clearance
can not be automatically adjust, which is very important. The
cylinder valve is an integrated part. OEMs can offer 38 different
sizes to choose from. During the repair, required quite tube
thickness can be calculated according to the formula. For
specific information. Refer to 2.6.8.20 Valve Clearance
Adjustments. With Double overhead camshaft layout, in the
drive sprocket on the intake camshaft there is also a VVT
actuator for adjusting the intake valve timing. For the detailed
working principle. Refer to 2.6.3.1 System Working Principle.
2. Timing Chain
Dual overhead camshafts are driven by a timing chain. Timing
chain must be replaced every 120,000 kilometers. Timing chain
system consists of timing chain, timing chain guide rails, timing
chain tensioner rail and the timing chain tensioner. Timing
chain tensioner tensioning is provide by the pressure from the
oil pump to ensure the timing chain tensioner maintain a
constant intensity. Timing chain lubrication is provided by the
oil pump nozzles. Refer to 2.6.8.11 Timing Chain Inspectionfor
specific information.
3. Intake Manifold
Intake manifold has four independent long ports, using inertia
to improve the engine torque at low speed.
4. Camshaft
Dual overhead camshaft (DOHC) has two camshafts. A
camshaft controls the intake valves, the other camshaft
controls the exhaust valves. The camshaft is located in the
journal in the cylinder head on the top of the engine and fixed
with camshaft cover. The cylinder head camshaft journal
drilling is used for engine oil channel. Engine oil flows to the
camshaft under pressure, lubrication each camshaft journal.
Engine oil flows through the cylinder lid to return to oil sump.
Cam convex corner is formed by machining, at the right time,
according to the appropriate amount, accurately open and
close intake and exhaust valves. Cam convex is lubricated by
high-pressure oil escaped from the engine camshaft.
EC718/EC718RV EC715/EC715RV 10/2009