General information
Some of the Honda models are equipped with an electronic valve timing adjustment system (VTEC). One of two different types of VTEC system can be used on Civic models (VTEC and VTEC-E).
The difference between conventional engines and VTEC equipped engines lies in the configuration and principle of operation of the valve train. The design of the engine block and all attachments and assemblies, as well as the schemes for organizing lubrication and cooling systems on both units are the same. An engine externally equipped with a VTEC system is distinguished by the presence of a convex inscription of the corresponding content on top of the cylinder head cover (VTEC).
The on-board processor of models equipped with the VTEC system is able to adjust the response phases and the amount of opening of the intake valves through the use of different sizes of camshaft cams. The processor, depending on the data coming from the information sensor, either turns on or off the system.
The following are used as initial parameters for both types of VTEC systems:
- a) Engine speed (rpm);
- b) Vehicle speed (mph);
- c) Throttle position sensor output (TPS);
- d) The current load on the engine, determined by the readings of the absolute pressure sensor in the intake manifold (IDA);
- e) Coolant temperature.
The layout and principle of operation of VTEC-E systems are somewhat different from those for VTEC systems (see below).
VTEC-E (D16Y5)
The camshaft is equipped with both primary and secondary intake cams. The cams differ both in shape and in the height of the rises, i.e. parameters that determine the duration and degree of opening of the valves.
At low engine speeds, the secondary valves are actuated by their own camshaft cams, which have a very small lift and a pointed shape (those. valves open only slightly and for a very short time), keeping the atomized fuel from consolidating inside the cylinder head. At the same time, good torque is developed with a high speed of response to gas.
If there is a need to increase the output of the engine, the secondary rocker arms are blocked with the primary ones using a special electronically controlled hydraulic device.
Note. The secondary rocker arms are no longer in contact with their own cams until the system is turned off. In this case, both valves open to full height and with maximum duration, providing an increase in engine speed and output.
VTEC (D16Y8)
The primary and secondary intake camshaft cams in this system are the same in shape and lift height. Between them is an additional third cam, also called intermediate. These intermediate cams are taller and less sharp in lift, resulting in greater valve opening and duration.
At low engine speeds, both the primary and secondary intake valves are actuated by their own cams and open to the same height and for the same duration (unlike the VTEC-E system). When it becomes necessary to increase the output of the engine, the rocker arms of both intake valves are blocked with an intermediate rocker arm by means of a special electronically controlled hydraulic device. In this case, the duration and height of the opening of both valves is determined by the shape of the intermediate cam, which is characterized by a greater height and a smaller peak of the lift.
Note. The primary and secondary rocker arms stop making contact with their own cams until the system is shut down.
The system allows you to achieve optimal torque at both low and high engine speeds, depending on the current load applied to it.
Checking the Status of Components
Valve clearance adjusters (VTEC only)
Four valve clearance correctors are placed in holders, forming a kind of hydraulic tappets.
1. Loosen and remove the holder assembly.
2. Remove the individual corrector assembly from the holder.
3. Use your fingers to check the freedom of movement of each of the correctors. If bite points are found, replace defective assemblies.
Phase distribution plate, bushing and return spring (only VTEC-E)
Four phase distribution plates with return springs (see illustration below) planted in the camshaft holders on the axis of the intake rocker arms.
A) Phase distribution plate
IN) return spring
WITH) Cam holder
Note. As you can see from the illustration, the assembly sleeve is equipped with shoulders to hold the spring.
1. Check up reliability of fastening of a spring on the holder of a camshaft and a plate of distribution of phases.
2. Inspect the components for scratches, chips, overheating, or other damage.
3. Defective parts must be replaced.
4. The order of assembly is clear from the illustration above.
Sync builds
1. After removing and dismantling the rocker assemblies (see Removal, condition check and installation of rocker arm assembly), also extract the components of the sync nodes (see accompanying illustrations).
Only VTEC-E D16Y5:
- A) Primary valve rocker
- IN) secondary valve rocker
- WITH) Blocker piston
- D) Blocker spring
- E) Timing piston
Only VTEC D16Y8:
- A) Primary valve rocker
- IN) secondary valve rocker
- WITH) intermediate rocker
- D) Timing pistons
2. Check the condition of the blocking spring (only VTEC-E).
3. Inspect the rest of the assembly (rocker arms with synchronizing pistons). If there are signs of wear, abrasions, deep scratches, nicks, or signs of overheating, replace the defective components.
4. Assembly is carried out in the reverse order to dismantling.
Note. Gather together the components of the assemblies of each of the cylinders, fasten them with a rubber band, only then install them on the axle (see Removal, condition check and installation of rocker arm assembly).
VTEC lockout solenoid valve
Faults in the VTEC lockout solenoid circuit cause the warning light to come on "Check engine" on the dashboard of the car. At the same time, a fault code is stored in the memory of the control units (DTC) R1259. The design of the VTEC shut-off valve with built-in pressure switch is similar to that used in the VTEC system of Integra models. A description of the procedure for checking the correct functioning of the assembly is given in Part Engine repair without removal from the car - Integra models of this Chapter.
Oil sprayer
See Removal, condition check and installation of rocker arm assembly.
Primary valve rocker
See Removal, condition check and installation of rocker arm assembly.
Secondary valve rocker
See Removal, condition check and installation of rocker arm assembly.
Intermediate rocker (VTEC only)
See Removal, condition check and installation of rocker arm assembly.
Camshaft intermediate cam (VTEC only)
See Removal, condition check and installation of rocker arm assembly.