Intake And Exhaust Valve Assemblies
| Item Number | Description |
|---|---|
| 1 | Valve spring seat (24 off) |
| 2 | Valve stem seal (24 off) |
| 3 | Valve spring (12 off intake, 12 off exhaust) |
| 4 | Valve spring retainer (24 off) |
| 5 | Valve spring collets (48 off) |
| 6 | Intake camshaft |
| 7 | Hydraulic tappet, inner |
| 8 | Tappet, outer |
| 9 | Cam lobe, central (smaller lifting height) |
| 10 | Locking pin, outer |
| 11 | Locking pin, inner |
| 12 | Return spring, outer tappet |
| 13 | Oil inlet |
| 14 | Cam lobes, outer (greater lifting height) |
The cylinder head incorporates 2 overhead camshafts operating 4 valves per cylinder via hydraulic tappets for the intake camshaft and mechanical tappets for the exhaust camshaft.
Camshaft Profile Switching
CPS is a system where the intake valves, at engine speeds up to approximately 3000 rpm, have a small lifting height of 3.6 mm, and at speeds above approximately 3000 rpm, have a greater lifting height of 10.0 mm. CPS, in combination with the VCT function makes it possible to control the cylinders' incoming air quantity in such a way that the Electronic Throttle Actuator (ETA) can be fully open. A fully open ETA, during operation, reduces the pump losses considerably compared with when the amount of intake air is controlled by the ETA itself. Reduced pump losses, in turn, cause a reduction in fuel consumption.
| Item Number | Description |
|---|---|
| 1 | Outer tappet |
| 2 | Locking pin, outer |
| 3 | Inner tappet |
| 4 | Locking pin with spring, inner |
| 5 | Oil inlet, hydraulic valve adjustment |
| 6 | Hydraulic valve adjustment unit |
| 7 | Return spring, outer tappet |
| 8 | Lug |
| 9 | Oil inlet, CPS function |
The electrical hydraulic valves are seat valves.
The valves have 3 inputs/outputs:
- Inlet, oil supply
- To/from tappet
- To return, i.e. oil pan
A solenoid is affected via an electro-magnet, which affects a valve that can assume 2 positions.
When the solenoid is not activated, the valve is only affected by the oil pressure on the intake side. The valve closes for intake but opens between the tappet and return.
The oil pressure is low at the tappet's outer locking pin and the valves lift a small amount.
When the solenoid is activated, the valve is affected from above by an electro-magnet that overpowers the force of the oil pressure.
The valve shifts position and closes between the tappet and return but opens the connections between intake and tappet.
The oil pressure is high at the tappet's outer locking pin that is lifted and affects the inner locking pin. Outer and inner tappet connect and the valves lift a greater amount.
The intake camshaft is equipped with 3 lobes for each valve. One centrally located with a small lifting height of 3.6 mm, and 2 outer lobes with greater (same) lifting heights of 10.0 mm.
At small lifting heights, only the centrally located lobe works on the valve, which occurs via the inner tappet. The outer lobes work on the outer tappet that follows the movement of the lobes. The return spring is compressed and ensures that the tappet is always in contact with the camshaft. When the centrally located tappet and the outer tappet are not joined, the outer tappet moves without affecting the valve. Thus the lifting height is small. At high lifting height, the inner tappet and the outer tappet are joined via the 2 lock pins.
The position of the lock pins is controlled hydraulically by 2 electro-hydraulic CPS solenoid valves. These valves are located in the camshaft housing.
| Item Number | Description |
|---|---|
| 1 | CPS solenoid valve - cylinders 3, 5 and 6 |
| 2 | CPS solenoid valve - cylinders 1, 2 and 4 |
One solenoid controls the valves for cylinders 1, 2 and 4 whilst the other controls the valves for cylinders 3, 5 and 6. The solenoids therefore control 6 valves each (when the engine has 2 intake valves and 2 exhaust valves per cylinder).
The position of the solenoids valves, on or off, are controlled by the ECM Refer to Electronic Engine Controls . .
The inner tappet works like a hydraulic tappet, which compensates for any wear. The valve clearance is therefore '0'.
The exhaust camshaft is conventional and has a lifting height of 10.0 mm. The tappets are mechanical (i.e. have valve clearance).
Camshaft Data
Intake
- Opening angle, 3.6, mm lifting height:
Crankshaft degrees - 152°
Crankshaft degrees - 76°
- Opening angle, 10.0 mm lifting height:
Crankshaft degrees - 240°
Crankshaft degrees - 120°
Exhaust
- Opening angle, 10.0 mm lifting height:
Crankshaft degrees - 240°
Crankshaft degrees - 120°
The intake camshaft has a VCT unit.
| Lifting height | Opens | Closes |
|---|---|---|
| Intake 3.6 mm | 32 BTDC to 28 ATDC | 120 ATDC to 180 ATDC (or 60 BBDC to 0 BBDC) |
| Intake 10.0 mm | 37 BTDC to 23 ATDC | 203 ATDC to 263 ATDC (or 23 ABDC to 83 ABDC) |
| Exhaust, 10.0 mm | 228 BTDC (or 48 BBDC) | 12 ATDC |
- BTDC = Before Top Dead Centre
- ABDC = After Bottom Dead Centre
- BBDC = Before Bottom Dead Centre
- ATDC = After Top Dead Centre
Camshaft Position in Relation to Load and RPM
| Item Number | Description |
|---|---|
| 1 | Range for lifting height 3.6 mm |
| 2 | Range for lifting height 10.0 mm |
| 3 | Small lifting height, 'early' camshaft |
| 4 | Small lifting height, 'late' camshaft |
| 5 | Large lifting height, 'early' camshaft |
| 6 | Large lifting height, 'late' camshaft |
By closing the intake valves early at low load and low engine speed, reduced fuel consumption is achieved.
| Item Number | Description |
|---|---|
| 1 | CPS solenoid valve (x 2) |
| 2 | Oil circuit, tappet CPS function |
| 3 | Calibrated passage (choke) |
| 4 | To bearing, exhaust camshaft |
| 5 | Tensioner, camshaft chain |
| 6 | Nozzle, camshaft chain lubrication |
| 7 | Oil circuit, hydraulic adjusting valve clearance |
| 8 | Vacuum pump |
| 9 | VCT unit |
| 10 | Oil inlet, rear |
| 11 | Return |
| 12 | To bearing, intake camshaft |
| 13 | To front bearing, intake camshaft |
| 14 | Return |
| 15 | Oil inlet, front |
| 16 | Bleeding |
The oil inlet, located on the front edge of the cylinder, supplies oil to the following:
- The hydraulic tappets
- The vacuum pump
- The nozzle for cam chain lubrication
- The intake camshaft's front bearing
- The electro-hydraulic CPS solenoid valves, front and rear
- The tappets with CPS function
There is a bleed valve (16) in the duct for the rear electro-hydraulic solenoid valves.
The duct is also equipped with 2 calibrated passages (3) to each tappet circuit (2) (i.e. the circuits after the CPS solenoid valves). A continuous flow through the circuit ensures the necessary stable pressure differences that are necessary for a stable transfer between the small and large tappet (or vice versa).
A filter is located in each passage.
The oil inlet, located on the rear edge of the cylinder, supplies oil to the following:
- The camshaft chain's hydraulic tensioner
- The intake camshaft VCT unit
- The intake camshaft's bearings
- The exhaust camshaft's bearings
To switch from low lift to high lift and vice versa as smoothly as possible, the transfer is only permitted when certain conditions are completed. These are:
- That the oil temperature is above +40°C (104°F). Calculated internally in the ECM, from, amongst other things, the coolant temperature
- Occasionally the volumetric efficiency is the same for low and high lift, which means that the air requirement is within a range where it can be managed initially by VCT control. This is to achieve as soft a transfer as possible.
- It is possible to adjust ignition timing to prevent torque peaks during CPS control
Refer to Electronic Engine Controls .