The following describes the engine lubrication system of the Desmoquattro engine as fitted to the S4(R)
The lubrication system is the wet sump type in that the oil reservoir in contained within the engine sump. Forced lubrication is supplied by an engine driven gear type positive displacement pump, a pressure relief valve limits the maximum delivery pressure. The pump suction is protected by a mesh strainer. The oil flow is cooled and filtered before being directed to the engine components. Transmission gears and bearings are splash lubricated.
A low oil pressure warning light is incorporated into the instrument cluster.
Key to Drawing.
A Mesh filter
B By-pass spring
C Oil pump
D Output to cooler
E Input to engine from cooler
F Con-rod big end bearings
G Clutch cover
H Oil delivery pipe to heads
I Head
J Piston Cooling Jets
K Main Bearings
L Cylinder
M Piston
N Gearbox
O Flywheel / ignition assembly
P Crankshaft
Q Cooler by-pass spring/reed
R Cartridge filter
Lubrication system operation
The oil pump (C) is driven by a gear on the crankshaft at 0.6 engine speed, capacity is stated at 2.6 liters/min @ 1000 RPM, the flow rate increases with an increase in engine speed. Oil pressure (measured at the crank inlet) is > 0.8 bar (11.6 psi) at 1100 – 1300 rpm increasing to > 4 bar (58 psi) @ 3500 – 4000 rpm with an oil temperature of 80° C (176° F) The oil pressure switch monitors the same position.
A cylindrical mesh filter (A) on the pump inlet, protects the pump from foreign object damage.
The pump incorporates a pressure relief valve (B) that regulates the maximum delivered pressure, excess oil relieved by the valve is returned to the sump)
The delivery from the pump, flows to the oil cooler, a bypass reed spring (Q) located in the filter housing bypasses the cooler if the flow resistance through the cooler exceeds the value of the reed spring.
Oil Cooler Bypass Spring/Reed Valve
The oil cooler is a single pass type with the flow entering from the left and returning from the right, a ¼” banjo connection provides a feed to the cams.
Oil Cooler Inlet
From the cooler, the oil flows to the cartridge filter (R) which is fitted with an inner relief valve that will open if the filter resistance exceeds its set value, this ensures proper oil circulation under all conditions. Note that the oil supply is not filtered if the filter blocks and causes the valve to open.
Leaving the filter, pressurised oil flows to two different lubrication ways:
1. Crankshaft
2. Main bearings & piston cooling jets
Oil is fed into crankshaft (P) through a bush and seal in the clutch cover (G).
As it flows into the crankshaft, oil lubricates con-rod big end bearings (F), a cavity within the crankshaft big end journal functions as a centrifugal sludge trap.
Oil from the crankshaft gallery is fed to the inner ring of the starter gear and the starter clutch (0) flowing through radial crankshaft drills.
The oil flow exits the left end of the crankshaft lubricating the bearing in the generator cover, oil flowing from this bearing provides splash lubrication to components within the generator case.
Pressurised oil is supplied to an annulus surrounding the main bearings via galleries in the clutch cover and crankcases, a 1.25mm radial drilling into this annulus forms the piston cooling jets, one per cylinder, the horizontal cylinder is fed from the right case and the vertical from the left case
Left Case
Right Case
The flow to the left hand main bearing passes though a drilled 8mm case clamping screw, the head of this screw is painted red to distinguish it, the function of this arrangement is to regulate the flow to the left hand case. Mistakenly replacing this screw with a normal un-drilled item will effectively shut off the oil supply to the left hand main bearing with catastrophic consequences.
Oil exiting the pressure fed components provides splash lubrication to the primary transmission, gearbox and gearbox shaft bearings
The camshafts, bearings and valve gear are supplied with un-filtered and un-cooled oil from a pipe (H) connected to the oil cooler inlet. The oil enters the rocker shaft covers on the left hand side, a cavity formed between the cover and the head directs oil to bores in each rocker pivot shaft and via drillings in the head to the left hand camshaft bearing caps, a cavity in the bearing cap, directs oil into the bore of the camshaft, a seal in the cap running on the camshaft maintains the pressure, radial drillings in the cam lobes provide pressurised lubrication of the cam/rocker contact. Rocker arm pivots are lubricated via radial drillings in the pivot shafts.
The closing rocker pivot shafts also direct oil to the right hand rocker cover cavity where it is directed to the right hand opening rocker pivot pins and the right hand cam bearings.
Oil exits from the pressure fed components into the cam chambers from where it drains via two drillings in the cam chamber to vertical drillings in the head, barrel and crankcase to the sump, this cam drain flow also contributes to splash lubrication.
Right Hand Rocker Pin Cover
Camshaft Oil Feed
Right Hand Rocker Pivot Cover
Garter type spring valve seals are press fitted to each valve guide.
Oil returns by gravity to the sump which is divided into compartments to provide a baffling effect and maintaining a flooded suction compartment. Oil flows between these compartments through the slots formed when the crankcases are mated. The pump suction compartment into which the strainer is inserted, is shielded to reduce the possibility of air entrained in the returning oil entering the pump. The crank is separated from the sump to reduce “windage”.
The compartment walls also contribute to the stiffness of the crankcases.
Operational Issues.
The oil filtration efficiency can be improved, in the process of development, the factory conducts long term tests where the engines are run for hundreds even thousands of hours, wear surfaces are examined and the data used to refine the system design and the lubricant to ensure engine wear is within acceptable industry norms.
In regard to oil filtration, wear will increase if the particle size is greater than the lubricant hydrodynamic wedge.
The OEM oil filter has an efficiency of somewhere between 40 and 80 percent @ 15 microns.
Amsoil
http://www.amsoil.com/storefront/eao.aspx produces a filter with an efficiency of 98.7 percent at 15 microns, it is able to do this by the use of nano technology to increase the amount of particle retention, providing an equal if not longer service life than the OEM item with the benefit of superior filtration.
During operation, minute hard ferrous particles are worn away and become part of the lubricant. Wear of soft plain bearings such as the big ends is exacerbated by these particles.
Being ferrous, they are easily removed by magnetism, one or two neodymium magnets fixed to the outside of the filter, will remove ALL ferrous material from the lubricant and reduce the load on the filter element. Regular magnets are not powerful enough to provide sufficient attraction.
There are no check valves in the system, when the engine is stopped, oil commences to drain out of the delivery system to the sump, if the bike is kept on the side stand just about all the oil in the cam feed drains from the feed cavities and delivery pipe. Some oil also drains from the cooler. The time taken for the system to drain completely is in the region of 24hs.
When the engine is started, the pump has to refill the system before pressure is developed. Times of up to 90 seconds have been reported to establish operating pressure at all points of the system. Lubrication during this period relies upon retained oil films on the components. In the absence of pressurised lubrication, wear on all components is accelerated. Clearly this an area for improvement.
Fitting a check valve in the cam feed oil line will retain a substantial amount of oil in that portion of the system. This valve should be fitted as close to the take off on the oil cooler as possible.
The oil cooler will also loose a similar volume of oil, this can be reduced by fitting a check valve in the feed line. On its own, this valve will not prevent the oil draining from the cam feed.
Given the precarious situation of the lubricating system during start up, it is advisable to not rev the engine until the system pressure has been established (at least 90 seconds).
The choice of lubricating oil plays an important part, fully synthetic oils with a viscosity of 15/50 or 20/50 having very high shear strengths leave a thick residual film of oil on all parts, the film is long lasting and provides maximum lubrication in zero pressure conditions encountered during start up. The drawback however is that when cold they take a longer time to reach the extremities of the system when the engine is first started.
When changing the oil, consider the amount of oil in the oil cooler that will not be drained, this will contaminate the fresh oil. The cooler would have to be removed to drain this, if this is done, fill the cooler with fresh oil before refitting.
When fitting the oil filter, fill it with fresh oil and lubricate the rubber gasket, hand tighten then turn an additional 1/3 turn..
The pump inlet screen should be periodically removed and examined for debris.
It is not uncommon to observe emulsified oil in the level sight glass, this is most always as a result of moisture condensing out of air within the crankcase. It can readily be driven off by heat, achieved by operating the engine at a high temperature for a period of time. Covering the oil cooler face helps this process.
Being water cooled, coolant leaking into the oil will produce a similar condition, coolant levels should be monitored if the condition persists.
The oil pressure specs seem to indicate that the relief valve setting is above 4 and less that 6 bar.
