Jag har klurat på hur oljesystemet fungerar. Vad är det som gör att oljan i tanken inte rinner ner i motorn? Rinner all olja ner i motorn när den är avslagen? Om det är så, hur i hela friden stannar den då kvar när motorn är i gång? Är det någon som har en vettig beskrivning av oljesystemet?
This is a working draft of my understanding of the oiling systems. I thought I should post it sooner rather than later. Everyone can help improve this writeup. I'll periodically edit this post to incorporate everything learned. Additions, corrections, or questions are all appreciated.
I have arranged the description headings in substantially the order in which oil flows through the engine. Item numbers referenced come from page 36 of the parts book (pic posted below).
Oil Tank:
The oil tank has 4 ports. On the right side, blue hoses connect for "supply" and "return" to the engine. The lower hose is supply. The upper hose is return. The return line runs inside the tank, and makes a 180-degree turn to dump oil back into the tank. The hose at the bottom of the tank on the left side is for crankcase ventilation. The crankcase vent hose connects to a pipe internal to the oil tank that runs to the very top of the tank. The hose at the top on the right side connects to the airbox and vents the oil tank.
Oil Pump:
The "oil pump" is actually two separate pumps driven by a common shaft. There is a scavenge pump and a pressure pump. The pressure pump supplies oil to all internal engine components. The scavenge pump returns oil from the engine sump to the oil tank (hence the name dry-sump system). The two pumps will be discussed separately in greater detail. It is interesting to note that the scavenge pump has a wider geroter (see:
http://en.wikipedia.org/wiki/Gerotor) and thus greater pumping capacity than the pressure pump.
Pressure Pump:
Oil is drawn out of the oil tank through the blue bottom hose. It runs through one hard-line external to the engine (item #5), and another hard-line internal to the engine (item #3 behind the alternator cover). Oil is thus delivered to the inlet side of the pressure pump. The outlet side of the pressure pump delivers oil to the oil filter, but connects to the FCV as well.
Flow Control Valve:
The FCV (items #8-11) is a pressure regulator. It simply shunt excess oil flow from the outlet side of the pressure pump back to the inlet side of the pressure pump.
Oil Anti-Return Valve:
In another post, I incorrectly postulated that this component (items #12-17) was an oil-filter bypass valve. I now believe the parts book's description of "oil anti-return valve" is correct. (In English, "anti-drainback valve" might be a better translation, though.) A very small oil pressure is required to open the valve. However, when the engine is shut off, this valve closes and won't permit oil to flow out of the pathways by gravity. Because oil is essentially incompressible, there is zero time lag for the oil to start flowing through the internal pathways (once the system is primed). This means that the instant the engine is started, all critical components already have oil delivery. However, this also reminds me that, after an engine rebuild, it is important for the engine to be cranked without starting for a while in order to prime the system and ensure proper oil flow at the instant of start-up.
Oil Filter:
The oil filter (item #19) receives oil by way of the pressure pump/FCV interaction, and the anti-return valve. The oil filter itself contains an integral bypass valve. Normally this valve is closed and thus all engine components receive 100% filtered oil. However, if the pressure differential across the filter media becomes too great, the bypass valve opens and allows partially filtered / unfiltered oil to be delivered to engine. Oil flows through the filter from the outside to the inside.
Oil Pressure:
According to Micah's measurements, maximum oil pressure is in the range of about 112 to 122 PSI at any RPM above about 5,000. Oil pressure can be measured by removing the oil pressure switch (item #18) and installing a gauge (M10 -1.0 thread). The oil pressure switch is electrically "normally closed" and remains closes until the oil pressure rises above about 6 PSI. Again, according to Mica's measurements, normal (cold!) oil pressure at idle is about 75 PSI. The oil pressure switch is located on the outlet side of the oil filter.
Internal Oil Pathways:
Filtered oil is delivered to all internal components. There appears to be three paths out of the oil filter. One leads to the front head. The other two supply oil to the RH and LH crankshaft main bearings. These are plain bearings. A pathway through the clutch housing directs oil to the rear head. There is no O-ring or other special sealing at the clutch housing/crankcase interface (only the usual clutch housing gasket). There is a bolt right next to the passage, but this would seem to be an area to watch for leaks to ensure the rear head is properly oiled.
Oil is delivered to the heads through the crankcases. There are two (one for each head) very small (0.5mm) orifices the oil must pass through to get to the heads. The bearings in the heads are ball bearings. Oil drains from each head back to the crankcase sump.
There is an outboard seal for the crankshaft in the alternator cover. Oil is deliverd to the alternator cover via the hollow shaft for one of the starter gears. This shaft has an O-ring at each end. Amauri has cautioned us to be careful not to damage these O-rings (and outboard seal) when the alternator cover is installed. The oil that feeds through the alternator cover and into the crankshaft lubricates the big-end rod bearings!
Scavenge Pump:
The sump is evacuated by the scavenge pump. The inlet to the scavenge pump is covered by a small screen (as would be normal for any wet-sump oil pickup). Oil is pumped out of the engine through the internal hard line (item #1) behind the alternator cover. Another hard line outside the engine (item #6) returns scavenged oil to the tank via the upper blue hose. One curious feature here. The internal hard line has a hole drilled in it near the top. Not sure what this does. Obviously some oil will bleed out on its way back to the oil tank. Maybe this hole is just to oil stuff inside the alternator cover?
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http://www.apriliaforum.com/forums/showthread.php?t=142566
