Yamaha dry sump PWC and oil level sensitivity.

Joined
Jun 21, 2009
Messages
1,204
Location
Missouri
I have had very little experience with dry sump systems, British bike and Yamaha VX1100 are exceptions. I understand what happens when wet sumps are overfilled, the level gets up where the crank counterweights begin frothing the oil. It would seem that dry sump systems would not have much problem with overfilling until there is little air space in the tank/reservoir. Yamaha VX1100 Waverunner have dire warnings about overfilling the oil tank, they'll start blowing oil into and wet the air filter. This dry sump motor is apparently sensitive to overfilling based on the warnings seemingly everywhere. I've even seen advice to keep the level between the low and full marks and don't fill to the full line. Why is this dry sump system that sensitive if indeed it is? I've run my Waverunner somewhat overfilled at times and haven't seen any problems.
 

ledslinger

Thread starter
Joined
Jun 21, 2009
Messages
1,204
Location
Missouri
I studied the oil reservoir a bit and have a better understanding of the system. At the top of the tank is a baffle and a vent hose or hoses that goes either to the valve cover, or the air intake, or both. Possibly these hoses are intended to remove vapors and vent/control air pressure in the oil tank. I suppose this acts similar to a PVC system in a wet sump system and runs the oil vapors through the intake and burns them in the combustion chamber which is less polluting than just venting the vapors to the atmosphere. All is fine as long as the venting system has vapors in it and not much oil droplets or liquid oil. A slight oil overfill might intermittently vent droplets or liquid oil such as during turns or when forces from hitting waves caused oil to splash up the oil tank vent connections. A more drastic overfill likely removes the air space near the vent, and fills the vent pipes with oil. This makes some oil go to the air box and wets the filter which can't flow when oil soaked, some gets run into the air intake for a smoky burn. I think the system is really more tolerant of a slight overfill (one quart? possibly) than the alarm associated with overfill on these engines. I suspect this is due to how dramatic a severe overfill looks when it happens. A typical situation is when the partial change oil quantity is pumped out (about 2.1quarts without filter, 2.3 with filter) and then full system capacity is put back in (full system - 4.5 quarts) which results in an over 2 quart overfill. A 2 quart overfill may cause wetting of filter and lots of smoking from oil induced into the intake, all very alarming. It just takes some getting used to that any oil change on the these engines is just a partial change, kind of like drain and fills on automatic transmissions. To do a full oil change requires several oil changes after running between, which usually isn't needed, but isn't that difficult with a good oil change pump. To really change the oil instead of just mixing new with old, likely would require about three partial changes. I know my waverunner has been overfilled by possibly a quart a couple of times since new, but I've never seen any indications of what must happen with severe overfills
 

ledslinger

Thread starter
Joined
Jun 21, 2009
Messages
1,204
Location
Missouri
Further study of oil tank plumbing verifies two vent hoses at the top of the oil reservoir, one goes to valve cover, the other to the air inlet through an oil separator. The oil separator looks to be a funnel shaped box that allows liquid oil to collect and oil vapor to pass through. The oil collected is routed to the oil pump by a hose at the bottom of the oil separator. Oil vapor is continuously routed to the air inlet to be burned in the engine.
 
Joined
Dec 21, 2005
Messages
178
Location
Georgia
Ledslinger, I think you are spot on. I have 2 FXHOs with dry sump systems and I always fill them to at least full if not a little over and haven't ever seen evidence of oil damage to the air filters or contamination of the intake tract
 

ledslinger

Thread starter
Joined
Jun 21, 2009
Messages
1,204
Location
Missouri
Considering another aspect of the lubrication system of dry sump VX1100 Yamaha PWC motors, they may have some tolerance to underfilling. The 4.5 quart system is fairly large for an 1100 CC 110 HP engine, and the system can likely function on little oil, though it would break down quicker and run hotter. Dry sump systems in general likely can still function on less oil than wet sump systems. Looking at the water cooling jackets on the front and back of the oil reservoir, there appears to be large cooling capacity. The outside of the reservoir where the plates that enclose the oil cooler mount, have ribs like cooling fins, as do the plates. Cooling water flow from the jet pump supplies a large amount of water to both the cooling system and the oil cooler. It appears the lubrication system of these motors has adequate capacity and oil cooling ability for long engine life. The oil system seems carefully considered to allow for long running at high load and speed.
 
Joined
Sep 30, 2013
Messages
13,489
Location
Indiana
I was guessing it was venting related before reading into your other posts. Was the point in a dry sump application this small? I always thought it was for large ships and such.
 

ledslinger

Thread starter
Joined
Jun 21, 2009
Messages
1,204
Location
Missouri
Dry sump systems are pretty common on motorcycles, particularly racing machines where they want engines set low in the chassis. I'll surmise several reasons why Yamaha made the first 4 stroke PWC engine dry sump. First since the parent engine in the design was the R1 motorcycle, which I'll assume is dry sump. Altering an existing design to wet sump would require some additional redesign. Possibly the main reason was it may be easier to design a dry sump system that will tolerate being inverted, as happens with PWCs, even though more modern PWC 4 stroke machines such as SeaDoo are wet sump. The third reason was while the vertical dimensions are more limited in a PWC, length is more available, which they utilized in this dry sump design. Wet sumps require a minimal vertical dimension and dry sumps less so. Dry sumps also allow engine to be installed lower, improving center of gravity making the machine less prone to rollover. Dry sump also allows oil system capacity, cooling capability, vapor control and lube deaeriation, for long periods of high load wide throttle running.
 
Top