View Full Version : Dry-sump oiling system explanation

ed apriliaforum com
03-07-2001, 09:21 PM
This is a simple explanation of how a dry-sump oiling system works in the RSV1000 Mille, SL1000 Falco, RST1000 Futura, and Pegaso 650. This oiling system can also be found on all types of race cars (F1, Indy, circle-track, even NASCAR). This dry-sump oiling system frees up lost horsepower and prevents oil starvation problems associated with long wheelies and high G-forces. Aprilia is the only one to use this dry-sump oiling system in all of their 4-stroke motorcycles. I strongly feel that other manufacturers should also use this system.

The basic dry-sump oiling system consists of two oil pumps, an oil filter, and an oil tank.

We'll start at the oil tank, since most of you know where that is located. The oil tank always contains a minimum level of oil. The oil is drawn down the bottom hose to the first oil pump called the pressure oil pump. The pressure oil pump pushes the oil through the oil filter, and then to all major lubrication points (bearings, crankshafts, cams, transmission gears, etc.) thru oiling passages just like in all other engines. This pressure pump is analogous to the single oil pump in a wet-sump engine.

Oil splashes off the moving parts and drains to the bottom of the crankcase. Here, is the main difference between dry-sump and wet-sump. In a typical wet-sump engine, the crankcase (oil pan) is very deep and full of oil. The crankshaft partly spins through this oil causing a HP loss. The single oil pump in a wet-sump engine has its pickup somewhere in the oil pan. Under certain conditions (high G-forces, long wheelies, stoppies, etc.), this oil pickup can be sucking in air and not oil. This will starve all the moving parts for oil. NOT GOOD!!!

In a dry-sump Aprilia engine, the oil does not sit in the pan, hence the bottom of the crankcase is "dry" and very compact. A second oil pump, called the recovery or suction oil pump, returns this oil back to the oil tank through a hose. This hose connects to the top of the oil tank. With a dry-sump system the "oil pan" is effectively moved to the side of the engine (now called the oil tank). Remember, because the oil tank always has oil to feed the pressure pump, the pressure pump will never run out of oil. No oil starvation problems!!!

This system allows the engineers to make a more powerful and compact engine, and provide adequate lubrication under all conditions (high G-forces, long wheelies, stoppies, etc.). It frees up lost horsepower by not spinning the crankshaft through several inches of oil. The crankshaft is pressure lubricated not "splash" lubricated.

04-26-2001, 10:13 PM
So how are the pumps powered? Are they electric or mechanical? And even though there are two pumps, I assume pumping the oil is more efficient than splashing it about with the crank?

ed apriliaforum com
04-26-2001, 10:36 PM
They are mechanical

08-24-2001, 08:39 PM
Why is the energy used to drive the two oil pumps
more efficiently harnessed than allowing the crank
to simply splash in a conventional oil bath?

Would a person travelling at more conventional
sport-touring speeds, who is disinclined to do
wheelies or lean extremely low, see any realistic
benefit beyond theoretical with dry sump lubrication?

I find it hard to believe.


ed apriliaforum com
08-24-2001, 10:15 PM
those are some good questions...it is my opinion that all high-performance engines even those in Sport-touring bikes should have dry sump lubrication.......I found most of the text below from a few websites about dry-sumps

"Unlike a wet sump system where oil is stored in the pan, a Dry Sump Oiling System stores oil in a separate tank - leaving the pan essentially "dry." An extemally-mounted pump, is used to "scavenge" or remove oil from the pan, deliver it to the storage tank, and send it back through the engine. In a typical setup, all but one of the stages is used to scavenge oil from the pan. A single pressure stage is normally used to return oil from the tank to the engine.

The primary advantage of a Dry Sump System is its ability to make more power. With very little oil in the pan, the rotating assembly is not burdened with the weight of excess oil (a phenomenon commonly referred to as "windage'). And because there is no internal pump, the windage tray or screen which serves to isolate sump oil from the rotating assembly, is allowed to run the full length of the pan. Keeping the rotating assembly free of windage allows it to spin freely and make more power. In addition, the extra crankcase vacuum created by the dry sump pump helps to improve ring seal for additional power gain.

Other advantages of a Dry Sump System include increased oil capacity, more consistent oil pressure, the ability to easily add remote coolers, and adjustable oil pressure. And because the pan doesn't store oil, it can be relatively shallow in depth to allow lower engine placement for improved weight distribution and handling"

The crankcase bottom end can also be more shallow and compact making it more rigid, which helps improve bottom-end life. Faster, more consistent oil pressure at startup also prolongs engine life.

Ricky J
08-27-2001, 06:42 AM
Aprilia decided to use the sixty-degree motor
because it's shorter fore-to-aft and allows a
chassis designer more leeway in postioning to
optimize weight distribution. A V60's disadv-
antage is added height, and they liked a dry
sump because it reduced this dimension. Cert-
ainly one of the most important reasons they
chose this system...

micah apriliaforum com
08-27-2001, 11:11 AM
For me the whole wheelie oil supply is the most important reason...not that I really need it.

rowdy lee
09-06-2001, 09:24 AM
Are you sure there is no mistake? The CRANK is LUBED by it's SPLASHING AROUND in the oil in the bottom of the oil pan? Perhaps there was some mistake in the article which was copied.....

ed apriliaforum com
01-04-2002, 12:19 PM
no it is not really lubed that way....the bearings have their own oiling holes and oil pressure. The article was talking about windage associated with having oil in a pan just under the spinning crank.

someone recently emailed me somemore useful info on this matter....he covers some things that arent quite clear in the above discussion.......it reads.....

there is an important point which I missed when I read your explanation of the advantages of dry sump oiling systems:

A big advantage of building dy-sump oiling systems is that you get free space under the engine as you don't need the room to store the oil. Therefore the enging can sit lower in the frame. This allows a lower center of gravity! A low center of gravity improves the handling of the motorbike (The reason why the boxer engine of BMW is good under this

Second, I don't think that the crankshaft in a good manufactured engine is splash lubricated. In a good construction the crancshaft is also lubricated by pressure and not by "splash" even in wet sump lubricated systems.
Splash lubrication in wet sump lubrication systems normally happens only when the engine is moved by bad road conditions or heavy riding.

Here comes the second advantage of dry-sump lubrication:
Because the crankshaft never hits the oil-level there won't be "dust" of oil in the crankcase which raises the oil consuption of the engine as the crank-case is "ventilated" and the oil dust can be sucked in from the engine by that way.
And this prevents the machine of burning oil. Burning oil is not good for the catalytic converter and other parts of the engine .

Hermann (the german)

02-11-2002, 05:46 PM
I am sorry, I had to laugh a little when I read this. The engine does not actually make more horsepower because of the dry sump system. It does spin freely without the crankshaft slamming into the oil bath and creating harmonic distortions. Hence on an auto, the harmonic balancer useage. Pro-stock drag racing cars have some of the most sophisticated systems next to F1 cars. The "stages" of the scavenge side of the pump will take oil from various parts of the engine like the valve cover area, oil pan and transmission areas before it is allowed to cause interference with the crankshaft. The oil "gallies" are cast into the engine and are not seen but for where the fittings appear. There is also not neccesarily a better piston ring seal from the vacuum created by the scavenge, as the vacuum is very low. Engine power is a result of cylinder pressure over time. If you free up the engines ability to rotate without any restriction, what you achieve is rpm over a shorter period of time, not power. Hence quicker revs. A dry sump is a more efficient way of lubricating the engine. There are drag racing and SCCA cars that run windage trays that keep oil from hitting the crankshaft. The have baffled oil pans also that eliminate oil starvation when braking, accelerating or cornering. Dry sump's only advantage over a good wet sump system is the ability to get the engine as low and compact as possible for Center of Gravity or for Instant Force Center. These are the first considerations when building a racing bike or high performance machine.