Oil delivery

[pete roper]

OK, this is going to be very simplistic but I hope it will clear up a few matters pertaining to how the oil delivery system works. While I can't be sure the subliminal message I'm getting from some posters is that they seem to think that the oil pump and delivery system is much the same a s a garden lawn sprinkler! Oil id pumped out of the sump and then just sort of casually sprayed around all over the place and hopefully some of it will get to where it's needed and make things slippery. Sorry, there is a bit more too it than that.

 

Firstly though lets look at the Guzzi motor. It is a very simple, robust and durable design and it will generally take abuse quite happily. One of the reasons for it's inherent strength is that it uses 'Plain' or 'Slipper' type bearings. These work by having a journal, (on the crank or camshaft.) that rotates in a bearing either in the crankcase itself in the case of the cam or in replaceable, bolted in inserts in the case of the crank main bearings and split shell type beaings in the rods. In between the journal and the bearing there is a gap, the bearing clearance, and this is absolutely critical because what prevents the bearing rubbing on the journal is a thin film of oil. This film of oil alone is ompletely inadequate to deal with the pressures being exerted on it by the forces of combustion but as the journal spins in the bearing, as long as there is an adequate supply of oil at an adequate pressure provided between the two parts, will form what is known as a hydro-dynamic wedge, conveniently at the point of greatest pressure on the film of oil!

 

The thing is to get a decent wedge happening you need to not only have a decent and CONTINUOUS flow of oil supplied to the bearing but the clearance has to exactly right and both the journal and the bearing need to be as near as damn-it perfectly round.

 

So how do you get the oil into the bearings? The clearance betwixt journal and bearing is about 1 to 1.5 thou per inch of journal diameter! If we were working on the 'Lawn Sprinkler' principle, especially with something whizzing around 6,000 times a minute we are scarcely going to get much oil into the bearings and it's going to be under bugger all pressure. So, what do you have to do? Well, it's pretty simple really, you feed the bearings from INSIDE the journal in the case of the big ends and through a series of drilled galleries in the case and crank to get the oil to where it needs to be.

 

So lets look at how oil gets to your bearings.

 

Well, it starts off in the sump. In the case of the V11 'Broad Sump' motor the pick-up protrudes down to close to the bottom of the sump from above, through the gauze screen designed to take out the 'Big Lumps' should any suddenly appear! The pick-up goes more or less directly to the pump, this in itself is important because, and here is one of the most important things to remember when dealing with anything that is being pumped, THERE IS NO SUCH THING AS SUCK! The oil pump doesn't *SUCK* oil out of the sump, all it does is create a low pressure area within the pump body and the gas pressure within the crankcase will PUSH the oil up the pick-up and into the pump. Once the oil is through the pump it is then under pressure and being forced along mechanically but until it gets to the pump it is only being pushed by a fairly weedy sort of pressure. For this reason it is important to have as few impediments to flow as possible, that means a short, wide, gallery with as few bends as possible. While the pick-up on the V11's is quite nice and large the oil does have to turn through 90 degrees, twice, before it reaches the pump and the gallery in the block is no bigger than the earlier motors.

 

Once the oil is through the pump and pressurised it is sent to the filter where the bits are strained out, (we hope!) the good news is that Guzzi motors are very clean and there isn't much inside them to wear or shed bits of 'emselves and load a filter up. Once filtered the oil then passes on to the oil pressure relief valve which is contained within the oil filter/thermostat housing bolted to the bottom of the block. The purpose of the relief valve is simply to prevent the oil pressure rising too high either when the oil is thick and cold and possibly at higher RPM. The oil itself has internal friction and if the pressure is too high it will both sap power and also try to spin the bearings. While the 'Ring' type main bearing inserts Guzzi uses are not prone to this and the back clearance of the shells to rods also seems to be pretty good a spun bearing is a rare thing in a Guzzi, or any other engine, nowadays but it can happen. Maintaining the correct oil pressure also means that the filter won't become over-pressurised, pop it's gasket or explode, which tends to be messy!

 

After this the oil will pass over the thermostat which, when it gets hot enough, opens and allows the oil to pass through the cooler before going off for delivery to the bearings. From there on the oil simply has to get to the bearings and it does this through a series of galleries and pipework bolted on to the bottom of the block, essentially though it's very simple. After the thermostat the oil delivery is split. Some of it is sent to the front main bearing, some of it to the back. Both front and rear mains have a groove in the centre of the bearing face that allows some oil to circumnavigate these bearings and from there go on to the front and rear cam bearings. Also, above this groove, in the journal of the crank's front and rear main there is a hole drilled at a 45 degree angle in the crank itself that goes up to the crankpin. The crankpin itself is hollow and cross-drilled so that once the oil has filled the gallery in the pin it can flow out thrugh the big end bearings and out of the side clearance of the rods.

 

The camshaft too has a gallery running down the centre of it and some, but not all, Guzzi cams have cross drillings to allow oil that is forced up the inside of the camshaft to spray out and feed various bits like cam followers with oil by splash, Some of the more aggressive aftermarket cams even have cross drillings in the cam lobes themelves.

 

Finally oil travells up one further gallery to the top of the block above the front cam bearing where there are two drillings, one to take the oil pressure sender unit and the other one that takes the feed to the rocker gear in the cylinder heads.

 

OK, that's how it gets there. Next we'll look at why the clearances are so critical and why even a momentary loss of pressure can be catastrophic.

 

Pete

[v50man]

Thank you.

[Garsdad]

Pete:

 

Dude, you rock. I am a fairly proficient mechanic, but I still marvel at how you are able to take a fairly complex process and break it down. I "know this stuff" but enjoy your post and certainly learn a little something every time I read them.

 

Besides, I know the general theory as it applies in automotive applications; you bring it down to a Guzzi-specific level that is of great help. I can read your description and see in my mind what is going where inside the cases.

 

Thank you for your effort.

 

Ryan

[badmotogoozer]

Ditto on what that other Ryan said. I can see it all in my head. Very well written!

 

Thanks Pete!!

 

Rj

[Dan M]

Well put Pete

[pete roper]

In the next day or so I'll try to have a bit of a rant about the 'Why' of oil supply being so important, thing is I've been sick with the flu for the last couple of days and have a backlog of stuff I really need to catch up on so pleae bear with me.

 

Pete

[KiloSjon]

Pete, thanks for this story, like it a lot!

 

If anyone has pictures to support this story, please share, it will help understanding... (for example of an oil pump, or the inside of a belly pan etc)

 

Get well soon!

[pete roper]

Pete, thanks for this story, like it a lot!

 

If anyone has pictures to support this story, please share, it will help understanding... (for example of an oil pump, or the inside of a belly pan etc)

 

Get well soon!

 

Kilo, while not directly V11 relevant if you want to see an examination of a Guzzi Big Block motor coming apart and going back together I did a photo journal of a Mk IV LeMans engine rebuild I did and it's posted up, with extensive pics at. Apart from the sump the motor is pretty much the same as the V11.

 

http://www.guzzitech.dk/english/index.htm

 

Look in the left hand column and go to the 'Engine strip. (With pictures.)'

 

Jens's site is actually a treasure trove of links, you'll find all sorts of interesting an vital stuff from people like Greg Bender and Greg Field linked there. If you want some good info? It's on Jens's site!

 

Why Denmark??? Why not! It's as good as anywhere else

 

Pete

[Tom M]

Thanks for the writeup Pete.

 

According to the FAQ here the '03+ motor's pistons are "cooled by an oil jet". This seems like a good place for someone to explain where that oil comes from.

[pete roper]

Thanks for the writeup Pete.

 

According to the FAQ here the '03+ motor's pistons are "cooled by an oil jet". This seems like a good place for someone to explain where that oil comes from.

 

Interesting thing that. It's not like it's anything new, most of the engines from the mid seventies to the early nineties at least had at least one drilling in the *shoulder* of the rod at about 2 O'clock in the big end, some of 'em had two, one at 2 O'clock, one at 10 O'clock, with holes in the big end shells that matched up. That way as the crank spun oil would be spat out of the holes. While I'm sure there *must* be a reason I can't see one? All the bits like the undersides of the pistons and the bores etc. are going to get a lavish and continuous spray of oil and vapour from the torrents of oil pouring off the side clearance of the rods on the crank, oil picked up by windage from the sump by the spinning crank and spray from the cam lobes and jets from the camshaft cross-drillings. Belive me, it's a hot and VERY wet environment in there.

 

While it may be cynical of me I suspect that a fair bit of the *need* for such things as under-piston oil jets is because they look good and are easily understandable on publicity materials. I mean a nice little *engineering* drawing of a rod on a journal with a piston on the end with a little fountain of oil coming off and hitting something obviously hot, like the underside of the piston crown, makes perfect sense, until you think that at 6,000RPM it's all spinning around at 100 times a second and the cyclonic forces are IMMENSE. The crank and everything else are spinning around in what, God forbid, if you tried to breathe it would be a hot, oily, swamp gas! How is any *jet* from a tiny little hole in the rod going to achieve anything?

 

One other thought to ponder in case you think I'm just a complete freak who hasn't thought it through. Neither Carillos, or the Argo rods we use in our race bike, or any other *performance* rod I know of use *oil jets*. Why? My guess is because puting holes in the shoulders of the big ends will weaken the rods and produce a stress point from which cracks could migrate. Look at an '80's Guzzi rod with the drillings and you'll see that they are countersunk top and bottom to prevent stress raisers! Sorry, I think it's a wank.

 

Pete

[Greg Field]

A wank?

 

Prob'ly, but it did result in one positive benefit we can all enjoy: The rod bearings introduced to work with these new rods are cheap—about 1/3 the price of previous rod shells—and they will work in all the earlier Guzzi engines. So, if you do not watch your oil level and consequently roast your rod shells, it's about $60 in parts to fix versus as much as $240 in parts for previous versions of the Guzzi rod shells.

 

Unfortunately, if you roast the rod shells badly enough that the crank is badly scored, you're all the way farked because the FABs (Farking Aprilia Bastards) who set all this in motion have yet to make an oversize version of these rod shells, though they have had a part number for them since at least 2002. This means you have to replace the $900 crankshaft, rather than $60 in bearings. We have had to do this under warranty because these shells are not available. Of course, if it were not a warranty situation, we could have used the V700-type shells, which are available in oversized versions and have exactly the same oiling hole in exactly the same place, but warranty requires us to use the specified parts. Oh, well. It's their money . . .

 

If this sounds haughty, I have earned a little haughtiness at the FABs's expense.

[Guest ratchethack]

. . . . This means you have to replace the $900 crankshaft, rather than $60 in bearings. We have had to do this under warranty because these shells are not available. Of course, if it were not a warranty situation, we could have used the V700-type shells, which are available in oversized versions and have exactly the same oiling hole in exactly the same place, but warranty requires us to use the specified parts. Oh, well. It's their money . . .

 

If this sounds haughty, I have earned a little haughtiness at the FABs's expense.

Absofreakinlootely amazerhowzing!

 

I'm doin' my launches lots more gently lately, and I'm gonna keep it up until my plate gets installed. . . . .

[jrt]

Interesting.

I had always assumed (yeah, I know) that the 'oil jet' was at the small end. It just made more sense to me there.

Well, one more reason I don't design engines.

[mike wilson]

Interesting thing that. It's not like it's anything new, most of the engines from the mid seventies to the early nineties at least had at least one drilling in the *shoulder* of the rod at about 2 O'clock in the big end, some of 'em had two, one at 2 O'clock, one at 10 O'clock, with holes in the big end shells that matched up. That way as the crank spun oil would be spat out of the holes. While I'm sure there *must* be a reason I can't see one? All the bits like the undersides of the pistons and the bores etc. are going to get a lavish and continuous spray of oil and vapour from the torrents of oil pouring off the side clearance of the rods on the crank, oil picked up by windage from the sump by the spinning crank and spray from the cam lobes and jets from the camshaft cross-drillings. Belive me, it's a hot and VERY wet environment in there.

 

While it may be cynical of me I suspect that a fair bit of the *need* for such things as under-piston oil jets is because they look good and are easily understandable on publicity materials. I mean a nice little *engineering* drawing of a rod on a journal with a piston on the end with a little fountain of oil coming off and hitting something obviously hot, like the underside of the piston crown, makes perfect sense, until you think that at 6,000RPM it's all spinning around at 100 times a second and the cyclonic forces are IMMENSE. The crank and everything else are spinning around in what, God forbid, if you tried to breathe it would be a hot, oily, swamp gas! How is any *jet* from a tiny little hole in the rod going to achieve anything?

 

One other thought to ponder in case you think I'm just a complete freak who hasn't thought it through. Neither Carillos, or the Argo rods we use in our race bike, or any other *performance* rod I know of use *oil jets*. Why? My guess is because puting holes in the shoulders of the big ends will weaken the rods and produce a stress point from which cracks could migrate. Look at an '80's Guzzi rod with the drillings and you'll see that they are countersunk top and bottom to prevent stress raisers! Sorry, I think it's a wank.

 

Pete

 

In a single, twin or multi engine you are probably right, although I think Norton had a pipe attached to the jet hole that led oil directly to the little end.

 

In a V-twin, however, one cylinder is in the "shadow" of the cylinder before it in the cycle of rotation and that cylinder is susceptible to suffer from oil starvation on the face of the cylinder nearest to the cylinder before it. That face is usually the thrust face, too. Oooh, bugger, this is really hard to describe in words. I'll try to find a diagram to post. Racers and suchlike have a whole series of different priorities, the least of which is long service life as it is known on road machines.

 

m

[mike wilson]

OK, somewhere here is an image gratefully borrowed from the Morini NL club site.

 

If you look at the crank, it's turning anticlockwise and throwing oil off as it goes. The right hand cylinder collects a lot of that oil, the left hand cylinder less. In both cases, the thrust face of the cylinder, which is the face to the right, will not be getting any direct fling. The left hand cylinder less then the right.

 

It is these issues that oil jets in connecting rods are designed to address. Of course, their mere existance briings up a whole host of other issues, such as where to place them for best effect and how to design them in with as little reduction in load capacity of the rod (due to the hole) and the bearing (due to oil pressure bleed off) as well as many other factors.

 

I love engine design - everything is a compromise. Nothing is absolute.

 

8-)