Dry Sump question... Oil flow from catch tank to sump.

Interesting that Ferrari 308 wet sump engine has the oil pump above the oil level line. This is not necessary; for example my 1750 GTV Alfa engine has the oil pump immersed in oil, as does I think (?) the Ferrari Columbo v12.

Regarding the dry sump comment here. This could only happen if the dry sump tank was completely empty, because as you say it is designed so that the dry sump tank drains by gravity into the pressure oil pump.

Now if the dry sump tank is 100% empty, then you will not get any oil pressure until the scavenge pumps have sucked oil out of the engine* and back into the dry sump tank and then finally the pressure oil pump sends the oil to the crankshaft, etc. I would imagine this would take long enough that damage to the crankshaft bearings would occur.

So if 4right is really correct, ie. his dry sump tank is really 100% empty (including the hose from the tank to the pressure oil pump) I'd be very worried. If it still had like a litre of oil then I would think that would be enough for the crankshaft bearings to survive until oil is returned to the dry sump tank ... note I said "I would think".
Pete
* I wonder, while the scavenge pumps are trying to restore the correct oil level in the sump by pumping the oil to the dry sump tank, if the crankshaft would hit the oil?

 

Just a point of reference, the sump 'tank' in the gearbox housing will hold 2.7gal or ~10L it takes 3.5gals to get to the crank and windage tray. The entire oiling system only needs 9L. It takes about 10.5L to get the oil to spill out of the dip stick tube port.

 

We are talking of theory: the reality is that the 308 drysump starts with oil in the pump, as I don't hear the rattle that I always hear with the wetsump (all the cars 3x8 I have or had) each cold start. If the oil tank looks empty, it doesn't mean the connecting pipe to the oil pump is empty, while you are 100% sure that the oil pump duct in the wetsump is empty at every cold start .
If you leave one year your drysump without starting, you can add half a liter in the tank before starting it, if you want to be 101% sure there is oli in the pump(i would check in advance if there is oil, after one year...): you cannot do it with the wetsump.

Nobody here looks to beworried about its wetsump always starts without oil but here everyone looks worried about that it can happen in the drysump after some months or so: why?

ciao

 

The drysump has two more liters capacity, more or less: in the tank, of course, as the sump is the same

ciao

 

this is the graph posted by Martin (thank you very much, Martin: very interesting).

Is shows that 1320 minutes after stopping the engine (means 22 hours) the oil level in the tank just goes down of 0,54 liters (half a quart, more or less). Now, I guess that in the oil tank there are 7-8 liters (10 liters total, one still in the engine, one in the pipes, one still in the sump, more or less). The decreasing curve clearly shows an asynthotic behavior: means the decreasing becomes slower and slower. We are talking of the level in mm over the MINIMUM of the oil checking stick (i don't know the correct english name, sorry), not to the bottom of the oil tank.

So, what are we talking about?

ciao
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I would add this: the 308 engine clearly shows it was designed to have the drysump: evidences are that all the crankcases (GT4 too) have the marks to drill the oil passages (for the scavengin pumps and so on) and that stupid too high position of the oil pump (wrong, for a wetsump). Probably they wanted to save some money in the GT4 ( a "road" car) taking out the drysump, or maybe they just wanted some more room for the trunk compartment, who knows. Then foreign EPA rules forced to do the same on the other later models.

ciao

 

To me 4right's oil system has a problem* as his oil tank should not ever end up 100% empty (unless doing an oil change), while Martin's obviously does not.
Pete
* note it might not be the oil system that has a problem, but something in his engine that is over worn that is allowing oil to leak faster than it should into the sump. A solution could be to use the car often so that the tank has little time to empty

 

Just to be accurate. This graph I made, shows the oil level decrease over 22 hrs. After months -i.e. over the winter months- I actually watch the oil level going down around 1,5 - 2 ltrs.

4right;
How long did your car sit till the tank was empty?

Best Regards
Martin

 

Thank you very much, Martin. The graph clearly shows that it would have taken months before empting (if it will happen, I don't think it can happen on a sound car).

In my opinion the piston of the relief valve (part 15 in the second picture I posted) in 4right car has too much play or the spring (part. 14) needs replacement.


Not many knows that you can convert a wetsump 308 to a drysump without changing the crankcase: all the crankcases are the same, they are just machined in a different way and you just have to open the holes for the oil passages, holes alrealdy predisposed/prepared from the factory since the beginning on every 3x8 car.

I think that I don't know is this: why the USA 308 GTB hasn't the dry sump? which was the rule that prohibited the drysump? Is there anyone here that knows why?

Thank you very much

ciao

Edit I had many drysump bikes and we all knew that you had to check the oil level within 30 seconds after stopping the engine (it was written in all owner's manuals) as the level goes a bit down just after stopping the engine (the oil runs fast, when it is hot, while runs very slowly when it's cold...)

 

I would like to add this: how anyone here can think that a car can start without oil and have to wait that a couple of scavenging pumps fill the oil tank, then the oil goes down to one meter long pipe to the oil pump and just then the oil pump starts to pump oil to the crankshaft bearings? Do you think Ferrari did such a s h it of oil system? how many startup do you think an engine can last, in such conditions? three? four? Come on, we are talking about nothing since three days. The world is full of drysump bikes and cars: NONE of them has the oil tank empty when you start it. If the oil tank drains completely (in less than one year...) means you have some big problems, a leak to the ground or to the sump, somewhere: no doubt about it.

We are talking about things I do as my work, so I know what I'm saying, but you don't need to be an engineer or an expert to think that it can happen just if there is a (big) failure somewhere in your engine

ciao

So: why did I have to waste so much time to explain an obvious thing? I will send an invoice somewhere...

 

If this is the case, it should also become evident with abnormal low oil pressure when warm/hot.
I once had a daily driver which had a pressure relief valve stuck open. It simply was rust and dirt on the piston.
Was easy to repair, but in the meantime it resulted in a worn camshaft and damaged crankshaft and connecting rod bearings. I want to say, that engine was toast.

Best Regards
Martin

 

Agree, but I haven't any other idea about the reasons. Maybe the play is not so big so the drain and the loss of pressure is not so big that can be seen immediately, who knows. It must be some too big play somewhere, but I just saw those two possibilities and the oil pump shaft seat (that I don't know how is done in that engine so I could be wrong). I don't put my hands on the car so I'm just talking about what I'm seeing on the drawings: a good engineer can do that without touching by hands nor having seen the reality, but if I could inspect the engine disassembled, it would help a lot...

Ciao

 

I have personal experience with dry sump systems in both cars and bikes that can totally drain the tank - so that there is NO oil available to be pumped - in less than a couple of weeks.

I have personal experience with two identical engines, one of which took weeks for the tank to drain and one that took less than one week to do the same thing. It is all about the clearances in the oil pump. Both engines had satisfactory oil pressure while operating so there was nothing "wrong" spec-wise with the oil pump.

I do not now, and never have been enamored with dry sumps EXCEPT for their use in competition vehicles designed to take advantage of the fact that the engine can be mounted lower in the bode/frame. There is no other advantage TODAY. It's the same as Ducati's Desmodromic valve system. WHEN it was developed, it served a useful purpose due to the limitation of valve springs; TODAY it does not but it is used because it's a "Ducati thing." Dry Sumps have a "Race Car" cachet and so they are used in non race cars for marketing purposes...people buy "Racing Oil" for street cars for the same reason...

 

I'd wager a big reason was that they didn't have room for the oil tank -- on the US 308, the air injection system and exhaust system take up much more room in the engine compartment and need some space around them for cooling, too (so they couldn't just pack it all in super tight).

 

The car had been in storage for over a year when I noticed that the tank was empty.

 

Then it shouldn't be anything to worry about. Just pour half a liter oil in the oil tank some minutes before restarting the car. And then check what's happen when you stop the car again

ciao

 

Thank you very much: I didn't know that

ciao

 

Yes and no, Mike. If the main pump is at the sump level, who cares if the oil tank drains.

But if the oil pump is higher than the sump, like in the 308, you cannot have your oil tank (and the connecting pipe...) empty, or the oil pump won't work for too many seconds at an engine restart.

Please read carefully my post No. 21, 40 and 44. And PSK post No. 41: they explain why the drysump solution is better in any case. Maybe not necessary, but it's better. Much more expensive too.

In racing, where you want continuative 100% performances from your engine, it comes usually as standard: means it's better. The westsump system works too, it's enough, ok: but it's not the best for a supersport car.

ciao

 

Having spent a fair amount of time recently designing a scavenge system for the 4L 328 build and adapting it over to a drysump setup I can say that it would take alot more then a few simple changes to convert to drysump as found on the Euro's. The biggest issue is the front timing cover, it's completely different.

As to the oil drain back issue, I wonder if the filter being used is causing this. The oil route is such that the tank feeds to the pressure pump, the pump feeds to the cooler and that feeds back to the block via the filter. The tank sits higher then the pump as does the cooler, so in theory the oil should have nowhere to drain too. Oil being a liquid though can syphon feed and is normally stopped by the filters check valve, filters without that would drain back down. Just my thoughts..

 

In the Ferrari's they don't go totally empty. They go off the stick and lower than the baffle so you really cant see it. Probably still has a quart or two in the bottom. We see it all the time at services. Drain the tank and a quart or 2 comes out and drain the sump and a couple of gallons come out.

We ran a Rodak in an LSR car. The only place for the tank was on top of the trans. We put a ball valve in line so we could turn it off after a run to prevent sumping all of the oil. The ball valve got a big red flag attached when it was closed though.

Old Maserati race cars needed to have their rear axles put on jack stands when shut down. They had no rear main seal and when they sumped all the oil ended up on the ground.

It is all SOP for anyone familiar with dry sumps and how they work. Not a mystery.


BTW. Ducati desmos have valve springs, quite stiff ones. The desmo stuff is mostly for their PR department or if the dummy on the throttle zings the motor.

 

Pictured: Ferrari engine model F106A021, N.1690, installed on 308 GTB drysump VIN 34465. Picture Copyright: me, Alberto Mantovani.

How can the oil go down from the oil filter to the sump, if the oil filter height is almost as high as the intake camshafts and the oil tank, means the highest points over the main oil pump level?

I just wrote that the crankcase is the same, not that you can have a drysump just drilling the crankcase. You have also to change the rear cam cover and install the scavenging pumps, plus the oil tank.

The oil route is this: scavenging pump in the sump (spiltted in two) - oil radiator - oil tank - gravity- main oil pump - oil filter - engine - gravity - sump

To change the oil you have to drain the oil tank manually (remove the temperature sensor in the oil tank or open the draining screw in the oil tank in the later models)

ciao
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Correct: also Toni Auto mechanics told me the same. They always have to drain the oil tank manually: I was there this afternoon so I asked them, as I was curious to know.

ciao

Edit:
Thank you, Brian, for sharing this: you know things in person, as you work on many engines with your hands and you see what real things are

 

Siphon feed, at shut off the oil flow is still moving and without an air gap the oil could in theory continue to slowly siphon feed into the sump if the filters bypass valve is open or possibly damaged. Just a thought as the route itself does not lend to feeding back via gravity alone. The scavenge section would have also drawn down the air pressure in the sump, also aiding in the siphon effect.

 

I had a coworker who used to take the valve covers off of TR engines to adjust the valves before he drained the oil. It was always an overnight job. In the morning when we came in there would be about 2 gallons of oil on the floor because overnight it sumped and the oil level went high enough to run out of the oil drain back tubes from the heads to the sump. And the heads are pretty high on those.