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

The oil level in the oil tank falls just until the level of the oil filter base, that is the highest point after the main oil pump, as I already wrote.

The oil tank cannot empty by itself, unless there are big problems somewhere: we are talking on the 308 engine and its oil system, as shown in the pictures and drawings. Ferrari put a draining point in the oil tank (my car has it, it was from the VIN 27127, there wasn't in the 1975 model, so you have to remove the oil temperature sensor in the oil tank for earlier models). The draining plug is the part No. 43 in the drawing here below.

In this picture you can see also the two holes you have to do in the crankcase to modify your wetsump crankcase into a drysump crankcase: you have to add the scavenging pumps and all their devices, the oil tank and a new rear camcover without the refilling cap

I repeat here agian: those are just the fundamental laws of hydraulics, so there is no opinion on those, just physics.

ciao
Image Unavailable, Please Login
Image Unavailable, Please Login

 

for the newbies...
Image Unavailable, Please Login

 

Yes simple physics... As in the physics of a siphon or what is also called self priming. You seem to have missed the oil route from the pressure pump to the filter.

 

Please pay attention: in the drawing there isn't nor the oil pressure pump nor the oil filter, so I haven't missed any route. Please read post No. 71: thank you very much.

ciao

 

We have now learned a lot about the 308 drysump system, but the question about where the draining oil finds its way into the sump is still unanswered.
After looking on the main pump's components in the spare parts book I think, the main shaft of the pump is the most probable possibility. The bearing is just a simple plain bearing bush. No problem - especially not for warm oil- to leak through that fit back into the sump.


Best Regards
Martin

 

It looks to me just like most dry sumps I am talking about. The hose from the bottom of the tank goes directly to the intake side of the oil pump. The oil drains via gravity THROUGH the oil pump itself - past the clearances in the oil pump rotors, on through the oil passages/past the bearings/clearances - into the sump. There is NO way around that happening, other than, as RifleD pointed out, either having a physical valve that can be turned off to prevent it or a spring-loaded check valve. I have seen both of these devices used and have seen engines destroyed because somebody forgot to turn the valve back on when starting the engine and I have seen the check valves fail as well.

Some folks make up an ignition cut-put switch that prevents the ignition from turning on if the oil valve is turned off.

I'm not in any way, shape, or form saying that any of this is worth worrying about in routine operation of a dry sump 308. Obviously if the car is driven regularly, none of this applies. But if the car sits for months it may. RifleD has pointed out that although it occurs to some extent, it never gets to the point where it the oil level in the tank would drop to the point where none is immediately available to the oil pump on startup. So with that being the case, there is no issue at all with these engines.

FWIW, some DS engines can drain the oil tank to the level where there is NO oil available to pump in as little as a week!

 

pay attention?? talking to me like a child isn't going to make me suddenly just accept your word as final. I don't give two wits what you do or what you believe as this topic is a silly waste of time. As pointed out there are many routes for the oil to seep thru over time, one of the biggest ones is the pump itself, it's not air tight.

And yes you have missed the route to the filter as it's not in your posts, my comment about siphon feeding was a supposition based on the physics of a moving column of water or in this case oil. Refer to TAV 16 of the 1976 308 GTB parts book for the route.

 

And the moral of the story?
Being not a native speaker, one should always double check before hitting the 'Post reply-button' and being super cautious translating when it comes to bossiness

Best Regards from Germany
Martin

 

Honestly it isn't a 'translation' issue, for me it's the dogmatic approach of having to be the last word on something regardless. It isn't so much the literal words as it's the intent behind them, and yes engineers are a cagey bunch with strong opinions and narrow views, it's part of territory I suppose.

The issue of oil draining back is a real thing and given the layout and all the variabilities I would consider it normal to a point, obviously sudden drainage into the sump would warrant inspection but a slow bleed back isn't abnormal, what would be abnormal is ZERO leakage back to the sump. As to what is considered normal? not a clue as I haven't the desire nor the time to calculate that over the range of temps and pressures involved for an ideal system.

 

I take the liberty to exclude myself
Around passing age of 50 I slowly noticed, that 'taking oneself not too important' makes many things a lot easier
Especially when it comes to things, which should be fun. Like our cars.
Sadly sometimes bossiness kills an otherwise interesting discussion here.
It's all style and behaviour.
BTW, living near Maranello and being a customer of Toni Auto doesn't automatically qualify for a strong opinion


Best
Martin

 

FWIW: taking my car for the bi-annual MOT this afternoon (on a trailer, since it will rain.. ;-) )I didn't use the car since last september. Own the car for 21 years now, never paid any attention to the oil level in the dry sump tank. What the h*ck did I know.. Checked the oil level before starting/warming up the car: it was just (not) reaching the dipstick but clearly visible.

Building up the oil pressure is easy/quick: just turn it over without choke and the car won't start anyway, but oil pressure was immediately there. Then a couple of pushes on the accelerator and the engine runs. Then checking the oil level with idling car: between max and min: about a third above min.

Went for an easy warming-up drive to the gas station for gas and tyre pressure and man, what a special experience it is, driving such a very early 308. Even below 3000 rpm and under 60 km/h.. Somehow I get to like the looks even more lately. Isn't she lovely..

I'd also like to make a small comment on the "friction" in the latest posts. I know that "Maranello-bloke" only through mail/PM, he has always been polite, helpful and quick with any question I had or topic we discussed. Talking about native/foreign languages: I think I manage english rather reasonable. At least I hope so. I think I could easily "go wrong" in German however (even though it's my "neighbor language"), which would a "German SMG" scratch behind his ears too, to put it that way. I think that, since English is a world-language, native english people are earlier misunderstanding pople who's first language is not english, than the other way around.

Let's all benefit from each others knowledge and input. And enjoy our cars ! I'm only 14 years older than my car, plan to make it to at least 85 (be as less annoyed as possible gives me the best chances, I guess) hope #19055 will outlive me. In the meantime let's drive those things !!!
Image Unavailable, Please Login

 

Thanks for posting that Emile, that was my concern with the oil tank being so low and the amount of time that it would take to get oil pressure moving. By the time that I get the car back on the road, it will need an oil change anyway, however, very helpful for future use when the tank is low.

 

This has been an interesting look at the 308 dry sump design.
But it strikes me that this is rather a "bolt-on" dry sump system as it still effectively has a sump unless I am misunderstanding.

One of the advantages of a full dry-sump engine design is you dont need a sump at all. The bottom of the engine can be a casting with the main bearing caps integrated into it and a small scavenge manifold mounted on the side with the scavenge pump on one end of it.
This gives the engine great strength and the block can be lighter because it does not have to be resistant to twisting so much.

Does the dry sump 308 engine still have the same flat bottom cover as the wet sump?

 

It is but has no baffling. You are correct in that they still have a large sump. All the street cars do but they are structural. I am aware of a Daytona comp car that was converted to a small minimal oil pan much like a dry sump purpose built race engine. For years the car had nothing but trouble with its lower end until an engineer had a look and told them the large original casting provided a significant amount of the structural support to the motor. The original Ferrari oil pan was reinstalled at the most recent engine overhaul and all the problems went away. The blocks are very minimal and on their own not a very good structure (in flexion and torsion on the V12) until the heads and oil pan are all bolted together. It is not unlike taking a nice rigid coupe and cutting the top off. You just destroyed the structural integrity.

 

http://www.ferrarichat.com/forum/308-328-sponsored-yellow-compass-group/168199-308-oil-sump-baffle.html

Makes the wet sump version pretty good
Pete