Old Man

Hello!

I'm trying to find out how Porsche does their dry sump systems. If this is the wrong forum, pointing me in the right direction would be greatly appreciated.

Here are my assumptions (well some of them, anyway):

1. The 911 has a traditional dry sump system (I know some newer Porsches have a "sort of" dry sump)
2. The oil level in the oil tank is above the level of the oil pump
3. There is no problem of no oil pressure when starting after the car has sat up for some time

If my assumptions are correct, what keeps the oil from the tank from leaking through the pressure pump and into the engine after the car sits up for a length of time?

Thanks!

theiceman

Yea on all three counts
There have been reports of oil leaking down. I think Steve recommends some type of check valve but I've never had an issue.
Always a good idea to disconnect the fuel pump and crank the engine after a long layup regardless of oil system configuration

r911

The Gamrothians make a check valve. It is effective but not inexpensive

Steve Weiner-Rennsport Systems

Answers:

1) Yessir,..that is correct.

2) Liquids ALWAYS find their own level after sitting so things can equalize over time. When the engine is running, the level in the tank is always higher than the level in the engine, hence the term; "dry sump" system.

3) Not a problem. The coaxial oil pumps (pressure & scavenge) both turn when cranking and you'll will notice immediate oil pressure once running. Brand new engines are cranked without fuel & ignition to help coat internal surfaces, however that's another story altogether.

Oil pump tolerances due to wear or production tolerances can sometimes allow oil to migrate from the case to the engine (see #2) which partially floods the bottoms of the cylinders and pistons. When this happens, you can see a cloud of smoke as the engine is started until its burned off momentarily. Oil pressure is immediate so thats not an issue.

Rothsport Racing offers a one-way check valve patterned after the Factory GT-3 one to prevent oil migration during long-term storage and this works quite effectively.

Hope this helps,

Old Man

Thanks for the replies!

I didn't want to get bogged down in specifics of my situation at first because I was more interested in the solution, but I guess I have to get into it a bit.

First, I'll confess that I don't have a Porsche, but I have a dry sump. I have the problem where after three or four days, the oil drains from my oil tank into the engine. Then when I start the car, there is a period when I don't have oil pressure and I'm not happy about it. If it took a month to drain, I might consider something like disabling the ignition or disconnecting the fuel pump, but that is just more trouble than I want to go through just to start the car after it sitting up for a few days.

I'm intrigued with the check valve you've mentioned, and maybe because I'm ignorant of it, I'm skeptical. Any check valve that is strong enough to hold up six quarts of oil seems likely to be able to resist what ever suction the pressure pump would draw (I don't expect that the suction is significant since it's a fluid pump) - or it would be such a fine adjustment as to be impractical. I also asked ARE (they make dry sump systems for race cars) and they didn't have a solution to my problem. But like I say, I'm ignorant and interested in how it works. In fact I talked with a guy who had a Ferrari with a dry sump who suggested they used something similar but I wasn't sure he really knew. So if you could point me to something like that, I'd appreciate it.

I really figured Porsche had a valve that was operated by the ignition (open when the ignition was on and closed when off) or something similar. But I didn't know so that's why I'm asking you guys!

Like I said, I'd appreciate any details you can give! Thanks!

gavonder

First, I don't have an answer for you, but I think it would help to tell us what car it is (since its not a Porsche). Also, find a forum specific to your car & you'll probably get better help.
Good luck.

Old Man

Ok... Now the truth will be known!

I have a Lotus Europa with a Ford BDA engine ('70s vintage twin cam four valve motor). If anybody here remembers the old Formula Atlantic cars, my setup is essentially the same. At this point, I'm not sure how much more detail useful - I'm happy to provide more to anybody who is interested/curious.

So now you know why I was trying to keep it on a theoretical level. It's a problem most people with my car don't have.

I am writing Rothsport for information on their valves (thanks Steve) and I'd appreciate any other suggestions you all might have. I really appreciate everybody's indulgence on this since it's certainly pretty far afield from what you came to this forum to discuss!

theiceman

oil leak down is not that far
most of us see it when we first turn the key being a flat 6.

r911

nice car but lacks Elan


- you could maybe try to prime it before starting - say crank it with no ignition; or monitor pressure and see how high it gets before the engine starts running

Old Man

He he he... Now that I'm not so flexible, I really wish I had an Elan.


I'm trying to get away from that. It is a street car after all.

It's not a Porsche in SO many ways, but I thought I'd post a couple of pictures for those who might be interested.

GothingNC

Sweet Europa !

I spotted one that looks just like yours at the NCMA the other weekend.

Old Man

No, you spotted mine! I was there! Thank you very much for the compliment! Maybe we can meet up sometime.

GothingNC

Cool, here is a photo I took.
I was there with the brown Porsche Targa.

Also, I have a neighbor that is putting one together.

Are you going to the Road Scholars open house on Saturday?

Old Man

I'm flattered that you took a picture of my car! Thank you!

I'm sorry I didn't get to see all the cars there. I think I saw your Targa, but I didn't get a chance to take a look at it. I got tangled up with a guy who brought a Caterham (Lotus) Super 7 (birds of a feather...).

I wasn't aware of the Road Scholars open house. What are the particulars and I'll try to make it. It would be cool to meet up.

GothingNC

Here is the link for the open house at Road Scholars, all are invited.

http://roadscholars.com/