Porsche 6 dry sump systems explained Options

[-JR-]

So I found myself looking at lots of posts on what guys have done for their 914-6 oiling systems and came up with an observation.

It seems to me that the mounting of the tank (especially in non-stock setups) doesn't seem to have any affect on the operation of the system. Particularly the height on the car relative to the motor. I would have thought that having the oil level higher than the collection area of the motor would eventually lead to the reservoir draining into the motor.

On a Porsche 6, is the return oil also pumped out of the motor?

On a front mounted tank, like the Patrick Motor Sports one, is bleeding the air out of the system to eliminate air locks a serious pit fall? I can if air gets into the pump line, that it could prevent oil from pumping. Much like a vapor lock on a fuel pump.

Does anyone have any experience with oil supply capabilities of a front tank VS a factory or rear mounted tank?

For those with front tanks, what is the ID of your feed line pipe?

I've seen where the return line comes off from. Does anyone have shots of where the feed line connects? Particularly on a 3.6? I've heard the others are all basically the same though.

Any other theory of dry sump operation specific to Porsche 6cyl engines would be great!

[Grngoat]

I've got a DW Design tank mounted in the stock location, but here is a 3.6 picture for you to look at. It's mine from underneath while I was mocking up the oil lines.



The 3.6 is quite a bit different than earlier motors because it doesn't have an engine mounted cooler. Nice part about that is, you don't have to get the cooler modified to clear the suspension mount like the earlier motors. But you do have to get an adapter from Smart Racing (or someone else) to be able to connect to the inlet side of the pump. That's the aluminum piece at the end of the braided stainless line. The outlet is the same as anyother 6, there is a 90 degree AN fitting hanging from it in the pic.

[-JR-]

I've got a DW Design tank mounted in the stock location, but here is a 3.6 picture for you to look at. It's mine from underneath while I was mocking up the oil lines.

The 3.6 is quite a bit different than earlier motors because it doesn't have an engine mounted cooler. Nice part about that is, you don't have to get the cooler modified to clear the suspension mount like the earlier motors. But you do have to get an adapter from Smart Racing (or someone else) to be able to connect to the inlet side of the pump. That's the aluminum piece at the end of the braided stainless line. The outlet is the same as anyother 6, there is a 90 degree AN fitting hanging from it in the pic.

Ah, so the feed line and the return are both on the belly and just on opposite sides.

I already knew of the lack of a cooler on the 3.6, but what's the reason for requiring the adaptor on the feed line? What fits on there in the stock version?

[Grngoat]

I don't have a good picture of it, but it's just a flat surface with a big hole in, with a threaded bolt hole on either side. So there's anything to thread a fitting in to.

My motor didn't come with anything attached there, just a plastic plug, so I'm not sure what was there. Probably a hard line with an o-ring that bolts with those two threaded holes.

[Grngoat]

Here,

http://www.smartracingproducts.com/pdfcat/...engine_fuel.pdf

Page 32 (the eighth page in this section) shows what the adapters look like. There are some other good diagrams in here that will help you.

[-JR-]

Here,

http://www.smartracingproducts.com/pdfcat/...engine_fuel.pdf

Page 32 (the eighth page in this section) shows what the adapters look like. There are some other good diagrams in here that will help you.

THX, these guys are in my favorites now.

Anyone else run into starvation problems? If so, what were the root causes?

[ArtechnikA]

...I would have thought that having the oil level higher than the collection area of the motor would eventually lead to the reservoir draining into the motor.

It does. This sometimes exacerbates the 'startup puff of smoke' phenomonon when the oil seeps up past the rings. But since the scavenge pump is (on average) 2X the displacement of the pressure pump, the excess gets pumped back into the tank quick enough.

On a Porsche 6, is the return oil also pumped out of the motor?

What? The tank feeds the pressure pump. After the oil's been through the bearings, it falls to the bottom of the engine, where the scavenge pump sucks it (and a lot of air) up and pumps it back to the tank, through the cooler on the way.

On a front mounted tank, like the Patrick Motor Sports one, is bleeding the air out of the system to eliminate air locks a serious pit fall? I can if air gets into the pump line, that it could prevent oil from pumping. Much like a vapor lock on a fuel pump.

First, you've got a couple of gallons of oil in the tank, and the supply outlet to the pressure pump is on the bottom. So there's a significant 'head' at the tank outlet. As important, oil's vapor pressure is far lower than gasoline so it's not going to boil. Cavitation is theoretically possible but I've never heard of it occurring. It'd probably be good practice to crack the fitting at the pump supply if the system were ever totally drained but as long as there's oil in the line I wouldn't worry. It is often described as good practice to use some kind of anti-collapse spring inside the supply line since it can see significant suction pressure.

Does anyone have any experience with oil supply capabilities of a front tank VS a factory or rear mounted tank?

The fast guys do it so it must be working ;-) It's a tradeoff. You can have a LOT more oil and you can put all that weight (and there is more weight...) in a better place. At the cost of $$$, complexity, and dealing with oil lines through the cabin.

For those with front tanks, what is the ID of your feed line pipe?

I have most heard AN-20, to get you in the ball park. You need a better number from someone who's actually done it on the same service (as yet unmentioned) that you are planning.

Any other theory of dry sump operation specific to Porsche 6cyl engines would be great!

You really oughtta buy Bruce Anderson's 'Porsche 911 Performance Handbook.'

[sixnotfour]

as you know the 3.6 does not have the engine mounted cooler as pictured.

[-JR-]

"It does. This sometimes exacerbates the 'startup puff of smoke' phenomonon when the oil seeps up past the rings. But since the scavenge pump is (on average) 2X the displacement of the pressure pump, the excess gets pumped back into the tank quick enough."

So I suppose the large breather on the top of the engine allows a oil flooded engine to rapidly remove crank case oil pressues? If the motor was flooded, I would have thought it might not crank or it could blow the case appart if it fired.

"First, you've got a couple of gallons of oil in the tank, and the supply outlet to the pressure pump is on the bottom. So there's a significant 'head' at the tank outlet. As important, oil's vapor pressure is far lower than gasoline so it's not going to boil. Cavitation is theoretically possible but I've never heard of it occurring. It'd probably be good practice to crack the fitting at the pump supply if the system were ever totally drained but as long as there's oil in the line I wouldn't worry. It is often described as good practice to use some kind of anti-collapse spring inside the supply line since it can see significant suction pressure."

Yeah, it was more under oil change circumstances I was thinking of a air lock. But if the pressure pump can supply suction even if it's dry, then there's no issue.

"You really oughtta buy Bruce Anderson's 'Porsche 911 Performance Handbook.'
"

I'll certainly be looking into it.

[-JR-]

Another bit of insite for a 3.6

[ArtechnikA]

So I suppose the large breather on the top of the engine allows a oil flooded engine to rapidly remove crank case oil pressues? If the motor was flooded, I would have thought it might not crank or it could blow the case appart if it fired.

The cynic says if you have -that- much oil flowing back through the pressure pump gears (a positive-displacement pump) it's worn out and needs to be replaced anyway.

The motor's not going to flood.

If it were going to be out of service a hugely long time (months...) you'd probably be draining a substantial amount of the oil out anyway...

If one were really concerned (possible but I have never heard of anyone doing it) you could crank the engine a few times with the ignition off to get a head start on pumping out some of the excess and building oil pressure.

But it's at this point that my theoretical knowledge tapers off and we can hope that you get some feedback from guys with front-mounted tanks.