Need Help with Type4 Dry Sump system

[Griznant]

Hello!

For starters, the car is a 912, but the engine is a built- Type4, so I figured I'd get better answers here than on the 912 forum.

I have a fairly raucous 2056 in my 912 that I put together a number of years ago. After a number of upgrades to the car in the handling department I found I would lose pressure on long sweeping turns. I responded by attempting to convert to a dry sump system. In doing that I used the following parts:

CB performance 2-stage oil pump that fits in stock location.
Slight mods to fan housing and a custom engine mount bar.
911 oil tank with filter
Oil thermostat
Temp sensor to switch fan on via relay
Stock oil cooler
Secondary Setrab oil cooler with fan mounted in left rear fender
-8 lines to fit the aftermarket pump fittings, to and from tank.

Oil picks up from the stock internal pickup, through the pump and sends it out to the thermostat/cooler/lines/tank. The feed line picks up from the tank, and sends it through the stock oil galleys/stock cooler/ bypassing the old filter housing (which has been hogged out to allow unrestricted flow behind the block-off plate).

What I discovered after a quick run is that even though my pressure was holding good at around 45psi+ when running, I just didn't like the system and thought I needed larger oil feed lines from the tank. After letting the engine sit for a few days I went out to start it and found that the crankcase had siphoned oil from the tank in the right fender and basically filled up to the pistons and you couldn't turn the engine over. So, I pulled the engine out, and apart, drained all the cylinders, resealed the engine, stuck it back in, and sat down to think about what I needed to do to fix the siphoning problem since I don't see a logical way around it. I put the engine back in.

Six years passed.

The car has sat since.

The engine is a beast, and makes GREAT power. The car has been plated and insured the entire time. There is NOTHING else keeping me off the road beyond sorting this mess out!

So, I made another mounting bar that hard mounts to the engine, and locates off 911 isolators at the body. This afforded me some space to mod the pump. I hogged out the inlet to the pump and welded in a bespoke aluminum tube with a 3/4NPT fitting on it to feed oil to the pump from the tank. I used an adapter to go from the 3/4NPT to -12 AN line, and had planned on putting a manual valve in place so I could shut the oil off when the engine is sitting so I wouldn't siphon oil from the tank. To keep from forgetting I was going to put a micro-switch on the valve to kill the ignition if the valve were not opened. I would rather have a solenoid valve to do this but don't know what one to use.

I still have the -8 lines out through the secondary cooler/thermostat/to tank. I don't think this is big enough, but am not sure, or what would actually be the right size to try and fit.

I need help from someone who knows a LOT more about dry sumps than me. I would like to use what I have, or at least modify it to work but if it won't then I'm open to suggestions. Fabrication is NOT a problem for me so any advice is GREATLY appreciated!

I MISS DRIVING MY PORSCHE!!!!

Thanks,

Grant

[John Rogers]

Here is how the setup was when my 914 had the 2.8L type 4 engine and I'll start with the engine sump.

- Used an Auto-Craft sump plate with studs to the case to hold it on, suction fitting was a 90 degree -16 welded to the plate.

- Auto-Craft 3 stage pump, one suction was on the sump, one was with a connection at the tank, both were -16 size, outlet went into engine oil passages.

- Outlet from engine went to a front mounted cooler, no thermostat, -12 size Earls hoses.

- Front cooler was an Earls that was as big as we could cram in the front trunk area with aluminum ducting out the bottom.

- Return line was Earls, -12 size to a dual filter unit we bought from Summit Racing.

- Outlet from filter went to the oil tank, was -12 size.

- Oil tank held 12 qts of oil but had to keep lever below top baffle so it probably around 8 or 9 qts actually.

- Puke tank was aluminum that vented the engine case and also the oil tank. Note that at high RPM the crankcase is actually under a vacuum which helps HP and offsets the power required to run the oil pump.

- Cooling was converted to a 911 alternator and fan with a fiberglass cover and duct work, used stock engine baffles and such. This was required because of the large size of the oil pump.

It worked great, was expensive but never let an engine fail!

[zig-n-zag]

The oil tank is mounted too high in relation to the outlet. But mounting the tank below the
outlet still won't stop siphoning like when parked on an incline.

Accusump has electric solenoid valves and key-operated. Another option might be
looking into one-way check valves.

[mcfoo]

I raced a 914-4 for many years with a dry sump system.

I literally had to install a ball valve shut off between the dry sump tank and the pump to prevent the oil from siphoning back through the pump and into the motor.

Of course the downside to that is forgetting to open up the valve each time you start the engine...luckily I never did forget as it became part of the pre start routine before every race.

Perhaps a key activated electric valve of some type might be the answer to a street car application something like they use in Accusumps.

Tom B.

[John Rogers]

The height of the tank and/or some sort of valve is not necessary. The easiest thing to do is to crank the engine and within a second or two with a good dry sump pump the oil will be sucked out of the case to a level that is low enough for starting. If you look at the oil tank in a 911 or 930 as we had, the tank is higher than the engine and the oil drains slowly through the pump to the case but since the scavenge side of the pump has higher capacity that pressure, the oil comes out quickly.

This is an item that many people worry about when not needed. You can call Auto-Craft and talk with one of their engineers as they have tons of experience with "flat" engines and can easily help you out.

[turboteener]

Worst case look at the electric shutoff valve that goes with an Accusump. You would wire it to be open when there is power to the switch and closed when power is removed. Add a huge warning light and maybe connect a hobbs switch to the horn so it warns you when the valve is closed and there is no oil pressure.

[Griznant]

Thanks for the advice!

I had seen that solenoid Accusump valve, and considered that as an option for the siphoning problem, and also have a brass ball valve but was paranoid I'd forget to open it which is why I was rigging up a micro-switch that would trigger when the valve was open to allow the ignition relay to energize. It was getting too Rube Goldberg-ish for my comfort level though.

I guess my main concern now is whether or not I have the lines sized correctly. The -12 line going from the tank into the pump is just to make sure I ALWAYS have a steady supply of oil that is at the pump feed since it low pressure. Since the scavenge pump-out side is -8 all the way up through the secondary cooler/tank and it is under pressure, I assume it will be OK. That's what the pump had on it to start with, I just didn't like the supply to the pump only being a -8 which is why I upped it to -12 via the mods.

Thanks again!

Grant

[John Rogers]

When it comes to the size of the lines, bigger is better. As I noted, we used -16 for the suction on both the 4 and converted 6 later on. For other lines we used -12 as the flow velocity will be slightly lower which allows more time for the oil to be in the cooler slightly longer and cool better. There are times, especially at idle when the sump scavenge pump will actually be sucking some air and trying to put the case under a vacuum at high RPMs.

[Racer Chris]

Originally Posted by Griznant

I guess my main concern now is whether or not I have the lines sized correctly. The -12 line going from the tank into the pump is just to make sure I ALWAYS have a steady supply of oil that is at the pump feed since it low pressure. Since the scavenge pump-out side is -8 all the way up through the secondary cooler/tank and it is under pressure, I assume it will be OK. That's what the pump had on it to start with, I just didn't like the supply to the pump only being a -8 which is why I upped it to -12 via the mods.

Thanks again!

Grant

-8 hose has too much drag for an oil hose over 2 feet long.
I've had excellent results using -12 for my entire (914-4) system, with a front mounted cooler and a mid-mounted tank.
When I used an oil pump with -8 fittings on it, I made short hoses and adapted up to dash 12 after only about 6 inches.

[mcfoo]

Originally Posted by john rogers

The height of the tank and/or some sort of valve is not necessary. The easiest thing to do is to crank the engine and within a second or two with a good dry sump pump the oil will be sucked out of the case to a level that is low enough for starting. If you look at the oil tank in a 911 or 930 as we had, the tank is higher than the engine and the oil drains slowly through the pump to the case but since the scavenge side of the pump has higher capacity that pressure, the oil comes out quickly.

This is an item that many people worry about when not needed. You can call Auto-Craft and talk with one of their engineers as they have tons of experience with "flat" engines and can easily help you out.

John,
Your advice is sound except that if the car is let to stand for any period of time and you have a 12qt dry sump system , all that oil can eventually find its way back to the engine sump ,overwhelm the sump and start leaking from every available orifice.
I once forgot to shut off my valve after putting my car in the trailer and whenn i went to remove the car you'd thought I had struck the Exxon Valdeze.
Oil everywhere on the floor, how much I don't know but it was a mess.
I'm not saying this will happen to everyone, but it happened to me.
Tom B.

[Racer Chris]

My oil system never bleeds enough back to the engine to overwhelm the sump capacity.
I don't have a check valve of any kind.
The (flat) bottom of the tank is even with the bottom of the sump and when the oil reaches equilibrium its still below the pistons.

911s are known for all the oil draining back to the engine over time. Thats why they often smoke badly on startup.

[John Rogers]

Hummmm, if the oil level goes up and then leaks out, maybe your engine is telling you something.....it needs to be run a lot more often and maybe the places where it leaked should be sealed? As I said, the oil tank and oil level in the 930 we used to own was above the sump area and there was never an issue. The same setup was what we used on the 914-4 and 914-6 race car engines and never had a problem. As Chris said, it is part of the 911 heritage.

[Racer Chris]

I just went back and reread the original post.
My advice is to maintain the system with less total oil volume, so that when the oil drains into the crankcase it can't hydro-lock a piston.
Oil tank level in a 911 is only measured correctly when the oil is at full temperature, ie. after the engine has run long enough to be certain that the pump has moved all the excess oil from the crankcase into the tank.
Also increase the scavenge oil line diameter to dash 12 as much as possible.
If you have enough oil to fill the crankcase to just below the cylinders (after total drainback), it is enough oil to prevent loss of pressure under any circumstances during operation.

Any kind of solenoid operated check valve seems dangerous to me.
In fact anything that might restrict or prevent free flow seems dangerous to me.

[mcfoo]

Originally Posted by john rogers

Hummmm, if the oil level goes up and then leaks out, maybe your engine is telling you something.....it needs to be run a lot more often and maybe the places where it leaked should be sealed? As I said, the oil tank and oil level in the 930 we used to own was above the sump area and there was never an issue. The same setup was what we used on the 914-4 and 914-6 race car engines and never had a problem. As Chris said, it is part of the 911 heritage.

Yep, the engine was telling me I forgot to close the valve.
Hey, just sharing an incident I had.
Had nothing to do with the quality of the motor, the frequency of use ,or my 15 years of running my 914 at the highest levels of SCCA production car competition.
The dry sump pumps I used from a local vendor here in Jersey were just not capable of holding back the tide so I addressed the problem the best way I knew how.
I have since moved on to six's ,so while I have acquired other issues thankfully this one is in my rear view mirror.
Tom B.

[Rich Hilgersom]

Grant,
The CB system is not a true dry sump. Its more of a wet/dry system.
Get your oil lines higher than the tank to prevent much of a pull back into the case.
-8s are fine, you can adapt from the 16mm in/outlets to -10s or even -12s but then you block the mounting bolts.

Search online for some discussions of opening up the 16mm in/outs and other mods.

-Rich Hilgersom

[Griznant]

Thanks everyone! Lots of good advice, and I'm going to see what I can make work, starting with using less overall oil. I probably had too much in the system and it had no choice but to fill up the cylinders when it sat for awhile. I'm also going to go with upping the size of the scavenge lines. If nothing else I can get it running again and see how it goes.