ehall

So exactly which model, etc. did you get?

bebbetufs

I would like to know your results. The AOS is a centrifugal separator/ inertial separator. If you T into the inlet pipes you may reduce the effect of the centrifugal system and end up with a lot of oil in your intake.

If you study the AOS you will see that it uses a centrifugal method of separating the oil and air. Spinning the mixture is a common way of separating liquid from gas. The fumes are let into the AOS on an angle. The point is to spin the mixture inside the AOS which throws the heavier oil outward where it clings to the walls and sinks back into the sump. This is one of the few noe aereated returns of oil to the oil pickup.

I think the better solution is to increase the amount of air going through the AOS by opening the top of it. It should increase velocity and separation.

Still, this is just theorizing so I'm interested in learning what actual results you get.

Here's a photo to illustrate

Tom M'Guinn

Yes, will report back if/when I ever get it done. The factory arrangement works well for me (no smoke at idle, etc.), so this approach will preserve it 99% of the time. That said, without the factory intake snorkel in place, I suspect the "draw" on the top AOS port is significantly lower than stock anyway, so maybe there isn't much harm left to do by opening the top port all the time. With a closed catch can in place, I suspect it just comes down to which approach throws off less oil, which may depend on how often you're driving hard and popping open the check valve. There's an engine management issue to consider as well with all that air blowing into the J-boot, and going either back into the motor unmetered or out the MAF (remember "turbo turbulence" and MAF clocking discussions?), but that's a discussion/investigation for another day...

URG8RB8

I was hoping to get this done quickly, but Precision is taking their sweet time building my new custom turbo. I am going to install everything at once so nothing I can do until I receive the turbo and the new custom pedestal.

fast951

Controlling how much flow/vacuum you have may be an issue. Too much vacuum, and it could suck oil out. You want the oil to drain to the oil pan. By adding vacuum to the port, are you going to "hurt" the oil flow to the pan?

All of this is theory. Wouldn't know for sure till someone experiments with it.

fast951

I understand what you are trying to do. But when you vent the crankcase pressure into the line, what is it going to affect the oil drain?

Is the pressure going toward the AOS? If yes, then no problem.

Is the pressure going toward the oil drain? If so, you may have a problem with oil draining out of the turbo.

Ideally you want vacuum and pressure relief acting on the crankcase only. Hard to implement and it has its own issues.

fast951

I would suspect people having crankcase pressure under boost, also have elevated pressure at idle (which causes the turbo not to drain properly and could flood). Is this the case? Can you guys confirm this?

I was thinking of a good solution to apply vacuum to the crankcase at idle, and to relief the pressure under load. All with minimal plumbing.

What do you guys think of using a 3-way valve. It will have 3 ports. One inlet and 2 outlets. The inlet is connected to one outlet at a time based on the status of the valve (Energized or not).
The Inlet (IN) is connected to the cam tower (or preferably oil pan). One Outlet (OUT1) is connected to intake manifold (vacuum source). The second outlet (OUT2) is connected to J-pipe (or catch can then J-pipe).

At idle (vacuum), IN is open to OUT1 (creating vacuum).
Under boost/load, Solenoid valve gets energized and IN gets routed to OUT2.

The solenoid activation can be triggered via TPS switches or based on actual boost...

A one way PCV between engine and input of valve is needed.
The OUT1 to intake must be protected by a one way check valve. So there is no chance to ever pressurize the crankcase.

The AOS and stock crankcase vent remain in place. The additional crankcase venting works in conjunction. Both system can share the same port at the J-pipe. Actually, the crankcase pressure vented to the J-pipe, if connected properly, can aid in creating suction at the AOS.

Now, who has the time to try it?

Tom M'Guinn

It seems like the pressure would usually be slightly higher below (where it's being generated) and work its way up to the AOS (where the top hole is always venting/reducing pressure, albeit too slowly under boost). Either way, however, when the check valve opens at .3psi, pressure will flow up from the drain toward the check valve (and down from the AOS toward the check valve) so can only help the turbo drain I would think? That's my theory anyway --if anyone sees a flaw in that logic, I'm all ears though! As you say, testing is in order, and the proof will be in the pudding...

Tom M'Guinn

Sorry, our posts crossed. Re your question, I do not have elevated crank pressure at idle. Using a diagnostic vacuum/pressure gauge shows that the pressure in the crank pulses a bit at idle, but at or under ambient (but we're talking a tiny tiny bit under).

If you use manifold vacuum on the crankcase, how do you keep it from introducing more air than wanted into the engine at idle? I'd say it's a vacuum leak, but the air would be sucking in from the j-boot after the MAF/Filer, so it would be more like a ISV that's stuck open a little. Maybe the ISV and a closed idle screw would compensate? Also seems like you'd want an air-oil separator on that vacuum line, no? I grew cold on venting pressure out the cam tower since it doesn't seem good to have air rushing UP the cam tower drain galleys. Maybe that's academic though? As for actuating the 3-way valve, would a map sensor (or hobbs switch set to atmosphere) that measures crank pressure be the best? Everything else is a proxy for what you really want... When I tested, crank pressure stayed at 0 on boost until I stayed in it long enough or unless I hit enough RPMs -- I don't think there is any one proxy that will always be right, other than an actual crank pressure reading. But if that adds unwanted complexity, then --for my motor anyway -- the best proxy is time on boost. The longer on boost, the more likely the crank has pressure.

If you make it, I'll try it out...

Tom M'Guinn

Just noticed this. In my planned approach, I'd never vent pressure into the line. Pressure could only come out of the line...

Teddy952

Plan would be to supply just enough vacuum so that the turbo won't smoke at idle. I'm guessing that one of the 1/8th inch vacuum ports on the intake manifold would be too much. Placing a restrictor in this line, similar to a boost gauge restrictor, would be a way to lower the vacuum if needed. A check valve would block the boost but I don't know how higher vacuum levels during deceleration would effect things.

marcoturbo

i wonder if a 1/32" restrictor in the line running between the crankcase or the cam tower and the vacuum ports would be small enough to avoid sucking too much oil in the intake. My Supra PCV routed from the cam tower to the intake without any restriction was sucking too much oil.

What about a drilled oil filler cap (or a custom dipstick) to add a second vent near the AOS ??

fast951

You have to limit the flow. But you are correct on all counts. If you have a closed-loop catch can you can connect to it. Again, it'll have to be tweaked..

The pressure is coming from the crankcase. Is it affecting the oil from draining back down? Would reducing/neutralizing the pressure promote better drainage?


If the crankcase vent is open to the J-pipe, why would it make a difference if there is pressure or not. It's the same as the crankcase vent now.
The 3-way valve activation is mainly to allow a direct path to the crankcase from the intake under vacuum and closing the path to the J-pipe (to eliminate suction from the J-pipe).

Basically you are constantly venting the crankcase to the J-pipe (pressure or not). Then, under vacuum you are creating suction (from the crankcase only as you blocked the J-pipe).

Again, this is all theory. We may find obstacles or additional benefits once tested.

fast951

Thank you for clarifying. I was thinking you are venting into the pipe/hose.

Have you tested the pressure in the hose? Being so close to the AOS, which is open to the J-pipe how much pressure can it hold?

fast951

You are correct, you want just enough vacuum to help the oil drain.
In the system you need a proper PCV valve (pref. from a turbo car as it also acts as a one way check valve). You also need a one way check valve close to the intake manifold (whatever it takes to eliminate any chance of pressurizing the crankcase under boost).

The flow will be first regulated by the PCV, but as you suggested a reducer/restrictor in the line may be needed.
I have seen some check valves that restrict flow as well. Now finding it may be a challenge.