I need another volunteer for tribute... I mean beta tester :P

[Sapphireho]

Originally Posted by Q8D

Reduce oil vapors in intake. Causes issues in the long run.

And excessive oil vapors is a problem with these motors? And exactly what "issues" has it been causing in "the long run"?

[KillerBMotorsport]

Originally Posted by Yoshoobaroo

Any idea on the pressure drop and the effect on the crankcase vacuum?

Originally Posted by dragoontwo

I can't imagine that there's any noticeable change in vacuum. Have there been AOS kits that show this?

Next to nothing. The only time there's a measurable change is when there is a significant volume added (large canister), or worse, using an AOS that relies on media for 'filter' suspended droplets. The media units can be very restrictive as they get caked. They can be clean chemically, but they never last as long as when new. So if you are using a media type, I'd replace the media instead of trying to clean it.

VTA makes a significant change (increase) in crankcase pressure. I do not recommend VTA setups ever, even with forced induction or race setups.

[KillerBMotorsport]

Originally Posted by Sapphireho

And excessive oil vapors is a problem with these motors? And exactly what "issues" has it been causing in "the long run"?

Suspended oil vapors can reduce potential octane. Over the long term, with DIT engines, it can have a significant effect on valve buildup.

[Q8D]

Originally Posted by Sapphireho

And excessive oil vapors is a problem with these motors? And exactly what "issues" has it been causing in "the long run"?

I don't know about FA24s specifically, but they are a problem on every fuel injected car I've owned and I doubt FA24s are any different. Vapors cause hot start up and idle issues due to oil residue around the throttle body valve over the short run (my Infiniti G35 started having these issues at around 20k miles, very common on VQs). Intake manifolds, heads and valves cake up with thick oil residue over the long run and lead to poor performance.

[KillerBMotorsport]

Originally Posted by Sapphireho

And excessive oil vapors is a problem with these motors? And exactly what "issues" has it been causing in "the long run"?

Originally Posted by Q8D

I don't know about FA24s specifically, but they are a problem on every fuel injected car I've owned and I doubt FA24s are any different. Vapors cause hot start up and idle issues due to oil residue around the throttle body valve over the short run (my Infiniti G35 started having these issues at around 20k miles, very common on VQs). Intake manifolds, heads and valves cake up with thick oil residue over the long run and lead to poor performance.

^ That's a good point, and especially dangerous with turbo applications where there's an intercooler providing ideal conditions for condensing anything suspended in the intake air. Liquid oil pooling over time is certainly not good, but with N/A applications, it's not something I'd consider dangerous. More along the lines of something else that can cause accelerated breakdown of seals. If you look at older DIT engines that have racked up considerable miles (AMG and Audi come to mind as they've been DIT for some time) they have notorious failures of breather lines, PCV components, and intake manifold gaskets. The common long term fix is installing an AOS to prevent exposing those components to liquid oil/blow-by contaminants.

Once you go higher up the food chain: Higher end AMGs, Porsches and exotics, you find those cars come from the factory with an AOS as part of the PCV system.

[Yoshoobaroo]

BMW has had these centrifugal AOSs built into their valve covers for a long time, even in the cheaper cars like the 328i and 128i. I’m kind of surprised Subaru doesn’t.

[KillerBMotorsport]

Originally Posted by Yoshoobaroo

BMW has had these centrifugal AOSs built into their valve covers for a long time, even in the cheaper cars like the 328i and 128i. I’m kind of surprised Subaru doesn’t.

Me as well. The EJ engines have a LOT of blow-by, but that engine design does go back to the 90s :/

I also noticed the Civic Type-R has one built into the valve cover. The OEM ones are definitely better than nothing, but on the few cars we've installed on that came from the factory with one, our unit still catches stuff. Like anything OEM, it's good enough for the masses.

[Yoshoobaroo]

Originally Posted by KillerBMotorsport

Me as well. The EJ engines have a LOT of blow-by, but that engine design does go back to the 90s :/

I also noticed the Civic Type-R has one built into the valve cover. The OEM ones are definitely better than nothing, but on the few cars we've installed on that came from the factory with one, our unit still catches stuff. Like anything OEM, it's good enough for the masses.

Yep, same deal with the BMW one. They probably have very conservative internal requirements for crankcase vacuum so they can’t afford a bigger AOS. They have statistics against them. The 0.01% worst case WILL happen to them because of their volume so it it understandable. They also need to account for a significant number of cars that will have poor maintenance even under warranty. The aftermarket doesn’t really have those concerns.

[KillerBMotorsport]

Originally Posted by Yoshoobaroo

They probably have very conservative internal requirements for crankcase vacuum so they can’t afford a bigger AOS.

You have to keep in mind here that if the AOS design uses internal volume as a means for separation (larger volume forces cooling and condensing of liquids in suspension) then it can absolutely affect PCV system pressure (low or high). With ours, it uses a vortex, and our specific geometry allows it to function very well at this smaller size. The advantage of using a vortex is that it's efficient over a far wider range of flow/pressure vs a standard swirl pot. Of course the downside of vortex over a swirl pot is that the vortex is a lot more complex from a design standpoint and more expensive to manufacture. The last several gens of 911s use two swirl vortex AOS units from the factory. One of the units is actually uses 4 really small vortexes within it.

Here's a plot showing some testing we did on an STi that has one of our MUCH larger units (again STi EJ engines have way bad blow-by by comparison). The engine is built and making ~500whp. The plots are: Solid Three AOS, Dashed Single AOS (normal configuration), and Wide Dashed is Vented to Atmosphere...