R&D Findings on Crank Case Ventilation

[falcon_wizard]

Good day folks,

I thought I would provide feedback on my experience and research relative to Crank Case Ventilation over the last year or so, in case it may useful to someone else.


Last year, I had my turbo’d engine built with forged internals, to which I had added a dual Air Oil Separator (Verus Engineering) with drain back. However, I was noticing abnormal oil consumption.

After much trial and error, we concluded that the oil consumption was due to an over pressure in the crank case, causing oil to seep past the turbo seals, even in normal ginger daily driving. So effectively, what first appeared to be a Turbo seal problem was in fact a crank case ventilation problem. The best understanding we have for this crank case pressure is tied to increased blow by associated with a built engine and increased power, particularly as the torque comes about 600rpm earlier than previously on the RPM range.
Another finding was that the engine was much less responsive at low RPM or when transitioning into throttle/boost, so “laggier” before torque would come on.

Findings were that ventilation with two (large) VTA only and no PCV was not effective, as atmospheric pressure outside was not sufficient to “suck out” the CC pressure building internally. We then went for a closed dual positive ventilation setup with a PCV on the manifold side, and one feed to the air intake upstream of the turbo inlet, so there would be a positive vacuum source in all driving conditions short of WOT. Each side would flow through the Verus AOS, which has very fine filters to keep the air clean.

First try with this set-up using STI PCVs was not adequate, with pressure still building in the engine and oil consumption. Adding additional VTAs on top of that did provide enough ventilation to resolve the issue and showed no oil consumption, however having a non closed loop system created other problems, including loss of vacuum affecting AFR and oil smells getting into the cabin. This test however confirmed our understanding that Crank Case Pressure was the cause of the problem and that adequate ventilation would solve the issue. We also noticed a significantly improved throttle response, resolving the “turbo lag” that was noticed completely, with essentially instant torque availability when applying throttle. So essentially, we found a solid correlation between CC ventilation and throttle response.

Moving on from that, we removed the VTAs to go back to a closed system, replacing the STI PCV with the Wagner Adjustable PCV Valve. The valve initially designed for V8s is available with an adapter that can fit for the BRZ. After careful tuning of the valve, the findings were that the problem with the STI valve was not about flow, but rather how quick the valve transitions from Idle (lower flow) to Cruise (higher flow). Tuning the valve on Dyno allowed us to confirm the setting required for the Idle adjustment so that the AFR is adequate based on the valve flow at idle, with the standard adjustment for the transition to cruise screw. Initial test with the Wagner showed no noticeable improvement over the stock PCI valve. However, when further adjusting the Cruise transition screw on the valve, it was quickly noticed that a faster transition to cruise setting got us back to that much improved throttle response we had experienced earlier. Further driving later confirmed that the oil consumption was also resolved, which would confirm to us that the set-up now provided adequate crank case ventilation.

Our understanding of this much improved torque response is that that a Crank Case that is under Vacuum is “pulled in” and does not have to work as hard, whereas a crank case that is under pressure has to “push against” the pressure built in, and therefore is much less efficient.

These results seem to correlate to R&D Findings done by DSSport, where they noticed up to about 5% power improvements when positive CC ventilation is achieved.
https://dsportmag.com/the-tech/quick...essure-part-1/

Here are great references I found that helped us get this far and solve these issues. Note that I have no affiliation with any of these companies.

-Various Good and Bad ways to ventilate a Crank Case, by Damond Motorsports:
https://damondmotorsports.com/blogs/...ye-bye-blow-by

-Article and R&D Study on the Wagner Adjustable PCV Valve:
http://www.engineprofessional.com/ar...Q315_34-44.pdf


Bottom line, here would be an executive summary of my findings in the last 12 months:

-Keeping the Crank Case under vacuum is huge for both reliability and performance.
-Achieving vacuum with a high power build for largely Daily driving is best achieved with a positive ventilation closed system, vice VTA. (Mostly Track use would likely use a lot more VTA instead, more suitable in constant WOT conditions).
-The adjustable PCV, particularly how quick it transitions from Idle to Cruise was critical in achieving proper ventilation.
-Once properly ventilated, the engine provides almost instantaneous torque and throttle response, which is truly night and day compared to before.
-The role and important of proper CCV and particularly the PCV is largely underestimated imo.

Corollary questions to this are:
-How many people have mis-diagnosed oil consumption (or other) issues actually due to poor CC ventilation ?
-How many people have power left on the table unharvested due to poor CC ventilation, with reduced throttle response that is considered “normal turbo lag” ?

Note: the car is an year round daily driver including cold winters, so the conclusions above are in that context, not that of a race or summer track only car. Set-up is with a GT2871R turbo with built engine, 310 whp, 260wtq on 94 octane.

I will post the details of the PCCV set-up in a separate post, including how the set-up was designed to operate all year round and have fail safes against freezing or clogging.

Cheers

[Ashikabi]

Does this only apply to the "crank case vent" or both the crank vent and regular PCV valve?

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[falcon_wizard]

Originally Posted by Ashikabi

Does this only apply to the "crank case vent" or both the crank vent and regular PCV valve?

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To have a closed system, both vents need to be used,in all but boost conditions one acts as a fresh air source while the other is a vacuum source. In idle, small acceleration or cruise conditions, the pcv side is the vacuum source and suck in air in from the CC and the crank case vent side connected to the air intake for example is the fresh air source. Under Boost, the PCV valve side closes, the then flow on the crank case side reverses and becomes a vacuum source due to the turbo siphon when it is spooled.

[Ashikabi]

Originally Posted by falcon_wizard

To have a closed system, both vents need to be used,in all but boost conditions one acts as a fresh air source while the other is a vacuum source. In idle, small acceleration or cruise conditions, the pcv side is the vacuum source and suck in air in from the CC and the crank case vent side connected to the air intake for example is the fresh air source. Under Boost, the PCV valve side closes, the then flow on the crank case side reverses and becomes a vacuum source due to the turbo siphon when it is spooled.

Very informative. Thank you. I'm curious how this applies to my LS since I don't have a crank breather. Perhaps a double PCV where one is up stream of turbo and one down stream

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[falcon_wizard]

Originally Posted by Ashikabi

Very informative. Thank you. I'm curious how this applies to my LS since I don't have a crank breather. Perhaps a double PCV where one is up stream of turbo and one down stream

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The damond motorsport article provides many options depending on the situation. What I tried to replicate is similar in principle to the kind of pcv system some stock turbo performance cars have from the factory.

[Joveen]

Man i would love to see how this setup is routed. Learning so much before going turbo is rewarding. Thank you for posting these findings.

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[Joveen]

Were you still using Verus AOS as a drain back in all of this? Not sure if I missed that in the reading.

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[falcon_wizard]

Originally Posted by Joveen

Were you still using Verus AOS as a drain back in all of this? Not sure if I missed that in the reading.

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Yes, I use the Verus AOS, with drain back (and heating) options. The Verus AOS is basically a dual AOS/Catch Can in one. When the Drain back option is used, it makes it an AOS, and one side goes to the PCV side, the other to the intake side. I'll post the set-up separately.

[falcon_wizard]

Here is the Positive Crank Case ventilation Design for the set-up I came up with. It is a variation of a configuration proposed in the Damond motorsport article, using the Verus Engineering AOS, the variable PCV and a Turbo set-up.

In addition, considering I use my car all year round including below freezing temperature, I took special measures to reduce the risk of the system freezing and causing issues, including adding fail safe VTA outputs that are meant to only open up if the AOS or a Hose get frozen of clogged. They are not part of the base system and would not be needed for summer only use or for people not living is cold climate.

Key parts used: (note this post is not intended to be a step by step guide)
-1x Verus Engineering AOS with Drain back kit, coolant Heating kit and cam plate. someone can use another Dual AOS setup with drain back and heating capability (for cold climate) instead.
-1 Wagner Adjustable PCV Valve with the optional inline adapter
-For the fail safe breathers for cold climate set-up:
-Two 1psi one way check valves and 2 breathers, with 3 way connectors.

Below is the sketch of the concept of the routing. Apologize in advance for the bilingual French & English notes – this is just my own personal drawing notes – the implementation differed a bit as well but concept is the same, see below:

Of note: in the context of a Positive (read: Vacuum driven) Crank Case Ventilation System like this, the Dual AOS set-up serves to ensure that the air being circulated back to intake manifold is Clean, so it's crucial in its role. The one thing I like about the Verus AOS is that it does not just separate oil by gravity or some other physical means, but through very fine filters. (see their website)


A couple notes where the actual implementation differed a bit from the concept design:

-3 way check valves were almost impossible to source, we used T fittings with simple 1 way check valves for the 2 fail safe breathers instead. We selected 1psi check valves on the basis of the measurements done in the DSSport Article above, where their GT-R never exceeded 0.9 PSI of crank case pressure at WOT once properly ventilated. When we measured pressure in the hoses during WOT and dyno pulls, there was barely any pressure in them, as the air is flowing though the block so there is no resistance. So 1 PSI should stay closed unless clogged of maybe very heavy WOT acceleration.

-The Adjustable PCV was fitted in between the Intake manifold and the AOS, instead of between the Crank Case and the AOS. This has the added benefit of preventing the PCV from being gummed by unclean air from the crank case. We did not add an additional check valve at the intake manifold, based on the Wagner PCV having a better than average back fire protection.

-We did away with the “summer (été) configuration” – and will simply keep the “Winter” set-up for the fail safe breather. The idea is that they are directly connected to the crank case ports in case something gets clogged, but should never open otherwise, to keep the system a closed system in all but abnormal/fail safe conditions.


For those looking to understand how a closed PCV system works, I recommend the readings posted in the links above. It’s not rocket science, but it may take a couple reads to fully understand it, as it’s not completely straight forward either. Essentially, the intent is that there is always (except in boost/WOT) a flow of air circulating through the CC that prevents pressure build-up. The air circulates one way during idle/low accel/cruise, and the other way in boost/WOT. This is why this config would likely not be relevant for a serious track car that is normally either in WOT, or Idle, but not much in between.

Below are some images of the set-up currently, without the Fail Safe breathers installed. I wanted to test the base set-up to ensure it works first prior to install the breathers with 1psi checkvalves. Normally those should only open if the system is clogged somehow or possibly in max boost conditions – to be confirmed upon more testing.

If anyone is interested, I can make a future post on the tuning of the Wagner Adjustable PCV valve – the instructions from Wagner are good, but as we had the benefit of a Dyno to check this out, there are few good data points we were able to get.

Summary Pros & Cons as I see them are:

-Pros:
-Effective at keeping crank case in vacuum.
-Much improved throttle response and instant torque.
-Closed system to allow better AFR control and avoid unmetered air coming in/out via VTAs.
-Bolt on – no engine mods required and pretty clean overall.
-Verus AOS has very fine oil filters
-Adjustable PCV easy to tweak.
-Can be adjusted to specific engine & set-up.
-Low maintenance (no catch can to drain)
-Winter operation, does not need to be disconnected in winter
-Failsafe to prevent problems if clogging/freezing occurs.
-Optimized for daily driving.

-Cons:
-Relatively expensive, considering cost of Verus AOS + options & adjustable PCV.
-Requires running coolant hoses for winter set-up.
-Risk of turbo siphoning too much air in WOT ? (No issue found to date, but may not work with larger turbos ? - worst case the AOS will filter it first and the oil will drain back)
-Risk of back fire through PCV valve – option could be to add another check valve, but may restrict air flow.
-Somewhat more complex set-up than others (ex: straight catch cans) (but still fairly simple once it is understood).
-May be over complex for dedicated track car, where PCV Valve is not as useful.


In closing, I’d like to mention that this configuration was established to meet my specific needs and conditions of operations, particularly daily driving with a turbo built engine with a higher level of blow by than a stock block. It’s also still in early deployment, so I cannot confirm provide long term feedback at this stage. There are lots of ways to approach CCV, each with their pros and cons, and your set-up, needs, budget and goals may dictate other solutions (or none at all). But considering we’ve been investigating this for over a year now, if it can be helpful to someone, I’ll be glad.

Cheers

[Infinity]

So many people seem to have issues with blow by when they turbo these cars. Did you have issues before you built the motor?

[falcon_wizard]

Originally Posted by Infinity

So many people seem to have issues with blow by when they turbo these cars. Did you have issues before you built the motor?

When I did the stage 1 turbo setup prior to building the engine, I did not have any issue that I was aware of at least. Power at that time was 270whp, 210wtq. With my experience however, I would say that having a similar ventilation set-up would have still been valuable to ensure the crank case is under vacuum and performs at its best. I am certain it would have performed better even if the pressure buildup was not to a level that became problematic.

Now built engines are normally built to looser tolerances by design to provide room for thermal expension when exposed to higher temperatures/power. So some amount of blow by is normal in any engine, but are likely hogher in built ones. That’s part of the trade offs.

[Tokay444]

The tolerances aren’t any looser on a built engine. The clearances/allowances are what is opened up. There are also tolerances on those allowances.

[falcon_wizard]

Originally Posted by Tokay444

The tolerances aren’t any looser on a built engine. The clearances/allowances are what is opened up. There are also tolerances on those allowances.

Indeed, thanks for correcting, tolerance was not the proper term.

[Grady]

Originally Posted by Infinity

So many people seem to have issues with blow by when they turbo these cars. Did you have issues before you built the motor?

Most turbos kits on these cars use gravity to scavenge the oil from the turbo. getting the oil out of the turbo is just as important to getting it in. Gravity it is more finicky then a dedicated scavenge pump.