[Kingtal0n]

Originally Posted by PoorMans180SX

So your solution for a high performance engine is? Enlarged orifices? Careful testing and analysis?

I can guarantee you that the system I'm building will keep oil out of the intake and intake manifold. It happens to include two catch cans. Are you just saying that the catch cans are extraneous? That each and every engine has an ideal setup that doesn't include catch cans regardless of power level?

To be honest, I don't care about "corrosion" in my intake system, I'd rather have zero oil in it than risk it reaching the combustion chamber.

For oiling the engine's parts, It is primarily the turbo you should worry about. Most of the other parts receive their own share of oil as necessary. Actually all turbochargers mix some of their oil supply with incoming air, there is nothing you can do about that. For example the engineers at Borg Warner warned me not to inject water pre-turbo because it will enter the turbocharger's oil supply and get into the drain to the oil pan.


Lets go over some high performance aspects commonly overlooked by novices and 'enthusiasts' (most of us are just enthusiasts without 'real jobs' in this field) Unfortunately, owning a shop or working on race cars as a mechanic/tuner is not a 'real job' in the field of the engineering car parts for longevity and performance. Manufacturers which produce those parts hire engineers (e.g. Borg Warner staff who design turbochargers) may posses fundamental engineering book-work knowledge which makes certain aspects 'common sense' which to many enthusiasts remains a mystery, we will now discuss some of those

1. exposed metal of any kind should NEVER be in contact with atmospheric contents as it will oxidize. Even aluminum and stainless materials will oxidize. Metal of all kinds is constant jeopardy, and the tighter the space, the thinner the materials, the more risk (i.e. compressor blades and housing distance). This changes the surface of the compressor wheel, and housing over time, atmosphere causes pits, grooves, essentially eating away at the surface, 'rusting' it. Therefore, all turbo-compressor wheels need some oiling, their blades, shaft, housing, either spray it in there manually or let the crankcase supply a fine coating. Never let it dry out as the atmosphere will attack it, change it.


2. air filtration is the other key to success. A high quality paper air filter is absolutely requirement for any 'daily driver' (longevity) setup. Atmosphere contains all manner of biological entities; fungus & pollen are found everywhere in the world's air, for example, they are live cellular structures which contain the materials of life: Chlorine, potassium, molybdenum, iron, sulfur, nickel, sodium, chromium, etc... as well as myriad complex structures containing long chain carbons and carbohydrate/proteins as with any living cell. It is typical in chemistry to apply HEAT and PRESSURE to force chemical reactions between such molecules to produce by-products. An internal combustion engine provides both: HEAT and PRESSURE to these substances thus allowing a wide range of conglomerates to form within the combustion chamber, a soup of random, sticky substances which are entirely unhealthy to an engine of any kind.
Also remember there are the dust, dirt, sand, glass-like inhalants which scar and scratch the engines parts as they collide with high speed, pitting and eroding the metal of an engine's internal parts.
None of that should ever get inside an engine. Air filtration is an extremely important, massively overlooked aspect of high performance engines and longevity solution. Filtration is practically the only thing saving an engine from erosion internally and to keep parts from collecting reacted byproducts which hinder function and performance.

Its not that hard, really. Keep your exposed metal parts oiled (common sense) and keep the air super-filtered (common sense). This goes for machines of all kinds. The more expensive, the longer you want it to last, the better oiled and cleaned it had better be. Atmosphere is NOT your friend. Even for breathing, the human body and it's lung tissue will last longer if the air is cleaner. Its obvious when you say it but nobody ever thinks about it when they go outside without a mask because our society isn't advanced enough and the air isn't filthy enough yet to make it mandatory to purify the air we breath. But this is changing... you may have noticed... air quality and recognition of what is in the air is becoming more prevalent. And it will not stop, the future holds many changes for humans living, breathing, you will see more filtration and more high quality masks over time.

So your solution for a high performance engine is? Enlarged orifices? Careful testing and analysis?

Most of the solution is above, keep your exposed metallic surfaces oiled and keep the air as super filtered as possible (and oil filtered, obviously).

the other end of the solution is simply to measure the crankcase pressure. I'd hardly call that careful testing and analysis. Use a 2-bar map sensor ($12 ebay) and log the crankcase pressure (Arduino can do it for $20, even HPtuners EGR 0-5V input can do it free using stock ECU on GM Engines) And any stand-alone can do that. Very inexpensive, very powerful tool.

Once you log the crankcase pressure it will be obvious what needs to be done, sort of haha.
Airflow through orifice can be calculated using simple engineering formula (online or by hand) but that is unnecessary with some common sense approach, I will elaborate now, this is the common sense method:

Size of orifice and pressure difference through a nozzle does not need to be a differential equation; its a steady state single-value since our target pressure never changes. This would be confusing if you don't know the GOAL. Luckily I will tell you the goal and explain why it is the goal. I am not trying to hide or cover details, I will use plain English and simple words so that all can understand without being an engineer or knowing engineering terms.

The goal is to produce the desired pressure drop of 1 to 3" of Hg at all times while also minimizing idle/cruise flow rate. This is an unspoken aspect to generating this pressure drop which is absolutely critical to understand.
I will lead an example

We have 3 variables to determine steady state pressure for idle cruise: fresh air inlet diameter, outlet diameter, and pressure difference.
pressure difference:
Our fresh air inlet is always assumed atmospheric (for idle/cruise there is no air filter restriction @ ~10hp or less engine power) so lets set that to 14.5psi
Our intake manifold is lets say 15.3" Hg vacuum (-7.5psi) So 14.5 - 7.5 = 7psi intake pressure absolute
So the difference in pressure is 14.5 - 7 = 7.5psi difference

Orifice diameters, Intake manifold pcv orifice and fresh air orifice we will adjust to show the effects now:
-----Idle/cruise pcv action-----
With:
Fresh air orifice diameter: 0mm & Intake manifold pcv orifice diameter: 10mm
Resulting crankcase pressure = intake manifold pressure of 7.5psi absolute (15" Hg)

Discussion: obviously if we block off the fresh air vent completely (0mm) the crankcase will be pulled down to intake manifold pressure and the engine's oil seals will be damaged, maybe even pulled into the crankcase.
This example shows us that the diameter of the fresh air vent is CRITICAL. Too Small and the engine will be damaged.
Next, lets oversize the fresh air vent.

With:
Fresh air orifice diameter: 25mm & Intake manifold pcv orifice diameter: 5mm
Resulting crankcase pressure = atmospheric pressure 14.5psi absolute (0" Hg vacuum in the crankcase)

Discussion: Now we see that when the fresh air inlet diameter is too large, there can be no PCV action, no vacuum is present in the crankcase. Note that there can be a very high FLOW RATE through the crankcase, that intake manifold suction is still PULLING on the crankcase to remove blow-by gasses. However, without the sufficient pressure drop, there is no true PCV action, there is no OIL-SEAL protection, there is no Reduction is light chain hydrocarbons due to partial pressure of evaporation, there is no prevention of oil aspiration to engine orifices, no pressure drop to pull oil from engine crevices.


With:
Fresh air orifice diameter; typical: 12mm & Intake manifold pcv orifice diameter: 3mm
Resulting crankcase pressure = 13psi~ (approx 3" Hg vacuum)

Discussion: This random example (not exact orifice diameters, just for example) is showing us that by adjusting the Fresh air inlet diameter, AND the pcv orifice diameter (often set very small by the pcv valve) we can achieve the correct pressure drop inside the crankcase for idle cruise. 0.5psi to 1.5psi is fine. This will protect oil seals, help keep oil inside the engine, and it will facilitate the removal and evaporation of light chain hydrocarbon byproducts of combustion (mostly gasoline fragments which would otherwise dissolve into engine oil).

Another key idea here is that we want our PCV valve orifice as SMALL as possible, the SMALLEST possible diameter to generate the necessary vacuum in the crankcase.
Why?
1. because in the event of a fresh-air inlet clog, the very small orifice will not provide enough powerful suction to damage the engine's oil seals. A large orifice can easily damage the engine's seals, as intake manifold suction is very powerful.
2. because the smaller the pcv orifice, the fewer air molecules per unit time can pass through it, which means fewer oil molecules "go along for the ride". In other words, smaller orifice = less oil aspiration over long period of time. You will see less oil inside the intake manifold after 50k to 100k miles using the smallest orifice.


Now the key to why catch cans should be avoided. A catch can adds crankcase volume. The very small pcv valve orifice we are using will take TIME to pull the crankcase down into a vacuum state, and that TIME is dependent on the volume of the crankcase.
Therefore, by adding a catch can (or any extra volume to the crankcase i.e. huge lines and cans) is going to slow down the ability of the intake manifold and small-orifice of the pcv valve to generate substantial vacuum inside the crankcase.
Basically, we want the SMALLEST crankcase volume possible because just like when using vacuum hoses, the vacuum signal will be STRONGEST when the volume is SMALLEST. Which allows us to also use a very small PCV orifice diameter.
Does this start to paint a picture? The small orifice which can protect the engine is only going to work when crankcase volume is MINIMAL. That means NO extra lines, NO catch cans, NO extra volume attached. By using those devices you are creating a situation where the PVC-orifice would need to be enlarged, which will allow MORE oil to pass the orifice and a STRONGER pressure signal from the intake manifold which can be dangerous to the engine's oil seals if the fresh air inlet ever becomes clogged. Likewise, we wish to use a slightly OVERSIZED fresh air inlet tube/orifice since this will protect the engine when that hose and orifice becomes wet with oil and gradually collects carbon deposits.

Finale:
Our goal is to MINIMIZE the potential for failure and MAXIMIZE the rate of pressure change inside the crankcase, thus we should use the smallest diameter PVC-orifice and smallest crankcase volume possible, with a slightly over sized fresh air inlet orifice.


---------- WOT pcv action---------
This is simpler than the above situation. Since the pcv valve is CLOSED, we only have two variables:
1. Fresh air inlet diameter (as above, same hole) as before, keep slightly oversized.
2. Air filter pressure drop (the pressure behind the air filter, where the fresh air inlet hose is attached on all factory turbo engines)

The size of the orifice in this case is set by the previous example, since a large enough orifice to supply the crankcase flow during idle/cruise through the pcv valve is usually sufficient at WOT on all but the most 'leaky' of bottom ends. In which case the choice must be made whether to conserve idle/cruise pressure drop or to focus on the WOT pressure drop.

So we will ignore the orifice diameter and focus on the pressure drop itself.

The pressure drop at WOT is set by the air filter. Since there is always some gradient Pressure (the difference in pressure from the post-air filter tube to the actual crankcase) we always shoot a little lower at the post-air filter region.
Our target post-air filter pressure is as before: approx 3" Hg (about 1.5psi of pressure drop is healthy). This is enough post-filter pressure drop to pull the crankcase to approx 1psi of vacuum (2" Hg~) minimum.
This pressure drop does the same thing as before, it protects the oil seals, keeps oil inside the engine, and removes the blow-by gasses which would contaminate the engine oil.

Measurements taken here (just off the valve cover for example) are also a valid indicator of engine health. The same orifice and air filter generates the same pressure drop everytime the engine goes to WOT. If the pressure suddenly increases, it is a warning that something in the bottom end is wrong. This is one of the most powerful prediction tools we have at our disposal (monitoring crankcase pressure at WOT) as it DIRECTLY ties engine health to some number on a gauge which can be repeatably relied upon to tell us whether the engine today is running exactly as healthy as it was yesterday.

And to repeat this monitoring can be done for less than $50 ($12 map sensor and a $20 arduino). even if one does not have access to a stand-alone.

How does one "set" the pressure drop using an air filter?
Luckily, by using a high quality paper air filter (many aftermarket companies such as AFE provide re-usable paper style air filters of any shape, while OEM paper is the best it can be difficult to fit a large enough one) the paper element creates the pressure drop when the filter is sized correctly, within some reason. And by simply driving the vehicle, the filter will collect a bit of dirt and the pressure drop will increase (more post filter pressure drop over time) so it sort of takes care of itself.
The factory papers for example start off around 0.5" Hg pressure drop for the first 200-500 miles. Then by 500miles usually you will see 1" to 1.5" Hg of pressure drop. Finally by 3000miles or so you will see 3" to 4" Hg of pressure drop... time to change the filter. This is by design, and it is a very creative aspect the engineers are using to protect the engine.
Explain:
As the engine mileage increases and the air filter becomes dirty, the post filter pressure drop also increases as explained above. Why is this so important?
Well, as the post filter pressure drop increases, that means the engine is breathing more and more from it's own crankcase. In other words, It starts to clean itself better over time, it starts to protect it's own oil supply more and more as time goes on.
This was done on purpose by the engineers who designed the engine. They assume that if somebody is neglecting the air filter, then they are probably also neglecting the oil filter and other maintenance of the engine. Therefore, the most important thing for the engine to do when it is being neglected is to start protecting itself, to start protecting its remaining oil supply and internal cleanliness. Therefore, the effect of 'quickly clogging paper filters' is entirely calculated to protect the engine even while it is being neglected by the owner.

I hope this has been informative and helpful in your journey to a truly clean high performance engine land