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You mean OEM baffles? I've tuned hundreds of engines- perhaps around one thousand engines since 1996~. Majority of them turbo, so name a few, 1zz, sr20det, 3sgte, 2jz-gte, RB26dett, 4g63, VR6, 02-07 LS including many truck variants, ca18, ka24, k20a, &c
Many of them come factory turbo. Some are just plain old truck engines or car engines converted to turbo. As you may well know adding forced induction is notorious for increasing blow-by and making crankcase PCV systems even more difficult to deal with.
In every single case, no matter what the engine type, I have never had a problem with oil blowing out of the engine once the PCV was properly measured and setup to OEM standards; That is, streamlines for evacuation and approx 0.8" to 1.5" Hg of vacuum at WOT. If you can meet these simple conditions by setting the crankcase pressure properly, then the OEM baffles will meet OEM criterion this is how they are tested, and there won't be any issues with oil leaking or oil blowing out of the engine. The only time oil should blow from an engine is when the piston is damaged and blow-by forces large compression pressure into the crankcase which causes high crankcase pressure to blow oil out of the engine. In this case, a catch can may be used to temporarily bandaid the engine so it can drive for a little while before the piston is replaced. That is the purpose of catch cans, when I see one, I think of a blown up engine. The same goes for engines built improperly for example bore-ing an engine without a deck plate, excessive piston-wall clearance, running an engine with forged piston hard before the pistons fully expanded in the bores, these all create 'broken piston' symptoms and excessive blow-by due to user error.
So if a vehicle comes with an external AOS piped into the PCV lines from the factory, then would you consider that OK? It seems your main criteria is OEM vs non-OEM installs of air oil separators.
So if a vehicle comes with an external AOS piped into the PCV lines from the factory, then would you consider that OK? It seems your main criteria is OEM vs non-OEM installs of air oil separators.
The only time I've seen an engine use an external OEM air/oil separator is when the OEM ties the valve cover baffle into the oil pan in order to help evacuate the crankcase pressure from the oil pan. In that case the separator is tied to the oil pan so any oil is returned to the oil pan, it is not collected. That is not a catch can device, it is a baffle just like inside the valve cover.
And this type of device is used to keep oil pan oil out of the induction tract anyways- not the other way around like people think.
Air/oil separators need to be connected to the oil pan so the oil does not collect. For every gallon of gasoline the engine burns it will produce roughly 1 gallon of water as well, blow-by gas contains MOSTLY water and CO2 which is present in PCV flow at all times. If we collect oil it will also collect the water and CO2 from blow-by gas which turns it acidic, light hydrocarbons leave and the remaining form conglomerates which are myriad carbon products, the collected soup becomes a small reaction vessel which can now contaminate the contents of the pcv system.
The only time I've seen an engine use an external OEM air/oil separator is when the OEM ties the valve cover baffle into the oil pan in order to help evacuate the crankcase pressure from the oil pan. In that case the separator is tied to the oil pan so any oil is returned to the oil pan, it is not collected. That is not a catch can device, it is a baffle just like inside the valve cover.
And this type of device is used to keep oil pan oil out of the induction tract anyways- not the other way around like people think.
Air/oil separators need to be connected to the oil pan so the oil does not collect. For every gallon of gasoline the engine burns it will produce roughly 1 gallon of water as well, blow-by gas contains MOSTLY water and CO2 which is present in PCV flow at all times. If we collect oil it will also collect the water and CO2 from blow-by gas which turns it acidic, light hydrocarbons leave and the remaining form conglomerates which are myriad carbon products, the collected soup becomes a small reaction vessel which can now contaminate the contents of the pcv system.
All of my air oil separators are plumbed into the oil pan.
All of my air oil separators are plumbed into the oil pan.
Okay, so they aren't catch cans. They don't catch oil. And Oil has nothing to do with PCV. PCV is
1. streamlines to remove combustion blow-by gas before it can dissolve into engine oil
2. A pressure below atmospheric at all times in the crankcase
Oil control is a part of PCV. Or rather, a product of PCV. Controlling oil is not PCV but PCV is controlling oil.
PCV is for:
A. piston ring function
B. Oil quality
C. Prevent Oil leaks
D. Engine lonegevity: prevent deposits, eventual wear, failure
E. Oil Control
I would say that only 20% of PCV is related to oil controlling.
Okay, so they aren't catch cans. They don't catch oil. And Oil has nothing to do with PCV. PCV is
1. streamlines to remove combustion blow-by gas before it can dissolve into engine oil
2. A pressure below atmospheric at all times in the crankcase
Oil control is a part of PCV. Or rather, a product of PCV. Controlling oil is not PCV but PCV is controlling oil.
PCV is for:
A. piston ring function
B. Oil quality
C. Prevent Oil leaks
D. Engine lonegevity: prevent deposits, eventual wear, failure
E. Oil Control
I would say that only 20% of PCV is related to oil controlling.
I've never referred to them as catch can. I run air oil separators on all my wet sump cars. The PCV valve is also deleted in these vehicles. Even new these vehicles have excessive blow-by into the PCV that would cause dramatic oil loss. Some like on the STi/FXT are due to cornering g force pooling oil into the heads, then that's slurped right up the vacuum lines and into the turbo inlet.
My C7GS has had no issues with sucking quarts of oil at a time into it's intake. But that's to be expected with a dry sump.
Cornering forces and pooling is insufficient drainback. Some engines are prone to oil pooling like nissan skyline rb25. There are oil drain back kits and other mods to the baffle which can facilitate drain back if needed. Separating it in or outside the engine and returning to the oil pan is fine. I am not against separation, all engines require some form. Drainback is on a per vehicle basis depending on application. These issues do not concern PCV which is:
1.streamlines which can remove blow-by gas
2.pressure below atmospheric at all times
Again the oil control is not necessarily centered around PCV end result. Oil control is needed, but whether we control it or not has little side effect with PCV #1 and #2
Do your systems ensure #1 and #2 and never physically collect oil anywhere it can stagnate in the presence of blow-by while being heat cycled? Then its OEM quality standards for all vehicles in the world.
Cornering forces and pooling is insufficient drainback. Some engines are prone to oil pooling like nissan skyline rb25. There are oil drain back kits and other mods to the baffle which can facilitate drain back if needed. Separating it in or outside the engine and returning to the oil pan is fine. I am not against separation, all engines require some form. Drainback is on a per vehicle basis depending on application. These issues do not concern PCV which is:
1.streamlines which can remove blow-by gas
2.pressure below atmospheric at all times
Again the oil control is not necessarily centered around PCV end result. Oil control is needed, but whether we control it or not has little side effect with PCV #1 and #2
Do your systems ensure #1 and #2 and never physically collect oil anywhere it can stagnate in the presence of blow-by while being heat cycled? Then its OEM quality standards.
Horizontally opposed engines have a physics issue with cornering. Even Porsche leverages an AOS to address the inevitable oil suction from the valve covers.
Can be solved with a drill bit in some engines. Not really a PCV related aspect, other than the fact the oil gets sucked into the PCV system. Its like saying turbocharger smoking is a PCV issue when there is insufficient drainback. Sure, vacuum helps the drain, but the fact it doesn't drain properly in the first place is a separate issue from the PCV system who's job it is to maintain a clean crankcase and low crankcase pressure. Drainage improvements is just a side effect.
Can be solved with a drill bit in some engines. Not really a PCV related aspect, other than the fact the oil gets sucked into the PCV system. Its like saying turbocharger smoking is a PCV issue when there is insufficient drainback. Sure, vacuum helps the drain, but the fact it doesn't drain properly in the first place is a separate issue from the PCV system who's job it is to maintain a clean crankcase and low crankcase pressure. Drainage improvements is just a side effect.
My point is, "it depends." Some engines need an AOS others don't. Often times it is more related to how the car is being operated. Like the high lateral g-force of a track car. Sometimes treatment of the symptoms is enough, especially when there isn't a cure for the disease. Other folks might not ever experience those issues in identical cars.
My point is, "it depends." Some engines need an AOS others don't. Often times it is more related to how the car is being operated. Like the high lateral g-force of a track car. Sometimes treatment of the symptoms is enough, especially when there isn't a cure for the disease. Other folks might not ever experience those issues in identical cars.
Yeah but I never said AOS was bad or unnecessary. I said all engines have them. And if you added one, it should tie to the oil pan like OEM, AOS isn't a catch can. They are also placed near warm locations heated by exhaust to maintain gas state molecules and promote drainage. There is a right way to do things.
AOS isn't a bad thing it is a necessary thing. So I don't understand why you felt the need to point out the obvious. Of course we all need it.
Yeah but I never said AOS was bad or unnecessary. I said all engines have them. And if you added one, it should tie to the oil pan like OEM, AOS isn't a catch can. They are also placed near warm locations heated by exhaust to maintain gas state molecules and promote drainage. There is a right way to do things.
AOS isn't a bad thing it is a necessary thing. So I don't understand why you felt the need to point out the obvious. Of course we all need it.
When most people are talking about adding an AOS they are not referring to the pre-existing crankcase ventilation. That's likely the source of the confusion.
My catch can is just slightly below half with oil when I do my oil changes. Just to think, all that oil would have been sucked back into the air intake and would have made a nice home on my intake valves. You decide.
My catch can is just slightly below half with oil when I do my oil changes. Just to think, all that oil would have been sucked back into the air intake and would have made a nice home on my intake valves. You decide.
No, the catch can causes the oil to be blown out of the engine because additional crankcase volume and friction has caused a drop in kinetic energy which prevents the engine's OEM internal oil/air separator from doing its job.
Imagine if you add length and volume to the engine's air intake system. What happens to the pressure at the throttle valve as the air intake tube gets longer and longer?
You do the same thing to the crankcase when you add lines and catch cans, you have adjusted the pressure and flow rate of the crankcase evacuation system(PCV) and then neglected to measure and correct the issue you have caused. You are your own worst enemy. The OEM knows what it is doing despite what you think and sales people tell you.
LOL. Uhm, ok. If you say so. Better your car than mine. By the way, the catch can hose is routed into the intake manifold, not the air intake. Go educate yourself.
Last edited by howe2011; 06-28-2023 at 09:13 PM.
Reason: typo
LOL. Uhm, ok. If you say so. Better your car than mine. By the way, the catch can hose is routed into the intake manifold, not the air intake. Go educate yourself.
I built an entire car to illustrate the principles I've outlined here. Please try to focus on what is being explained. The picture is just a reference for line friction in fluid tubes so you can understand the relationship between friction and pressure/flow. The tubes get longer when you add a catch can and extra lines which changes the crankcase pressure. Now oil is blowing out of the engine because of high crankcase pressure. This also means that oil is blowing into the ring packs at the end power stroke and into the combustion chamber- the catch can has increased the oil consumption of the engine the rings will eventually become sticky with hard carbon buildup and stop rotating, which leads to eventual wear and engine failure. You have doomed the engine to early failure in this way. The high crankcase pressure is also contaminating the engine oil which circulates throughout the circulatory system and is leaving carbon deposits in oil orifices which will also create additional wear and eventual failure.
Here is MY engine & setup with 250,000 miles
The high mileage engine helps us understand that proper PCV setup can control oil and protect the engine lifespan- this engine will go 500,000 miles or longer if maintained properly.
The truck engine with OEM valve covers and no valley cover mods help us understand that there is nothing wrong with the OEM PCV system as so many owners claim.
The turbo helps us understand that even with double the engine output and potentially double the blow-by gas @ 750bhp (600rwhp) the OEM PCV system is more than adequate.
You must measure and set the crankcase pressure just like when you install a new tire, fuel pressure regulator, boost controller, &c there are many items on the vehicle with adjustable pressure, transmission pressure, coolant pressure, whatever. They all need to be set properly. The crankcase is just one more item to set properly. If you overlook this simple measurement and setting then it can easily remove a large chunk of engine lifespan and ruin the engine permanently.
Assembled this in 2017 using a free engine. 600rwhp pump gasoline, no spray or additives, daily driver.
Use AFE Pro-guard maximum filtration air filter.
This is the first time I've heard a claim that catch cans will lead to eventual engine failure.
Its not the catch can's fault exactly. Its people neglecting to measure and set the crankcase pressure and flow rate, or they use a breather which is even worse. Catch cans interfere with the flow and pressure. It can be re-set properly but nobody is doing that. And a breather is never correct, it cannot be corrected.
Look at the short line between my valve cover and intake tube. Imagine I extended that line by 3 feet or 6 feet or whatever volume and length a catch can system would add. Now, determine the new pressure of the crankcase using that information by accounting for the additional friction of the lines and disorganization of the can volume. Also you must account for moving the additional fluid mass of the crankcase which will create a delay between the idle/cruise and wot suction sides of the PCV system.
The result will be eventual engine failure. Carbon deposits, piston ring malfunction, cylinder wear, oil orifice obstruction. Oil will blow out of the engine and accumulate in the valve cover baffles. Oil will force its way past engine seals and begin to leak from seals. The whole PCV system is obfuscated by the additional mass and friction of added lines and turbulent reaction vessel. I've seen it in a thousand engines imported from Japan. In 2000's I would inspect 40 imported engines every couple of weeks.
This is where I first noticed the catch cans and aftermarket filter modifications are ruining the engines we imported. I No longer accepted import engines with these modifications after reviewing hundreds of them and realizing the mods are causing failure of the crankcase conditional, the engine quality is greatly diminished in the short time of 50k to 100k miles.
06-27-2023, 08:28 AM
