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Part2 'catch up'
Everybody's favorite topic: air filtration
Then compares oil molecule size with dust and debris. Finally discuss impact of fungus and pollen and elements of water injection, calculate temp drop due to meth spray on paper.

When I say cast, I mean brittle materials as opposed to ductile. There are only those two types, brittle or ductile. Hyper pistons are brittle, and feature low expansion coefficient, so I consider them as cast pistons.
The cast piston checklist applies to all engines, any engine. But if the piston is forged it can tolerate a much higher temperature and it also must warm up before it can expand fully in the bore which can take 20 to 40 minutes. Cold starts are the bane of forged internals, the most wear and tear. A cast piston engine can be in boost almost immediately after it is started in comparison due to tight cylinder wall clearance when cool still.
The cast piston is not the weakest link in terms of power output of most OEM engines. There are many ways to protect them from harm while making enough power to deform connecting rods, which by far seem to be the limiting factor when it comes to squeezing turbo induced potential from any engine, as the crank and pistons tend to be sometimes twice or more as capable. Stuff like filtration seems trivial because air is invisible i guess... but once you realize what is in the air that you don't see, the size and quantity of things such as pollen and fungus, and there is much more, and then calculate how much air moves through an engine per second or minute or whatever... those microscopic things start adding up quickly. Millions becomes billions trillions etc... and they are enormous compared to oil molecules... its like giant buildings raining down on a pile of leaves. Big disruption to the oil film in millions of locations in short time, ruining the piston ring seal little by little, getting caught between ring and sticking to the ring, preventing a complete seal that would have been possible. And the sheer quantity of trapped particulate, much of which has been smashed and burnt so its all disorganized carbon oxygen and nitrogen radicals obfuscated, sticky tar like seems the most common deposit formation after traveling along in engine oil some ways, you might call it 'atherosclerosis' of the oil system. Please understand I am summarizing these details, this is the short version, there is a book of writing involved in explaining every part of a single cell and how many of each thing there is. And that is just barely scratching the surface of air contents, there are so many other types of debris to consider. It isn't worth getting into; just filter the air properly and forget about it.
Most pistons are easy to break at high output if you do not pay attention to the variables listed and part of it is keeping the ring seal free from debris which involves superior filtration no matter how much power you want to make.

Review pressure drop, oil leaks due to pressure, engine baffle, gas velocity & separation, contains Dsport article, and gas kinetics

It doesn't matter how you get the vacuum into the crankcase. A vacuum pump is great, but complexity, cost, maintenance are not favorable in daily driver apps. So we usually find other ways to generate a vacuum. Turbo can drive a suction using the air filter. There are also exhaust driven styles which sometimes work well, but I don't see much success using those on turbo downpipes where it is common to have a too-small of downpipe and exhaust gas pressure prevents PCV from working optimally.

Next there are electric pumps found on all kinds of different cars for various reasons. Sometimes people like to use these for crankcase vacuum, I've never done it but it seems pretty simple compared to the belt driven version and if it works it works right?

Here is an example of somebody using electric pump for PCV in crankcase pressure monitoring and control
BW S362 SXE TwinScroll Project - EvolutionM - Mitsubishi Lancer and Lancer Evolution Community
Upon inspecting the 15amp fuse it had blown so it was not working when under boost. This might explain why I had oil pushing past the rear main seal. I swapped in a 20amp fuse and it works like it should and pulls ~5" at idle. Because I monitor the pressure with my AeroForce Gauge it allows me to set a warning light. I now have the warning light come on anytime the PCV presssure exceeds 0psi.
I hope this example helps put PCV into perspective. You must control the pressure somehow, electric pump, belt driven, exhaust driven, turbo driven, find some way to achieve the goal of low pressure in the crankcase.

2,340 Posts
@Kingtal0n Bookmarked this thread myself. I have the Twins Turbo dry sump setup, which uses a 5-stage ARE pump. I suspect my oil leak comes from the fact that during assembly, the guy who built my engine bored out the valve cover PCV hole for a larger fitting, at the same angle as the stock fitting. It... doesn't seem to seal very well, and from reading all this, it sounds like pressure in the exhaust valve cover is a fair bit higher during WOT. Oil gets pushed out of the valve cover, runs down the engine, and works its way toward the back of the oil pan.

I'd suspect the RMS if it weren't for the fact that it was dry when the transmission was pulled last.

Thanks for putting the effort into this thread and sharing it. :)

248 Posts
Following up regarding my evac system.

Seems to work perfectly fine, I haven't noticed any smoke etc from the exhaust. Car was tuned last week and made 600whp with the setup, and it pulls decent vacuum just holding a hose to my hand when revving - didn't put a gauge on the oil filler cap. So far so good and I am happy with the setup. My car is a stock bottom end and I Iimagine you could have more blowby in a built motor with looser tolerances or different ring & piston setup.

keep livin man, L I V I N
1,525 Posts
My brain just exploded!
  • Haha
Reactions: Kris9884

477 Posts
from when I volunteer'd at a JDM importer shop

Oh, people loved them catch cans. The cans would sell the car like dress up items. Even after I learned about proper PCV and started tuning a bunch of cars the shop owner still put those cans on everything because of the bling factor, shiny accessories. Something extra in the engine bay to show off. You can't vent an engine like this for high mileage,ill effects occur. But in the short term? You would never know something is wrong.

Heres a shot of the approaching nighttime when we are unloading 44 engines per from high cube containers, I would inspect, pressure wash, decide if I want one. How to spot the cleanest one? Lots of them had mods, big turbos, ecus (we had a stack of 'TOMS' and similar for 2jz) and of course everybody wanted the ones with big turbos...

I find that the only engines really worth keeping are the mostly stock ones, untouched. Seems like even the high mileage stock engines already look very clean, no need to really wash it much, the oil looks great, the color of the parts inside the engine is just tinted gold from frequent oil changes. Hmm... no oil gushing from various corners. At the time I thought it was mostly the air filter keeping stuff clean, but eventually with conceptualization of carbon chain turnover inside an engine (or a cell) you can't ignore the ill effects of letting them loose around the oil system or blood stream, it is similar with atherosclerosis, buildup on the inside diameter of a tube which is already very thin to pass fluid as blood or oil. I will absolutely go out of my way to force the engine breath from it's own crankcase as much as possible to collect as many dangerous free carbon conglomerates before it can interact with and become part of the crankcase structures.
It takes both clean air and a functional PCV to maintain the crankcase and engine health for long term.

I have a thousand pictures.
I told them to stop bringing back modified engines unless it was a crazy good deal. Those terrible green foam filters would ruin turbos, decks, embed material to intercoolers, damage blades, stuck to throttle valves, sandblasting the intake with debris. Large turbo setups always struck me as an oily mess, but I wasn't putting it together with PCV quite yet in those days. Didn't yet understand the stereochemistry of hydrocarbons and reaction intermediate myriad possibilities depending on the chain structure. Organic chemistry was very helpful with that. But PCV is more than just a cleaning evacuation... its also an oil leak prevention mechanism. A ring function booster mechanism. A gas density reducer and pressure reducer, helps oil return to the pan and will free up friction caused by pressure on a descending piston. PCV performs so many incredibly useful and important functions within the engine crankcase service I feel that it is the most important one of all to pay attention to. I prioritize it in every setup, people want me to tune their cars I always start with the crankcase. It might be the last thing they finally implement but its the first thing we talk about on the huge list of stuff to do before I will tune it.

Thats an automatic TT 98-02 model rhd Supra, purchased at auction with 188km for $8000 in like 2007. I think its fine to post prices because its so old and out in the open, this can never happen again, its like saying what the cost of gas was in 1960. You could buy a paper and a coffee for a nickle or whatever.
At the same time I remember a white 95' TT 6-speed for $6600 and I drove that car for a year with the twins in non-sequential. The auction prices in those years were crazy lucky random I think. Prob also because the cars were illegal to import here. Yet I could walk out of the court house with a title without issue and got progressive insurance easily so long as the car could land here from a container somehow. I was able to eventually outright buy a S15 at auction for a ridiculous low price and drive it for years daily. You didn't even need to modify them, the quirkyness of right hand drive was already enough is enough with this thing.

These days, good luck finding just the engine untouched. I'm not saying mods are bad but you can't always undo a mod or the ill effects of making changes to something without realizing the full impact of what you are doing. suck squeeze bang blow you think you know how it works, but there is always something. Every molecule matters, even the molecule that diffuses at rest when the engine is off and sealed... its still breathing, water can permeate through plastic and metal, there is always some potential for concern, and if there is anyway air exchange may occur it can permanently ruin the engine.

And thats just from time at rest, while the engine is off, in the corner of a room somewhere.
I sometimes see pipette tips with their lid left open in the normal air.
If you knew how ordinary air particulate influence health and lifespan and heart disease, you will probably spend alot of money on air filter. By the way, eat your vegetables and buy air filters.

47 Posts
I wanted to wait to post until I had a little bit of time to test my new setup. Previously I was using a freed catch can with 2 -10an lines from each valve cover. I was battling some oil drain problems with my turbo and tried multiple drain setups including the one precision makes now. If I pulled off my intake with the car running I had oil coming out of the compressor. I also noticed how dirty the oil looked after just a short amount of time. This thread had me revisit the thoughts on using a pcv system. I currently switched to a pcv on the drivers side valve cover and a -10 an line pre turbo on the passenger side. I wasnt sure how well the factory pcv would work with a built 1050 whp 2j so I'm using a me wagner adjustable pcv. Dual Flow Adjustable PCV Valve – M/E Wagner Performance Products I only have 750 miles on this setup but there is no more smell and oil usage is minimal.

477 Posts
I appreciate everybody giving PCV a chance, it won't let you down if you are methodical in the setup and testing of the system the way I have shown (will show below also)

I'm going to go ahead and predict the future, and make a couple of observations so when I'm gone you have this to carefully read and realize what happened if something goes wrong.

As more and more people will set their engines up this way, I predict many will attach these lines for PCV and few will measure their crankcase pressure or perform necessary pressure testing.
For every 5 to 10 setups perhaps 1 or 2 will experience oil blowing issues and not understand why. I'm going to warn and show right now:

If you blindly install a pcv valve, setup pcv system, and attach the crankcase vent to the turbo intake, All without measuring crankcase pressure AND performing a pressure test: It might go poorly in the long run.

Please allow me to explain the two possible failures individuals might experience
1. IF you fail to perform a complete pressure test and the PCV valve you decided to use LEAKS under pressure, the engine crankcase pressure will rise, cause oil leaking, and fill the valve cover baffles with oil, leading to intake manifold filling with oil over time.
This not usually an issue for Supra PCV valves, which are designed for forced induction. Nevertheless they should be tested because often aftermarket or production quality of PCV valves can VARY GREATLY in my experience. Even if they appear identical from the outside, their innards can be different or 'wrongly' configured, it sounds dumb but the pcv valve is quite complex and I've purchased identical PCV valves from various aftermarket sources and found MASSIVE differences in quality. For example I Recently got some supra PCV valves from rock auto which would only seal very well when held perfectly right side up. Which is very strange to me considering they install to the OEM valve cover sideways. You can often test them with your mouth -> Blow into them sideways vs standing up right and about 50% of the time the little needle inside seems to improperly seal when sideways on some of these valves.
So warning #1 is: After you setup your PCV system the way I described previously, you MUST ABSOLUTELY Perform a PRESSURE TEST. And because this test is so critical I have produced a video to show exactly how to perform this critical test. Do it exactly like I do in the video, pop the pcv valve, check the pcv valve leaking rate, it should be very minimal, barely noticeable. Also obviously Check make sure all plumbing is leak free as it will impact turbo performance and piston temperature. Leaking air molecules cause turbine wheel demand increase in speed to make up for the leak, which raises EGT and EGP and causes piston temp to rise possible breaking the piston or overspinning the turbo shattering it to pieces. If you've never had shards of a turbine shoot out the back of an exhaust system on a dynojet and embed to a wall 6 inches from where you were just standing you wouldn't quite understand how dangerous this can be to you or the engine.

If you do not perform this test you have no one to blame but yourself when the engine baffles fill with oil and intake manifold fills with engine oil!
Perform this test frequently! I've had hoses blow off days after performing this test, couplers get torn, shit happens! Keep checking!!11oneone!

2. Measure the crankcase pressure at WOT.... or else!
Updated 6/11/22: Added video of "how to measure crankcase pressure"

Every .10volts is worth around .66" Hg of or .328psi of pressure for linear 1-bar map sensor. (0.5 to 0.7" Hg per 0.1volt)
Our target is 0.5" to 1.5" Hg up to 3" Hg is great for WOT.
Idle/cruise I recommend target cruise 0.5" to 1.0" Hg also by using necessary restrictor.
Remember these systems are no longer OEM when we modify the engine and air filter. As the filter ages or power is increased, the pressure drop will also be increased. So measure now with a new filter, and then measure again at 5k miles or whatever to compare. Same thing with increasing power: Measure now with 400hp will be different than later with 600rwhp or 800rwhp, more power, more CFM flow, more pressure drop.

If you do not measure the engine crankcase pressure at WOT it could also lead to oil blowing out of the engine regardless of how you setup your PCV system. This includes oil through the pcv valve into the intake manifold! But Tal0n, I thought the pcv valve slams shut at WOT under boost? Yes, but, A. WOT crankcase pressure can drive oil into a baffle which is then later vacuum'd up by intake suction during a cruise and B. A tiny bit of flow still persists through during the transition from vacuum to boost and, The instant before it closes there is still some flow reverse, amplify that by hundreds of WOT runs and you have an oily intake!

In the video I show how the crankcase pressure rises with a vent, and notice my crankcase pressure is only .3 to .5psi at that time.
That is because the piston rings have not been invaded by oil yet, and the baffles are not full of oil yet.
If I leave the venting open and let the crankcase pressure rise to 0.5psi~ for a while, it will gradually increase over time, ring function will decline, rings will start occluding oil (Oil will work its way into the ring pack) and the baffle will gradually fill with liquid oil, all of which causes increasing blow-by and increasing crankcase pressure over a long period of time when using a vent system. Notice my engine has 220k miles and has VERY little blow-by... whereas there are many examples of high mileage engines with a LOT Of blow-by, the difference? Where is the difference? It is the crankcase pressure condition during the engine operation for high mileage.

The PCV is a pressure setting, just like boost pressure, it must be set by US, WE are boost controller, WE are the PCV crankcase pressure controller.
If you blindly connect turbo intake to crankcase and just assume its good... It might work fine. Or not. How will you know? It must be tested! Measured! You don't blindly assume the fuel pressure is good, why would you blindly assume the crankcase pressure is good?
When you next open the intake tube and find a bunch of oil in there, you have nobody to blame but yourself for not measuring the crankcase pressure at WOT. There is no way to fill the turbo intake tube with engine oil if crankcase pressure is being controlled properly.
The pressure drop applied to crankcase at WOT comes from the AIR FILTER (all engines, turbo, non-turbo, same ideaology). The AIR FILTER must be sized correctly, for example 1000CFM @ 0.5" Hg pressure drop is TOO MUCH FILTER for an engine that only uses 750CFM of airflow. You can't just buy any old air filter and attach the crankcase... it may not work well! The filter flow rate needs to match the engine's HP flow requirement to drive the crankcase pressure DOWN.

I don't have a video yet of measuring crankcase pressure but I feel the need to make one more and more as more people start using the PCV system and setting it up properly (I've said these things to 10+ automotive forums by now and words... are often not fully understood well enough it seems...)

The easiest way is using a 1-bar map sensor (or 2-bar if you suspect there is alot of pressure for some reason like a broken piston).
Provide the map sensor with voltage and power from a source other than the vehicle. I use 6x AA batteries to make 12 volts and then I drop that down to 5v using a reliable power supply. Don't use the car battery to power your map sensor as during WOT the voltage often snakes around causing the map to read differently. It will introduce error. Also don't directly use 5v, make a 12v first and drop that to 5v using a power supply device. This keeps the voltage steady the entire time.
Connect the map sensor inline between crankcase and the turbo intake tube as shown below.

You can measure close to the turbo intake which tells you how much pressure drop the filter is supply (tells you about the filter restriction)

And you should also measure here near the crankcase, which tells you more about crankcase pressure and less about the filter restriction (It will read higher closer to the crankcase because of pressure drop at some distance, dp/dl which stands for difference in pressure with respect to length of some tube)

The baseline voltage of map sensor at barometric pressure with the engine off should be a steady number, for example at sea level I Record 4.34v engine off.
Then, start the engine, Pcv valve suction will drive that voltage down somewhat. It may go 4.23v at idle or 4.05v at idle or whatever. Different cars, engines, pistons, pcv valves, different numbers result. You can modify the orifice of the crankcase vent tube (the hose between turbo intake and crankcase) to be smaller or larger to adjust the idle/cruise crankcase pressure. Factory Nissan SR/RB engines for exmaple from the old days have restrictors often built into their hoses (not all but some do) to achieve a low crankcase pressure at idle.

Next, go WOT with the engine and watch the multi meter (or log the voltage if you can) Its fine to simply spot check with your eyes for a couple of WOT runs, using a traditional multi meter, no need to log the voltage, and indeed logging may introduce variables so I don't even recommend it.
During WOT you want to see a voltage less than baseline when the engine was off. When the engine was off it was 4.34v right? So at WOT it should be less than that. Ideally you would like 3.9v or something in the 3.6v to 3.9v range, indicating there is a substantial crankcase pressure drop at WOT which will be extremely protective of the engine oil and preventing oil from blowing out of seals / oil leaks / oil mess.

And thats it! Measure crankcase pressure, perform pressure test. Profit. Don't come back to the forums after you connect everything correctly and complain about an oil mess- It wouldn't happen unless you neglected one of these two critical tests. Either the pcv valve is leaking or the air filter is not providing enough pressure drop on the crankcase at WOT, its that simple.
Sorry about all the words just predicting the future and the more people that are aware of these two simple tests and pitfalls the better they will guide the future, I feel that this thread now contains everything one needs to understand about PCV, the words are here, read and understand and protect all your future engine investments. Good luck
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