crackcase vent filters??

henry0844

can we run the small k&n type filters on the crankcase vent ports on the valvecovers? just pondering this and wondering if anybody knew if it would be ok. does the ecu need that recirculated crankcase vapor to be in the intake charge to run properly? I know that Honda people have been doing this for years. wondering if it's ok for our cars too.

1slow370

well thats honda people. it's not a gas recirculation thing so much as it is a performance thing. The stock pcv system is designed to to keep pressures in the crankcase down, this works like a vacuum pump on a drag car and helps the piston rings seal, and reduces the amount of power needed to move the pistons down. thats why turbo guys have problems with "boosting the crankcase" or actually pressurizing it because most N/a pcv systems aren't designed to see positive manifold pressure. a better way to go is the good old catch can route, if you really want to get experimental and gain that .5hp you could go with the exhaust venturii system, where you weld a pipe on an angle into the exhaust collector hook the pcv system up to that and use the exhaust flow to pull the gasses out of the crankcase. those little filters are supposed to only be used on the "intake" side of the pcv system(which is not related to the intake manifold but which side it breathes through). pcv is also an emmisions thing but it has a purpose.

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L33T Z34

I have two K&N 62-1340 on my Z. No problems.

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	K&N 62-1340 on Left.jpg (198.4 KB, 240 views)
	K&N 62-1340 on Right 1.jpg (196.5 KB, 198 views)

henry0844

thanks for the explanation. I was wondering if it would affect performance in any way. L33, how do u have the driver side filter set up? 5/8 elbow? or does it fit parallel with the valve covers?

6SPD_FTW

Don't do it don't do it. PCV flow is about 80% fuel vapors from the oil. Cycling those vapors into the manifold and burning them is calculated into the ECM's fuel map. It is very important for a smooth idle and best performance. Pinch one of those hoses off or unplug it with the engine idling (being mindful to plug the giant vacuum leak you just created) and see how the engine starts acting. You'll see how important it is.

Late,
Trav

xsnapshot

^What? Don't spread miss-information. The ECU does NOT take into account "fuel vapor" as part of the fueling process. And how does "fuel vapor" come from oil? It doesn't. What happens if one engine has more blow by than others? How would the ECU account for that? It doesn't.....

The PCV valve is responsible for what it's name implies; Positive crank case ventilation and it's purely emissions related. It sucks up blowby gasses/oil and deposits them into the intake tract, where they are ingested/burned. This is much cleaner than venting to atmosphere.

The blowby/oil could be considered a performance detriment, as Its been shown to lower the effective octane of the mixture in cylinder. If you don't mind breaking a few laws, then vent the crank case to atmosphere and plug the intake ports. Just make sure your atmospheric vent is free flowing enough that pressure is not building up in the crank case from blowby. I will repeat that.....check your vents/filters regulary because you do NOT want pressure building up in your crankcase.

It could also be argued that leaving the PCV system in place will help minimize pumping losses, as it places the crankcase under a vacuum, which reduces resistance on the rotating assembly. This resistance however, is extremely minimal, and I doubt you'd notice any measurable reductions in mpg or horsepower because of it.

henry0844

thanks for the info. i was thinking of running some intakes and running the k&n's. I was also thinking it would be a good alternative to the typhoon kits notoriously pita install due to wrong sized hoses.

6SPD_FTW

Ya know, I rather take a bit of offense to you saying I am spreading incorrect information because I am not. You are.

Blow-by is what leaks passed the piston rings on the power stroke - "It sucks up blowby gasses/oil and deposits them into the intake tract"....yeah....that stuff. Guess what blow-by is???? 70% unburnt HC's - raw fuel. PCV is to prevent a positive pressure buildup in the crankcase (as a result of blow-by) and to prevent FUEL DILUTION of the engine oil, which causes corrosion of internal engine parts. It's also why PCV valves are designed to close completely on backfires to prevent fuel vapors in the crankcase from being ignited. The fact that a little bit of engine oil gets sucked up into the PCV in the process is the problem that people install catch cans for.

Our engine, as most these days, uses a variable-orifice PCV valve....at low load and high vacuum, it flows less, whereas at high-load and low-vacuum it flows more (because high loads produce much more blow-by), i.e., it accurately matches ventilation flow with blow-by production. Do you REALLY think Nissan (or any manufacturer) is going to design an engine that completely disregards PCV flow into the fuel map? NO. It is correct that no two engines will produce the exact same amount of blow-by at a given load value and there are differences from engine to engine as to blow-by characteristics. Saying the ECM doesn't compensate is just plain dumb. No two injectors deliver EXACTLY the same amount of fuel, no two air filters or intake manifolds deliver EXACTLY the same amount of air, no two engines are EXACTLY alike. That is why we have a closed-loop feedback control system, i.e., an AFR sensor (or O2 sensor depending on your application). It's basically the ENTIRE reason vehicles are controlled by a computer these days. The three-dimensional map of long- and short-term fuel trims is how the ECM compensates for not ONLY PCV variation, but variation in anything that would affect the AFR, e.g., wear and tear.

So yes....if you use a crankcase breather and disrupt the PCV system, the ECM will readjust and it probably won't be enough to upset driveability. But without manifold vacuum continuously cycling fresh air through the crankcase, I wouldn't even want to take the chance of fuel dilution and corrosion of internal engine parts. A catch can is a much smarter idea than just deleting the PCV, and a catch can can be fabricated for <$10 with an air compressor moisture trap from Home Depot or Lowes. Did it myself and it works well. Plus, you have the added benefit of knowing that when the catch can starts catching lots and lots of oil in there that your piston rings need help.

Late,
Trav

O&G

All I know is if you use breather filters on the crankcase ventilation intake ports, as opposed to using the silicon hose to connect it to the intake runner and your F.I., under boost oil will flow out the filter and down onto your exhaust manifolds! No bueno. N/A should be OK though.

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BigT

I've run two diff catch setup's in my old turbo mitsubishi's.

First, I ran a ventilated catchcan. While this seamed to work, motor would puke out more oil than I wanted it to which would cause that nice mayo build up in the can. While it wasn't a horrible thing, twice the can filled up too much and shot the little air filter into the air. Also, I ran no pvc with this setup as the intake manifold would injest air from the little filters during idle and sometimes cruise. This reaked havic when trying to get the car to idle with large injectors and cams.

Then, I built my own "recirculated" catch can. It was actualy a dual can setup and also ran no pcv valve. Instead, I ran one large line from the valve cover to a 150psi one- way air check-valve, then from that valve to a sealed can, and finally to the intake manifold. This helped with keeping solid vacuum in the valve cover during cruise and idle. The sealed can kept any contaminents (oil, mayo, boogers, etc) out of the intake manifold. The other sealed can was connected to the valve cover with two smaller lines, followed by a third fitting to the air intake. (not intake manifold)

During cruise and idle, the makeshift pvc system used vacuum from the intake manifold to draw out nasty vapors and fuel back into the intake manifold to re-burn. (just as a stock PCV setup would do, but better as it would not leak boost, more on that later) I never had a tuning issues while running this. A properly running engine should not produce enough "blow-by gases" to cause any problems.

When going WOT, the air intake tract would create a ton of vacuum. At this point the intake manifold would fill with boost and the 1-way check valve would close. The vacuum from the intake pipe would pull gases out of the valve cover.

One thing I noticed after using the dual can setup, the cans filled up much much slower. Was the system flawed? Absolutely not. What it did do was create enough vacuum and at the right times to "draw" or "pull" the nasty stuff out, instead of letting the engine "push" out anything and everything - (engine oil).