crackcase vent filters??

L33T Z34

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

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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

xsnapshot

Think about what your saying for a second. "70% of blowby gasses are unburnt hydrocarbons". I'm not sure where you came up with that number as it's likely NOT true. What about all the other non-hydrocarbon gasses that are present? The overwhelming majority of combustion gasses would be non-hydrocarbon gasses. Anything not consumed during combustion will be very minimal. However let's assume it is true.

70% of the blowby gasses (which is a small amount to start with) gets sucked back into the intake tract. Want to guess how much %-wise this unburnt hydrocarbon mixture is vs amount of fuel injected into the cylinder during combustion? Basically negligible. The ECM has NO WAY of measuring this. Your mass airflow sensor tells the engine how much air is getting in through the intake and thats ALL the ECM injects for. So yes I am saying that NISSAN does not account for blowby gasses in the AFR equations. I can also tell you for certain that Subaru does NOT account for blowby gasses in their modern ECM's as well. I have a fair bit of experience working with Opensource tuning on the Subaru's and have seen the effects of running crankecase breathers set to VTA on aggressive and daily driver vehicles. In short there are no problems (at least with AFR anyway...emissions is another story). I'm not as familiar with Mitsubishi, but I'm pretty sure they don't account for it either.

The ECU's AFR correction is also not 3D. Its 2D. Think of it like this. (just guessing on the actual g/s values)

MAF sensor g/s ECU correction %
0-10 x%
11-30 y%
30-50 z%
50+ a%

Oil contamination is not really a concern. The oil gets really hot and the fuel is vaporized. Even with just VTA crankcase breathers, you should really be fine unless you never let your engine get up to operating temps. If anyone is really that concerned about fuel dilution then get an oil analysis done after your first oil change of running VTA breathers.

Also an AFR and an O2 sensor are one in the same. In fact there is no such thing as an AFR sensor. The O2 sensor just measures the ratio of oxygen in the exhaust tract to that of the ambient air. Then calculates the air fuel ratio based on that data.

Additionally your comments about the air filter and the manifold not delivering the same amount of air is meaningless. Only air that makes it past the air filter will be measured by the ECM (which then tells the injectors how much to inject), and all of that air will go into the engine to be burned. Perfect air-Cylinder distribution is inconsequential because there is not an O2 sensor at each cylinder. The system's O2 sensor is only being read far enough downstream that cylinder exhaust will be mixed. I would agree that air-cylinder distribution is important, but its not adjusted for in the ECM.

I'm glad you've had good luck with your setup. I'm not saying all of what you said was miss-information, just the part about the ECM using blowby as part of the air fuel equation.

6SPD_FTW

I've never personally analyzed blow-by gases like the EPA has, so I don't know for a fact. I have read in several places that blow-by is mostly unburnt fuel - and the 70% figure is what was attached to those statements. The flame front extinguishes itself as it gets close to the relatively cool cylinder walls, aka, barrier layer. If that layer does get burnt, you overheat and melt pistons. Blow-by is mostly hydrocarbons because the piston rings (hopefully) never actually get exposed to the by-products of combustion until the exhaust stroke. The rings and cylinder walls are protected on the power stroke by that boundary layer of unburnt fuel and air...which is what would be blowing right by the rings. Blow-by shouldn't be exhaust by-products unless it's happening on the exhaust stroke. If exhaust gases are leaking passed rings on the power stroke, you got some real serious problems and probably a few pistons with holes burned through them.

The ECM has no way of monitoring PCV flow....I know this. As far as it being figured into the base fuel map, all I know is Toyota must be more advanced that Nissan or Mitsubishi or Subaru because Toyota ECM's DO factor PCV flow into fuel delivery (particularly at idle and light-load driving). Toyota ECM's have no way to monitor PCV or modify it, however it is still factored into the base fuel schedule. I assumed Nissan...and all other manufacturers....would do the same. I suppose Toyota is ahead of the curve on that one. Nissan's, I suppose, just threw it on there and use the AFR sensor and feedback control to compensate for it.

And how is there no such thing as an AFR sensor? I thought it was a pretty common thing on vehicles these days. I know for a fact my 370Z has two of 'em. It also has O2 sensors too - two of them as well. I know because I've logged them before on Autoenginuity. The AFR's read 2.2V in closed loop and the O2 sensors read anywhere from 0-1V, depending on load.

Just having a VTA setup on the PCV is fine short-term. But without circulating some fresh air through there, it is absolutely impossible that all the water vapor, fuel vapors and oil fumes are going to do anything other than sit in the crankcase and contaminate the oil. Whereas if you leave it alone and install a catch can to prevent oil from getting siphoned through the intake, you get the benefit of knowing your oil isn't getting turned to sludge. I'm leaving mine alone because I plan on my Z lasting well beyond 200,000 miles on the original engine. Each to their own, but I don't think it's a smart idea.