Oh ok, that makes sense. But does that mean that combustion will not happen as intended with the cans installed? Sorry, just tryin to get a feel for this

The blow by is created after (and by) combustion ... so no impact on combustion whatsoever.

It means your combustion (and whole upper end, really) will be slightly cleaner, because you're not tossing oily vapors back into the intake to be re-burned. Improves octane by 0.00001% or something probably, too.

In a nutshell:

(1) Why is the crankcase ventilated? If the crankcase wasn't ventilated, you'd get oil leaks at the engine seals due to pressure buildup.

(2) Why didn't Nissan just design it to ventilate to open air instead of recycling it into the intake? Emissions reasons, the EPA doesn't like you ventilating oily vapors.

(3) Why doesn't Nissan install a catch can from the factory, thus meeting EPA *and* not putting dirty oil vapors into the intake? Because you usually have to empty a catch can even more often than you change oil, and if you let it go too long and fill up, the liquid oil will get sucked into your intake via vacuum while the car's running, and that's *really* bad. Most people have a hard time even changing their oil on time, there's no way a consumer car can have catch cans from the factory. They'll just fill up and dump into the engine anyways, possibly catastrophically. Keep in mind cornering/braking/accel G-forces will make the fluid in the can crawl up the walls. You have to keep the level low enough to not walk up to the vacuum line and get sucked in as liquid. Good can design can help with those problems.

alright that really clears alot up. thanks guys

I'm currently looking to do this mod in my car....what are some companies you guys might recommend?

As far as this thread goes, I like this dual can design.....Good job SIXPAX:tiphat:

Saikou Michi

... link is at the beginning.

What happened to all the pretty pictures? :eek:

All I see are broken links....

oil catch cans
 

Any idea of the pressure level in the PVC lines before/after the dual oil catch can?

Must have been temporary, I see them all.

I'm not a scientist, but I would guess no change. Lines are longer after, but I figure the pressure is all the same.

Can you just run the lines to a point under the car and just let the overflow oil and vapors drip/flow out? I don't give a **** if the EPA doesn't like it. Would be simpler than the cans.

You would get a CEL and a crappy idle if you ran it open like that.

I don't think it would give a CEL really. You'd block off the PCV lines on the intake and vacuum sides (so no vacuum or intake path peaks for CELs), and run the lines from the valve covers to open air (probably with a simple filter). People do it on older V8's all the time (you see those tiny air filters they mount on the valve cover, that's their "PCV" straight to air). It would serve the basic purpose of not letting excess pressure build in the crankcase, and it would filter any air that was drawn inwards under conditions where the crankcase pressure goes negative. There are probably some subtle points being missed though (if nothing else, it might still be nice to have a pair of them with opposing one-ways so that you get some fresh-air exchange). I wouldn't recommend it just for all the subtle unknowns.

(Here's a discussion about doing such a thing on an LS1, you can see some of the smaller points being debated there: Can you replace the PCV valve and line with 2 breather filters? - LS1TECH )

Indeed, these are the little filters you see at the auto parts stores, called crankcase filters.

Also, I use a catch can on our 6.1L Hemi and it catches a hole lot of blow-back oil/sludge. It is a very nice quality piece that is very easy to empty as the bottom section unscrews. made by Billet Technology... I was thinking of getting these for my 370z, but getting 2 seemed expensive.

By the way, a note for California cars... both these crankcase filters and catch-cans do NOT pass SMOG (visual insp.). :(

http://billettechnology.com/wp-conte...stalled017.jpg