Crankcase ventilation discussion and sort of survey

[fredio54]

yes, but, when they say "positive" dont they mean "by force" rather than "would be under pressure if not for this" ?

any source of vacuum is good. thing is when (if?) you flog your car the throttle plate is never closed for very long, and thus the vacuum is not happening much...

fred.

[neogenesis2004]

If I were to run the kit from JEGS posted previously then the breather would be under constant vacuum because the exhaust would never provide it with positive pressure (I think??). From my reading the main implementation of the PCV valve itself is to vent in fumes from the crank case to be burnt off under vacuum. I think that JEGS kit might be a real winner.

[neogenesis2004]

Well, to answer my own question. I google searched crankcase venting through the exhaust on google and found many hit of v8 guys doing this for many years on both NA and blown motors. The general consensus is that it works effectively when installed correctly. You are supposed to mount the port on or close to the collector so that you get maximum velocity. Also they say it is best to mount the port at a 45 deg angle WITH the flow of the exhaust so that you wont get any backpressure. All of these guys additionally eliminate any pcv system they may have as they say they get around 10inHG just at idle.

[fredio54]

really that much mercury? that sounds really good.

dont know if it would be legal here or not, but may lookinto it.

fred.

[neogenesis2004]

I'm gonna do this me thinks. I think I'll use hard tubing and flare fittings though and bend it to fit. That way I don't have to worry about rubber hoses melting. Maybe some AN hardware to give it some bling since I'm doing it all the way anyway.

[evo626]

The jegs kit uses the venturi effect to make vacum. Just before warned this will eat your cat up if you dont run a catch can on it.

evo

[fredio54]

infact it will eat your cat if you run a rich mixture and put it in before the cat. infact the cat will create a back pressure that might pressurise your sump. you want it in a high flow low pressure location. feeding O2 in before the cat with anything other that 14.7 mixture will cook it...

fred.

[evo626]

Also on the jegs kit those valves are one way check valves so pressure shouldnl't go back into the system.

evo

[fredio54]

good point. silly me. would be less effective at in the high pressure area though. collector or after cat seem best.

fred.

[M2cupcar]

that was on the first engine that came apart. This one has produced about two table spoons of oil in the last ~750 miles - of which it has seen ~15psi every time it was driven. My catch can has nothing in it for filtering- just two right angle brass fiittings for in and out, and then a barb on the bottom to drain. Haven't had ANY oil make it to the intake.

[oddballracing]

The lines on my breather are -6AN, FYI.

[fredio54]

Originally Posted by M2cupcar

that was on the first engine that came apart. This one has produced about two table spoons of oil in the last ~750 miles - of which it has seen ~15psi every time it was driven. My catch can has nothing in it for filtering- just two right angle brass fiittings for in and out, and then a barb on the bottom to drain. Haven't had ANY oil make it to the intake.

mines different to yours, but also never saw another oil stain on the air filter where it dumped to before after i installed it. definitely a goer.

[evo626]

What are you using for your catch can?

evo

Originally Posted by M2cupcar

that was on the first engine that came apart. This one has produced about two table spoons of oil in the last ~750 miles - of which it has seen ~15psi every time it was driven. My catch can has nothing in it for filtering- just two right angle brass fiittings for in and out, and then a barb on the bottom to drain. Haven't had ANY oil make it to the intake.

[defiler]

So what would be the effect if you didnt have the hose going from the turbo intake to the catchcan, just the one coming from the breather?

[fredio54]

the turbo draws air in from that line.

so no "slight suction"

fred.