How To: Poor Man's Oil Breather/PCV Blockoff

[jetskibruce]

The best solution for the ski is what yamaha did - put the correct size pipe into the intake to lower crankcase pressure. It is about horse power.

http://nutterracingengines.com/racing_oil_pumps/crankcase_vacuum_facts.html

http://www.gixxer.com/showthread.php?p=3678041

[Rip'nTear SHO]

As I was looking into the racing engine info on some other web sites it seems that engines like a lower pressure in the crank case. The blow-by and pressure is highest at high rpm and power levels. Solutions are: a separate pump that has the capacity required, the exhaust scavenging, and the intake manifold. Seems like the tradeoff is some amount of hot air in the intake vs better performance with lower crankcase pressure. One potential problem with pressure in the crankcase was the real possibility of forced oil leaks. Seems like the yamaha engineers know what they are doing. lol

These are the items that will help create a negative pressure in the crankcase to help ring seal......if you look at the dinky large hose that is being blocked off.....you'll see that it doesnt have the rigidity to maintain patency whilst creating the amount of vacuum/neg pressure ur talking about to create a potential ring-seal benefit......make sense? You need a purpose made scavenging pump/system to get the benefit ur talking about....I highly doubt that floppy PCV hose is doing anything but pulling hot air back into your engine.

[jetskibruce]

So, it probably doesn't make too much difference and you may see a gain. I guess you are changing oil very frequently? There are too many threads on the internet that already discuss this. So, just do it if it makes you happy.

[hitman]

The best solution for the ski is what yamaha did - put the correct size pipe into the intake to lower crankcase pressure. It is about horse power.
http://nutterracingengines.com/racin...uum_facts.html
http://www.gixxer.com/showthread.php?p=3678041

Whoa! I had (just sold) a K4 Gixxer and I remember reading about the "pair valve mod" a while back. I thought this sounded a lot like that. Never did it. Does not seem worth it. Nobody has ever definitively documented any gains from it whatsoever.

[planiack]

Is everyone sure that you dont need the suction from the intake? just a thought...

You are correct, you do need suction from the intake for a PCV system to function properly. The problem is that when you supercharge or turbocharge an engine, there is pressure in the intake and the PCV system does not function properly. In our vehicles we installed a one way check valve ( the kind that GM used on their AIR system) It effectivly scavenges the blow-by gasses outof the crankcase and just send them out the exhaust.

[allstar71]

The hose is connected before the supercharger so there is still vacuum actually it is prop higher vacuum than what you would have in a n/a engine

[5001craig]

Disconnect PCV from Intake???

Been thinking about removing the PCV going into the intake for some time after initially reading this thread. Then, two days ago I got my intake manifold upgrade done and when we pulled my Riva intake pipe, there was oily $hit on the white SC intake adapter! The only thing I can think is that this is coming from the PCV. It looked nasty.

I have a Groco strainer I was (past tense) going to use for water filtering and thought I'd run the PCV hose into the strainer mounted in the engine compartment.

Now, I am wondering about this... Anyone have any thoughts? Are you guys disconnecting your PCV from the inlet? Is PCV only for emission purposes?

Thanks.

[mjh3ides]

I pulled my R&D BOV hose off to replace the valve with an HKS & found an oily film inside. It's never looked like this before, so it must have happened when I overheated it a few weeks back. I was planning to pull the IC anyway to install the diverter, but now looks like I'll have to pull & disassemble the SC housing too in order to clean it out...PITA. A catch can would have saved me a lot of work. I saw JD1's kit eliminates the oil breather box entirely.

[txgp1300r]

pro stock race cars were running a belt driven scavanging pump to suck down the crank case...they say it made a few h.p. but who really knows except maybe warren johnson etc.