Blow Thru Breather

[KrnAznEP]

I noticed that the rear valve cover pipe to the intake would need to be replaced and my drawout was getting a catch can and venting the rest. After reading this fourum
http://www.3si.org/forum/showthread....+thru+breather.
I was a little confused on what to do. Is it bad just to vent it? I know right now it's sucking tiny bits of oil into the manifold. So what is the simplest/right thing to do for a blow thru design.

[2old]

Best? Keep it set up the same way as OEM:

The problem is not that the crankcase is "under vacuum" or "under pressure" it's both. The crankcase pressure should match the pressure in the intake track so the oil does not "blow upwards" nor suck the oil downwards on a the intake stroke.

The easiest: vent it, although if you are turbo you might starve the cylinder walls of oil since the oil would be sucked into the crankcase more then normal under boost.

[talskinyguy]

Wow that is wrong info.

Idealy you want your crankcase under vacuum, just keeping fresh air moving through the case works well too. Putting a vent on the crankcase is also fine, and won't harm anything, but you will probably want to put the vent after a catch can. The biggest thing to remember is you never want positive crankcase pressure.

Crankcase pressure has nothing to do with the oil getting to the right places.

[2old]

The crankcase is under positive pressure relative to the intake pressure... (it's only negative relative to ambient because of the vacuum caused by the intake) Unless you are saying that is an air pump somewhere that I I don't know of.

I am not saying that if you vent to air you will blow up the engine... The people that designed the engine had to design it to reduce the probably of failure so that you you get a failure after N million manufactured hours. If you are are going to say what is "best" for the engine you stick with how they routed it OEM because that takes into account these "incremental design" decisions.

Although I have seen a piston melt onto the side of a cylinder causing catastrophic failure and the car did have oil...

Edit: also the reason I said you can have positive is that when at full boost you aren't going to get a vacuum in the crankcase relative to ambient... Otherwise you could have used the vacuum generated for the power brakes instead of having to store the vacuum in canisters)

Edit, edit: Maybe I am just dumb... But if the vent had "nothing" to do with lubrication it would have made more sense for the engineers have vented the crankcase on the low pressure side of the turbo since you would have increased the pressure differential between the combustion and crankcase side of the piston increasing power and fuel efficiency while still maintaining emissions.

[DCIV]

I really just want a breather on mine. I hate all those tubes, plus my new plenum comes in contact with it.


Coop

[KrnAznEP]

The thing is that the Dejon Intakes don't have any holes for the rear valve cover to intake hose? http://www.3sx.com/store/comersus_vi...dProduct=26483