Air cleaner dilemna

speedo · speedo's Garage

Replaced the factory air cleaner with K and Ns. Factory aircleaner was connected to the oil tank which vented into the aircleaner allowing oil fumes to be burnt. I don't have that capability with the K and Ns. I solved this problem in my race car by venting the oil tank to a small Peterson catch bottle in the front of the car that was vented to the air and had a small drain. I have another catch bottle but it is going to be an awkward mount in the engine compartment. Can I just block off the port on the tank? Or does it need to vent? I don't want to butcher the air cleaner bases by trying to cram a vent into them. Solutions...thoughts?

Speedo

speedo · speedo's Garage

Anybody?

tctnd · 11-24-2013, 06:56 PM

It must be vented. Either into the intake or into a can then outside.

E Sully · E Sully's Garage

Crankcase Vent 2.4 w/ Webers

KTL · 11-25-2013, 02:00 PM

Has to be vented. The crankcase vent is attached to the oil tank and that case vent pushes a lot of air & oil vapor. If you don't vent the oil tank, that pressure is building up in the tank itself or "stacking up" and backing the pressure into the crankcase, which will create leakage somewhere.

JFairman · 11-25-2013, 08:55 PM

Piston blowby gas has to go somewhere and thats what crankcase ventilation is for. That's combustion exhaust fumes that leak past the piston rings down into the crankcase mixed with a little fine oil mist. Plug it and the rear main seal will probably be the first thing blown out by the crankcase pressure.

If you vent it into the engine compartment from the oil tank the engine cooling fan will be sucking some of it in and blowing it over the heads and cylinders to cool them and some also gets blown through the heat exchangers if they are on the car.
That's not a problem but if you use heat or the defroster in cold weather you'll be blowing some piston blowby fumes into the interior and breathing it. That's not a good thing.

Either vent it back into the intake which can increase the chance of detonation during hard acceleration but pollutes the air less and is better for the environment or vent it down under the engine tin through a hose so the engine fan doesn't suck it in and blow it into the interior of the car if you use heat or the windsheild defroster in cold weather.

KTL · 11-26-2013, 10:09 AM

I would not vent it freely with an open hose. Needs a container to catch oil in the event the main oil tank pukes a bit of oil.

If you fill the oil system slightly full, a catch can on the system can collect quite a bit of oil. On my racecar i've drained more than just a few oz. from the catch can after i've recently changed the oil & topped off the tank at operating temp. Definitely need to ensure the tank is only 1/2way up the dipstick if you're not venting the tank to a catch can or back into the intake.

JFairman · 11-26-2013, 10:59 AM

Yes you should have a catch can in the crankcase vent line after the oil tank. There are many different aftermarket ones with a small K&N type air filter on top and a drain valve on the bottom.

Porsche put a really nice black plastic one on the mid eightee's 911 turbo. Maybe they put it on other years and models too, I don't know.
It's an upright cylinder with a hose on the bottom that drains any oil collected back into the oil tank.
The blowby gas inlet hose at the top is offset to the back side so blowby fumes spin or rotate around inside the catch can after it blows in. The rotation of the blowby fumes inside the catch can helps seperate oil mist as centrifical force helps it collect on the inner sides of the catch can.
Then gravity runs it down and out the hose on the bottom and into the oil tank.
It's a good design and is lighter than aluminum ones.

tobluforu · tobluforu's Garage

Do a search on tech board, big thread on catch cans.

moneymanager · 12-01-2013, 05:42 AM

PMO supplies its carbs with K&N housing covers with connections for plastic tubes from the oil vent.

HawgRyder · HawgRyder's Garage

Crankcase ventilating in some instances is so important that the builders go to extremes to create a vacuum inside the sump.
I have seen engines with pumps driven by belt, gears, and direct drive to get this effect.
Bob

JJ 911SC · JJ 911SC's Garage

Speedo

Here is the best one I've seen so far; This is the way I'll be going...

Check pics at Post 19 & 21 of PMO 40's or 46's on a 3,0 204 hp ROW 911 engine

Ronnie's.930 · 12-05-2013, 08:03 AM

Quote:

Originally Posted by JJ 911SC

Speedo

Here is the best one I've seen so far; This is the way I'll be going...

Check pics at Post 19 & 21 of PMO 40's or 46's on a 3,0 204 hp ROW 911 engine

It will be interesting to see what you think of the effects of the oily fumes in the engine bay with it vented that way (especially if you use heat). I vented mine as JFairman suggested above (used a hose on the top, rather than a filter, and ran the hose under the car by way of the space in front of right shock tower).

JJ 911SC · JJ 911SC's Garage

Quote:

Originally Posted by Ronnie's.930

It will be interesting to see what you think of the effects of the oily fumes in the engine bay with it vented that way (especially if you use heat). I vented mine as JFairman suggested above (used a hose on the top, rather than a filter, and ran the hose under the car by way of the space in front of right shock tower).

I never have the top up so it might not matter but if it does, I'll vent under.