Breather Re-Route ?...I know, I know...

[psychodad]

Sorry in advance for starting another Breather Re-Route thread, but this a WHY not a HOW inquiry.

I’m all for something if it works; but I’m also the type that’s needs to know why and how, not just that it does. Based on what I’ve read; it seems to solve everything short (no pun intended) of erectile dysfunction.

Correct me if I’m wrong, but the mod is to eliminate burning moisture laden air that’s vented from the crankcase. Also correct me if I’m wrong, but doesn’t this only happen for a short duration each time the engine comes up to temp; it’s like a big exhale and then a big inhale when the engine cools. After the engine warms up isn’t the air movement basically static ? Granted the inhale can pull in moisture laden air; but there’s a big average humidity difference between let’s say Phoenix and Seattle. From what I’ve read it sounds like those with collectors get an ounce +/- after a 1000 +/- mi. That just doesn’t seem like enough to cause a problem ??? You can see (in my mind) why I’m questioning a performance gain; since the moisture issue is probably only a certain duration of time, not a continuous thing.

It seems to me the positive venting as designed would be more beneficial than just relying on natural venting. Now in a perfect world (in my mind) the breather hose(s) would be lengthened with an inline cooling point at the lowest point (think distiller), and include a tee / collector / drain; and still terminate in the air box to maintain a vacuum.

OK now please tell me where I’m wrong in my thinking. But please don’t waste your time typing if your reply includes…”full of ****” or ”gained at least 10 HP ”.

Thank you in advance for your helpful and knowledgeable comments !!!

[konarider94]

oil will pool in the airbox. and everything inside gets coated with oil. its just nasty and purely done for emissions from the factory. i doubt the airbox has much if any vacuum. vacuum should happen in the velocity stack and definitely after the throttle plate. if there is a large vacuum in the airbox your air filter is too dirty. i realize there will be a small amount, i prefer to vent mine to atmosphere.

It seems to me the positive venting as designed would be more beneficial than just relying on natural venting. Now in a perfect world (in my mind) the breather hose(s) would be lengthened with an inline cooling point at the lowest point (think distiller), and include a tee / collector / drain; and still terminate in the air box to maintain a vacuum.

lots of audi owners do this. they run the pcv into a catch can (oil separator) and then a line runs back to the factory location in the intake. a vacuum on the pcv will have a positive effect on power and provide greater differential pressure to keep the rings seated better reducing blowby. many big v8's run the breather into the collector of the header to use that as a vacuum source. moroso makes a kit to do it. i think the gains from airbox vacuum are too small and prefer to keep my setup clean.

[rchuff]

That's why I did this ;did not want hoses all over and it is cleaner . When breathers look oily I take them off and clean them . (Stainless ) no oil all over the inside of the box. WORKS GREAT

[buellbradski]

I've noticed the airbox gets dirtier on humid days . I tried doing a simular setup as rcuff but decided to just do what kona said and dump it into the atmosphere. My second atempt I used a petcock at the end of the hose then a filter 8" up. It worked well but one 90degree humid day filled it up after 200 miles then sprayed my leg a little threw the filter.
So my final atempt seems to work well and is the easiest. Just t the two together and run the hose out behind the foot peg. It doesn't stand out as much is simpler and no oil in the airbox or my pant leg. Also I pluged the holes in the airbox by looping a peice of hose in one hole and out the other.

[greasyxb9s]

There is always air moving around inside and in and out of any crank case. This is caused by the pistons moving up and down.Pcv valves are run to let air out but not back in which in turn creates a negative pressure or vacuum in the crank case. This helps keep oil in the motor and away from seals and gaskets. It also helps the rings seal better. That's why drag cars run lines to headers and some race cars even run vacuum pumps to keep a even more negative pressure in the crank case..... especially forced induction intakes cars with turbos and superchargers. Pressure will get around the rings.... that's why there is such things as a leak down test..... its just how well you can get the rings to hold the pressure.

Straight venting to the atmosphere is no big deal diesel trucks have been doing for years..... just keep the oily residue off the tires.

[snrusnak]

^what they said. Primarily what greasy said, the pistons moving up and down is the primary cause for the pressure build up in the crankcase.

There is not a huge performance increase, it's usually mainly done for cleanliness, but I noticed the hot oil vapors were getting on the IAT sensor causing incorrect readings, and after doing the mod(open to atmosphere) the readings are more accurate and the bike runs better.

Also like said, it's often done on performance engines in cars with catch cans.

[greasyxb9s]

This was my racing kart motor. If you look at the top of the engine near the harness you can see a bundle of clear tubes. These were my vents from the crank case. There were 3 3/8" lines from the case and a 1/2" line from the valve cover. All the lines were vented to a catch can with a 2" filter. This motor was built by me. It had the crank welded and offset ground 10mm and used a 90mm piston with a 2 ring design. It had a 1mm gapless compression ring and a 2.5mm oil ring. The motor turned 9500 rpm and made 65hp at 8400rpm with 62 ft lbs of torque at 7200rpm. Now this motor started life as a Honda gx390 out of a generator and only turned 3600rpm stock....

So no you can see how important it is to vent crank case gases. I had one 1/2" line from valve cover to start the season, on the first warm up lap it blew the pto side oil seal coating me in oil.....

[psychodad]

Great reading and thanks !!!

Greasy,
That's a beast of a kart motor !!! Cage kart and offset ? Not much clearance between clutch sprocket and axle sprocket ??? Asphalt ovals I asssume; what size and what part of the country do you run in ? Many moons ago I ran small dirt ovals with the old built-up 5HP B&S's in a Laguana chassis.

[greasyxb9s]

Yes its an offset kart and no we run dirt.... nothing like open wheel dirt racing. I live in pa one of the biggest kart racing states.

[psychodad]

Same here. East or west ?