breathers?

sorry im not sure if this is the right sub forums so here it goes

i always see breathers on cars and on shelfs but what do they do? and how does on install them besides attaching the fliter? thanks

breathers allow blow-by gases from the cylinders to escape the crank case and prevent a pressure build up that could damage the engine.

breathers allow blow-by gases from the cylinders to escape the crank case and prevent a pressure build up that could damage the engine.


And:
The standard breathers on an engine are routed into the engine air intake (for emissions control). Aftermarket breathers which vent to atmosphere are often not emissions compliant.

The gas that comes out of your breather is partly air, partly exhaust, partly oil and party fuel.

And:
The standard breathers on an engine are routed into the engine air intake (for emissions control). Aftermarket breathers which vent to atmosphere are often not emissions compliant.


For cars made after about 1970 yes, for older cars some are, most aren't. :)

how come when i disconnect the stock breather, the car idles at around 3krpm?

how come when i disconnect the stock breather, the car idles at around 3krpm?
You're disconnecting the system at a point where the engine is "seeing" a large air leak into the intake.

You're disconnecting the system at a point where the engine is "seeing" a large air leak into the intake.
and i would stop this from happing how?

and i would stop this from happing how?
By reconnecting the breather. Or by plugging it up.

Some cars, like many european makes, use a closed system... meaning there is a big hose that gets direct manifold vacuum to the valve cover. The system is sealed. The benefit there is that oil leaks are rarely a problem and there is good crankcase ventilation. The bad news is that every oil leak produces a vacuum leak.

Most other makes use a PCV, or positive crankcase ventilation system that employs a valve in that hose and a breather somewhere in the system. Under idle and part throttle situations it uses a weighted valve to meter the air getting sucked in from the crankcase. That way there is plenty of air being let in and out without causing a vacuum leak.

Both systems work well; the european system does wonders for oil health but tends to suck in a lot of vapors and therefore can cause emissions problems. The PCV system doesn't do as well on the oil health, but doesn't suck in as many HCs from the crankcase to bother emissions.

sorry im not sure if this is the right sub forums so here it goes

i always see breathers on cars and on shelfs but what do they do? and how does on install them besides attaching the fliter? thanks


Lots of times when people say "breather" they are talking about the inlet rather than the outlet. If the unit has a filter it is designed to allow air into the crankcase rather than out of.

The darn thing is with most systems is that when blowby is at it's lowest the system does the most good, when WOT and the blow-by is at it's worst the system does the worst job and can even back pressure some of these inlet devices.

It is sometimes nice to design a system that works better at WOT than at idle and if it happens to be a V engine then use one side for inlet and the other bank uses the (pcv) valves for the outlet.

Yup... if I'm designing an engine for PCV operation without smog comliance, I put breathers in every available hole. At WOT when you're making the most blowby, you're also making the least vacuum to evacuate it. Let the bad stuff out any way you can :)