Breather tube

[rodsmith]

I've heard of people routing the breather line to drain on an exhaust pipe. I guess the theory is to burn residual oil instead of having it end up on the belly. Thoughts on whether this is a good idea?

[AKKen07]

Actually I believe the intent there is to create a suction/vacuum effect on the case which somehow decreases the potential for oil leakage etc. I think aerosplat has an explanation on their website. I have the parts from them to install the system but haven’t convinced myself all the extra clutter is worth it.

[alaskabearhawk]

Lots of previous discussion on the forum on this topic. FWIW I decided to wait to install one. I don't want to fix a problem that I don't have.

https://bearhawkforums.com/forum/tools-technics-and-best-practices/30679-venting-breather-tube-into-exhaust

https://bearhawkforums.com/forum/bearhawk-general-discussion-news/81473-air-oil-separator

https://bearhawkforums.com/forum/bearhawk-general-discussion-news/19818-breather

[marcusofcotton]

The exhaust suction to provide crankcase vacuum is also used by auto racers for a slight increase in power. Of course their running considerably higher rpms where it may make more of a difference???

[Bcone1381]

I've heard of people routing the breather line to drain on an exhaust pipe. I guess the theory is to burn residual oil instead of having it end up on the belly. Thoughts on whether this is a good idea?

Rod, I think "....to drain on the exhaust pipe." means the breather does not penetrate the exhaust system. Rather the Breather Tube is positioned entirely outside the exhaust system but very close to the exhaust system to cook off the oil drips . Plus its position would be passively heat the breather exit to prevent ice from forming and clogging/blocking the breather. (My understanding is The standard fix to prevent a frozen breather from causing engine failure is a whistle slot is cut into the tube upstream of its exit point.)

I have only heard about this and I have no experience with it. It seems like a good idea though. I'll say "I see no harm." But with no experience my input has no credibility.

[rodsmith]

Yes Brooks, I'm talking about having the breather tube drain on the exhaust pipe, not vent into it. I'm aware of the kit to connect it to the exhaust but that also requires an air-oil separator. I have enough going on behind the engine without the additional plumbing that entails.

[svyolo]

A lot of (maybe most?) cars have head/crankcase breather tubes that vent into the intake. They burn it off. Some diesels do something similar, with a side benefit of less oil usage/leaks. I am not sure why aircraft motors don't do something similar, but there is probably a reason. I had room so I installed an ANTI-SPLAT air/oil separator. I have no idea if it will be an improvement or not.

[dramsey]

I have experimented with a few options in air oil separators (granted on a Continental IO550). I never return the oil/water mixture to the engine, but rather catch it in a container attached to the liquid outlet of the separator, so I can monitor its effectiveness. I started with an Andair separator venting the gas side out my cowl exit. I still got oil on the belly and with 3 quarts used per oil change the separator only caught 2 tablespoons, consistently each oil change. I heard good things about the antisplat system so I tried it and tied it INTO my exhaust. I then had a belly free of oil but my oil consumption went up (but I think the data was contaminated by wearing rings that I had to replace). The antisplat separator caught only caught about 2x the oil/water mixture that the Andair caught. Still nothing to write home about as far as effectiveness. When I felt that the vent piped to the exhaust was sucking more oil mist out of the engine, I decided to just use the Antisplat separator but route the gas side outlet just above my exhaust pipe to burn it off on the outside of the pipe. That caused the amount of oil in my catch can to go down, to around that of the Andair. No doubt that having it in the exhaust sucks more out of the engine. But I still get some oil on my belly. So, if you goal is getting oil off the belly, then using the antisplat system tied into the exhaust does work for that. Just dont get overly dilusional that these air oil separators are really catching much oil. In my experience at least, they are not.