Why do some people have problems with the breather tube? By FACE PLANT FOR LIFE (Read 2,570 times)

[Bashan]

Luke ready for take off:

See Luke's finally being good and everybody is attacking him. Including me! Somebody needs to report me to me...or something...

[cyborg]

Wish i had one Bull,,i'd be making models till i fell down from exhaustion,,,i'm running dry sump mills right now a whole different beast ,,,but i may investigate your idea on my stella i pickup this next saturday,,,,after break in it's getting a pinasco pipe and carb kit,,,i havn't had horrible problems with my wet sump engines but i have had some oil in the aircleaners from time to time and your idea sounds like the ticket,,,,

[Bashan]

That's cool you're doing those kinds of measurements Bull, I don't think anybody has done that. I have always thought why have the case vent on the valve cover? That is just an opportunity for pressure waves to build up in the cam tunnel and disrupt the venting process. These would change with different RPM and might be benign at one throttle setting and become quite destructive at another. It would be interesting to see if you could record the pressures at a wide range of RPM, a graph. I bet you'd see pressures fall off precipitously at some RPMs and increase dramatically with others. The vent on the top of the case always made more sense to me. You're not giving the pressures a chance to focus within the tunnel, an ideal place to set up compressive forces as the larger volume of the case waves translate into the smaller volume in the tunnel. Just something I've thought of.......help me.

[Deleted]

The Otto cycle engine has 4 distinct cycles, intake, compression, power and exhaust.

Intake: during this cycle the piston moves down creating a pressure differential, allowing the fuel/air charge to enter.

Compression: during this cycle, the piston moves up and compresses the fuel/air charge. As it does this some unburnt fue/air charge escapes by the piston rings through places like the ring end gaps. This very small amount of unburnt fuel/air charge does create a small pressure within the crankcase and contaminates the oil.

Power: during this cycle the expanding gases do push the piston down and some unburnt fuel/air charge espapes as in the Compression stroke. Since this is under so much pressure a larger amount escapes. This is the main factor in creating the pressure buildup in the crankcase.

Exhaust: During this cycle the spent gases exit the engine and creates a minor momentary pressure reduction in the crankcase, but no vacuum.

As you can see of the four cycles, two cycles generate a pressure in the crankcase.

Therefore it is not possible for this engine at any rpm to NOT develop a pressure within the crankcase.

If as you suggest,Bashan, we mentally seperate the crankcase from the Cam cover, there would be moments of lower or reduced pressures, but they would still exist. Also to measure the pressure time latency from crankcase to Cam cover would be meaningless, but if it were done my guess would be something Nanosseconds or Picoseconds time interval

If you examine the Cam cover cover there is a plate in it that helps to reduce the amount of oil particles that are picked up by these hot gases. Most of these particles accumulate on the plate and drop back into the engine. Still some are carried by the pressure and gases to currently vent on most scooters.

As previously explained, the percentage of unburnt fuel/air charge can be reduced and at the same time generate more power by using one of the new Pulstar Plasma plugs which are just being adopted by mainstream auto makers. But you would still generate the crankcase pressure and perhaps even more of it.

As to using the crankcase pressure, gases and cleaning the oil; that is a worthy goal as it not only cleans the air and will provide miniscule mileage gains, but more importantly it can provide a cooling effect to the combustion chamber during the Compression and Power cycles.

This cooling effect and recycling the crankcase gases I have dynamically live tested. It works great except there is still too much oil trapped within these gases. These of course could cause carburetion problems without a liquid/vapor seperator.

As to measuring this crankcase pressure say at 100rpm intervals and plotting it would not provide any meaningful information. Also it could be harmful to the enigine as it possibly blows past seals and gaskets carrying large amounts of oil with it.

A volume test could be useful in diagnosing an engine that is becoming too worn, by comparing the crankcase volume to exhaust volume. It could be achieved dynamically, but there are better more established ways to perform that testing.

If you want to read about the new Plasma plugs, this is meaningful technology and not a gimmick. here is a link:

bloodycars.com/enerpulse-explains-mechanism-by-which-pulsed-energy-ignition-plugs-enhance-fuel-economy/

[Deleted]

My apologies to the OP, as I did not mean to hijack your thread. I meant only to add meaningful, useful information to a discussion.

[rks]

"If the Chinese had engineered this system with a liquid/vapor seperator it would have been more reliable and oil making its way into the air cleaner box would be almost nil, and could be handled by the engine on the clean air side of the air cleaner box. This would also decrease emissions and allow the capture and burning of HC, not to mention oil pollutants."

So why not just install a "catch can" between your valve cover and air box. Mine has a chunk of copper pot scrubber stuffed in it to aid in condensing the vapors....have never had a drop of oil, or any other liquid exit the outlet tube. I replaced the breather box with a K&N Cone Filter 2 years ago.....but outlet tube connected to OEM air cleaner would be an option. This would keep your air filter bone dry....Bob

s1271.photobucket.com/user/rks3526/media/Breather%20Catch%20Can/IMG_0074.jpg.html

[cyborg]

I had always thought about charging the fuel so the molecules were more evenly dispersed in the combustion chamber with no clusters of them being close together for a more complete burn,,,interesting read ,,,thank you

[richardv]

WOW! All this technical talk is making my head hurt. Time to go for a walk I think.

[Deleted]

RKS, while the technology your device is based on is proven, it is also very old. It was used in 'oil bath air cleaners' until the early 1960s. The problem with that technology was during that automotive era, engines were not as close toleranced as they are today. If your solution works for you, then by all means do what you want.

As for me personally, I prefer something more automated and less risky.

[Deleted]

CYBORG, dispersing the fuel more evenly so that it dries out has been a goal of automotive engineers for quite some time. One way to achieve that is 'swirl technology' where the valve ports and the piston dome are designed to increase the velocity of the air/fuel charge entering the combustion chamber.

Another way to accomplish it is the 'prechamber' that Honda engineered on their CVCC engines. A small air/fuel charge was taken into this area by a third valve and allowed to dry. This aided not only performance but fuel mileage as well.

Yamaha has started using a third valve on their Zuma 50cc scooters, which implies they may have adopted this technology. btw.. they increased the compression ratio to 12:1 and added FI. this has allowed them to increase the mpg to an advertised 132mpg

www.yamahamotorsports.com/sport/products/modelhome/690/0/home.aspx