Crankcase vent vacuum setup removal = bad

[koko64]

You know, during some recent mental ruminations I did consider getting hold of some old style carb SS oil separator cavities and put them behind the Monster left side cover...
I thought about running a hose from the stock oil separator box and looping it back to extra cavities to give more volume again and eliminate the hose to the airbox. Maybe the extra volume would mitigate any losses from not running the hose to the airbox vacuum.

If you have to eliminate the stock oil separator cavity then fit a substitute from another model that might fit in some odd space. Then run that cavity to the atmosphere. It will at least catch some goop and restore some crankcase volume to the breather system. There may be some trick alloy or carbon race style ones around that look the part. Since space is at a premium on a HM this could be a solution.

Running a breather filter directly on a HM crankcase breather valve is tricky because how can you not wheelie all the time on a HM?

[scduc]

I'm going to try the TPO kit with filter covers and run the crank-case vent line up to the mid tank. I'll post my findings once my tech has it all tuned up.

[hunduc]

I'm going to try the TPO kit with filter covers and run the crank-case vent line up to the mid tank. I'll post my findings once my tech has it all tuned up.

very interested in the result (especially because we have the same bike)... keep us posted pls.

[koko64]

Ok guys, I'm gonna dyno test pods with breather to the world Vs open air box with breather to the air box. I'll do another thread for that.

I have tested the breather hose with the open air box both connected and disconnected and couldn't see any difference, but my bike was not flat out racing, just diagnostic power runs up to 8500-9000 max (held open enough to test but not too much for the old girl). I found no difference that I could be sure of attributing to the crankcase breather system. But my bike isn't a high revving desmoquattro under racing conditions.

I'm gonna leave the oil seperator box under the seat and put a little filter over it or some filter foam cable tied on, or not. I think having a flash looking filter on the end of the breather is a little risky, but if you put it on the oil seperator box at least oil wont puke onto your wheel. You will also have some 'fake' crankcase volume added to relieve some pressure.

I'm giving notice of the test as a courtesy as this has been a very interesting thread. There is also self interest as I also need some advice regarding the crankcase breather aspect.
If the pods have the same power I will keep them (given some jetting as they have 30% more filter area, but 'flow from the side'), if not I will go back to the open air box.

I will consider running the vacuum hose to the front of one or both of the pods and test that. I'm guessing that this will give a more direct vacuum to the crankcase, but I could be wrong. I am also considering buying another seperator box and placing it behind the steering head where the bottom of the air box was, and running the crankcase hose to it for extra volume and maybe also to the pods.

Even if I choose to not use the vacuum set up I am interested in providing plenty of virtual crankcase volume with a second oil seperator or breather cavity as I will have the room. I better try that before using the hole saw on the front of a pod and finding it made no difference!

If the open air box negates some of the vacuum scavenging effects of a 'closed' or ram air airbox then the extra volume method looks promising. I could run a cool looking filter from that.

I have been spending some dyno money as an educational process. I tend to theorize alot over a few beers but I have committed to some practical testing. Testing various concepts and how they interact is important to me so it's been worth it. All the 'experts' I have consulted have said that I should learn by just doin' it, as there is no accessable course for me down here. I may have to go to the States for a course/holiday.

If anyone has any advice it would be appreciated before I embark on another reckless adventure!

Cheers

[hunduc]

sounds like a much needed experiment, so kudos for undertaking it. up to this point we only had anecdotal evidence (both for and against of course...). i eliminated the oil breather this spring, and i did not notice any difference. but i never ride my bike even close to its limit.

no useful suggestions from here, just curious about the results. keep us posted, and good luck with it. 

[EEL]

Ok, I'll start by saying I havent read all 10 pages of this thread. But I got the general gist.

I dont really understand what the big hubbub is. For the sake of making this simple lets just focus on the duc twin motor.

1) For one piston moving up in a duc motor (into the head), there is one moving in the opposite direction. So the change in displacement on the crank side is effectively balanced. Ok so maybe the pistons dont seal equally but in theory if they were both perfectly sealed, all should balance out.

2) Now lets assume that the crank is not perfectly sealed and that some of the compressed slug of air leaks past the piston. So now you have a positive differential on the crank side. There are two locations where the positive pressure can leak to. Thru the other piston or thru the breather. Like in nature. The release is mostly going to be from the easiest source. The breather valve.

Personally I couldnt care less up HP values. If I did I wouldnt have bought a 2V air cooled motor. But I think this would have to be quantified by a dyno. I have no idea which way the results would go.

But to say that seals can prematurely fail from excess overpressurization is a wee bit extreme. I could see premature failure happening on an improperly tuned motor with engine compression way off spec. If you run a compression test and both are within spec, I dont think you're going to have any issues on way or another.

That being said, even if you had a breather hose connected to your airbox, an out of spec piston with bad compression could still result in premature failure of the seals. Just like a k&n setup.

So comparing apples to apples I dont think you will see a problem either way.

[ducatiz]

Ok, I'll start by saying I havent read all 10 pages of this thread. But I got the general gist.

I dont really understand what the big hubbub is. For the sake of making this simple lets just focus on the duc twin motor.

1) For one piston moving up in a duc motor (into the head), there is one moving in the opposite direction. So the change in displacement on the crank side is effectively balanced. Ok so maybe the pistons dont seal equally but in theory if they were both perfectly sealed, all should balance out.

2) Now lets assume that the crank is not perfectly sealed and that some of the compressed slug of air leaks past the piston. So now you have a positive differential on the crank side. There are two locations where the positive pressure can leak to. Thru the other piston or thru the breather. Like in nature. The release is mostly going to be from the easiest source. The breather valve.

Personally I couldnt care less up HP values. If I did I wouldnt have bought a 2V air cooled motor. But I think this would have to be quantified by a dyno. I have no idea which way the results would go.

But to say that seals can prematurely fail from excess overpressurization is a wee bit extreme. I could see premature failure happening on an improperly tuned motor with engine compression way off spec. If you run a compression test and both are within spec, I dont think you're going to have any issues on way or another.

That being said, even if you had a breather hose connected to your airbox, an out of spec piston with bad compression could still result in premature failure of the seals. Just like a k&n setup.

The question is how much pressure is built up in the case and how much ventilation (or vacuum) is present to account for it?

The easy solution is to put a pressure gage on the case vent.   

From my experience (which is limited to forgetting to put the oil fill cap back on) there is plenty of pressure generated in the case WITH the breather/vacuum system still in place on the airbox.  I know this because when I leave the cap off, oil sprays out like crazy and it's due to pressure, not moving parts at that location. 

Removing the vacuum part of the equation would make that even higher.  How much?  I don't know. 

[junior varsity]

next thing we'll see is koko64 doing a miniature EGR setup too...

[EEL]

The question is how much pressure is built up in the case and how much ventilation (or vacuum) is present to account for it?

The easy solution is to put a pressure gage on the case vent.   

From my experience (which is limited to forgetting to put the oil fill cap back on) there is plenty of pressure generated in the case WITH the breather/vacuum system still in place on the airbox.  I know this because when I leave the cap off, oil sprays out like crazy and it's due to pressure, not moving parts at that location. 

Removing the vacuum part of the equation would make that even higher.  How much?  I don't know. 

If you just think it though, you can surmise that its not a whole lot of vacuum. The same principle that applies to the breather applies to the airbox.

Its like sucking thru a straw, no matter how powerful you suck you can only get so much pull. The rest is just wasted effort. Since the breather hose is directly connected to the airbox. There is an effective short circuit in the static vacuum developed in the breather line because of the gigantic hole present in the airbox to bring in air. Its a trade off. You get more airflow in the box for lower static vacuum.

I hope someone does measure so we can all see that its going to be negligible

If you want more substantial vacuum, make the airbox fresh air intake SMALLER.

[ducatiz]

The stock airbox intake is tiny.  my 05 monster had a nozzle that was about 3 x 0,5 inches.

[koko64]

next thing we'll see is koko64 doing a miniature EGR setup too...

I got the little K&N A/F ratio meter. As they say great minds...

[koko64]

The stock airbox intake is tiny.  my 05 monster had a nozzle that was about 3 x 0,5 inches.

Well at least there is a well documented performance trade off in that case, open up that air box! I bet you did.
The resonance and air flow issues win over the crankcase vacuum issue. Certainly with the carbed bikes.
I may well purchase another oil separator box and put it up front to satisfy the crankcase volume principle if I can't stomach taking the hole saw to the front of the pod. A trick carbon one would look cool and give the impression i know what I'm doing! Picture it over a few beers with the boys, "Yeah, that's for increased crankcase volume, trick".

It's about competing principles and theories isn't it? I mean I know tuners who will do anything to keep the intake charge pure and will plumb the breather hose to an exhaust pipe to use vacuum assistance. The drag racers claim significanthorse power increases doing this but to vent to the intake charge is anathema to them. They would rather use a separate pump.

My EGA readings at idle went up by 0.4-0.5 with the breather hose attached to the air box. Even with a leaner idle mixture setting via the IMS and Slow Air Jet Screw my richest A/F ratio at idle was with the crankcase breather attached. I wasn't expecting that. I have had good leakdown tests by the way.. 175-180 psi cylinder pressure.
Although it would seem obvious I wasn't really expecting that result.

But first I will see if pods rob power. They may just be a less inefficient air flow system than the compromised standard air box. A correct air box ala Jako might just give the best of both worlds.

[Bill in OKC]

Now try a dyno run with and without the reed valves in the crank vent.  I'd really like to know if there is a difference there.

[koko64]

Isn't that the race set up that has been mentioned?

I mean with no reed valve venting into a huge breather/oil seperator box and then back to the air box via a auto type one way valve? The breather box gives the extra volume and often sits in the tail section.

That link explained it well, the Corsa set up.

One question, if the reed valve is doing it's job, why do we need a filter if venting to the atmosphere? Chris Kelley has mentioned just leaving the oil seperator nozzle bare. A mate of mine has a little K&N filter on it as some do.

Another question is, why provide breather cavities for extra crankcase volume when you can vent to the world?

[ducatiz]

Another question is, why provide breather cavities for extra crankcase volume when you can vent to the world?

i've always understood those boxes were meant to catch oil.  sort of a centrifugal nautilus design..  like the old VW oil bath air filters -- the oil never gets sucked into the vacuum because it has to go past several right angles, against gravity.