hi! well as the topic subject suggest I have no clue about how the oil breather works or why one hose comes from the air box and the other from the engine, one has a chamber and the other one too on the same ugly black plastic box under the seat... could anyone clear me following questions: [popcorn]
1. how does it work..
2. are both chambers connected?
3. the amount of space of both chambers, does it matter?
I am going to relocate, of course I am building a new not so ugly plastic "thing", but I need to be certain not to f%cked up the bike.. thanks!
Oh, yes, 620ie 2002 Monster [thumbsup]
I'm going to give you a simple answer. Piston rings do not create a 100% seal, therefore some blow-by gasses enter the crankcase. These need to get out of the crankcase or...well...just imagine if you ate a bunch of bean burritos and someone corked your rectum and throat. Back in the ancient history of motorized vehicles, cars, not so much motorcycles, blow-by gasses vented from the crankcase through a pipe from the crankcase (road draft tube) and fresh air came in through a filter in the oil filter cap. Well, at least until there was excessive blow-by. At that point blow-by gasses would puff out both ends.
Back around 1963 the EPA decided this was an easy source of pollution to clean up. Manufacturers were required to use a closed system, known as Positive Crankcase Ventilation. This was usually accomplished by a tube from the crankcase to either a "PCV" valve or small orifice into the intake manifold and fresh air entered from the air cleaner Assembly into the engine. There were exceptions, like my 79 BMW (car). Much simpler, an oil separator in the valve cover and a hose to the a hose to the bellows on the air flow sensor
Same idea on our Ducatis, but execution is a little different. Crankcase pressure is controlled by the breather valve. There is no fresh air intake since our big twins since there is always some positive pressure. The hose from the breather valve goes to the breather tank, which has to functions. One is as an oil separator, the other is to supply a hopefully sufficient volume to collect blow-by gasses until they can be drawn through the intake system to be burnt in the engine.
The jury is out on whether removing the breather tank and venting to the atmosphere or not in terms of performance, probably because it makes little difference on our two valvers and probably less if you run an open air box. IMO, the only two reasons for eliminating the breather tank are aesthetics or modifications like pod filters. If you want to create n new breather tank it should be at least the same volume. If you want to vent to atmosphere mount the filter high so oil can return. Also, do not over oil the filter.
I am not sure what two chambers you are asking about. Hope this helps.
Volume is over 900 cc and there are two chambers.
First chamber --> channel to next chamber slows down flow --> second chamber --> hose to air box AND a low return channel from chamber two to one. The oil that is separated from the crank case gas will return to the case when the pressure is off (bike stopped). The exception is when there is too much of it building up - then it will go into the air box and either be sucked into the intake or follow the dedicated drain hose from box to ground.
So, in my limited know-how, two chambers might be a good idea and the return channel from chamber one to two should be at the bottom, as should the main hose from valve to box (to allow oil return flow).
My local+European race regulations require me to have a closed system - as the box. I have no idea if the box is necessary on street bikes or does anything for performance.
Ah, what I am calling an oil separator you are referring to as two chambers, which indeed works.
Did some ega/dyno testing quite awhile back on my old 900. Compared breather to airbox Vs breather to atmosphere. I found no significant difference in power. I still ran the oil seperator box, just disconnected the hose from the airbox and plugged the holes. But my old girl ain't a high revving racer. [laugh]
What was different was that the idle mixture was richer with the breather hose going to the airbox (by more than I expected). 'Spose a uncontaminated intake charge is a good thing.
We did the K&N breather thing on my brothers 01 M900 (filter off the breather box), and his bike picked up 100rpm at idle and runs cleaner plugs.
I like leaving the oil seperator box/breather cavity. It adds crankcase volume to the breather system.
Did you test with both a stock and open air box?
Only open airbox. A simple test of hose on/hose off with the breather box in place.
Maybe a stock, closed airbox would have had enough vacuum to help scavenge crankcase pressure. But I reckon the performance increase of the open airbox easily outweighs that on a low revving two valver. I went with the K&N filter on the breather box/oil seperator. No more condensation in the oil sight glass window or oil in the airbox as a bonus. I would stick with the breather box to simulate more crankcase volume to ease crankcase pressure. The little K&N filter certainly lets the pressure out, it's a significant opening with the filter area!
With the low air volume at idle, the crankcase mist was having a significant effect on the a/f reading. Taking the hose off leaned the a/f ratio at idle a little more than 1/4 a turn of the IMS and 1/2 a turn on the SAJ! On the plugs it was like from dark brown to tan on road testing low speed/around town operation. Certainly enough intake charge contamination to "trick" the EGA.
On my brother's IE 900, he picked up the 100 rpm we were looking for at idle that I couldn't get on the bleeder screws without causing "hanging". He's pretty happy that a cool lookin' little filter solved that problem. Maybe I should check his bikes compression..
ok, I already removed the oil breather box and this is what I found:
1. no oil or traces of oil in any of the 2 chambers...
2. air-box is really clean inside, so no oil has ever passed from the breather to the air-box...
3. since, so far this is what I have understand from everything you all have said, what the breather does is mainly is collect gases which then flow to the air-box right?
4. decided to use pod filters now that I am tearing all the electrical harness apart for hiding wires, so if I am not correct please tell me so, the reasonable thing to do is put at the end of the hose coming from the crankcase an oil filter and of course all this high enough so that the filter wouldn't get soaked in oil, right?¿
thank you very much!
Quote from: cmejia1978 on December 23, 2012, 08:54:57 PM
ok, I already removed the oil breather box and this is what I found:
1. no oil or traces of oil in any of the 2 chambers...
2. air-box is really clean inside, so no oil has ever passed from the breather to the air-box...
3. since, so far this is what I have understand from everything you all have said, what the breather does is mainly is collect gases which then flow to the air-box right?
4. decided to use pod filters now that I am tearing all the electrical harness apart for hiding wires, so if I am not correct please tell me so, the reasonable thing to do is put at the end of the hose coming from the crankcase an oil filter and of course all this high enough so that the filter wouldn't get soaked in oil, right?¿
thank you very much!
You got it!
Quote from: cmejia1978 on December 23, 2012, 08:54:57 PM
ok, I already removed the oil breather box and this is what I found:
1. no oil or traces of oil in any of the 2 chambers...
2. air-box is really clean inside, so no oil has ever passed from the breather to the air-box...
3. since, so far this is what I have understand from everything you all have said, what the breather does is mainly is collect gases which then flow to the air-box right?
4. decided to use pod filters now that I am tearing all the electrical harness apart for hiding wires, so if I am not correct please tell me so, the reasonable thing to do is put at the end of the hose coming from the crankcase an oil filter and of course all this high enough so that the filter wouldn't get soaked in oil, right?¿
thank you very much!
That and don't pull extended wheelies.
Quote from: koko64 on December 23, 2012, 03:45:52 PM
On my brother's IE 900, he picked up the 100 rpm we were looking for at idle that I couldn't get on the bleeder screws without causing "hanging". He's pretty happy that a cool lookin' little filter solved that problem. Maybe I should check his bikes compression..
have you checked the idle mixture? sounds like it's lean if winding the bleeds out won't raise the idle.
i haven't ever checked this, but i'll try next time i get a chance. i could do a 400 next week, maybe i'll try to find something bigger.
the air breathed out of the engine contains oil mist. the boxes are just large volumes to slow the breathed air enough for teh oil to drop out. a really large hose does the same thing. the hose coming out of the breather in reality is probably large enough.
i have a customer with a bimota supermono, bmw f650 single engine, and it has a single 5/16 hose from the engine to the airbox as a breather originally. it used to pump oil out the hose. with a clear hose you could see the oil making its way up the hose. he made a special box and it still did it.
an m18 fitting screwed into the centre of the alt cover (normally plugged, where you can get in to turn the crank) with a 1/2" hose out and around fixed it completely. all clear hose so we could see what was happening, never saw a drop of oil in there. the centrifuge at the centre of the cover due to the spinning alternator would have helped too, but the point is you need enough hose volume to allow the air to move with out dragging oil with it. a 650 single moves a lot of air in/out per cycle, and the breathing issues are worse with larger engines or fewer cylinders. if you look at the late bmw 1200 motor they run a hose close to 1" out of the plate that covers the cam gear access on the back of the head to the airbox. on the cam gear is a vane plate to once again give a centrifuge there. one guy who built a hot r1100s had one out of each side. the more breather volume you can get out the better. these days 4 cylinder bikes have windows in the bottoms of the bores between the cylinders, so the piston coming down can push air across into the others. with pistons rising and falling evenly spaced apart the breathing externally becomes much less of an issue.
look at the systems ducati put into the sbk, even the old 888 had a big carbon box under the tail. they have to catch all the oil due to dropping regs too, but there is hp in reducing crankcase pressure with good breathers. vacupan systems are better, but now illegal. just like open breathers.
Quote from: brad black on December 25, 2012, 03:54:11 PM
have you checked the idle mixture? sounds like it's lean if winding the bleeds out won't raise the idle.
~~~SNIP~~~
+1
I had an M900 that nearly drove me mad with that 'til I turned the trim up.
Quote from: brad black on December 25, 2012, 03:54:11 PM
have you checked the idle mixture? sounds like it's lean if winding the bleeds out won't raise the idle.
i haven't ever checked this, but i'll try next time i get a chance. i could do a 400 next week, maybe i'll try to find something bigger.
It was rich as buggery til we tuned it. Now its on the rich side of acceptable with a much stronger idle. I should clarify. I could raise the idle no problem, but not without hanging. The plugs were sooty and response was rich and fluffy, so I was having to open the air bleeds too much to compensate. Without touching anything the breather change leaned things at idle.
A PCIII is in the bikes future.
is it a 2001 (888) or 2002 (st)? i had in my mind it was 2002.
2001 900S. Last of the old chassis style. Nice bike.
why not just flash load it?
I'll see what he wants to do.
It's running so well now. I suspect it has a DP ecu or has been flashed to those specs from how much better it runs with an open airbox. I'll talk to you about it next time I'm down the shop.