| Author | Message | ||
     Andymnelson |
I posted this over in the Knowledge forum, but it seems things don't get answered too often over there. Maybe the mods can move the discussion there after answers are brougt forth? I have an '03 XB9S. My question is this: While I understand the obvious benefits of re-routing the breather lines out of the air box and not having our engines re-burn the spooge, has anyone experienced negative effects in how your engine runs after such a mod? Here's my hang up- a PCV (positive crankcase vent) valve always has the hoe running into airboxes- where there is vacuum. It would seem to me that a system with such a design would need said vacuum to function properly. Perhaps it's not enough vacuum to amount to anything, but I would suspect that for a properly operating system you would need it. My thoughts on an alternative? Maybe a couple of small filters capping off the stock lines INSIDE of the air filter. This would give vacuum still, but filter the spooge, which can in turn run back down into the motor. In the meantime, I have done this: I noticed that I really only get any oil coming out of the rear head, since it's hose is so short. So I bought 2' section of vac hose from NAPA and routed it forward, around the throttle body and then around and into the airbox. This extra length of hose seems to do the trick, almost in the same fashion as my filter in a filter idea. I have not had any oil inside my airbox since doing this and about 600 miles. EDIT: holy crap I can't spell :-p "Breather Questions"... (Message edited by andymnelson on September 02, 2008) | ||
| Point_doc |
I did this... (Message edited by point_doc on September 05, 2008) | ||
| Andymnelson |
Cool. Hard to tell, but it appears to be basically what I was suggesting? | ||
| Andymnelson |
Perhaps my question was too buried in my post: "My question is this: While I understand the obvious benefits of re-routing the breather lines out of the air box and not having our engines re-burn the spooge, has anyone experienced negative effects in how your engine runs after such a mod?" Anyone? | ||
| Point_doc |
After installing the filter, I felt that my throttle response was sharper. I rode the other week with a tuber that had the breather line running exterior with a filter and I was surprised of how much junk that would exit thru the filter, especially during deceleration. After viewing this, I most likely will move my line to run outside the air box. First I am going to design, model and machine (cnc) a catch-can. For now, I will continue with my current setup. | ||
| Wantxbr |
Andy American Sport Bike has found on the Dyno that you actually gain HP with the Breathers rerouted. You don't need vacuum for the breather to work properly. Install a catch can and you will see the kinda of junk that is going in your Throttle Body. Point Doc wrote: I most likely will move my line to run outside the air box. First I am going to design, model and machine (cnc) a catch-can. Really!?!?!?!?!  (Message edited by wantxbr on September 03, 2008) | ||
| Firebolt32 |
I actually just installed one on Monday. There is an obvious difference when shifting. It's so much smoother feeling to me. Very easy to do...I'll post some pics when I get home from work. | ||
| Teeps |
Andymnelson Posted on Tuesday, September 02, 2008 "My question is this: has anyone experienced negative effects in how your engine runs after such a mod?" I have noticed nothing negative since then. But note: the law of placebo states there will, always, be improved performance perceived by the doer. | ||
| Al_lighton |
With an inline 4 or parallel twin engine, the crankcase volume is constant. One piston is going up at the same time one is going down. Intake vacuum on the breather lines can be beneficial to evacuating the blowby gasses from the crankcase and it enhances ring seal to do so. So power gains from routing the breathers out of the intake are less significant. On a common crankpin twin like HD and Buells, both pistons are going up and down together, 45 degrees out of phase. There is a huge amount of pumping going on below the pistons. The intake draw on the breathers is much less significant for crankcase gas evacuation because of the positive pumping occurring on the bottom side of the piston. Al | ||
| Andymnelson |
Thanks Al. I think this is the answer I was looking for! I was trying to rectify taking the vacuum out of the equation, and not ending up with too much pressure in the top end and ending up with oil leaks and such. Thanks for the input. | ||
| Retrittion |
I want to do this mod but I need some pictures that show the how/where/what -- either that or someone in the Olympia WA area that has done it and can show me. I don't know about everyone else but I work better when I have seen what it is supposed to look like when I finish (so I know that I buggered it up and need to redo it, yeah?).  | ||
| Andymnelson |
Fair enough, but which mod? Several things have been discussed here: 1) I simply lengthened the read head breather tube to help diminish the spooge in my airbox 2)Point_doc put a filter on his breather tubes inside of his airbox 3) Others have removed the breather lines form their airboxes and mounted a catch can and filter elsewhere on their bikes | ||
| Moosestang |
There is not any actual vacuum pulling crank case gases(and oil) out of the engine, is there? On my car, I have a vacuum hose that connects after the throttle body so it is exposed to intake manifold vacuum. I installed a catch can that filters out oil, but still allows the vacuum to suck the combustion blow by out of the crank case.  See the aluminum can on the left of the air filter, that thing collects a good 4oz. of oil over a 3,000 mile period, maybe more, maybe less, it depends how I drive. That oil would normally go into the combustion chamber and be burned with the gas/air charge. Not that big of a deal on a stock motor, but enough oil will lower the octane of the fuel and could cause detonation. Now i've taken my air box off and I know the breather hoses are inside the airbox, but before the throttle body. Therefore no vacuum. I did not see any oil inside the airbox and didn't feel any inside the hoses. Is this really a concern? | ||
| Andymnelson |
My concern is that since there IS a certain amount of vacuum in the airbox, if the engine design relies on said vacuum then removal of vacuum may not necessarily result in poorer performance, rather have such negative consequences as blowing out gaskets and creating oil leaks due to the built up pressure in the heads. Not saying that's what happens, rather just asking the question. | ||
| Cycleaddict |
take a look at the bottom side of the breather assembly (it is inserted into the top of the rocker box )the holes that actually let the crankcase pressure into the "umbrella " valve are so tiny, (4 rectangular slots, about the size of a paper match) i don't see how these motors can effciently vent crankcase pressures ???i've seen larger vents on 5 h.p. Briggs motors ! | ||
| Moosestang |
take a look at the bottom side of the breather assembly (it is inserted into the top of the rocker box )the holes that actually let the crankcase pressure into the "umbrella " valve are so tiny, (4 rectangular slots, about the size of a paper match) i don't see how these motors can effciently vent crankcase pressures ???i've seen larger vents on 5 h.p. Briggs motors ! Maybe that's why you see so many oil leaks.  |
