| Author | Message | ||
     Bigbadbuell |
i see alot of people talking about using a catch can and making all kinds of systems. why doesn't any one use a exhaust pull ?? i have used them on drag cars and what not and they work good. the only think i can is maybe some small mods to the valve in the rocker cover. but if any one knows why don't these people use one?? i would rather just let it burn up in my exhaust than draining catch cans and cleaning up spills and pukes. hollar back Bigbadbuell | ||
| Tx05xb12s |
I would be interested in hearing more about this too. Currently I am running hose from my PCV valves to a catch can, which is vented with a K&N filter. Interestingly enough, I have yet to drain any oil out of my can, but I did get a few drops of what appeared to be water drip out the first time I rode it after the conversion. The can has been empty after the four rides since. I'd be interested to know if the sucking action routing out to exhaust would provide a performance increase or create a problem with the function of the engine. Anyone done this on an XB? | ||
| Pwnzor |
Shouldn't be any oil in the can, it should be some sludgy water. I drain mine after every ride and get about .5 to 1 oz. of fluid. It won't "burn up" in the exhaust because water doesn't burn. It would escape in the form of vapor, as most of the water does in the catch can system. What ends up in the can is the small amount that cools enough to condense into liquid. Negative pressure in the rocker boxes is a bad idea for some reason I can't recall other than I read it somewhere on this board from somebody in the know. The breather/catch can systems are cheap and easy to install. | ||
| Old_man |
It seems to me that such a system would create a suction on the crankcase which may not be a good thing for the engine. | ||
| M1combat |
I think the oiling system uses gravity to feed the cams and all that stuff down there... Negative pressure in the rocker boxes would impede the flow? | ||
| Bigbadbuell |
Well the reason i asked i have used on many many drag cars that i have put together. And also i have hp gains with a crank case draw we gotten almost 30 hp. and its easy i will take some pics and make some drawing to show yall how i do it on drag cars. we also used a s10 vac pump for smog control later bigbadbuell | ||
| Bigbadbuell |
oo ya the neg draw on a crack case is a super common thing and also there is a flapper valve that uses presser to open it in the head. Its alot like pcv valve but just burns out the exhaust. All u need is a one way valve its a smog valve for a 86 threw 93 mustang. and then all u need is 4 inchs of pipe with 3/4 pipe treads and then angle the pipe in the side of header collotor at 45 deg angle. and then just run the rubber lings form ya rocker cover to the one way valve. how easy is that ?? i will get some part numbers for the smog valve and a drawing or a pics of a set up. later bigbadbuell | ||
| Bigbadbuell |
I think the oiling system uses gravity to feed the cams and all that stuff down there... Negative pressure in the rocker boxes would impede the flow? the oil system is a system that under pressure and it and the other parts that are oiled form the oil flying around over spray shouldn't stop. things still flow in a neg pressure evnroment just like they do in a postive one | ||
| Firemanjim |
Vacu-Pan set-ups were just coming into play in the early 70's when I was doing a bit of bracket racing. We used a valve on the header-3/4" pipe welded in at 45* angle-- IIRC it was a one way from a GM smog pump(gulp valve) and ran hose to a flapper type smog valve from mid 60's Oldsmobile. The gulp one way valve was to keep any positive pressure pulses from engine and the flapper valve was to separate any oil out.Might want to hook it to hole in cases for timing instead of rockers. | ||
| 2_spuds |
Here is a link to a discussion on crankcase checkvalves and negative pressure benefits. http://www.eurospares.com/sucker.htm | ||
| Bigbadbuell |
the only thing pulling it form a diff loaction would it suck the umbrelle valve back threw and maybe cause damage to that part ???its just a rubber flapper and oo ya i am looking at 2000 x1 motor i anit really shure what ever one else has. | ||
| Cyclonecharlie |
XB's don't use the umbrella valve(they were removed) when they started using the PCV valves. I have XB rocker boxes on both of mine and routed up and out the back. Don't see the need for all this extra stuff(catch cans or a breather into the exhaust) Seems like it would damage the packing in your(costly) exhaust system............Charlie | ||
| Raceautobody |
Well instead of plumbing it before the muffler why not to the muffler outlet tip? Al | ||
| Bigbadbuell |
on the plumbling it wouldn't really burn or vaporsize the smog blow buy and water vapor and doesn't ya exhasut all ready burn oil and foisle fuel any way??? soo how would a lil more hurt i belive i am going to set up a system better than the catch can any day but i think i am going to swap to xb rocker covers thanks for the comments | ||
| Bigbadbuell |
hey jack u can make a negtive presser set up wiht a one way valve with exhasut like blowing over a drink straw the bottom of the straw will make a vaccum. i will get some drawing or post some pic here soon when i get back to may shop later bigbadbuell | ||
| Cyclonecharlie |
Wes, The XB rocker boxes are a big improvement over what you have, I put them on my 2000 cyclone. You can eliminate the breather set-up on the side of the heads altogether(replace with bolts to hold throttle body)..........Charlie PS And the parts are fairly cheap, always a plus. | ||
| Blake |
On a street bike venting the crankcase to the header will eventually gunk up your muffler and make a real mess over time; think hot tarry glop dripping from your tailpipe. And as already mentioned by smart folks above, if you don't know what you are doing, you could end up with a very poor crankcase venting system. My catch can has yet to accumulate any oil. | ||
| Oldog |
BBB: I have a can and I get oil water mix vast majority is water, are you building a race bike or a streetable one? have you sold the CF yet?? I agree with Blake the crank breathers in the exhaust is a bad idea for the street. | ||
| Bigbadbuell |
bad news on the carbin fiber i was going to load it up on the truck but it roll and kissed my buddies truck and busted the fount vender and wind srence. the reast will make it up here soon. plus i had street mustangs with that set up and it doesn't have any gunk or nasty in it and i like the idea of removing the blow bye in motor. | ||
| Djkaplan |
How exactly does a Harley engine deal with the internal volume change during crank rotations? With only 45 degrees of separation, there has to be a point where the volume is dropping pretty fast. Does the internal pressure rise to accomodate this? How much of this pressure makes it past the tappet blocks and through the pushrod tubes? What happens to this pressure? | ||
| Jackbequick |
It all vents through the breathers on the rocker boxes as near as I can tell. If you hold your finger over the end of a breather tube (on a tee with both breathers on it) you feel an intermittent pulsing there at idle. The pressure seems to rise and fall but I don't think it ever goes negative (suction) or even falls to zero. The rate of the pulsing increases with the RPM and it feels like a continuous light stream of air at higher RPM. If you pinch the breathers off (I did it once by accident) higher speeds will cause oil to vent from the vent up under the rear fender on a M2. That vent comes off the transmission case if I remember right. So if the breathers are not open, the pressure vents through the primary/transmission area of the case. But that appears to bring some oil with it, probably from all the oil sling from the gears. Jack | ||
| Bomber |
next time you're at an AMA flattrack race, wander into the pits and take a look at the linear mile of hoses running around the outside of the XR750 mills seen there -- one of the major issues they are trying to address is exactly the subject of this thread -- there's lots more ju ju inside where ya can't see it, such as timed breathers and the like given the relatively understressed natiure of our engine's operational environment, the catch can is a simple, practical way to address the spooge that some, not all engines produce -- me, while not laying awake at night, I wonder why some engines, Blake's for instance, propell no oil into the catch can, and other's, like mine, DO send some sppooge into the aforementioned containment vessel ------- | ||
| Djkaplan |
I think he may mean he only finds spooge in his catch-can, not oil in it's natural state. I still wonder how the engine deals with the volume and pressure changes in the crank. The crank is vented through the the rocker covers, but the path that connects them is pretty torturous - throught the tappets and pushrod tubes. The engine can't be blowing all this volume back and forth through the tubes, could it? I think the crankcase must be pressurized by the pistons as they come down together and depressurizing to a certain degree as the pistons go back up. I'm sure this is the reason why engine oil is forced into the primary when the seal at the crank fails. Some of the excess pressure must be bled through the tappets and pushrod tubes, but all of it can't be, not at the speeds the engine runs at. This engine is so simple, yet so much of it remains a mystery to me. | ||
| Bomber |
Dj likey correct -- not oil, perse, but certainly oily spooge -- thanks for your clarification -- still, some seem to produce spooge in prodigious amount, some much less so, most all seem to be dependant on operting parameters and meteorilogical conditions -- large variance -- ah well take off the fittings at the rocker vents, and start your motor -- place your hands near the vents -- the path does seem rather circuitous, but there's lots of volume coming out, for sure -- dunno if it's ALL of it, but a large amount | ||
| Djkaplan |
Not a lot of volume comes out of my breather lines, especially when the bike is warmed-up. Most of the positive pressure and volume seems to be at start up... a lot of it goes away after the bike warms up. I think most of this is cause by blow-by at the rings when the engine is cold. After the piston expands, the rings seal better and blow-by lessens. I'm assuming all of this, btw. You know what that means... I'm still at a loss as to how the engine deals with the pressure rise and fall in the crankcase. If all of it somehow goes out through the rocker covers, how does the engine deal with the vacuum that must be left when the pistons go back up? What the hell is going on in there? | ||
| Cyclonecharlie |
DJ, If you really want to know, put a pos./neg. pressure gage in the timing hole and see what different rpm's give you for pressure(+ or-). Not sure what you would do with the info...........Charlie | ||
| Road_thing |
Seems like we had this discussion a few years back... Read through this stuff and see if it helps. Blowby past the rings also puts pressure/volume into the crankcases--it's probably hard to separate that effect from the pumping effect of the pistons. rt | ||
| Rocketman |
What is the purpose of that conical shaped coil spring in the oil filter housing with the ball valve on it? Could it be that the spring tension has a relationship to excess crankcase pressure or excess oil bag pressure? Is it the reason for blowing oil out of the vent or blowing the cap off the oil bag, or has it nothing to do with either? Rocket | ||
| Blake |
DJ, Once the engine gets to cranking, it can actually setup a resonance in the crankcase such that the entrapped vapor there (it ain't air) is pushed and pulled back and forth so quickly that it just doesn't have time to exit via the breather system. The breather system is there to allow blowby to escape. Blowby should subside above idle and for larger throttle openings, read higher combustion pressures, as the rings are then subject to higher pressures that greatly aid their sealing to the cylinder wall. That's the general theory anyway.  | ||
| Blake |
Additionally, the umbrella valves in your rockerboxes are one way valves. They only permit exhausting of the crankcase. |
