superfluous vents

[MotoMike]

Seen in my welcome post on the right side timing gear cover, is a vent tube that someone put in. Also, where the compression release hardware used to exist someone alos attached a ven hose. both run over the top and back down behind the engine to exid in front of the rear wheel. as far as I can tell no oil exits either.

My mechanic friend in San Diego told me that they were added by someone who did not know what they were doing, that Ducati had the engine sufficiently vented and the extras were not needed. And the one on the timing case was vandalism.

thoughts?


viewtopic.php?f=3&t=3&start=40

[DewCatTea-Bob]

" on the right side timing gear cover, is a vent tube that someone put in. Also, where the compression release hardware used to exist someone alos attached a ven hose. both run over the top and back down behind the engine to exid in front of the rear wheel. "

____ Okay, I gather that somebody in the past had added those two additional motor-vent hose/tubing-lines and routed them both to vent-out in front of the rear-tire (and possibly in-between the tire & the inside of the rear-fender) ?
So then what about the stock-vent hose/tube-line? _ Did that one also get routed to vent-out in the same way?
__ I'm thinking that the guilty-perp had figured that he could reduce the internal-pressure within the motor by allowing the lowered air-pressure (between the fastly rotating tire & the fender), to help suck-out the (increased) air-pressure within the running motor... (perhaps the perp had figured that providing the extra air-passages for internal-air to get expelled [& perhaps even pulled-out?], would then give the motor an extra-edge since the underside of the piston would then have an easier-time compressing the crankcase's remaining internal air-pressures?).
Hard to say just what the actual-thinking was behind that added (breather?) mod.
__ Even if I figured correctly on what the intended concept was behind that, I don't agree with it providing any worth-while advantage.
As the stock one-way air-valve originally provided by Ducati for their non-off-road models, helps keep internal air-pressures form getting any higher than the external/atmospheric air-pressure, fairly well enough.
__ For off-road DUKE-models, or when-ever I've removed the side-cover which includes the stock air-valve,, I've always reduced the length of the stock clear-plastic/rubber-hose that's fastened to the stock hose-spout (found on the left-rear side of the motor-case), to just enough length to accept an automotive-type PCV-valve, and then route another (usually smaller) air-hose from the PCV-valve's outlet, to be attached very near the top-side of the drive-chain, so as to help keep the chain oiled (with the slight oil-mist that's expelled)... A good idea which Ducati also chose to do (in a more direct way), within their 160-motors !
__ Whether ya like my chain-oiling idea or not, I highly recommend my idea of adding a PCV-valve in-line (as close as possible to the motor), within the stock air-venting hose-tube line ! _ As that will help keep the internal crankcase-pressure in a negative-state (during running) !


Dukaddy-DUKEs,
-Bob

[MotoMike]

They had the stock vent running up to the top of the frame and along the right side to the rear where it exited clear of the body work and was zip tied under the license plate holder. It is a pretty good sized tube, probably 3/4". I think what my mechanic friend was saying was that this vent was adequate. I don't know where it was supposed to exit to atmosphere.

where is the one way valve at?

pressure in the crank case... wouldn't the volume under the piston be compressed on the down strok but a partial vacuum on the up stroke? both situations offering opposition to movement and steal a bit of power? wouldn't the best situation for power be a very free breathing crank case that offered little oppositon to the free movement of air in and out of the crank case? I know this is not a very earth friendly method. As to the green outlook, I can see keeping a slightly negative pressure in the crank case to keep all the products of running in the crank case.

I hadn't considered exiting the stock vent on or near the chain. more good ideas Bob.

`

[DewCatTea-Bob]

" They had the stock vent running up to the top of the frame and along the right side to the rear where it exited clear of the body work and was zip tied under the license plate holder. "

____ That's as like stock (for the non-Monza type DUKEs), except the long stock hose-tube was attached along the LEFT-side frame-tubing.
__ It now seems that I had given the perp/them too much credit for some kind of logical-thought processing. _ Cuz if "they" didn't have all three vent-outlets venting at a similar type of spot (like all somewhere between the tire & fender), then all those vents could not work-together for any common-goal.
And thus it seems your friend is right... the perp didn't have any sensible-idea of what they were doing.


" where is the one way valve at? "

____ On models which Ducati intended for city-riding, the stock air-valve is always located within the airfilter-body/side-cover.
A new flapper-unit works okay, but once they've become well-used, they then no longer do their job real well.
If ya ever hear the 'slow-farting' sound (right as the engine is coming to a stop), then your 'air-flapper' is still in fair working-shape.


" wouldn't the volume under the piston be compressed on the down strok but a partial vacuum on the up stroke? "

____ Relative to each other, that's certainly correct.


" both situations offering opposition to movement and steal a bit of power? "

____ Yes, that's also true.


" wouldn't the best situation for power be a very free breathing crank case that offered little oppositon to the free movement of air in and out of the crank case? "

____ Now this thought is where extra careful thinking needs to be more considered...
The answer to THAT wording (of the question) has to be 'no'. ...
To us, 'air' SEEMS like next-to-nothing, but actually, it does indeed have quite a fair amount of heft ! _ And requiring the engine to have to throw that fairly hefty-mass back & fourth (compressing & stretching) repeatedly, would rob a bit of power which could be better used for forcing the rotation of the alternator-flywheel instead (for instance).
So understandably then, it would actually be better overall, if somehow all air within the motor-case could be vacuumed-out & kept free of all air,, in order to relieve the internal motor-parts from having to deal with any air !
A PCV-valve helps to do such action -(of keeping internal air-pressures as negative as possible), as best as can be done. _ And so that's actually better for both our 'green-world' AND our motor's running !!
__ If you can't put separate PCV-valves on all three of your vents, then I'd suggest connecting your two extra vents to each other, (if not plugging them both separately). _ However, I can see where an added air-valve on the cyl.head (& connected to a hose-tube), would help to keep the common-problem/issue of oil-seepage from the head-covers, down to a (better) minimum.
And now that I think of it, I really wish I had tried that idea to see if it would actually help that issue! _ I think that it would have to help (that common dirty-head issue).


DUKE-Cheers,
-Bob

[MotoMike]

So the Duc singles have leaky heads? I was impressed with what I thought to be a very oil tight engine. outside is pretty clean. maybe the vent in the compression release hole is doing something.

I said the stock vent passed down the right side. don't know why, its' on the left.

hmm. negative better than free flowing. just as a nerdy academic exercise I consider: that all that hardware spinning around in the crankcase would benefit from a less dense atmosphere if it didn't contribute to changing the volume of the crank case. that is to say all the gears and fly wheel would experience less windage by having less air or a partial vacuum. but the piston seems to me to be different. akin to trying to suck on a soda bottle compared to sucking on an open straw. so on the up stroke in a closed crank case seems to me would rob a fair bit of power. I guess there are lots of people, probably Bob included, who have practical experience where they have determined the reduced windage on all the coponents spinning in the partaial vacuum would outweigh any loss of the upstrokes effect on pulling a bigger vacuum. I know in hot rodding we try to reduce the oil suspended in the crankcase atmosphere to reduce drag.

Seems like I recall seeing some motorcycle that had a mechanical timed crankcase breather. I suppose this was an effort to address these issues. Cant remember what it was on though.

[DewCatTea-Bob]

" So the Duc singles have leaky heads?

____ Well not really (when ya put it that way)... It's just that after about 500-miles of normal riding, (more or less depending on the amount of dust on the roadways driven), the cyl.head (as well as other places), pick-up dirty-dust which sicks to the very-light oil-mist -(that must seep from most all the seams between the head-parts), which over time gets slightly oil-coated over those surfaces -(which then pick-up the dirt).
__ On the cyl.head, there are four spots which contribute to this common-issue fairly more so than the rest of the seam-areas... And that's the two-pairs of upper screws for the pair of valve-covers. _ Those two upper screws (on each valve-cover) are both located in holes which go-through into the holes for the rocker-pins (within the head), and thus without any gasket-barrier to help prevent oil-misting from escaping though that pathway.
That's why some post-1970 DUKEs finally started coming with 1mm-thick aluminum-washers for just those four cover-screws !


" I said the stock vent passed down the right side. don't know why, its' on the left. "

____ It seems then, that I must still not understand exactly what you're trying to point-out with that wording, for making whatever point. (?)
Can anyone else here who gets-it, please try to bridge-the-gap for me?


" negative better than free flowing. "

_____ Yes, I believe so...
___ The question here is, which is tougher (aspect 'A' or 'B') for the engine to cope/deal with (thus rob the greater amount of power),, EITHER,
_'A' - the underside of the piston being forced to suck-up & thus create an even lower air-pressure within the crankcase, which will then of course make it even harder for the piston to be pushed toward TDC, (since the piston has to push the air above it seemingly while at the same time also having to work against an increased negative air-pressure -[suction] that's created below itself, in the motor-case),, OR,
_'B' - the underside of the piston being forced to reciprocate (as close as possible to) a standard-atmospheric volume of air equivalent to the cylinder's displacement.
___ For anyone who's kind-of lost at this point, I -(DewCatTea-Bob), am not in agreement that 'B' is easier for the engine/piston to cope/deal with, (for a motor-case that has FULL-venting, versus a motor-case that maintains "negative" -[with respect to std.atmospheric-pressure], crankcase-pressure).


" that all that hardware spinning around in the crankcase would benefit from a less dense atmosphere if it didn't contribute to changing the volume of the crank case.
but the piston seems to me to be different. "

____ Yes, I certainly agree with that -(that any air within the motor-case tends to impede otherwise free movement of any moving-part within, [regardless if what-ever moving-part tends to alter the internal air-volume, or not!] ) ! _ (However, with our relatively low-pressure atmosphere, that included drag is not really worth getting much concerned with.)
And that point made, it can also be understood that as a std.atmospheric-pressure increases, the internal drag-factor would also increase and become more & more significant (for ALL internal moving-parts to deal with!) ! _ (And with that common-sense thought held in mind, ya may want to skip-down to the similar reasoning of the sentence pre-marked with this * mark.)
But that common-sense thinking applied to moving-parts which don't alter the internal air-volume is not so difficult to grasp, as is the additional effect that the working-piston has.
And so it seems that I must pull-a-rabbit-out-the-hat to come-up with a convincing point for backing-up my (likely correct) view-point ! ...


" so on the up stroke in a closed crank case seems to me would rob a fair bit of power. "

____ It certainly SEEMS that that added effort would tend to rob a bit of power but, probably not a 'fair-bit'/noteworthy-amount, at least when compared to making the piston throw a cylinder-volume's worth of air back & fourth. _ And besides, even if the created-suction under the piston was indeed significant, that very-same added-suction would, (much like a valve-spring), give right back (to the engine-power), that which it had just taken,, during the following down-stroke of the piston !


" I guess there are lots of people
who have practical experience where they have determined the reduced windage on all the coponents spinning in the partaial vacuum would outweigh any loss of the upstrokes effect on pulling a bigger vacuum. "

____ I'm really doubting that (in reality) any reduction in 'air-drag' on all of the internal moving-parts, would come close to an amount of savings that could fully compensate for the loss of the (relatively slight), (pushing)- pressure below the piston (IF that [temporary]- loss was indeed actually a permanent-loss every time the piston was raised ).
So, therefore that considered ratio -(aspect of give&take), is actually a NON-concern !
____ And now finally to my "rabbit in the hat" ...
_ * Much like the previously-mentioned common-sense thought, it should be easy to understand that the more air that gets into the motor-case, the denser & heavier (& thus harder) it is for the piston to move (a cylinder's volume of) it back & fourth and compress (within the motor-case's volume) !
And going the opposite way, if the air within the motor-case could be reduced-down to become a 'total-vacuum' (and maintained that way), then since a total-vacuum canNOT possibly be made to become even more of a vacuum (than it already is), then the raising of the piston would thus create NO increased difference !
(And here's the "rabbit" itself)...
With that point understood, then it should stand to reason that keeping the crankcase's air-pressure as low as possible, would then make the (repeated) reduction of the internal-pressure, (caused by the raising of the piston), that much less significant,, but MORE importantly (on-the-other-hand), the (reduced) air-pressure within the motor-case is then going to resist the DOWNward-movement of the piston that much LESS ! - (That's along-with somewhat less [slight power-robbing]- air-compressioning into the crankcase, of course!)
__ So bottom-line... let's all say NO to letting any air get into the motor-case !


" Seems like I recall seeing some motorcycle that had a mechanical timed crankcase breather. "

____ Not sure if I've ever heard of such before. _ I guess if well sealed & properly timed with the (normal) delayed-movement of air-mass (like camshaft-tech does), then I suppose that kind of one-way venting could possibly work to more greatly benefit the engine.
However, I would have to examine the theory as to how it could possibly do the job any better than a PCV-valve or a reed-valve type 'air-flapper' like those used on DUCATI-models -(which came stock with such).


Fun-Cheers,
-Bob

[Jon Pegler]

Norton twins had a disc valve driven by the camshaft, that was timed to expel crankshaft gases on the downstroke and close when the pistons were travelling up.
I'm not convinced that it was very effective. Having owned a number of Nortons over the years, they all tend to be a bit oily.
I've always found the standard breathing on Ducati singles to work farly well.
Any other breather pipes are usually not necessary.
Your friend in San Diego was probably right.

[MotoMike]

[quote="DewCatTea-Bob"]"


"It seems then, that I must still not understand exactly what you're trying to point-out with that wording, for making whatever point. (?)
Can anyone else here who gets-it, please try to bridge-the-gap for me?"

___Bob, I was not making a point here, you had asked where the stock vent was routed. I got my left and right mixed up and was just correcting my answer.


" And besides, even if the created-suction under the piston was indeed significant, that very-same added-suction would, (much like a valve-spring), give right back (to the engine-power), that which it had just taken,, during the following down-stroke of the piston !"

__Aha! That, I had not considered and it makes perfect sense. I believe you have convinced me.

As I said before it was just an exercise. fun to think of these things and be surprised when something pops up you had not expected and would not have considered if not going through the discussion. Thanks Bob

[MotoMike]

Norton twins had a disc valve driven by the camshaft, that was timed to expel crankshaft gases on the downstroke and close when the pistons were travelling up.
I'm not convinced that it was very effective. Having owned a number of Nortons over the years, they all tend to be a bit oily.
I've always found the standard breathing on Ducati singles to work farly well.
Any other breather pipes are usually not necessary.
Your friend in San Diego was probably right.

Thank Jon. I didn't know that. Not sure if that is the one that I remembered. seems it might have been one of the old Italian Marks, but don't know for sure.

[DewCatTea-Bob]

" I was not making a point here, you had asked where the stock vent was routed. I got my left and right mixed up and was just correcting my answer. "

____ Ohh!, now I get it. _ Thanks for that clarificationing _ (I had previously taken/interpreted that wording completely differently.)


" That, I had not considered and it makes perfect sense. I believe you have convinced me. "

____ Well that was too easy ! _ As I believe that you had read my post well before I had finished it.
(I had then been having much trouble trying to enter my additional/updated post-edits due to 'Server Unavailable' type notices repeatedly presented instead of the expected w.site pages !)


" As I said before it was just an exercise. fun to think of these things and be surprised when something pops up you had not expected and would not have considered if not going through the discussion. "

____ Right-On Mike, as that's how & why I got involved to such an extent with the subject,, as it seemed at first to be some kind of brain-twister/teaser that was somewhat fun to work-out, and get my mind into-gear with. _ So thanks for that.
__ Everyone ought to think-out such twisters every now & then, or you'll loose your ability to solve such puzzling presentations.


Fun-Cheers,
-Bob