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  #31  
Old 22nd October 2019
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i assume you are talking about umbrella float.
if you view this as a closed system, what only can escape is what sneaks past the piston assuming leak past crank seals are too small to be of any significance.
assuming once again the numbers only, the blowby is pretty much consistent at .0626 or .0125 from the pedia.
while there is a slight transition to positive it occurs only near the peak value where it is high enough to overcome umbrella/atmospheric pressures.
for grins and giggles, this would occur in the last 20% of the cycle and the law of averages controls 80%. the basic over-all pressure is negative. the newer designs are more u-tube and open ended at that so it does not take much to move the oil.
the bag has restriction and it has to rely on the umbrella and it is of smaller volume so the readings will be diff.
the only way to tell would to put a data logger on the machine and run it through the paces.
as a side note, all the oil has to do is get to the pump, past that, no longer needs any assistance as the pump takes over. also is that with the u-tube, rising oil level in the flywheel compartment would just spill over, by gravity, perhaps hd way of controlling oil pooling at high speed.

Last edited by bustert; 22nd October 2019 at 22:18..
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  #32  
Old 22nd October 2019
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This my gatherings on 'extra' air.

Ring flutter around 5000 RPM and higher is thought of as the main culprit on a healthy engine.
Gasket / air leaks react the same as ring flutter but at a lower RPM.
They allow more air into the engine that add to the positive and take away some of the negative (vacuum).
So the introduction of air leaks into the crankcase lowers the RPM at which pressure changes affect the system.
Worn / stiff breather valves that do not fully close will allow more air at atmosphere into the crankcase.
This lowers the vacuum and contributes to higher positive pressure on downstroke changing the ratio at a lower RPM.

assuming once again the numbers only, the blowby is pretty much consistent at .0626 or .0125 from the pedia.

That's why I believe stroke timing has it's say in the midrange.
Couple working pressure with the increasing speed of the pistons which helps to equalize positive and negative pressure during operation.
As engine speed increases, there is not as much time to build vacuum on upstroke or positive pressure on downstroke due to the faster changing piston positions.
Just as you can inhale air slowly and fill up your lungs but faster breathing will not allow you to fill them due to the faster time that you exhale.
This would make for a shorter range of (both vacuum and positive) pressure that would be able to build in the crankcase.
So the internal pressure is more stable until extra air (blowby from ring flutter or other) is induced into the crankcase.
But stability doesn't help scavenging as much as pulsations do.
So there may be more oil pooling when the pressure is stable which contributes to higher windage and positive pressure during that time.

I wouldn't imagine it would pool up to the shaft though without other issues beginning.

edit:
There would be massive wheel drag before then.

Least not forget about the timing of the breather valve closing.
Guess we could call that umbrella flutter. The faster it closes, the more vacuum is kept in the crankcase.
The slower it closes, the more air is allowed to lower residual vacuum.
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Last edited by Hippysmack; 22nd October 2019 at 22:46..
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  #33  
Old 23rd October 2019
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if this is true, hd designed the engine wrong and all would be doing it.
bit busy at the moment putting up metal on my extra shop but will jump back later.
also of note, this is not consistent data between engines with diff hours run time so it does not hold water (actually gas).
the sportster engine can easily take 8k so banging out at 5k does not make sense.
will be back.
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  #34  
Old 23rd October 2019
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Don't get me wrong, I'm not saying it's dead at 5000.
But there does seem to be a pattern emerging.
This is Aaron's breather vent testing.
Around 5700? there is a dip in HP.
It does pick back but rises slower after that. Of course there are lots of factors in that though.
That dip is a sliding figure also.



At the point, there is more blowby and you should be getting better scavenging.
And as long as the breather valve is up to par, you shouldn't have excess oil in suspension.
But higher windage can pick up oil faster. Again, it's all a balance.

This where he tested different breather valves.


But for those of us that live between 4000-5000, we can end up with sustained time around that dip.
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  #35  
Old 23rd October 2019
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first on the subject of so called ring flutter.
there are two type and a good engineering design is the first weapon to prevent it, the very reason i believe this issue is not that. the history of the hd design does not support that.
as far as dyno runs, you can run ten and get diff results and dips and twist are common and not always accountable to a certain mode of operation. it is a good tool but i have seen "seat of the pants guys" smoke the so called dyno tuned engines.
AXIAL FLUTTER:
this type usually begins at the ring gap and mostly at medium load and high rpm. this would fall into the cruise range but then again, who cruises at high rpm (guilty as charged) and it would tend to rule out hard acceleration since engine demand is high, so it is a crap shoot. on this point, even "IF" you attribute the so called dip in the graph, probably WILL not be there on the road, toooo many variables!
this ring movement refers to the lifting of the piston ring off the bottom flank contact area and as i said begins at the gap as it is the weak link (spacing). this allows motion of the ring ends which in turn sets up a wave pattern that gets transferred to the entire ring, sorta like throwing a rock into the water.
engineering with low ring heights and more pressure on the gap area has a tendency to reduce this flutter.
past engineering, what elese to consider?
1. excessive ring height clearance
2. loss of ring tension which compounds gap loss of pressure, of note: diff ring shapes play a factor
3. mechanical contact (head strike)
4. fuel burn issues, aka, knock and such
5. worn out piston land grooves
6. groove base gas volume too low due to build up behind the rings.

i am going to break this up so as to be readable.
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  #36  
Old 24th October 2019
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There have been many engineering changes over the years to combat wetsumping and ring seal. Check.
There is an article from the MoCo somewhere around the house, can't find it right now, regarding ring flutter from the IH days.

But Evos also battle excess blowby at high RPM. That's how gapless rings came about.
Then they found gapless rings sealed pretty good but weren't very helpful for scavenging (less blowby - positive pressure) in the mix.
So the problem hasn't been engineered away.
It may be better but it's also important to note that the these tests were performed on healthy engines.
Adding to your list, results will vary depending on compression ratio, piston size, health of the oil pump and a host of differences including varying degrees of wear as you mentioned.

Undoubtedly, Aaron spent some time on this.
According to him, the variable breathing methods tested were within the repeatability of the measurement.
And again, he was just looking HP changes.

10 best pulls from the stock configuration.


10 best pulls from timing plug vent configuration.


Just sharing what I've learned Buster, the only thing I'm really good at is tearing stuff up.

Last edited by Hippysmack; 24th October 2019 at 06:17..
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  #37  
Old 24th October 2019
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RADIAL RING FLUTTER:
excessive increase of gas pressure on the ring sliding surface during combustion. this disturbs the balance of forces briefly and forces the ring to lift off the sliding surface (ring to wall). when this happens, the ring can no longer seal and the constant repetition leads to ring fluttering.
reasons:
1. worn rings (loss of pressure force between ring and wall and ring stiffness)
2. out of true bore which allows ingress of combustion pressure into gap and ring to wall
3. asymmetric piston wear from bent connecting rods. the ring will follow a slight oval travel path due to being out of plumb. this oval pathway allows combustion pressure to enter the top ring land, piston ring and cyl wall on the side with less contact.
4. excessive, crowned wear on the sliding surface of the piston ring due to excessive height clearance.
5. damaged ring edges due to incorrect honing. ( the ring is torn open and frayed on the ring edges, more pronounced on cast rings without coating). gas pressure enters and lifts the ring off the wall.

the straw and "BB" rule.

if i take a straw and shove bb's through one end, eventually they will exit the other end. the hd when started is like shoving bb's into the straw and eventually a point is reached, bb in/bb out. it can only vent what comes in, it is a closed system unlike a car engine.
when you exceed a car's pcv system, what happens?? well, it backs up through the c/c air inlet usually plumbed to the air cleaner, not counting newer systems.
what happens when the hd vent is exceeded?? remember it is closed!!
for grins and giggles, say a stroke produces 24cc of vent, now multiply by rpm. now calculate orifice capacity and subtract the diff, the given rpm where it is exceeded will be the tipping point for a transition to a positive pressure. we know this is a scaled process, sorta creeps up on ya!
the umbrella is not an on/off switch, in fact, it might not even reach full open. with the law of averages, the negative and positive balance out and the victory goes to the strongest and can last the longest, aka, vacuum wins. this is what you are seeing via the manometer.
another point of interest is volume, the ratio between piston up and piston down. for grins and giggles let us same piston up and piston down are equal, this equates to a 2:1 ratio.
for grins and giggles, take two bicycle air pumps, one 2" dia and the other 3" dia, but both having the same stroke. which one will achieve highest pressure per timeline frame?
so the big "?" is can oil flow with negative pressures, why sure, all that is needed is a diff'l. also of note, a negative pressure also reduces aeration oil the oil.
how you say, well, pressure has a tendency to make the bubbles smaller, aka less surface area to interact with fellow bubbles. now with reduced pressure, the bubbles expand and surface area increases which allow more interaction with fellow bubbles which then has the effect of joining the two. if you ever scuba dived, and look up, you can see this in action.
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  #38  
Old 24th October 2019
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on the graphs, you can still see variation, point made. vented out the timing plug basically just tightened the graph but diff'l is still not that great.
it is like going down hill with skates one with dragging bearings and one with well oiled bearings, gravity being constant, yes there will be diff'l but not by much.
remember the ole brain tester?
drop a pound of marble out an airplane and a pound of feathers out at the same instance of time at 5k feet, which will hit the ground first???
back to the graphs, this will all change with even the slightest of change with a controlled variable. put this out on the track or road, was a good tool anywho.
i know you are a hot rodder so you know a run in the morning will be diff from a run in the afternoon.
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Old 24th October 2019
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Why is the ratio of positive and negative pressure important?
It takes a balance of the two to run a Sportster engine.

Piston upstroke creates negative pressure and suction of oil from the sump.
It pulls oil up in the form of oil mist to be tossed around on the moving metal parts.
So it is important for lubrication and it does keep down aeration as you mentioned.
But without the reciprocating piston downstroke, there wouldn't be a lot of force to help splash it around other than the spinning wheels.
The upstroke pulls oil into suspension (air/oil mist) so the downstroke can help blow the mist around working in conjunction with flywheel and cam rotation.
Negative pressure is also important for ring seal as it allows the rings to fully seat on the bottom of the ringlands during upstroke decreasing blowby.
Too much negative pressure is detrimental to oil scavenging as it allows more oil to be pulled up into suspension instead of moving toward the scavenge port in the sump.
The bulk of gravity oil on the sump floor is heavier than the moving air.
But the spinning action of the flywheels can pull that oil up to be slung around the wheels creating more drag as it does.
So it's important to get the excess oil in the bottom out of the engine as fast as possible to keep down flywheel drag.
That's where the positive pressure comes in.

Positive pressure is important for oil scavenging as it works in conjunction with splash lubrication as well as the suction of the oil pump.
The positive pressure generated by the downstroke pushes oil toward the scavenge pump to be sucked vertically into the oil passage to the pump.
So there is a balance of positive and negative pressure that has to be maintained for overall engine operation.

The role of positive and negative pressure can be confusing.
Even though there is a positive 'push' on internal pressure through piston downstroke, the overall internal pressure is still negative.
It's just less negative than it was before the downstroke. This creates a pulsing effect on oil in the sump which helps shift the oil toward the scavenge port.
Even though there is normal blowby throughout the RPM range, the vacuum created buffers that.

edit:
The dyno charts are, of course, specific to the test subject and each engine is different.
That dip is a sliding figure depending on specific engine conditions and yes ambient temp conditions.
I have tuned my carbs different in colder weather on V-8s at times to compensate.

Last edited by Hippysmack; 24th October 2019 at 16:01..
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Old 24th October 2019
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while there maybe some little of that going on, not as much as you think. i have been inside many industrial engine blocks while running hunting down issues.
the majority of pre-jet engines oiling is from connecting rod sling off and some from wheel shaft drain off, or head drains to the shirt.
stop and think, closed system right. if that is so, when the vent closes, the back flow would be nil, this has to be so because the rings need the vacuum to assist them. if you have oil pooling on the floor, the wheels could pick it up but for the piston up wash to suck up pooled oil, do not see that happening.
from pictures you showed, the newer oil jet engines are more open and open at the top more so that in the past. if that is so, piston up wash would draw from the least resistance and that would not be from the floor.
as an after thought, inertia from wheel wash would have the tendency to remove aeration, so where would be the next source, well, it is the cam gearing and i speculate that this is way more that the wheels present.
while there is fluctuations in pressure, law of averages is dominate be it below or above atmospheric. when time and excessive or vent over-run happens, the system goes positive and the magic numbers are already shown by posted testing.
the only way for you to be certain is electronic monitoring.
remember, the positive or diff'l will be a very small part of the cylce so the pressure to lift the valve off seat will be a narrow band also. bb in/ bb out, or blow by in / blow by out.
well the bondo must be dry by now, gotta go shape it.
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