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-   -   Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods (http://xlforum.net/forums/showthread.php?t=2073932)

Hippysmack 5th August 2019 18:52

Quote:

Originally Posted by needspeed (Post 5767859)
For what you're trying to find out, wouldn't that work just as well as a manometer?

Possibly, but what fun is that? :laugh

I held off even trying since Aaron once posted he tried one with no real result.
But we don't know exactly what his criteria was.

I'm wondering if the slack tube would react slower and more constant than a vacuum gauge.
But looking at the testing so far, the biggest variants would be at idle and upwards of 5000.
(unless there is a problem that needs addressing)
Would the vacuum gauge work too fast to be usable?

needspeed 5th August 2019 19:18

I can only relate what happened on the one bike I used it on. At idle the gauge needle fluctuated rapidly from negative to positive readings. I wonder what a manometer would show in that circumstance?

Just above idle (1500 rpm) the needle showed a rock steady vacuum. Small, but a vacuum. Remember though that my system is a bit different than the one you're working on.

Quote:

Originally Posted by Hippysmack (Post 5767861)
...Would the vacuum gauge work too fast to be usable?...

Why would that matter?

Tomcatt 5th August 2019 19:53

Quote:

Originally Posted by needspeed (Post 5767859)
I've used an automotive vacuum gauge, usually used to measure intake manifold vacuum, to measure crankcase vacuum on my old ironhead. It will read negative and positive pressure.

For what you're trying to find out, wouldn't that work just as well as a manometer?

Yes it will, it's just that they usually read in in/HG and aren't as sensitive as a gauge (or manometer) reading in in/H2O. It's just a matter of what range is needed.

Tomcatt 5th August 2019 19:56

Quote:

Originally Posted by needspeed (Post 5767873)
I can only relate what happened on the one bike I used it on. At idle the gauge needle fluctuated rapidly from negative to positive readings. I wonder what a manometer would show in that circumstance?

Same thing. This is where easily adjustable damping (think needle valve) is nice to have.

You also have to keep in mind that longer and/or smaller ID hose running to your gauge or manometer will also damp your reading.

Hippysmack 5th August 2019 20:17

Quote:

Originally Posted by needspeed (Post 5767873)

Why would that matter?

I just pictured it working as it did on the carb and if so, it bounced so much I could get a reading.
It's good to record above idle readings but as in my idle to throttle deal with the cap off,
It'd also be good to be able to see what's happening at idle.
Dammit, the bowl seal had to break now....

60Gunner 5th August 2019 20:32

I think what was discovered was during braking and acceleration with the at the full mark, oil ran into to line at times and I stead of draining into the cam check, followed there instead. At least that's what they figured was happening.
There, now ya read that on the internet too.

Tomcatt 5th August 2019 20:42

Quote:

Originally Posted by 60Gunner (Post 5767894)
I think what was discovered was during braking and acceleration with the at the full mark, oil ran into to line at times and I stead of draining into the cam check, followed there instead.

So what?

That has nothing to do with what is being talking about here which is reading pressure/vacuum by tapping into the vent line.

Tomcatt 5th August 2019 20:45

Quote:

Originally Posted by Hippysmack (Post 5767892)
I just pictured it working as it did on the carb and if so, it bounced so much I could get a reading.

That's why you damp the gauge. Some gauges have adjustable damping built in.

dieselvette 5th August 2019 21:07

Quote:

Originally Posted by needspeed (Post 5767873)
At idle the gauge needle fluctuated rapidly from negative to positive readings. I wonder what a manometer would show in that circumstance?

I think the fluid's resistance to movement (mass) would cause it to move a lot less than a gauge. On the other hand, without an orifice or needle valve to dampen the reading I suspect the fluid could blow clear out of the tube or be sucked in. All depends on your setup. If that happened then suddenly you've compromised your breather system by adding a vent - start over.

Which is why I would start with oil in the tube and use a needle valve, and after playing around with it until comfortable then maybe switch to water for a more standardized measurement.

I don't mean to be presumptuous, but my take on Aaron's testing is essentially that direct measurements don't matter - dyno results is what matters. There are only so many ways to modify the breather setup, and certainly all options have been tried in the racing world. So if you're experienced with these motors then trying to measure is probably an unnecessary step in the diagnostics. And I think we're really going off on a tangent playing with this, but it's educational I guess.

bustert 5th August 2019 21:25

does all of this really matter???
my grin factor says no.
a dyno run is just a tool, nothing else and to be honest, a good dyno run and real world is two diff animals.
you can have two identical engines and one dyno's out with more of everything and then have one that produces more after-peak power, which one would i take, sure, the long winded one.

60Gunner 5th August 2019 22:23

You know what, tee off your vent hose in the tank.

dieselvette 6th August 2019 00:00

Thinking out loud about that crappy oil cap I had - there is one thing I can say for certain - with the stock, old umbrellas and whatever blowby was occurring - there must have been at least momentary pulses of pressure in the oil tank , enough to push past the spring-loaded o-ring on that temperature stem.

Would a better vent at the heads have fixed it?

Or were the pulses not even getting there and were only in the cam chest/tank? In that case, an umbrella at the cam chest may have worked better.

Get the check valve as close to the source as possible to minimize CC pressure. Shorter line the better.

Get it as far from the source as possible to minimize oil puking. Restricted breather bolts, etc so pulses are dampened.

Hippysmack 6th August 2019 00:26

Using the adage from Dr Dick,
When in doubt, do as the factory did.
If you have oil puking, first replace the umbrellas.
Then if you still have oil puking, do a compression / leak down test to see if you have low compression / excess blowby.
Is so, inspect the top end for ring / valve leaks.

If these don't fix it (especially with engine conversions) research the breathing mods before performing any.

Did you replace the breathers and try that?
The pulses go everywhere in the entire breathing path, CC, cam chest, oil tank, rocker boxes...
When I pulled my oil cap, I could hear the air pulsing inside it.
That's why the breather valve works in top or the bottom.
The air is pulled out at the vent opening no matter where it's at.
The closer you (vent) to the source, the lower overall CC pressure will be.
Too low and you impede scavenging.
Those that have done the Deimus mod effectually lowered CC positive pressure a little.
The vent location doesn't control oil puking, Too high of pressure from blowby and increased intake air does, gasket leaks also.
I don't think the breather bolt holes dampened anything but rather raised overall CC pressure behind it.
The negative pressure on upstroke needs to compensate for the positive pressure on upstroke.
Adding more positive without adding more negative = oil puking.
Negative is also increased with blowby.
But negative could minimize if the pistons pull oil up into the rings while positive is still increased with more cylinder volume = oil puking.
Leaky valves in the heads can cause extra blowby past the rings into the crankcase.
Did you really think there was a short answer to all this? :)

dieselvette 6th August 2019 01:38

Quote:

Originally Posted by Hippysmack (Post 5767941)
The pulses go everywhere in the entire breathing path, CC, cam chest, oil tank, rocker boxes...

I disagree. At least, partly.

Certainly there are pulses everywhere. But they will be most dramatic below the pistons, less so at the cam chest, and even less at the valve covers. This will vary depending on RPM, and how restrictive the paths are.

Consider an open hole at the timing plug. This will definitely breath air in-out pretty dramatically. Connect a 6ft hose to that fitting, and notice a net outflow with much more subtle pulses. Now I would think you have a similar scenario when you get to the heads - even with no umbrellas at all, the pulses here would be a lot less dramatic than at the timing plug.

For this reason, I think the krankvent at the cam chest would net the lowest overall CC pressure - for better or for worse. Because the pressure goes higher there with each pulse than it does at the heads, more air would be pushed out with each pulse. (Of course the difference in venting methods would vary with RPM, in the same way that exhaust systems perform differently at different RPMs)


(Edit: actually a krankvent at the timing plug would net the lowest overall cc pressure, but that is impractical)

Tomcatt 6th August 2019 01:47

Is there some end result you're seeking with this discussion?

Hippysmack 6th August 2019 02:19

I think he's trying to convince himself to do the Deimus mod.
There is nothing wrong with this mod.

But the pretense for doing this mod thinking your solving a crankcase pressure problem takes more diagnosis than speculation.
We need flow rates on the different breather designs before concluding it's necessary.
I'm just saying 'wanting to' is different than 'needing to'.

You are not pushing all the pos pressure out on downstroke but rather cycling the air that's there thru pos and neg directions.

If there was an airborne fly in the crankcase, he'd hit his head on both sides of the cam chest wall as he was pushed and pulled thru the splash ports.

You may have higher pressure in the crankcase due to the splash ports being partially blocked by the squirters.
But that pressure is also being sent up the head drains.
If you tapped into the crankcase wall, you may end relieving pos pressure there (reducing scavenging).
That would also take testing.
The MoCo intentionally bottled up pressure in the lower end.
It wasn't to satisfy the EPA.
So any changes you make, think about what the equal and opposite reaction will be. :geek

60Gunner 6th August 2019 03:12

I noticed no difference in the strength of the pulses in the cam chest or the heads. I do have some additional hose length both before and after the Krankvent in the heads. Also the horseshoe before is 3/8" but the roughly 2.5 feet after is 5/16.
I'm going to reduce the length of the line after tho now that I know I'm not getting any oil out of it. I may even run no hose off it for awhile.

dieselvette 6th August 2019 04:56

I'm not interested in doing any mod, unless there is a reason to. My reasons would either be to reduce oil dripping, or to solve a cc pressure problem. I don't expect either problem because I'm not increasing displacement, and I'm reducing blowby with new rings. But we'll see.

I am interested in simplifying the diagnostics, for posterity. I think it's simple enough -replace this, replace that, etc as previously mentioned. But it seems like Hippy is looking for more than that, so i'll indulge.

Quote:

Originally Posted by 60Gunner (Post 5767967)
I noticed no difference in the strength of the pulses in the cam chest or the heads.

In earlier discussion there was some speculation (from Hippy I think) that the pathway from cam chest to heads *can be* inadequate. From what you're saying, it's plenty open. So that's worth noting.

I'm an idiot, and I still can't wrap my head around, or can't remember, why higher CC pressure leads to wetsumping, except that if it's what i'll call "really high" then windage causes more oil to be suspended?

Four Speed 6th August 2019 10:38

Quote:

Originally Posted by Tomcatt (Post 5767957)
Is there some end result you're seeking with this discussion?

What would be the fun in that?:p

Hippysmack 6th August 2019 14:18

Quote:

Originally Posted by dieselvette (Post 5767975)
I'm not interested in doing any mod, unless there is a reason to.
I am interested in simplifying the diagnostics, for posterity. But it seems like Hippy is looking for more than that, so i'll indulge.

In earlier discussion there was some speculation (from Hippy I think) that the pathway from cam chest to heads *can be* inadequate. From what you're saying, it's plenty open. So that's worth noting.

I'm an idiot, and I still can't wrap my head around, or can't remember, why higher CC pressure leads to wetsumping, except that if it's what i'll call "really high" then windage causes more oil to be suspended?

My apology's, I assumed that's where you were thinking.
Where I'm going with this discussion is simply understanding.
edit:
I've been compiling this information in the pedia already.
But it isn't helpful if the information is not clear or is not viewed.
This thread was started in the interest of exposing some of these intricacies to people that want to understand Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods.
Also to help me understand it too.

I've learned a lot so far here and that's what it's all about.
Thanks again to bustert, for introducing the slack tube.

Oil tank:
Into the oil tank, oil is sent by the scavenge pump. This is not gravity doing it.
It is pressurized by the scavenge gerotor action.
As we know, the displacement pump doesn't make pressure, only flow.
Just as in the feed side, the scavenge side outlet from the pump is restricted.
This restriction is what builds the pressure. Pressure has energy.
The energy is present as long as the restriction remains (up the return line).
When the oil reaches the tank, the oil is dropped down into it.
The energy it took to get the oil to the tank is released into the air above the oil and flows back to the cam chest through the vent line.
At the same time CC pressure is pulsing the vent line but the released energy is stronger than the pulse so it flows back to the cam chest.
The scavenge gerotors create more power than the air below the pistons.

CC pressure:
The air below the pistons initially is charged by the beginning of the downstroke.
This initial surge is what gets bottled up temporarily until the restriction from the splash ports is overcome.
This creates a little more initial energy in the CC but that is only temporary until the surge gets to the splash ports
(where that energy is released into the cam chest.
That pressure is further restricted in the cam chest by the small holes at the lifter blocks it has to go thru.
When the pressure gets into the pushrod tubes, that energy is released into the rocker boxes.
Then restricted again by the umbrella path and released at the head vents.

I'm not sure inadequate is the right wording.
The head breathers manipulate CC pressure (create more restriction to make higher pressure inside on purpose.)
Newer (OEM) engines don't have the actual problem of wet sumping like older engines did (possibly because CC pressure was raised) upon normal riding conditions.
Higher CC pressure actually helps scavenging (pushes the oil to the scavenge port for pump pickup).
But higher CC pressure also picks up more oil in suspension (creates more dense air/oil mix).
Too high density oil is more difficult to separate from the air and pushes it's way past the umbrellas into the head vents.
The air/oil density can be increased with excess blowby (think 5000+ RPM) and engine upgrades.

And yes, higher windage especially from excess blowby or bigger pistons, does create more oil in suspension (higher density air/oil mix).
....wait for it.......
When doing engine upgrades, the Deimus mod will lower the higher pressure created from bigger pistons, more compression, bigger valves etc.
But, before calling the dogs and peeing on the fire, testing should be done before and afterwards for flow rates of crankcase pressure to know for sure if a mod is needed and if it was successful.
Willy Nilly doing mods can be a recipe for adding more problems than you had to begin with.

We are working at this point toward ways of testing CC pressure to be able to address this in a more controlled way.

edit:
Ill add that we mis-name wet sumping as oil puking out the vents.
That is a CC pressure problem, not wet sumping.
Wet sumping is simply too much oil left in the sump due to not being scavenged fast enough (several different reasons why and some do not involve the oil pump).
But wet sumping can lead to too high of oil density that pukes oil.

Also, anybody that has questions or refutes, please chime in.
As stated, this is all about understanding... for all of us.

spoon 6th August 2019 15:20

Holy Smokes!! This is impressive. I have been reading this from the start. To see this topic continue at the pace it has, with actual testing vs just speculation is impressive. I don't have anything to add except that I am following with great interest. I would think all engine folks are, or should. I think there is an answer for both puking and wet sumping to be found.

Hippysmack 6th August 2019 16:38

Yes, I believe there is an answer of sorts.
To what extent is yet to be determined.
But that cannot be achieved without a better understanding of how it ticks.
That is the main thing I'm hoping that comes out of this.
Speed shops and engine builders I'm sure (hope) have done a lot more towards knowledge on this subject.
And some keep it close to the vest in the interest of not divulging to competitors.
Good folks like Hammer Perf and NRHS have helped us along in understanding.
edit:
I can't leave out DK Customs.
Thanks to all for your efforts. :clap

That's the key though, understanding.
Hopefully, this will help us all a little better.

Tomcatt 6th August 2019 17:46

Quote:

Originally Posted by Hippysmack (Post 5767958)
So any changes you make, think about what the equal and opposite reaction will be. :geek

Honda does on its' MotoGP V4's. They partition the crankcase to functionally create two v-twins. No pumping losses pumping air from side to side as the piston pairs travel up and down. Pressure changes (pulses) as the pistons travel up and down are actually a net zero. Pressure built as the pistons come down then helps push them up. There is a loss as the crankcase air is heated by the pressure changes but that is lessened by pulling a vacuum on the crankcase(s). F1 engine crankcases are "partitioned" the same way to minimize pumping losses. There's also the ring seal and related benefits. This is the way things are moving as efficiency is optimized and losses minimized.

Current "best practice" is pulling a crankcase vacuum. On our Sportsters (at least the later ones) the oil tank is vented to the crankcase, it's a closed system. There is no pressure differential between the crankcase and tank to "help" oil move to the tank, just the scavenge pump pumping it which Harley has improved with a larger scavenge pump.

Hippysmack 6th August 2019 21:35

Honda have 45 degree V-Twins? :dunno
That is where the 'condition' begins that we have.
If the piston travel was further apart, CC pressure would be more constant than it is as you mentioned.

To go further, all Sportsters are vented to the cam chest.
Can you explain "best practice" is pulling a crankcase vacuum?
As we've seen, vacuum is being pulled already.
Are you suggesting a vacuum pump?
There really is no need for a pressure differential from the tank to the sump since the oil pump is capable of loads of flow pressure to the tank.
That is unless too much vacuum is present keeping the oil away from the scavenge port in the sump.
(which is the big concern of using a vacuum pump)

60Gunner 6th August 2019 21:53

How much do you really think line length and size before and after the valve means?

bustert 6th August 2019 22:22

well, after the system stabilizes i do not think it really matters.
going back the the control room, the manometers lines could be several hundred feet considering the rig was 204 x 204 feet or around 1 sq. acre and that the tanks were well over 100 feet below the control room.
it is wise to use a valve for initial start and in the case of intake pulse, acts as a dampner but they make better gauge snubbers than a valve. on compressors we use murphy gauge/snubber valve or the mechanical gauge would not last long and hard to read, however, it still showed average, who cares about the spikes.
the same with well tests, we looked to average since some wells flowed in spurts. did it matter to sales, NAW, that came after the sales meters but test show capacity and issues. automobile the same.
hd can solve the whole issue by using a hybrid design in the sportster when the sump is wet and the flywheel compartment is dry, not a new concept.
on the honda, they use a die cast type of engine case and a lot of what you see actually go in hand with beefing the case. often wonder why hd never got on that wagon.

dieselvette 6th August 2019 22:26

2 Attachment(s)
Quote:

Originally Posted by Hippysmack (Post 5768033)
My apology's, I assumed that's where you were thinking.

No apologies needed. I started out basically trying to do forensics on my motor, without the complete picture. Now that have a better picture, I want to know more details.

One fear I have is that if you end up with too much information on the wiki, it will not be as helpful. So I hope I can help you narrow that down.

Quote:

Originally Posted by Hippysmack (Post 5768033)
Oil tank:
Into the oil tank, oil is sent by the scavenge pump. This is not gravity doing it.
It is pressurized by the scavenge gerotor action.
As we know, the displacement pump doesn't make pressure, only flow.
Just as in the feed side, the scavenge side outlet from the pump is restricted.
This restriction is what builds the pressure. Pressure has energy.
The energy is present as long as the restriction remains (up the return line).
When the oil reaches the tank, the oil is dropped down into it.
The energy it took to get the oil to the tank is released into the air above the oil and flows back to the cam chest through the vent line.
At the same time CC pressure is pulsing the vent line but the released energy is stronger than the pulse so it flows back to the cam chest.
The scavenge gerotors create more power than the air below the pistons.

The scavenge pump takes what it's given - air or oil, and moves it to the tank.

It has two inlets - first from the CC passage, then from the cam chest drain.

I tend to think of the tank more as a gravity air/oil separator. The vent back to cam chest gives the air a place to return to the engine.


Quote:

Originally Posted by Hippysmack (Post 5768033)
CC pressure:
...
This creates a little more initial energy in the CC but that is only temporary until the surge gets to the splash ports
(where that energy is released into the cam chest.
That pressure is further restricted in the cam chest by the small holes at the lifter blocks it has to go thru.

Not sure what you mean by splash ports? I included some pictures. Front and rear inside cam chest. Not sure where these passages go - are they leading to the pushrod tubes or the CC?


Quote:

Originally Posted by Hippysmack (Post 5768033)
Newer (OEM) engines don't have the actual problem of wet sumping like older engines did (possibly because CC pressure was raised) upon normal riding conditions.

Are you sure, or just guessing? Just trying to recall where we learned that newer models have higher CC pressure.

Quote:

Originally Posted by Hippysmack (Post 5768033)
Higher CC pressure actually helps scavenging (pushes the oil to the scavenge port for pump pickup).

It doesn't make sense to me why CC pressure helps scavenging. Is the scavenge port "vented" into the cam chest where it meets the pump inlet, or is the port sealed to the pump inlet?

dieselvette 6th August 2019 22:54

Quote:

Originally Posted by 60Gunner (Post 5768109)
How much do you really think line length and size before and after the valve means?

Quote:

Originally Posted by bustert (Post 5768114)
well, after the system stabilizes i do not think it really matters.
going back the the control room, the manometers lines could be several hundred feet considering the rig was 204 x 204 feet or around 1 sq. acre and that the tanks were well over 100 feet below the control room.
it is wise to use a valve for initial start and in the case of intake pulse, acts as a dampner but they make better gauge snubbers than a valve. on compressors we use murphy gauge/snubber valve or the mechanical gauge would not last long and hard to read, however, it still showed average, who cares about the spikes.
the same with well tests, we looked to average since some wells flowed in spurts. did it matter to sales, NAW, that came after the sales meters but test show capacity and issues. automobile the same.
hd can solve the whole issue by using a hybrid design in the sportster when the sump is wet and the flywheel compartment is dry, not a new concept.
on the honda, they use a die cast type of engine case and a lot of what you see actually go in hand with beefing the case. often wonder why hd never got on that wagon.

Bustert you are right that when measuring pressure it makes no difference how far the line goes or how restrictive, but I think 60Gunner is asking about flow out the vent which is a different subject.

I think hose length matters a lot if you don't have an effective umbrella. But if you have a perfect umbrella then it will make no difference whatsoever.

In fact a long enough hose and you don't need an umbrella at all, because the air can't turn around and go backwards that quickly with every piston upstroke (like a properly tuned exhaust pipe, no reversion).

I defer to this again - and there could not be a better explanation of how the stock breathers work:
http://xlforum.net/forums/showpost.p...5&postcount=34

Quote:

Originally Posted by aswracing (Post 5310625)
I was surprised at how little air movement there was at the end of the hose. When a motor is started with nothing screwed into the timing plug, there's a massive inhalation and exhalation evident. But apparently, necking it down to a 3/8" hole and connecting 2 feet of hose adds a pretty significant restriction. Air flow was nowhere near what I expected.

No hose = lots of air in/out
With hose = pretty much only air out, not in

Hippysmack 6th August 2019 23:35

Quote:

Originally Posted by dieselvette (Post 5768116)
One fear I have is that if you end up with too much information on the wiki, it will not be as helpful. So I hope I can help you narrow that down.

What you see in this thread is more random information than what's in the wiki.
The "I think"s, "It worked for me"s, "Mines better than yours"s, are all left out for the most part unless it came from someplace like Hammer Perf and others.
Unless it's appropriate for the subject at hand also.
A short 'how to' article on certain subjects here and there may be in first person.
But, the wiki is not a conversation so we have to keep in mind the person needing the info doesn't care to read that my carb bowl seal busted while they are researching CC pressure. :)
It's a history book, as well as loaded with technical 'how to's for both OEM and mods including tools, pics for clarifications and inspirations as well as 'where to buy's in some cases and 'how to get by's.
Plus tons more...:coffee
I've included some information we've discussed so far in the main CC pressure page but have yet to consolidate from this thread.
The info from the first part of this thread was already there when I started this thread actually.
Frankly, I got to a point that I was getting confused as well as irritated with some of the suggestions in so many of these threads that just didn't jive.
We all theorize in life as well as mechanic work from time to time.
But there are so many different aspects of this subject matter, the whole picture needs to be taken into account.
So I had to learn the mechanics of the beast and got to a point that well, I needed some help, thus this thread was born.
Here is the EVO CC Pressure page again that I'm working with.
Everybody is welcomed to look it over, review, bless me out or whatever you see fit. It's end purpose is to help the next guy so whatever it takes is what it takes.
http://sportsterpedia.com/doku.php/t...:ref:engmech04
Subject headings like the ones in the first part of this thread are there and searchable from the menu at the top right of the page.
So someone wanting to search for breather data or testing can simply click that heading on the right and go straight there instead of having to read the entire page.
(as I realize it is a LOT to take in)
But I wanted to keep all of this info one page as there are way too many aspects that either relate or depend on each other in this subject matter to have to link from page to page.
I am willing to redesign the whole page if it would be easier to use.
So please don't hesitate to mention something if you think of it.
There are some obstacles with the formatting but we've been able to cross those hurdles so far.
End result, it needs to be as easy to follow as possible.
But keep in mind, this is definitely one of those topics that are both factual and theorized as is evident in most every thread and other website I've visited on the subject.
That's why we need more testing data to either verify or debunk.
I'm up for either as long as it is verifiable.

60Gunner 6th August 2019 23:58

Im not sure what testing or data is even possible to verify or debunk anything.

Hippysmack 7th August 2019 00:20

Quote:

Originally Posted by dieselvette (Post 5768116)
The scavenge pump takes what it's given - air or oil, and moves it to the tank.
It has two inlets - first from the CC passage, then from the cam chest drain.
I tend to think of the tank more as a gravity air/oil separator. The vent back to cam chest gives the air a place to return to the engine.

Correct.
The oil tank serves several purposes.
It's of course the oil reservoir, an air/oil separator, CC pressure buffer.. leave anything out?

This is from the REF section:
I have not updated this page since the start of this thread or even read it since for that matter.
http://www.sportsterpedia.com/doku.p...talk:ref:oil20

Oil Tank Pressure

There should not be any noticeable pressure in the oil tank due to the generated pressure being vented back into the cam chest.
Because you can't physically pump more oil out of your motor than you pump in, the larger return pumps air also.
(in addition to the return oil in order to make up the volume difference)
You will see this if you remove the cap off the oil tank and start the motor.
The return oil enters the tank in spurts with the air in between the spurts.
This in turn means more volume gets put back into the tank from the return side than gets removed from the tank by the supply side.
So the tank gets pressurized and that cant be allowed to happen.
It's the vent line's job to allow that extra air volume to exit the tank and go back to where it came from, the gearcase.

During normal operation;
With the tank cap / dipstick removed, tank pressure is vented to atmosphere from the top of the tank.
With the tank cap / dipstick installed, tank pressure is vented to the cam chest.

During shutdown;
The oil tank vent is connected to the cam chest and the cam chest is vented out the breather valve(s) in the cam cover or heads, respectively.
So if you have pressure in your oil tank and the vent to the cam chest is not blocked then the cam chest is also pressurized.
If the cam chest is holding pressure, then your breather valve(s) can not be venting properly.

Bottom line is that if the vent system is working properly, you shouldn't have excessive pressure build up in the oil tank.

Conditions where oil seeps or spews from the oil tank include;
Blocked oil tank vent line / hose.
The vent line being blocked will keep the pressure in the tank until it builds enough to blow out the cap.
Blocked / stopped up crankcase breather vent.
With blocked or non-working breather(s), engine performance will also suffer.
Too much oil in the engine, oil tank or both.
Check your FSM or owners manual for the proper amount of oil to add.
Sportsters are known for wet sumping (condition where oil from the tank seeps into the engine while not running).
Once the engine is started, the oil pump scavenge gerotors will return the engine's sump oil back to the tank.
(in theory, at a rate faster than the feed gerotors can send oil to the engine from the tank on a warmed up engine)
There are conditions that would slow the speed at which oil returns to the tank however.
Too much standing oil in the sump added to worn oil pump internals, condition of the pressure relief valve and oil filter can slow the pump's ability to clear the sump.
Oil can drain down into the motor from the tank for a number of reasons when it has been sitting for a long time.
Then, the dipstick will give a false reading because some of that oil went into the engine.
If you already have 1-2 quarts seep down the feed line and into the engine and then add more to the oil tank, the excess oil will either blow out the breather valve(s) or the oil tank.
Oil level should only be checked or added to with a warmed engine as per the FSM.
If you're not sure of the collective amount of oil in the system (as in buying a used bike), drain the engine and oil tank and refill with the proper amount.
(when draining cold oil, you will not get all of the existing oil to drain out of the engine)
So, it may be better to drain and add the proper amount minus a half quart, run it up to temp and recheck, then add some more if needed.
You may not be able to see or access the sump drain plug as it may be blocked by the frame.
86-91 engines have a pressure relief valve set at 30-35 psi.
During a cold start, the pressure relief will dump unfiltered oil into the gearcase until the oil heats up enough (lowering oil pressure) and the relief valve closes.
Likewise, repeated start/stops before allowing the oil to heat up will dump more oil into the engine faster than the scavenge pump can return it to the oil tank.
Oil lines not routed to the correct fittings.
If you've removed or replaced your oil lines, double check that they are connected to the right fittings.
Replacing the hollow head breather bolts for regular ones.
On 91-up engines, installing a regular bolt in place of the OEM hollow bolts can cause this issue.
That would block crankcase pressure up in the engine and cause degradation of engine performance.
If upgrading to an aftermarket A/C, you must account for an alternate method to vent crankcase pressure if you're not using the OEM hollow bolts.
A plugged up oil filter should not cause this issue.
All spin on oil filters have a pressure relief valve built into them.
It is designed to still deliver (unfiltered) oil to the engine in the case of blockage of the filter media at no extra pressure increase.
Oil tank blew up in cold weather.
04-up models have plastic oil tanks. The belief is that some moisture gets frozen in the vent line on 04-09 tanks causing the rupture.
It's a plastic tank so it is not going to be anything like a pressure cooker if it does happen, just messy..
The worst of it is replacing all the parts (and not being able to ride while waiting for parts to arrive).
The newer upgraded tanks have a better venting design to prevent this.
In 2010, the MoCo put a 10 psi relief valve in the oil tank (presumably to prevent this sort of issue).
The relief valve will prevent having to replace the oil tank but the jury is still out on the actual cause of the problem.
This has happened to a handful of XLFORUM members (statistically, a pretty small number).
But there are plenty of riders who have ridden in below freezing temperatures that haven't had a problem.

Crankcase Pressure / Venting in the Oil Tank
Air inside the tank doesn't get there because of CC pressure alone.
Ambient air resides in the upper portion of the tank above the oil level.
The air was there first. Then the oil was added. If you add too much oil, there will be even less air in the tank.

This would result in a need to move crankcase pressure out of the tank faster to keep up with incoming pressure.
A lower oil level in the tank would facilitate more area for CC pressure to collect before venting out.
Some have claimed that lowering the oil level in the tank reduces wet sumping.
There may some truth to that in the short run for reasons above.
But that is more like using a band-aid to cover a more important underlying condition of too much total crankcase pressure.
That condition doesn't just go away when you lower the oil level.
There should be a variant oil level in the tank depending on many factors.

The displacement of ambient air and CC pressure in the tank relies on the engine breather vent(s).
If the engine can't breath, the system locks up. However, it may be compounded due to air/oil separation once there.
In the drawings below, a syringe is used to example crankcase pressure being applied into the oil tank:

http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

Since it's not the oil pump scavenger's job to separate the oil/air mist, both crankcase pressure and oil end up in the oil tank.
So one function of the oil tank is to allow for air to separate out of the oil once there.
The oil falls to the bottom while the air separates from the oil and goes into the tank vent back to the crankcase.
From there, the air gets circulated out the engine breather vent(s) and back into the intake to burn off hydrocarbons.
(or sometimes re-circulated into the scavenger passage)
So, in essence, the oil tank acts as an oil / air separator like the breather valve but the air only expels the engine from the engine's breather vent.

http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

The piston movements in the HD engine are not in apposing positions to balance out the displacement of air.
They are mounted on the same crank pin and oscillate into a small volume crankcase.
Crankcase air pulses from a pressure condition to a vacuum condition inside the engine.
With the pistons movements being so close together, air is pushed and then pulled with each piston's up and down stroke.
This 'push-pull' condition affects oil scavenge from the engine to the oil tank.
Crankcase pressure and oil is both pushed towards and pulled from the scavenger passage in the sump.
Likewise, so is pressure to and from the oil tank.
As far as the oil tank is concerned, picture blowing up a balloon halfway, then letting the air out and repeating.
On one hand, you can picture both oil and CC pressure being pushed to and from the oil tank.
On the other, the oil pump scavenger creates more flow pressure than the force of CC pressure.
So one could also see that as the oil pump sends oil/air to the tank on piston down stroke and negative (vacuum) pressure pulls air back thru the vent.

If the oil tank vent line is plugged up, the oil pump will still send air/oil pressure into the tank.
The air pressure can't leave the tank but the oil is recirculated from the tank into the engine by the feed side of the pump.
Pressure will build in the tank until the cap blows, oil leaks from the cap or the oil tank splits (plastic). \
You still have the same amount of pressure on the engine side of the plugged up vent line.
And that pressure is still being vented out the engine breather(s) as normal. However, a plugged vent line will hinder oil pump scavenging.
This will result in less oil going to the tank and more oil gathering in the sump waiting to be scavenged.
And that can lead to wet sumping with more oil in the sump than usual.

Hippysmack 7th August 2019 00:33

Quote:

Originally Posted by 60Gunner (Post 5768136)
Im not sure what testing or data is even possible to verify or debunk anything.

The more we thunk it, the more we'll know. :)

bustert 7th August 2019 00:35

when did hd start pulling oil directly out the flywheel compartment???

Hippysmack 7th August 2019 01:09

Quote:

Originally Posted by dieselvette (Post 5768116)

Not sure what you mean by splash ports....
... are they leading to the pushrod tubes or the CC?

From Evo Engine Oil Routes:
http://sportsterpedia.com/doku.php/techtalk:evo:oil02

Drainage:

86-90 engines:
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

91 engines:
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

92-03 engines:
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

04 Up engines:
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

Splash Ports:
Notice the port size.

86-90 engines:
http://sportsterpedia.com/lib/exe/fe...mini_blitz.jpg

91-99 engines:
Port size was enlarged.

http://sportsterpedia.com/lib/exe/fe...siahstites.jpg


00-03 engines:

Port size is smaller.

http://sportsterpedia.com/lib/exe/fe...1_by_bruce.jpg

04-up engines:
Port size is even smaller
Maybe this will help a little.

http://sportsterpedia.com/lib/exe/fe..._by_bsaman.jpg

http://sportsterpedia.com/lib/exe/fe...eherdad_it.jpg

I need a closer pic of these ports if anyone's got one.
http://sportsterpedia.com/lib/exe/fe...eherdad_it.jpg

Hippysmack 7th August 2019 01:15

Quote:

Originally Posted by bustert (Post 5768142)
when did hd start pulling oil directly out the flywheel compartment???

I'm not as versed on early IHs but I'm guessing when the gerotor pump hit town ....77 on?
Yes, when they got rid of the breather trap (76<)

dieselvette 7th August 2019 01:20

Quote:

Originally Posted by Hippysmack (Post 5768132)
I am willing to redesign the whole page if it would be easier to use.
So please don't hesitate to mention something if you think of it.
There are some obstacles with the formatting but we've been able to cross those hurdles so far.
End result, it needs to be as easy to follow as possible.

Yep, and thanks again for your work on this so far. And I agree that being candid is the best approach. I have some suggestions about ways it could laid out in and order that's easier to understand, but Im holding off until all the facts and myths are cleared up, as im sure you are too.

Hippysmack 7th August 2019 01:24

Quote:

Originally Posted by dieselvette (Post 5768152)
, as im sure you are too.

Exacery. :)

needspeed 7th August 2019 01:41

:doh
Now I regret praising your extensive list of links and credits that were at post 352 because now I can't find them. :( A visit to post #2 doesn't get me there.

Refer to post 402 and 403.

Hippysmack 7th August 2019 01:58

Well ...I think we've been modded. :headbang
That post was apparently not for the long range, nor is this one I'd imagine.

That's OK.
I edited page 2 to link back to the article in the pedia, go to the bottom of that page to see all the credits. :(

Hippysmack 7th August 2019 02:49

Quote:

Originally Posted by Hippysmack (Post 5768033)
Newer (OEM) engines don't have the actual problem of wet sumping like older engines did (possibly because CC pressure was raised) upon normal riding conditions.

Quote:

Originally Posted by dieselvette (Post 5768116)

Are you sure, or just guessing? Just trying to recall where we learned that newer models have higher CC pressure.

I guess I need to clarify that.
From 77 Up, there were many changes to the engines.
Along that path, oil routing, oil pumps, pressure reliefs, CC pressure paths, CC pressure itself and a list of others changed.
It wasn't always the oil pump that made a difference in wet sumping.
It's the big picture (which I still don't have a full grasp of) that changed.

Re:
where we learned that newer models have higher CC pressure.
Deduction basically.
OEM engines went from 883cc-1100cc-1200cc increasing volume of pressure produced.
The engine internals (splash ports are clearly smaller. that's how most of CC pressure leaves the source)
Routing to the head breathers with the restrictions I mentioned earlier will raise the pressure starting from the source.
Breather bolt hole size is a restriction also.
If you put all this together (and add it to the rest), one could deduce the initial surge is higher from restrictions as the year model changes occurred.


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