The Sportster and Buell Motorcycle Forum - The XLFORUM®

The Sportster and Buell Motorcycle Forum - The XLFORUM® (http://xlforum.net/forums/index.php)
-   Sportster Motorcycle - Bottom End (http://xlforum.net/forums/forumdisplay.php?f=205)
-   -   Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods (http://xlforum.net/forums/showthread.php?t=2073932)

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.


All times are GMT +1. The time now is 11:38.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
XL Forum® - Linson Media LLC