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

Hippysmack 2nd July 2019 00:01

Aftermarket Breathers / PCV Valves
 
There is a product called a Krankvent that can be plumbed into the lower, 6 o’clock position as an alternative to a stock foo-foo valve.
But they are not cheap. Automotive PCV valves are not really made to handle the revs or air volumes of a Harley.
While a car engine is bigger, it has one piston coming down while one goes up.
So there's not much change in internal crankcase volume, so not as much breathing to be done.
A Harley has two pistons and rods on one crankpin, so is one giant air compressor.

Some guys have found that plumbing in a 77-78 foo-foo valve on the later model engines improves breathing.

Finding a better breather valve:
The breather valves that work best on crankcase breathers have several features:
Low-inertia, i.e. they don't take more than a breath to open and close.
They operate at low pressures ~1-30psi.
They preferably have a floating type seal.
They should be transparent, so you can see if they block up with blowby, solids, bugs etc.
They should be easy to open and clean occasionally.
They should push-fit into your breather line.

Metal diaphragm valves with e.g. springs are hopeless.
Also avoid other types of valves designed to work at high pressures e.g. plumbing valves.
Avoid car PCV valves as they are metering as well as non-return valves and are unsuitable.
Automotive PCV valves are designed to let some air back in.
The ball and spring valves will not be able to work fast enough to keep all the air out.
When air is allowed to be drawn back into the engine, it creates a mass that must be compressed by the pistons on downstroke as it is being vented out.
This robs some power and will cause the engine to work harder (creating more internal heat at higher RPM).

Aftermarket PCV's: 62)
Mercedes Benz P/N# 271-018-00-29 ~$13.
Reed type PCV valve. Fast acting. Used for their C 230 Kompressor engine.
Dims: 2-1/2” long by 1-1/8“ with an I.D of 1/4”.

McCaster Carr P/N# 4610K17 ~$6.
Umbrella valve. Vacuum check valve.

Autozone P/N# PCV1174 (PV272) ~$5.
Ball/spring based PCV valve.
Makes a clicking noise during operation.

Mercedes Benz P/N# 271-018-00-29 63)

Regarding horsepower gains from different breathers
From aswracing on testing breather vents for HP gain:

Many years ago, I spent most of a day dyno testing breather check valves.
I was writing for Battle2win magazine at the time and published my findings there.
The article is here at Nightrider.com: Do Crank Vents work?
I spent several hours on the dyno testing whether or not various breather arrangements affected the power of a motor.
Mainly it was a test of these breather check valve devices, but I also tested the recycling of the blowby versus venting to the atmosphere.

http://sportsterpedia.com/lib/exe/fe..._aswracing.gif

The result labeled “kuryakyn” is the one that's recycling the blowby.
So named because I used a kuryakyn adapter to send the blowby back into the intake tract.
All the others are vented to the atmosphere.

The bottom line was that none of them added a single iota of measurable horsepower, despite the grandiose claims of up to 7% from the manufacturers.
The only thing I could get to show up on the dyno at all was the removal of the blowby from the intake tract.
You can read all about the results in the Nightrider article above.
One of the companies involved, ET products (maker of the Spyke Krank vent) took exception.
I very carefully retested using their suggestions, but I got the exact same answer.

===== Engine Venting Mods =====
See also Breather Venting / Relocation http://sportsterpedia.com/doku.php/t...:ref:engmech05 for a listing of breather mods from the XLFORUM. \\

Engine breathers control when CC pressure exits the engine. \\
So when you're discussing engine breathing mods, you're also discussing changing crankcase pressure. \\
Revised crankcase breathing is an area where you have huge potential to create unintended consequences.


The stock vent system doesn't keep up with the increased pressures and volume of air from modified engines very well. \\
The MoCo somehow balanced the engine design factors to come up with a compromise that worked. \\
Once you change CC pressure / compression ratio and etc, that equilibrium is disturbed. \\


aswracing on venting mods:
<blockquote>I've induced scavenging issues mostly from using gapless rings. But not from venting mods. \\
However, I've dyno tested venting mods until I'm blue in the face and never found a single horsepower there. \\
(except for pulling the blow by out of the intake tract, which is good for a small across the board improvement) \\
S&S cases have no scavenging issues due to the strategic placement of the reed valve (in the sump). \\
The scavenge inlet sees pressure but is isolated from the vacuum when the pistons go back up. \\
</blockquote>

Hippysmack 2nd July 2019 00:06

Wetsumping
 
See also the "wetsumping" link from post 1.

Wetsumping during shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing.
The foregoing addresses wet sumping affect on horsepower.
Later engines are not competition engines. Maybe the earlier Sportsters were, but those days are long gone.

Wetsumping (at sustained high RPM) is a condition when the oil pump isn't removing the oil as fast as it's feeding it.
If the cam box fills with oil, it comes out the breather and right to your air cleaner.
It's been a chronic issue on XL's for years, happens on the 5-speed bikes as well as the 4-speeds and the ironheads.
But often on the head breather models (91-up), you never know like you do on earlier bikes with the breather on the cam box (pre 91).

Wetsumping can also be attributed to the Density of the air / oil mix in the crankcase.
The higher the density (not volume) of the fluid (air / oil mix), the more it drags on the rotating parts it contacts.
As the density increases so does the fluid drag it imposes on the rotating parts (read flywheel assembly).

This drag robs power. That's why we mess with it, to reduce the power loss.
Example: If they are the same size (volume), what takes less power?
Stirring a cup of coffee or stirring a coffee milkshake? It's the one that's less dense.

So now we know that less drag = more horsepower and the air is the medium that gets the oil out of the cases.
The 'leaner' (less oil in the air), the less the drag (air / oil is less dense).

The oil pump was updated in '98 and then in '07 and you rarely see this anymore (while putting around town).
But it still happens on high rpm and race motors from time to time.
It's always the best sealed motors that have the issue, especially gapless ring motors.
Vacuum (45° configuration as mentioned above) in the crankcase interferes big time with scavenging.
The 98-up style pump can be fitted to the older bikes (they've even been fitted to ironheads).

The late model bikes can easily wet sump if ridden aggressively on the street, however.
And they've been known to wet sump with only 3 back to back dyno pulls.
The results are dramatic when it happens. It is not anything like a barely noticeable loss in performance.
The scavenging gets behind to some degree in a single drag strip run.

Beyond that, about all you can do is lower the oil pressure.
But don't go down that path unless you establish for sure you are wetsumping and other measures won't fix the situation.
Read more here on the Homemade Oil System Bypass for reducing the oil pressure in the REF section of the Sportsterpedia.
This mod will send a small amount of pressure side oil back to the tank instead of into the engine.

Hippysmack 2nd July 2019 00:08

Bad Ring Seal vs Wet sumping
 
Wet sumping and oil spatters from the crankcase are two different things.
Daily driver owners with oily air cleaners can get these two ideas confused.

Bad ring seal helps evaquate the sump from oil.
But on the other hand, it increases the flow rate through the crank vent system to such levels that a lot of oil droplets join in.
Apart from leaking cylinder base gaskets and push rod tubes, large blowby and high crank pressure also contributes to even larger ring leakage.
It's a vicious circle.

Sometimes owners who struggle with an oily air cleaner problem seem more concerned with wet sumping.
When they should concentrate in evaluating and improving ring seal.
And ideally also route the crankcase breather lines to a catch tank instead of the A/C.
Re-routing the vent(s) from the breather to a catchtank has many advantages.
Not least it is a powerful tool to monitor the state of the engine.
There should be more water than oil in the catch tank.
At least if air temp is 20C or below.

Hippysmack 2nd July 2019 00:13

Liquid Drag vs Fluid Drag
 
Liquid Drag

This is an this example of 'liquid drag' (as opposed to fluid drag, our real life medium).
Consider a 5 gal pail of latex & paint mixer that gets powered from your electric hand drill.

What's the difference between liquid and a fluid?
In this example, it's that a liquid is non-compressible (oil).
A fluid is compressible(air or air-oil).

Stick the mixer in the middle of the pail about 1/2 way to the bottom in the center of the paint mass.
Hit the trigger and the drill wants to twist out of your hand (liquid drag on the mixer).
As the mixer accelerates the paint, the drag reaction at the drill gets less.
And you can see the paint moving fast around the mixer and slow at the pail wall.

Eventually you steer the mixer near the wall to get that stuff mixed and an important change happens.
The reaction at the drill gets less, the drill speeds up and the paint near the mixer speeds up with it.
But the rest of the paint away from the mixer stops moving (as if its hanging in it's own 'miniature sump' away from all the commotion.

That explains the less reaction force on the drill.
You're moving less than the full 5 gal now (and moving that small amount better with less drag) even though the amount in the pail is unchanged.
This is important to understand.

Summary so far:
You're mixing the dickens out of 1/2 gal and cutting 4-1/2 gal out of the picture.
And that 1/2 is really moving and it's taken less force to move it because your moving less.
(less volume don't jive with the density-not volume- as in above)
It's exactly the same if now you change to a 55 gal drum.
1/2 gal going fast but 54-1/2 not moving.

So the addition of a sump (containment area) allows a greater quantity of oil (paint) to be present in the case (pail) without any extra drag.

Some of that oil is able to drop out of suspension so it can separate into the sump.
Once the used oil gets sump trapped things are going good.
But there are drag losses geting it to the sump as it flies outward off the rods.
Some will land on the inside of the case near & on the parting seam.
Some will travel down the inner walls of the wheels then fly off to the case wall.
Some will fly up under the pistons where it needs to eventually find its way to the case wall also.

In this chaotic environment, gravity isn't going to do much to drain it down to sump when there are giant flywheels whizzing 1/8“ from this case walls.
The wheels are going to set up a following flow on the walls.
The better the following flow, the less oil in commotion. That's good.

But good movement is because of good dragging.
But drag is bad.
Good dragging sucks power.
So does not dragging because the oil is slow moving.
Oil is now making the fluid more dense.

And what if you got no sump like 99.99% of 76< motors?
This kind of drag is the main liquid drag.
Its a 'no win' situation.
A robbing Peter to pay Paul situation.

Fluid Drag

Above, we've touched on the idea that oil in the flywheel cavity of the cases probably creates a drag on the rotating lower end, robbing power.
And the amount of oil probably affects the amount of drag.
More oil = more drag and causes it to increase the density of the fluid.
Fluid, not liquid.

This drag is like the drag that makes running in a swimming pool so difficult.
This drag is sometimes the only drag that gets considered.
The idea that 'the dryer the better' don't paint the whole picture.
That drag is smaller than the power used up to physically 'pump' the oil-air fluid as the motor spins.
The more dense the fluid, the more power is lost to pumping it.

No matter the density of this fluid, its the action of the pistons that moves it from the flywheel cavity.
On 76< motors, logically the way to accomplish this is to open the breather valve as the pistons fall so the max amount of 'fluid exhaust' occurs.
Then close the valve as pistons rise.
77> motors have a reed valve or umbrella flapper that accomplishes the automatic opening and closing of the 'fluid exhaust port'.
And it is not adjustable.

In this example when the valve closes, then the piston rise creates a giant vacuum in the case.
(with the vacuum being greatest at the highest point of piston travel)
Just after this highest point the pistons start to fall again.
This is when the valve opens again. (max exhaust right?)
This vacuum sucks the previous expelled fluid back into the case resulting in the crankcase not actually getting dry.


77> engines deleted the timed open and closed breather valve as is in 76< motors.
The the camchest is always open to the flywheel cavity with a one way valve between the motor and the outside environment.
The slang term “FooFoo” comes from the annoying sound that it makes when it gets clogged up with oil residue.

Hippysmack 2nd July 2019 00:42

The breather bolts in 91 Up engines have 2 different size holes through them.
91-03
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

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

The MoCo manipulated crankcase pressure with them I believe.
The crankcase splash holes were restricted to keep more pressure in the crankcase.
They introduced piston squirters (feed pressure from the pump) into the crankcase.
Since more oil in the CC means higher pressure and more drag, what were the affects?

The scavenger gerotors were not redesigned larger until 2007.
So for 04-06 models, they got the same return rate (as previous models without the added oil).

So I feel that the smaller breather bolt holes were designed to move CC pressure out the breathers faster than previous models.
(instead of bottling up CC pressure)
The smaller hole creates higher pressure. Higher pressure equates to faster flow.

So wouldn't the smaller holes actually control CC positive and negative pressures better in the higher pressure environment?

Hippysmack 5th July 2019 04:54

Vacuum Pump for Reducing Crankcase Pressure
 
BTW, anybody can jump in when you feel like it.
I'm not preaching here, I'm thinking out loud.

I've added some to post 6 on blowby and to post 10 on breather valves.
__________________________________________________ __________
Considerations for running a vacuum pump:

A vacuum pump, in general, is an added benefit to any engine that is high performance enough to create a significant amount of blow-by. 81)
(that's high performance enough…. not worn enough)
It will, in general, add some horse power, increase engine life and keep oil cleaner for longer (in a high performance engine).

1. Positive pressure is removed around the rings / ringlands.
There is no opposing force to keep the rings from seating on the ringland bottom.
On piston upstroke, the rings sit against the bottom of the ringlands.
On piston downstroke, the rings sit against the top of the ringlands.

2. Piston downstroke (positive pressure) aides in sump oil scavenging.
And unfortunately, vacuum pressure fights the oil pump.
You need more positive pressure in the crankcase to force the oil out of the sump.
However, if the vacuum on upstroke is lower, there will be more than normal negative head pressure by the time the downstroke happens.
Less pressure on downstroke means less force pushing against sump oil to scavenge.
Too low of vacuum head pressure when downstroke begins and you end up with more oil left in the sump.
(which marches toward a wet sumping condition)
So a multi-stage oil pump that doesn't depend on crankcase pressure assist will be better suited with this setup.

3. The updraft on sump oil is lower, creating more loose suspended oil.
The updraft is what aides in bringing oil into suspension with the air.
Once suspended, the 'mix' is able to 'float' and it will move in the same fashion that air will move (wherever it's pushed or pulled).
The mix separates on impact when it hits the crankcase / cam chest walls, cams / bushings etc.
Loose suspension (lower pressure) drops the air /oil mix ratio faster upon impact.
Tight suspension (higher pressure) drops the mix slower.
During high CC pressure, more oil is left into suspension by the time it reaches the breather valve.
When it hits the breather valve (on impact) more oil stays in suspension past the valve and out the vent.
Lower pressure hitting the valve drops the ratio fast enough that less oil is left in suspension by the time it reaches the vent.

4. Lower vacuum in the crankcase also hinders splash oil due to the lower updraft.
So it is possible to starve splash lubrication in the interest of lowering crankcase pressure.
Windage is also lowered and this is the propellant for splash oil.

5. Crankcase pressure is lowered even more below atmospheric pressure.
However, combustion chamber blowby (thru the rings) adds positive pressure to the crankcase at the same time it's being lowered.
So there is a balance there like when you turn on a single water faucet.
1/2 a turn cold, half a turn hot gives you warm water.
1/2 a turn cold, full turn hot makes the water hotter.

6. Gapless rings allow less blowby during upstroke which creates less fill pressure in the crankcase.
(thus, lowering vacuum head pressure at piston downstroke)
This may be the reason gapless rings increase wet sumping.

In summary:
Racing bikes can pump enough vacuum into the engine to create better ring seal = more power at high RPM.
This is fine as long as the oil pump system is modded to return more oil to the tank by itself, without the need for CC pressure assist.

The use of a vacuum pump on a Sportster street engine can easily create wet sumping issues.
Street bikes will only occasionally see high enough RPM to warrant a vacuum pump but even then still running on the OEM oil pump.
So the possibility for wet sumping goes up on them.

If you want to run a high level of crankcase vacuum (18 inches HG or more); 82)
There must be provisions in the engine to supplement the lubrication loss (splash oil through windage).
There can be problems with at least wristpin lubrication also.

Running a vacuum pump also would require scheduled diagnostics.
The amount of vacuum pulled depends on the general status of crankcase pressure at the time of use.
(I.E. current conditions such as; ring seal, breather valve wear, vacuum leaks, head valve leaks etc.)
You can't just install one and forget about it else you've defeated the purpose of installing it.

So it is possible to run a vacuum pump on a street engine.
But there are more considerations than just hooking one up.

bustert 7th July 2019 21:44

all things said and done, anything can be done.
man can make it, man can break it
i mentioned this before but i cannot not find the picture.
this was a race engine that the scavenge pulled from normal channels PLUS and added port to the flywheel compartment. this was a dry sump mc engine.

there is one more facet to the stone
race cars run high rpm and cam profiles do not lend themselves to making usable manifold vacuum so vac pumps are used. the same with boosted systems.

as a side note: what IF you vented from the flywheel compartment is a controlled way and yet have enough diff'l to move oil around. this can be achieved via a set pressure reed assy. hd, like all american engineering, band-aide to get by. hd just keeps it design to reduce cost and venting through the heads is archaic to say the least. eventually, the oil tank will be a pan like appendage under the flywheels, isn't bt going that route?

Hippysmack 7th July 2019 21:49

You're right.
I think if you sit down with it, you could probably accomplish several ways to scavenge outside the box.
I'd like to take apart a ProFlow to get a visual of how they accomplished the multi-stages.

edit:
Most of the information I could find was involving the use of a vacuum pump on autos.
There's not much published, I could find, on using them with motorcycle engines.
Doesn't mean anything other than speed shops may not want to divulge their secrets.

They are used for compensation as well as for better ring seal....but mostly advertised for ring seal.
There are pumps spec'd for vacuum measurements and also ones spec'd by RPM range.

But, along with the addition of a vacuum pump, there is also an addition of a performance oil pump.

If you vented from the crankcase area:
Splash is important element in the sump area.
Would that affect how well splash worked?
I guess you could tap into the side-top with a vent line and a reed valve.
Not sure of the affects though.

Hippysmack 8th July 2019 02:28

Once and for all, what is the affectual difference between venting from the cam cover and the heads?
I just can't find a downside to either other than heat hardening the umbrella faster.

When both are working properly, what's the diff?
I've read that CC pressure moving up the pushrod tubes interferes with drain oil traveling down the tubes.
I can't see that being an issue.
Drain oil mainly goes into the head / cylinder drain holes from the rocker arms spraying the valves.
Separated oil from mist falls back into the tubes.
But that oil is also pulled down on piston upstroke.
And air/mist once again goes up on piston downstroke.
Where is the problem in that cycle?

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

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

bustert 8th July 2019 04:16

hd using cooling jets so splash is really not a killer need.
as for a band-aide, while it does work as they put it but i wonder if a better mouse trap would be to add cooling via a rifled connecting rod. the concept is not new and used in commercial engines.
thing about engines and designs is that diff pistons require diff rings. the top ring is usually a consideration but the second one more relaxed. then they have ones with lower skirt rings usually found on trunk type pistons.


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