HarleyTechTalk

this is the theory why vacuum in the crankcase makes power, I copied and pasted

As RPM increases the rings start to get pushed upward on the outer ring edge due to the pressure behind them due to the blow-by build up in the pan, this causes a reduction in ring seal to the cylinder walls, this causes more blow-by. It also causes the rings to "flutter" which further increases blow-by.

The increased pressure in the pan (due to the fact that in a higher performance engine you cannot get all the excess air pressure out of the engine with just breathers (much less engines with PVC systems that are sealed) then PUSHES oil entrained in the air past the rings on the intakes stroke when the engine is SUCKING in air. During the intake stroke oil is also SUCKED past the valve guides. The net result is oil contamination of the fuel (the same way a PCV system contaminate the fuel by sucking oil into the intake), which effectively reduces the octane rating of the fuel. This reduces HORSEPOWER, and on a nitrous or power adder engine can actually burn a hole in the pistons from the increased heat in the chamber due to the faster flame front.

The vacuum pump can reverse every one of these problems by reducing, eliminating or even putting a negative pressure on the engine. The net result is better ring seal, less or no oil contamination, less oil leaks, cleaner oil, longer engine life and MORE HORSEPOWER. An added advantage is your engine builder can use lower friction ring packages because the resulting blow-by is mitigated by the Vacuum pump.


I have seen this theory work on the dyno and the track.  Drag cars found more benefit from this when some classes were required to start running mufflers.  Muffled systems created more crankcase picture, they also had trouble with the typical evac systems that just ran from the valve cover to the header collector.  Too much vacuum causes tooo much reduction in oil mist in the crankcase,  some guys thought in caused wristpin failure.  10" vacuum seemed to be the optimum for a big block chevy.  It would be interesting to see how much crankcase pressure a v-twin makes at max rpm

Quote from: Max Headflow on February 04, 2016, 10:24:07 AM

Quote from: strokerjlk on February 04, 2016, 10:09:14 AM

this is how they were routed on the nitrous  motor .

Bet the nitrous keeps them lines clear.. 

The water from the catch can smelled like moonshine .  That was when I was running E-85

Very nice job on the catch can!   

Put me in the camp of thinking routing up and back would be better than low then high.  Your lines will fill up with glop, and if it's the cold weather sputem (maybe we could call it head cheese?) that stuff will congeal and plug the line.   Like a sewer line trap. 

Run em like Jim, or use the banjos pointed up (or fittings pointed up in a WorkTruk style back plate)then route lines up and back, at least when the engine is parked the fluids are going to run in two different directions from the highest point. 

At least when the lines are run up, the fluids that gravity pulls out of the fittings is stopped.  If there's enough oil/spooge being force out the lines when routed up I would think you would have a really serious case of carry over if you ran lines down...

Two things.

1.  Has anybody actually done vacuum testing on the crank case to see if a vacuum pump is needed.  The testing on my Evo with a good oil pump showed I was running in a vacuum.  I hate to bring up somebody else's testing but I did watch them do some testing on the T-vo.  Case pulled a vacuum.  No testing on a TC but I would like to revisit the S&S read valve with the newer 3 stage pumps.  I think these pumps could be a possible cure for the pressure differential problems the valves create.

2.  Had a customers bike that ran the breathers up under the tank and seat and then down to the ground back by the swing arm.  The junk in the lines going up would clog, but they were 1/8 or 3/16 inch ID.  Might not be a concern with 1/4 or 5/16th.

.....and as always.  Looks good.

A friend and I did vacuum testing many years ago on Evo's.  We compared head breather to case breather.   The head breather maintained a few inches of vacuum.  The case breather would show pressure, no surprise...   

At the time the original KrankVent had just come out and a buddy who was friends with the Spyke guys sent me one to check out.  So we performed the test again but installed the krankvent.   

Putting the Krankvent on the case breather changed the result to work just like the OEM head breather.  Vacuum maintaiend.
Putting the Krankvent on the head breather made no difference at all. 

REgarding spooge plugging the lines going up.  When I ran a single 5/16" line from a 'T' between the banjos I did see some accumulation of crud.  At the moment I'm running the lines straight down through a T because I didn't have enough hose available to run two lines up and back.  Just haven't gotten around to changing that... and I'm not getting anything out of the current line either, surprisingly.

That is why the SnS reed valve is such a popular item for new builds and rebuilds of motors.
They advertise that it stops high rpm oil carryover completely.

Quote from: Nowhereman on February 04, 2016, 12:06:31 PM
That is why the SnS reed valve is such a popular item for new builds and rebuilds of motors.
They advertise that it stops high rpm oil carryover completely.

Is it?   It's been around forever.. In fact my SnS cases came with one.. Still sitting is a box somewhere tho.. There were issues with them early on causing oil carry over... One of the reasons why I didn't install it.. 

Quote from: Nowhereman on February 04, 2016, 12:06:31 PM
That is why the SnS reed valve is such a popular item for new builds and rebuilds of motors.
They advertise that it stops high rpm oil carryover completely.

My 120 doesn't have any carry over issues.  I'm using the latest version of Harleys stamped breathers, with the drain opened up.  On the other hand my top end isn't swimming in oil either.

The conclusion I came to with the krankvent test was that the breather umbrellas serve the intended purpose of creating a vacuum in the crankcase.  No externals needed unless retrofitting a acse breather.

If a rocker box is being inundated with oil it's going to escape out the breathers no matter what you do.   There's no vacuum pulling oil away from the breather exits, the umbrella comes off its seat when the pistons travel down the cylinder and any blow by comes into play.  So any oil that has worked its way into the breather seperator will tend to be moved toward the exit anyway.   Umbrella is a one way valve out, not letting air back in.  So the oil goes with the air.

Quote from: hrdtail78 on February 04, 2016, 11:13:34 AM
Two things.

1.  Has anybody actually done vacuum testing on the crank case to see if a vacuum pump is needed.  The testing on my Evo with a good oil pump showed I was running in a vacuum.  I hate to bring up somebody else's testing but I did watch them do some testing on the T-vo.  Case pulled a vacuum.  No testing on a TC but I would like to revisit the S&S read valve with the newer 3 stage pumps.  I think these pumps could be a possible cure for the pressure differential problems the valves create.

2.  Had a customers bike that ran the breathers up under the tank and seat and then down to the ground back by the swing arm.  The junk in the lines going up would clog, but they were 1/8 or 3/16 inch ID.  Might not be a concern with 1/4 or 5/16th.

.....and as always.  Looks good.

Vaccuum pumps on street bikes would be a waste of time IMO but several of the gas class guys have and do run them in drag racing. Also Bennetts Performance LSR bike runs one and it has helped them with oil control and ring seal...



My Street bike-

My Evo testing was a bottom breather and ET vent.  Same concept but has a metal valve. 

The S&S valve for the TC might be the hot ticket for oil carry over but it wasn't good for sumping.  That is why I think that a pump that scavenges from the crank and cam chest separately might work.

so if one was to try that Jason.. would you tap and thread into the bottom of the cam chest and then into the bottom of the crankcase, then dump back into oil tank? 

Had a s&s reed valve in my s&s case twin cam.  Took it out and have less oil carry over with just the standard harley breathers. Actually very little.  I also route breather under the tank and then down to catch can. I look at a catch can as a quick way to monitor general health of motor

Quote from: UltraNutZ on February 04, 2016, 01:03:11 PM
so if one was to try that Jason.. would you tap and thread into the bottom of the cam chest and then into the bottom of the crankcase, then dump back into oil tank? 

It isn't as easy as the Evo.  When I looked into I could only see a couple of locations that would work.  06 and later cases.  It looks like you could tap into crank case back on the RH case back where the oil enter and exits the engine.  Looking at the inside.  There are two cavities back there that might be a good spot out of the way somewhat of slinging oil.  This could be plugged and then the cover for the oil lines could go on and nobody would ever see it.  The other place that might work is right under the numbers on the LH case.  A small 1/16 npt is all that would be needed.

Simple test.  Read pressure in the case with out valve, and measure oil in sump. Install valve and read pressure in case and measure oil in sump.  A spintron would be helpful.

I might be off base with my thinking about a 3 stage and the vent.  But my thought is.  If you tax a single rotor with getting oil out of the crank and the cam chest.  The valve will create more pressure in the cam chest over the crank cavity.  The difference in head pressure (not sure if that is correct term) between these two cavities would help feed the pump from the cam chest.  Have independent scavenge rotors would nullify the pressure differential.

Sorry for the OT, Max.

BTW,
Can looks good Bruce-
Don't see any problems with the can as it appears to be pressure fed and gravity will return anything not collected in the can right back to where it came from which shouldn't be an issue. Simply allows the release of any pressure and a clean place to collect any mist, muck, or whatever-as long as you aren't running any one way check valves along the route.
Don't see any kinked or curved lines where oil will get trapped...

Quote from: hrdtail78 on February 04, 2016, 01:48:56 PM

Quote from: UltraNutZ on February 04, 2016, 01:03:11 PM
so if one was to try that Jason.. would you tap and thread into the bottom of the cam chest and then into the bottom of the crankcase, then dump back into oil tank? 

It isn't as easy as the Evo.  When I looked into I could only see a couple of locations that would work.  06 and later cases.  It looks like you could tap into crank case back on the RH case back where the oil enter and exits the engine.  Looking at the inside.  There are two cavities back there that might be a good spot out of the way somewhat of slinging oil.  This could be plugged and then the cover for the oil lines could go on and nobody would ever see it.  The other place that might work is right under the numbers on the LH case.  A small 1/16 npt is all that would be needed.

Simple test.  Read pressure in the case with out valve, and measure oil in sump. Install valve and read pressure in case and measure oil in sump.  A spintron would be helpful.

I might be off base with my thinking about a 3 stage and the vent.  But my thought is.  If you tax a single rotor with getting oil out of the crank and the cam chest.  The valve will create more pressure in the cam chest over the crank cavity.  The difference in head pressure (not sure if that is correct term) between these two cavities would help feed the pump from the cam chest.  Have independent scavenge rotors would nullify the pressure differential.

Sorry for the OT, Max.

The discussion about carry over and getting oil out of the motor is on topic IMO... Kind of the reason I added the can..  Not sure a spintron would do what you are thinking tho.. A quick response pressure transducer and storage oscilloscope would be good tho..   

So.... I don't want to brag or anything, but since people are showing their drag bikes with catch cans here's mine...





Wait wait... before a mod deletes this, it's on topic. Those little catch cans are made for racing minibikes, and are only about 20 bux. Might be perfect for a Harley. Also, look on top of the engine in the first pic... that's a fuel pump driven completely by impulses from a fitting on the intake manifold. Could one of those be used to purge the lines on a setup like Max's?

I have VERY good 15 foot times

edit... link to catch can.... http://www.bmikarts.com/Aluminum-Catch-Can-for-Seat-Strut_p_1886.html

So who made the manifold and flywheel?

http://www.arcracing.com/

  The engine also has an Isky cam..... Tim Iskandarian, Ed's son. Has a whole business around small engine racing. You can spend a LOT of money on these things

Quote from: UltraNutZ on February 04, 2016, 01:03:11 PM
so if one was to try that Jason.. would you tap and thread into the bottom of the cam chest and then into the bottom of the crankcase, then dump back into oil tank? 

That would be similar to the vent lines etc. that I used on my old Shovel stroker:



I was running Delkron cases with the removable bottom plate with an oil drain fitting. I had a line running from there to a fitting I had drilled & tapped into the cam case breather cavity (I also added external oil drain lines to the heads after plugging the internal returns that drained to the lower end)

I was also playing with the Krankvent which shows in the rear of the rigid frame in that pic.

~John

Quote from: Max Headflow on February 04, 2016, 09:58:16 AM

Quote from: turboprop on February 04, 2016, 09:49:42 AM
You are not taking into account piston ring blow bye and air that is returned from the oil tank to the case via the vent line.

Not sure what you are saying.. The purpose of the vent line between the tank and engine only to keep the pressure in the tank and motor the same.   Blowby / leakage is the main reason why there are breathers in the crankcase (actually up in the heads)..

I do not agree. The oil pump pumps oil AND air back to the oil tank. The oil tank is sealed. The air that is pumped back to the tank then travels via the vent line back to the engine and is expelled through the case vents.

To prove it. Pinch off the case vent line on a harley engine. The oil cap will pop off.

Quote from: turboprop on February 04, 2016, 08:05:53 PM

Quote from: Max Headflow on February 04, 2016, 09:58:16 AM

Quote from: turboprop on February 04, 2016, 09:49:42 AM
You are not taking into account piston ring blow bye and air that is returned from the oil tank to the case via the vent line.

Not sure what you are saying.. The purpose of the vent line between the tank and engine only to keep the pressure in the tank and motor the same.   Blowby / leakage is the main reason why there are breathers in the crankcase (actually up in the heads)..

I do not agree. The oil pump pumps oil AND air back to the oil tank. The oil tank is sealed. The air that is pumped back to the tank then travels via the vent line back to the engine and is expelled through the case vents.

To prove it. Pinch off the case vent line on a harley engine. The oil cap will pop off.

On my evo the oil pump is a pro flow it has geroter gears and l also vent my cap.
Oil pressure when the motor is hot 30 psi at idle.It also has a two piece shaft so you can easily remove the pump on a Fxr the pump is no longer made and I have a new one for a spare.
John


Added: I have head breathers and two case breather.I just vent the case breathers with a small filter.Would it be better to put a crank vent on,is that just a one way valve going out??

Quote from: turboprop on February 04, 2016, 08:05:53 PM

Quote from: Max Headflow on February 04, 2016, 09:58:16 AM

Quote from: turboprop on February 04, 2016, 09:49:42 AM
You are not taking into account piston ring blow bye and air that is returned from the oil tank to the case via the vent line.

Not sure what you are saying.. The purpose of the vent line between the tank and engine only to keep the pressure in the tank and motor the same.   Blowby / leakage is the main reason why there are breathers in the crankcase (actually up in the heads)..

I do not agree. The oil pump pumps oil AND air back to the oil tank. The oil tank is sealed. The air that is pumped back to the tank then travels via the vent line back to the engine and is expelled through the case vents.

To prove it. Pinch off the case vent line on a harley engine. The oil cap will pop off.

tomaydo tomahhdo.   

Yes, the scavenge pump has more volume and since it pumps more the tank will pressurize without the vent..   It won't pop the cap off one a 07 up bagger.. They screw on..   Then why don't they just vent the tank outside?

I think the venting is an emissions/EPA thing as to why the oil tank is not vented to the atmosphere.

It is really pretty simple. The oil pump pumps oil and air back to the tank. The tank is sealed so where does the air go, it goes back into the engine and is expelled though whatever vent system the engine has.

Some racers, and even warmed over street bikes will have a filter tee'd into the vent line between the tank and engine.

@John - the 30 psi at hot idle is somewhat typical with that pump. I assume you know about the S&S jets under the upper cap that canoe used to adjust the oil pressure. My red bike is running a 40 jet and has 30 Lbs at idle as well. Have been tinkering around with the idea of either soldering up a jet and drilling it to a smaller size or bleeding some of the pressure back into the tank.

@Max - Like many on this page, I too have a Jarz catch can rigged up on the red bike and noticed much less 'stuff' in the can after I vented the cap on the oil tank. This reenforces my hypothesis about the air flow from the tank to the engine and out the engine vents.

Will add that I think that with less air being expelled out the heads vents, that the oil being expelled through the head vents is reduced because there is less air flow to carry oil through the passageway and out the vent.  Again, my observations on several bikes supports this.

Yes the pump returns air with the oil back to the tank but that air was in the crank case with the oil to begin with, it does not add air to the closed system. The equalizer hose (vent) just allows the head space in the tank and the crank case to have equal pressure. On an engine with healthy ring seal and umbrella valves you will get a vacuum on the oil fill plug.

Quote from: turboprop on February 05, 2016, 02:25:28 AM
I think the venting is an emissions/EPA thing as to why the oil tank is not vented to the atmosphere.

It is really pretty simple. The oil pump pumps oil and air back to the tank. The tank is sealed so where does the air go, it goes back into the engine and is expelled though whatever vent system the engine has.

Some racers, and even warmed over street bikes will have a filter tee'd into the vent line between the tank and engine.

@John - the 30 psi at hot idle is somewhat typical with that pump. I assume you know about the S&S jets under the upper cap that canoe used to adjust the oil pressure. My red bike is running a 40 jet and has 30 Lbs at idle as well. Have been tinkering around with the idea of either soldering up a jet and drilling it to a smaller size or bleeding some of the pressure back into the tank.

@Max - Like many on this page, I too have a Jarz catch can rigged up on the red bike and noticed much less 'stuff' in the can after I vented the cap on the oil tank. This reenforces my hypothesis about the air flow from the tank to the engine and out the engine vents.

Will add that I think that with less air being expelled out the heads vents, that the oil being expelled through the head vents is reduced because there is less air flow to carry oil through the passageway and out the vent.  Again, my observations on several bikes supports this.

Are you running the one way valves in the heads or the cams case breather?  Evo motor or TC?  Makes a difference...