Crankcase Venting 101

Hi Schultzy,
Prolonged high rpm operation will spew oil from the Husaberg crankcase as a result of having a small crankcase capacity and minimal breather baffling.

Installing a check valve reduces pulsing consequently reducing oil spewing.

Oil spewing is considered normal for Husaberg, however, it need not be with a simple revision.

Kind Regards,
Dale

LINEAWEAVER said:

Hi Schultzy,
Prolonged high rpm operation will spew oil from the Husaberg crankcase as a result of having a small crankcase capacity and minimal breather baffling.

Installing a check valve reduces pulsing consequently reducing oil spewing.

Oil spewing is considered normal for Husaberg, however, it need not be with a simple revision.

Kind Regards,
Dale

Click to expand...

Dale,
Pardon my ignorance of Husabergs since this is my first one. By installing one of the valves & creating some vacuum in crankcase, that doesn't interfere with trans oiling? Is everything under the same vacuum, crankcase & gears?
Thanks,
Doug

Hi Doug,
I think for the most part it is safe to trust Dale's recommendations without question. This is not his first rodeo.
The answer to your question is no, the breather mod will not adversly affect transmission lubrication.

Hi Rancheroracer,
Crankshaft cavity scavenging operates via pressure differential between the main crankcase and said cavity. By installing a check valve in the engine vent line a vacuum is created in the entire engine assembly, however, the pressure differential between the crankshaft cavity and main crankcase remains the same.

Hope this helps.

Sincerely,
Dale

I was thinking of just fitting afilter to the pipe. Oil fumes do indeed lower the octane of the fuel. Would this be better, or is the suction of the crancase needed?

Vegard, I've seen a few installations like husabutt did but without a check valve. No extra vacuum and it still works. Since the engine is already fitted with a reed valve internally the crankcase will still produce its own "vacuum".
However suppose that you are crossing a ditch with deep cold water that quickly cool your hot engine and the gasses in the cavity inside it. What happens? I think that there is a risk that you get suction inside the engine which sucks in ditch water via the breather tube whose open end is submerged in the muddy ditch water. Not good for your engine if it actually managed to inhale the water. With the exhaust pulse air injection valve that husabutt fitted in the breather line he'll positively prevent that to happen.

I wonder what would happen if you connected the exhaust pulse air injection valve to the exhaust manifold, would it produce real vacuum in the engine?

Hopefully the "vacuum" in the frame tube is very moderate with a clean air filter after all so if you just fitted a breather filter splash proof and well above the water line I would guess you'd be all right. It has the advantage of simplicity. I'm running an installation much like husabutts but the valve is at the open end and I've never seen water in the oil even after deep crossings where the open end was submerged deep in the wet.
101...

I use my bike 98% for supermote, the last 2% MX... So.. No water...

Check my gallery to see Bobzilla's awesome job on my-now bike.

Smorgasbord said:

I wonder what would happen if you connected the exhaust pulse air injection valve to the exhaust manifold, would it produce real vacuum in the engine?

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It does indeed and I speak from experience as I have been doing such for some two decades.

Kind Regards,
Dale

So, LINEAWEAVER, it is hard to tell wether your competitors eyes are tearing from the fact that you got ahead of them with your vacuum perked up engine or wether it is because of the oily smoke coming from your exhaust?

Smorgasbord said:

So, LINEAWEAVER, it is hard to tell wether your competitors eyes are tearing from the fact that you got ahead of them with your vacuum perked up engine or wether it is because of the oily smoke coming from your exhaust?

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No smoke as a true void (vacuum) is created in the small crankcase.
ie no flow = no oil loss through the exhaust. :wink:

Kind Regards,
Dale

PS
I simply took an old idea and applied it to the built in fresh air EPA exhaust induction introduced in the early eighties.

In effect it will be a two stage vacuum pump then, where the reed valve and the piston is the first stage and the exhaust pulse air injection valve the second using the exhaust pulse wake which at best may be a really strong vacuum. LINEAWEAVER, you are indeed a genius!
BTW, how do you connect the exhaust pulse air injection valve to the exhaust?

If I understand this correctly you gents are suggesting to run the breather pipe/tube from the head to the exhaust pipe with the check valve in between thus creating significant crankcase vacuum. A constant vacuum will lessen pulsing thereby reduce oil spewing and will even eliminate it.
A couple of questions then.

How does this increase horsepower?

It seems that by scavenging oil mist via vacuum greater oil loss would occur.

Would you place the port on the headpipe near the cylinder head or further downstream?

Any photos?

Thanks,

Eric

Oil loss through valve guides and piston rings would, at least theoretically, be reduced with a vacuum in crankcase and rocker box as the pressure difference to suck the oil in would not be there any longer. The lack of pulsation (no gasses left that can pulse) in breather port might add to oil preservation. Maybe that all of this makes up for the increased boil off of the oil that the vacuum would promote. It could even be an advantage to have the oil degassed to get rid of voilatile components like fuel, water, oxygen and deteroriation products that you would not like to be there? Someone wrote that oil mist lowers octane numbers and if you don't get the oil mist in the combustion chamber you could perhaps increase compression a bit and you'd perhaps gain some power? I have no idea why it would cost so much power to have air in the crankcase. The Formula 1 (if they are still around) engines are supposed to run with vacuum in the crankcase to gain power, no idea how the vacuum is produced on those engines though. It would be very interesting to see a photo of the exhaust pulse air injection valve connection to the exhaust manifold on a Husa-berg.
But would you get cavitation in the oil pump and with that a lower oil pressure/flow?

Also, how would oil mist in vacuum be possibe? With no gasses left to bear the droplets? They would immediately drop to the bottom as they are created. Thinking of it this way it seems like you are doing the environment much less harm and you gain power...

How important is vacuum in the crankase? I'm into cars mostly, and I always seal the inlet-crankase hose, and fit filters.. Oil fumes won't be sucked out this way. Is this bad on a Berg?

What happens if I just fit a filter on the head vent?

But what if you don't get the oil mist in the engine any longer because of excessive vacuum, what will then lubricate the rockers, cams and follower bearings? Is the oil throw-off from the timing chain enough?

Vegard, if your reed valve still works you'll get the proper vacuum in the crankcase. Why don't you just fit that breather filter on the head vent. If you find that it dribbles oil too much then a bit of rubber hose in between would allow most of that oil to settle on the walls of the hose, to run back before it can ascend all the way up to the breather filter. Many engines do not use any vacuum at all in the crankcase and it still works fine. When the pressure is higher in the crankcase the fumes gets sucked out anyway by the lower atmosphere pressure.

Gentlemen,

Dry crank singles (those already equipped with a reed valve crankcase) benefit from the additional check valve only with regard to oil containment.

Many OEM singles employ a pulse air system which draws from the inlet box. In opposition to deactivating said system (common practice) I often simply replace the air box tap with that of the crankcase spigot.

The majority of OEM multi cylinder street bike engines are also equipped with such a system. I once again take advantage by routing the crankcase vent to the scavenging inlet.

A vacuum in the crankcase reduces pumping losses and improves ring seal. (a result of increased pressure delta above and below the piston and ring assembly)

I would like to take credit, however, such is old school technology and has been around since the sixties.

I am indeed beginning to realize that unlike crankcase scavenging many of you have not been around since the sixties and therefore much of what I have to say comes across as brilliant. Some content is indeed brilliant, however, I cannot take credit for that which is not my own.

Kind Regards,
Dale

Reprint:
Concept: Apply a vacuum to the crankcase. Rather than putting a breather on the valve cover to let pressure out, actually suck the air out to create a vacuum.

Benefits of Crankcase Evacuation:

1) Cleans up installation (prevents oil leaks from crankcase sources)

2) Reduces parasitic losses from pistons pumping air

3) Improves ring seal

4) Increases HP by 4-7% depending on the application

5) Eliminates PCV and possibility of oil being sucked into intake system

Tech / Method:
Basically seal the crankcase and run a line from the crankcase to an air pump (or other source of vacuum) and from the air pump to a breather tank. Additionally, if necessary, use a vacuum relief valve to ensure vacuum does not get too great. If you put more than 12in vacuum on the crankcase, you can suck the oil off the front and rear main bearings. That would be a bad thing. Alternatively, with the crankcase sealed up tight to achieve good vacuum, you don't want your pump failing either which would allow a severe buildup of pressure in the crankcase then.

Typically, crankcase evacuation systems employ either a "race type" belt-driven pump or use exhaust as a source for vacuum. Both of those can have problems for street application. The belt-driven pumps are almost always specified for full race applications and therefore would need rebuilt every few thousand miles. If you use the exhaust as a source for vacuum and you have mufflers, you may end up with a buildup of oil in your exhaust ahead of the mufflers. Electric pumps can be used but our experience was they are problematic and don't produce enough vacuum.

I'll leave it as it is then

LINEAWEAVER said:

Hello friends,
For what it may be worth:

If one can insure a slight crankcase vacuum (in particularly regarding a large displacement single) power shall increase coupled with a reduction in oil spewing. Such technology is certainly not new as it has been used by the drag racing community for many, many years. Simply look to the nineteen sixties era blown altereds with their exhaust scavenged crankcases.

On many a fours cycle engine (including Harley Davidson Big Twins and Rotax Singles) I have placed a high speed one-way check valve in the crankcase vent line. Doing such has proven true to form for some two decades now. (As a matter of fact their are over the counter CNC pieces now available through most HD speed merchants.)

Regarding the Husaberg engine:
Power output did not improve using such a device primarily as a result of the OEM crankcase reed valve. However, If a reduction of oil spewing is your primary objective an auxiliary check valve could be just what the doctor ordered.

An automotive air pump check valve serves the purpose nicely @ a fraction of the HD cost. One may purchase KEM part number 174-176 or cross reference said number to that of your local automotive vendors inventory (Kragen, etc.) .

Hope this helps.

Sincerely,
Dale

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Dale,
Is the use of this check valve going to eliminate the oil from running out on the ground in the probable event of being upside down and pinned by the bike?
I ask because on my 01 501 I just had a filter and the hose run up to the steering head and it worked fine but had the disadvantage of loosing oil while bottom side up. I know you are supposed to remain wheels down but I am working on my freestyle tricks and am in the process of doing a jump where I stay upside down for extended periods of time and the only thing holding me back is the loss of oil. :twisted: