Technical advise requested. Crankcase pressure.

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pete.v

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Does the Norton Commando engine require some crankcase pressure to operate to its optimum?
 
swooshdave said:
http://www.accessnorton.com/breather-valve-problem-t7562.html#p78786

Jim was running negative pressure.
Click to expand...

Ya, I get all that and I am trying to sidestep all the vacuum/added hp/wetsumping garbledyGoop.
Am I trying to fix something that aint broke? Maybe.
I am sure the knowledge I seek will most likely come from someone with racing history...... but is SOME pressure, even a very little, helpful for oil scavenging and/or will no or negitive pressure effect intake flow and/or upper end lubrication or something else?

This is what i am really asking for......

With or without one way breather valve, I have lots of pressure in the timing chest. I would like to work toward a static evironment. No pressure, no vacuum, by adding a breather from the timing chest in conjunction with the one on the lower rear left.

Does anyone see how this could be harmful.
 
pvisseriii said:
swooshdave said:
http://www.accessnorton.com/breather-valve-problem-t7562.html#p78786

Jim was running negative pressure.
Click to expand...

Ya, I get all that and I am trying to sidestep all the vacuum/added hp/wetsumping garbledyGoop.
Am I trying to fix something that aint broke? Maybe.
I am sure the knowledge I seek will most likely come from someone with racing history...... but is SOME pressure, even a very little, helpful for oil scavenging and/or will no or negitive pressure effect intake flow and/or upper end lubrication or something else?

This is what i am really asking for......

With or without one way breather valve, I have lots of pressure in the timing chest. I would like to work toward a static evironment. No pressure, no vacuum, by adding a breather from the timing chest in conjunction with the one on the lower rear left.

Does anyone see how this could be harmful.
Click to expand...

As mentioned many times the reed valve will get you closest to the neutral pressure in the crankcase. Because you have a 72 to ideally equalize the pressure in the timing chest you need to drill some more holes through to the crankcase as several folks have pointed out before. Or add a breather to where the later bikes have one, in conjunction with the one from the crankcase.
 
pvisseriii said:
...... but is SOME pressure, even a very little, helpful for oil scavenging
Click to expand...

Short answer: No.

and/or will no or negitive pressure effect intake flow and/or upper end lubrication or something else?
Click to expand...

First of all there is no such thing as negative pressure, you can't get below zero. What you're talking about is relative pressure - relative to the atmosphere but that is not a good norm.

Unless you fit a really powerful scavenge pump AND work on the breather system the absolute pressure is still in the region of several 100 kPa and any kind of detrimental effect of scavenging is purely theoretical there (like boiling the oil etc. ) The 2.4 litre V8 engines I used to work on are pretty mean in terms of scavenging power - and the ones I'm now playing with aren't too far away from that - and we don't even waste a thought in this direction. Ah, and more often then we like we see pressure peaks above atmosphere inside the crankcase so the scavenging power installed in that kind of crankcase is about a gazillion times higher than that of a Norton (and our crankshaft seals work the other way round.... 8) )

Fluids flow because of a pressure drop and the lowest possible pressure in the system - if properly set up - is the scavenge pump entry. As long as the pressure inside the crankcase is lower than the atmosphere the oil has absolutly no urge to seek a way out other than the scavenge pump. It's that simple.


Tim
 
Tintin said:
pvisseriii said:
...... but is SOME pressure, even a very little, helpful for oil scavenging
Click to expand...

Short answer: No.

and/or will no or negitive pressure effect intake flow and/or upper end lubrication or something else?
Click to expand...

First of all there is no such thing as negative pressure, you can't get below zero. What you're talking about is relative pressure - relative to the atmosphere but that is not a good norm.

Unless you fit a really powerful scavenge pump AND work on the breather system the absolute pressure is still in the region of several 100 kPa and any kind of detrimental effect of scavenging is purely theoretical there (like boiling the oil etc. ) The 2.4 litre V8 engines I used to work on are pretty mean in terms of scavenging power - and the ones I'm now playing with aren't too far away from that - and we don't even waste a thought in this direction. Ah, and more often then we like we see pressure peaks above atmosphere inside the crankcase so the scavenging power installed in that kind of crankcase is about a gazillion times higher than that of a Norton (and our crankshaft seals work the other way round.... 8) )

Fluids flow because of a pressure drop and the lowest possible pressure in the system - if properly set up - is the scavenge pump entry. As long as the pressure inside the crankcase is lower than the atmosphere the oil has absolutly no urge to seek a way out other than the scavenge pump. It's that simple.


Tim
Click to expand...

Thank you Tim, so adding another breather at the timing chest will cause no ill fatted issues in your opinion?
 
Quote,
Unless you fit a really powerful scavenge pump AND work on the breather system the absolute pressure is still in the region of several 100 kPa and any kind of detrimental effect of scavenging is purely theoretical there (like boiling the oil etc. ) The 2.4 litre V8 engines I used to work on are pretty mean in terms of scavenging power - and the ones I'm now playing with aren't too far away from that - and we don't even waste a thought in this direction. Ah, and more often then we like we see pressure peaks above atmosphere inside the crankcase so the scavenging power installed in that kind of crankcase is about a gazillion times higher than that of a Norton (and our crankshaft seals work the other way round.... 8) )

You don't get near as much benefit pumping a V8 engine down as you do from a single or 360 degree twin. A V8 engine suffers very little from pumping losses as there is always a piston going up when there is a piston going down so the volume of the crankcase stays pretty even.
I see average crankcase pressure of around 60 KPH with the CNW reed valve system on a Norton. That is measured with a absolute pressure sensor mounted in the tach drive hole and monitored with a digital scope..
I also had to put the engine seals in backward on the racebikes with the pump. Jim
 
Very informative reports to me. Jim what units are 60 KPH in say PSI?
Must remember to reverse seals in Peel's deal.
 
Steve, You won't be able to reverse the seals with a exhaust scavenger as you will not have scavenging at low rpm and the oil will leak out. Pressure in PSI ? Don't know right off but pretty small. Jim
 
Hm, ok, Jim, maybe saved me some learning curve mess reversing seals back.
Hope low rpm ain't much pressure issue one way or the other.
Peel may have a few *air intake* leaks built in to rocker covers, tending to nullify very low sump pressure, but a sump vacuum regulator valve may be exactly what Peel needs in head.

If your reading is in 60 kPa units, then = 0.008702264 PSI. Yes indeed rather low, so almost 15 PSI ambient pushing in on your flipped seals. Might help the corrosive gases lingering too.
 
hobot said:
Hm, ok, Jim, maybe saved me some learning curve mess reversing seals back.
Hope low rpm ain't much pressure issue one way or the other.
Peel may have a few *air intake* leaks built in to rocker covers, tending to nullify very low sump pressure, but a sump vacuum regulator valve may be exactly what Peel needs in head.

If your reading is in 60 kPa units, then = 0.008702264 PSI. Yes indeed rather low, so almost 15 PSI ambient pushing in on your flipped seals. Might help the corrosive gases lingering too.
Click to expand...


No- Atmospheric pressure at sea level is around 100KPH so 60KPH would be 40 below ambient. Jim
 
Just to clarify the objectives of the CNW reed valve;

1. It is not designed for nor does it have any effect on wet-sumping. [oil tank draining into the crankcase on a parked bike]

2.It is not designed to make more power. For the small amount of gain on a steetbike you would be better off skipping breakfast and saving your money.
[ it is valuable on a racebike where every little bit helps and you already skipped breakfast ]

3 . The valve and it's related case modifications are designed to stop oil leaks, eliminate blown crank seals, lower oil temperatures and lower oil consumption. Hopefully this will give longer engine service.

Originally the reed system was developed as a way to get a little more power on my racebike but it turned out to be a great modification on a streetbike.

I designed this system and turned the production over to CNW some time back so I don't have a vested interest in advertising these things. Just hope it helps. Jim
 
Well I sure would like to do some crankcases. One of these days it could happen. I would like to see some good aluminum barrels also and the list goes on and on.
Presently fuel injection systems are keeping me busy. I have been doing the first few installations and changing a few minor details to make them a little easier. I now have them set up for an o2 sensor which can be temporarily installed. Then all you do is set the ECM to autotune and go for a ride. It adjusts the fueling tables for whatever engine or modifications you happen to have. Then you remove the sensor and go back to the simplicity of a non-feedback system.
Then I will be doing a run of timing gears. They are now well proven and I am ready to buy some bar stock and run a batch. Jim
 
Ok I like being set straight. 40% of 1 bar 100KPH or 14.7 PSI = 5.88 PSI.
I think that ballpark Peel may reach with the planned air leaks from top down.

Off set the crank from the bores some in your new cases to ease the TDC jerks.
Compression release for wuzzes like me. Belt drive cam chain? Alloy cradles with built in provision for linkages. LH brake rear sets that work a master cylinder instead of cable. Built in outrigger bearing in inner primary case that bolt to rear cradle. Belt drive jack shaft to place real 3 wire alternator behind barrels.
Oil in frame fitting kit for easy sighting and draining. Triangulated roo bars for drop hazards like me.
 
comnoz said:
You don't get near as much benefit pumping a V8 engine down as you do from a single or 360 degree twin. A V8 engine suffers very little from pumping losses as there is always a piston going up when there is a piston going down so the volume of the crankcase stays pretty even.
Click to expand...

Sorry but that is simply wrong referring to said engine. That would be the case if the sump bays would be connected with large enough openings to allow pressure distribution which in itself is already a loss in engine power. Don't mistake this engine with a road going V8.

Get yourself this mag: http://motorfan-i.com/special/ It shows every single component of a 2009 F1 engine in detail (and discusses it but that would suppose you're capable of reading Japanese... :wink: )



Tim
 
Tim, It is correct that I know nothing about said f1 engine and would not learn much from a Japanese language magazine. You have gotten my curiosity up however and I will have to do a bit of research. Jim
 
F1's gained 'free'r' power by opening up/removing barriers to the cross pumping air friction between block bore sleeves of opposed piston motions. This is in addition to lowering vapor pressure-windage density drag inside.
 
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