Crancase breather on a listeroid twin

[Geno]

I like the idea but I wonder how much of the blow by gasses would be condensed and returned to the crankcase in such a setup. I burn WVO and that's the last thing I want in my oil.

Thanks, Geno

[potter]

If this hose was open how could you have a vacume in crancase 

[oliver90owner]

Jens,

Have you checked the pressure in your inlet manifold/ air cleaner? it should be very close to atmospheric.

If you engine is leaking from gaskets it is simply down to you to fix them with decent properly sealing ones, as they are rubbish.  I am sure you car engine does not leak oil like this?  OK some do!

The crankcase pressure is kept at or very slightly below atmospheric to allow oil seals to work (crankshaft seals, for instance).  The original Listers had felt seals only, on the cranks and relied on a tiny under-pressure to avoid oil wicking outwards.  Most new cranks have lip seals.  These should only need to operate at atmospheric pressure.  All engines have a breather of some kind.

I am amazed that you would think your compression rings were 100% efficient!  Remember they are fitted with a gap between the ends of the rings and this can only increase in size as the engine components wear.


Regards, RAB

[cujet]

On my twin, I installed a brass hose barb on the bottom of the intake manifold. It makes a good bit of suction and I use it to collect crankcase vapors. I simply locate a hose above the breather right now, with plans for a better system soon. While I have not hooked it up to a PCV valve yet, I am fairly certain it'll work just fine due to the strong suction pulses. My plan is to use a standard old world style PCV valve on an adaptor located on the crankcase plate. Maybe I'll adapt it to the breather elbow.

I was planning on leaving the original breather too.

Chris

[oliver90owner]

I will try to come up with some sort of low power vac pump to help out

Why?  If the engine crankcase is open to atmosphere it will breathe sufficiently.  You do not need a vacuum in the crankcase.  If your gaskets are leaking they should not.  Change them for good ones or install them properly.

If there is excessive blow-by, you have a problem.  Listers did not have this problem nearly 80 years ago.  So is this a new invention or what?  What has changed?  KISS principle worked wonderfully in those days.  Still should.

Regards, RAB

[oliver90owner]

Jens,

Read my posts!  Into the inlet will be near to atmospheric (slightly less, depending on the pressure drop across your filter).

I have some seeping through castings as well.

All I can say is never buy an Indian car.  It would never even hold water!  You should have bought an engine not a seive or metal sponge   Little wonder people have gases leaking into the cooling system - porous heads, porous liners, porous gakets and porous pistons by the sounds of things

One hundred hours and the crank seals have failed.  That is equivalent to failed seals on your car at 5000 miles.

There is a light flow of smoke coming out - stuff that was not enough to push open the spring on the breather valve that is on the crankcase access cover.

Over time that 'flow', if it is prevented from escaping will build pressure.  It has to go somewhere.  It will not go back the way it came. It must either condense or compress.  Laws of physics.

RAB

[oliver90owner]

Re the crank seal - you are assuming that there are seals on the crank.  I do not know if there are seals there

No, I am not assuming anything.  I know.

BTW, I don't know why you are having such an issue with applying a bit of vacuum

KISS

You will go ahead and apply all the vacuum you want.

Will it do any good?  Doubtful.  Any air you draw in from outside will need to be filtered?  Dust drawn into crankshaft seals will only accelerate the seal/crankshaft wear.  Any contaminating dust in the oil the will accelerate general engine wear.  Something else to go wrong.  More complication.  However hard you try you will not get more than 15psi suction (about 100,000Pa).  Probably adversely affect your belt tracking problems and create more soot down your exhaust pipe, for all we know. 

I was wondering where the accumulated gases from your 100 hours run time have gone - surely not into the atmosphere?  If there is so little you may not have noticed it.  If you are looking for an excuse to do it, don't worry, just go ahead, but be careful the crankcase doesn't implode when you get a really good vacuum - you know the quality of these Indian castings!!!

RAB

[oliver90owner]

Do I detect a tone of crankiness ?

Depends on your sense of humour.

One or two aspirins will relieve a headache in around twenty minutes?  So will the whole bottle do the same job in one minute?

I sometimes - well often - shake my head and chuckle at where you are coming from, when I read your posts threads.

RAB

[snail]

Jens,
     I realise that you don't know me, but I'm with you on the vacuum thing.
The singles run under considerable vacuum. I temporarily replaced the breather valve on a single with a 3mm sheet of soft silicone rubber.( The original was off for a clean up.)You wouldn't believe the deformation in that rubber! I would imagine that dust etc was not thought to be a problem, or couldn't be dealt with using 1920's technology.
     The twins are a whole different ball game.They are "designed" to run under pressure. The reason I say this is that there is no mechanism for generating vacuum, but there will always be some blowby (however slight). Ergo positive pressure.
     My 'roid twin used to leak oil from the end of the camshaft, mains, tappets (slight, and probably not a bad thing) and anything with the slightest clearance. I also have a Dursley twin and I fully expect it to leak volumes from the sliding oil filler cover.(I no longer use the 'roid, and the genuine article is a "long term project" at least 2 years so far, and counting....)
     Many moons ago,I suggested putting a slight restriction in the intake to generate some vacuum for the breather (never tried it, got mains power!). There was talk on this forum that putting extra air into a diesel is counter - productive if you don't need the extra power. Having slightly less air shouldn't be a problem if you only want 80% or so power. My Powerline twin came fitted with a restrictor in the form of an undersized hole in a gasket on the inlet manifold!
     You are already part way there, try a larger hose and some restriction. If you don't like it take it off!
Hell, tinkering is what it's all about isn't it?

cheers,

brian

[oliver90owner]

I would imagine that dust etc was not thought to be a problem, or couldn't be dealt with using 1920's technology.

Snail,

Dealt with admirably.  The small amount of underpressure was controlled by the breather and  the crank seals were felt.  They were not supposed to drag in large volumes of air, just enough under-pressure to stem any outward flow of excess oil.  A large area for air filtration, unlike the miniscule contact area of a lip seal.  Wasn't 1920s technology either - had been around for about 20 years or more before the CS came out, as they used the same ideas on the previous engines.

Regards, RAB

[cschuerm]

Jens,
As I was catching up on this thread, I was thinking to myself that a good solution would be a venturi in the intake manifold tied to a crankcase vent port, but then I see great minds think alike!
Please continue your hobby tinkering and talking about it.  That's kind of the point of this forum and how we share ideas, successes, and failures.  If this was cookbook science, it would pretty much make for a boring hobby. 
As has been pointed out, the singles generate substantially lower case pressures than the twins.  I'd think that anything you do to decrease the internal pressure will have some positive results although it's doubtful you'll ever manage to create a clean roid :-)
Now, since the topic is all about differential pressure..... you have your roid in a box already.  Just seal up the box, run the vent outside of the box, then pressurize the box!  Much easier to push clean air than suck crankcase vapor.... VBG!

chris

[sarawnw]

Hi All


Sealing the box would make the engine sound level much lower too.  Should probably bring the intake outside though,  run it through a muffler and air cleaner.  that way, the compressor pump required would be smaller.   

Just run the exhaust inside the box, alot of pressure would be generated then.  Use the breather to let out the excess pressure. 

Just brain storming,  I have small leaks to.  The thread is very interesting and I am glad you started it. 

sara

[carlb23]

you can always salvage an old smog pump off an early to mid 70"s GM product and belt drive it.

[AdeV73]

My initial aim was for more like 6 to 12" WC and I might try additional vacuum to see if that improves anything. (BTW, I believe it's roughly 26" of WC for one PSI)

Sounds like a good result with that venturi - but I think you need to start looking at a supercharger...  This will give you better vacuum (more airflow past the venturi), you can continue to use your hot intake air (the supercharger will make it even hotter, but you're not worried about getting lots more power, you just want to use up the hot air, and compressing it will get some more in, maybe back to a cold air charge's worth); and so long as any power increase from the supercharger out-does the parasitic effect of driving it, you're quids in!

Plus, how cool would it be to have a supercharged listeroid? 


The only downside might be that superchargers are quite noisy; but I guess you could just throw another rug over the 'roid's box, job's a good 'un

[1958steveflying]

Jens

   If you want to cool your intake air and leave the intake inside the enclosure for noise reasons, bring the pipe out to an intercooler with a fan blowing on it and back in to the engine. Easy to monitor and control the intake temperature. You can also have the venturie and breather pipe outside to keep an close eye on the content going into the intake from the engine.

  Steve