Catch Tank ----------------------

[h701micra]

you obviously hav,nt studied a CG pcv system, paul is right the pcv draws only from the mesh and front rubber pipe that is fitted between the exh mani and g/box (not from the head or chain area) then it travels along the sealed galleries/oil separator under the cam cover
removing the pcv like most of the members looses that oil separation function and as a result the oil mist from the crank case is vented to the catch can
this oil is probably what you guy,s are collecting in your cans oil that should be in the engine
View attachment 34376

I haven't studied the CG at all, but it doesnt draw or create flow from the head/chain area, that's where the crankcase vapour comes from in the first place to be drawn out. Unless the CG is somehow blocked which I doubt being so similar to the GA engine.

I've drawn a diagram that I thought I'd already put to describe how its drawn and expelled. Vacuum and boost changes the direction of flow there's no 1 way of flow. So yes Paul is right... as am I

Again you're still stuck on just oil. They catch condensation and fuel vapour too not only oil... So its waste oil that can easily be replaced and its quantity is so small
In a percentage state. Your looking at 80% condensated water 15% oil and 5% blowby vapour

 

[frank]

I haven't studied the CG at all, but it doesnt draw or create flow from the head/chain a
In a percentage state. Your looking at 80% condensated water 15% oil and 5% blowby vapour

i dont dispute those figures at all mate, so you are removing a cupfull of water every few months ? (bearing in mind that for ever gallon of petrol bunt, a gallon of water is produced anyway, and some dragcars run water injection)
and you are removing a tiny amount of hydrocarbon ? (ie, fuel)
and in doing this you are losing the oil scrubbing effect that pcv systems give ? (and contaminating the oil as a result)

 

[r-reg-sr]

,,,,,,,,,,,,,,,,,,+ added weight of catch tank and the content its sposed to burn

 

[r-reg-sr]

can speak for myself only as non turbo i get a little dark stuff pooling under throttle body bottom of inlet-mani,,,,,,,sort of catching it?

my pipe snapped off the air box

 

[h701micra]

i dont dispute those figures at all mate, so you are removing a cupfull of water every few months ? (bearing in mind that for ever gallon of petrol bunt, a gallon of water is produced anyway, and some dragcars run water injection)
and you are removing a tiny amount of hydrocarbon ? (ie, fuel)
and in doing this you are losing the oil scrubbing effect that pcv systems give ? (and contaminating the oil as a result)

Water injection is a different system... as its clean water. not condensed and contaminated, and potentially days old
You're removing the oil scrubbing effect... as its no long needed.. there's no oil to scrub as it no longer enters the air way
PCV systems are a form of catch can anyway. The oil entering the air ways has so many negative effects

I recommend you read this
http://auto.howstuffworks.com/positive-crankcase-ventilation-system1.htm

 

[h701micra]

can speak for myself only as non turbo i get a little dark stuff pooling under throttle body bottom of inlet-mani,,,,,,,sort of catching it?

my pipe snapped off the air box

The pooling in your inlet is exactly what a catch can is designed to take out your airway and keep it clean

 

[frank]

can speak for myself only as non turbo i get a little dark stuff pooling under throttle body bottom of inlet-mani,,,,,,,sort of catching it?

my pipe snapped off the air box

Yes i,ve had CG engines that did that too zed (not the current engine tho) and they drank a bit of oil too.
But fitting a catch can wont stop the oil consumption tho, a typical 5year engine wont produce that gunk in the inlet mani (and our engines did.nt do it when they were 5 years old either) but most 15 year old engines will do it

 

[h701micra]

But fitting a catch can wont stop the oil consumption tho

Nobody said they would
But they'll keep it out the inlet

 

[frank]

Nobody said they would et

So if the engine is still burning oil the catch tank is ineffective then andy, paul captured that small amount of oil ^ in how many weeks ? Yet he has been burning half a pint of oil per week for the last 12 months.
The pcv system removes the blowby water/fuel because it removes it at source (the wire gauze near the piston skirts) then harmlessly burns them off during high vacuum conditions ie, when idling. We,re talking a few parts per million here, else it wont pass the mot h/c idle emissions tests
But fitting a catchcan like the members have allows those water/fueil contaminates to circulate around the engine

 

[h701micra]

So if the engine is still burning oil the catch tank is ineffective then andy, paul captured that small amount of oil ^ in how many weeks ? Yet he has been burning half a pint of oil per week for the last 12 months.
The pcv system removes the blowby water/fuel because it removes it at source (the wire gauze near the piston skirts) then harmlessly burns them off during high vacuum conditions ie, when idling. We,re talking a few parts per million here, else it wont pass the mot h/c idle emissions tests
But fitting a catchcan like the members have allows those water/fueil contaminates to circulate around the engine

Woah what? Have you gotten a little confused? Just when I thought we were getting somewhere we're back to square one. Open the links I've took time to post. It gives you the information you need to help you understand what I'm saying. At the minute you're ringing the point at hand. We've already proven near the start of this thread the effectiveness of a catch can the fact it takes the blowby and water out of circulation

A PCV system is in no way connected to oil consumption.. A lack of one maybe so in an extreme condition

PCV remove crankcase gases or in this case catches them in a can.. yes they're caught and condensed into the can... they dont just carry on circulating. If they're removed completely then the H/C readings will be lower than those that have been recirculated and burnt off unless you can assure they're being 100% burnt off completely.
The cam cover is the source.. it worked for engines up to near on 50 years ago when the original PCV system was thought of. Heat rises.. blowby and water is hot.. so it rises to the cam cover... it isnt all going to go through that little pipe connected to the PCV so it travels up the timing cover and is pulled out through using the flow through the 2 ports
Its massively basic to understand which confuses me as to why this discussion continues.
Or translated into Pauls example.. The oily air (our contaminants) from the frier (engine) cant all be extracted through one extraction point (PCV) and the area is too large (volume in the crankcase). So what's left escapes through the window (timing cover) and extracted by wind (vacuum flow)

Oil consumption is where oil gets into the cylinder due to number of factors and burnt off, this is basic stuff.. That is in no way physically related to the use of a catch can whatsoever. You cant expect a catch can to all of a sudden heal piston ring issues or stem seal issues... they're there to catch oil vapor, fuel blowby and water that arise in the crankcase. Not magically repair an engine
Paul's case he has a sealing issue with his piston rings... how can you relate that to catch can? This is what I would like an explanation for.
Especially as his catch can still collects the contaminants we expect to see. They'll be less as his crankcase pressure will be lower than normal, he has a crank scraper in place to reduce vapour and not a 100% seal on the piston rings... all contribute to the reduction in crankcase pressure and oil vapour volume therefore less to catch

 

[pollyp]

My catch can is plumbed between the rocker cover port that leads to the camshaft top region of the engine, and the turbo inlet which is ambient pressure.

This port expels out vapours including oil n water mist only when the crankcase is under +ve pressure and that only happens during high boost n blowby, which is infrequent.
Most of the time its under -ve pressure off-load and sucked by vacuum into the manifold. That's why it hasn't caught much.

If I had fitted a catch between the pcv (that leads down to the crankcase wire gauze port) and the inlet Manu vacuum, it'd show a different story n capture more mist.

My oil consumption is a seperate matter caused by the rings or bore finish and sump leak.

I don't think the catch can will affect the rate of any oil consumption issue cos if its fitted and caught the mist from entering the inlet, then whohoo the inlet stays cleaner and u have to keep emptying the collected contaminated oil.
Without a catch can like oem, the oily mist would simply coat all the inlet components after the point of entry, re-enters the chambers to be burnt, carbon up the components and never returns back to the sump in liquid form anyway.
So if ur losing oil via the pcv carrying too much mist then its gonna be gone anyway irregardless of fitting a catchcan or not.

Only end difference is the oil mist leaves the engine in a manageable liquid form with a catchcan (could be returned back to sump but not recommended with all the contaminants) whereas without a catchcan it leaves the engine in gaseous burnt form but builds up a carbon coated trail behind.

 

[pollyp]

Hmm thinking further, I think one of the causes for oil being lost in vapour form (as well as via leaking seals n rings) is due to excessive crankcase pressure from poor blowby.

Imagine the huge spray mist u get from a waterfall, that's the engine components churning up n spraying the oil mist around the case.

Now if we place a fine mesh gauze on one half of the waterfall (crankcase metal gauze) with a small extraction fan blowing the mist through the mesh (engine inlet vacuum), the water spray would easily condense on the mesh n flow back into the pond while the slow wind blows through the mesh.

The mesh has a limit to how much spray it can hold back.

Now if we apply a strong gust of wind (excess blowby pressure) it would try to carry n force most of the lightweight spray droplets through the overwhelmed mesh (through the course wire gauze & into the inlet Mani) plus the excessive blast will carry the remaining spray out the other open un-meshed end of the waterfall (camshaft open breather port)

This type of excessive oil loss was dramatically demonstrated when my stock piston last broke its ring land under boost and milky oil & water vapour gushed/forced out by the massive blowby through both the pcv into the inlet mani and out the camshaft breather port into my catch can.

 

[frank]

Yes paul, you are the only one i can see that is still running the pcv system that draws the fumes from the wire mesh near the piston skirts at idle/high vacuum, the other members in that link have blocked the mani pipe and vent the fumes from the top of the engine.
And you have fitted the catch can to the pipe that is designed to let the fresh air in while the pcv system is circulating (where the felt pad is in the airbox)
Put your finger on that pipe while the car is idling and you will feel the vacuum, and put your finger on the curved pipe between the exh mani and g,box and you will feel a strong vacuum too ( ooen the throttle and that vacuum/circulation disappears)
Andy, any k11 owner lucky enough to have an engine that does,nt burn any oil wont have any black gunk in the inlet mani, and because their healthy engine is,nt burning oil a catch can has nothing to catch, their pcv system will be removing any water vapour at source near the pistons like i,ve explained and will pass it through the engine during idle, you only have to look at the water vapour from your exhaust on a cold morning to see that an engine inhales gallons of water vapour every week.
If the member then fits a catch can, that water vapour etc is allowed to circulate around the engine and eventually is vented out of the top of the engine (along with some unseparated engine oil)

 

[h701micra]

In one breathe you say their engines don't burn oil in the next breathe they do at idle due to a pcv system. Which is it?
I've explained my point thoroughly. Its so severely basic to understand I'm near blue in the face explaining it. It's borderline an azzydot conversation here where facts are displayed and ignored

A pcv system allows them into the inlet to be burnt. They're going to build up on inlet components regardless
A can simply collects rather than allowing it into the air stream

You think they're bling frank you go with that theory
I'll stick with facts and evidence to prove otherwise. I'll stick with time attack crews and put this to their knowledgeable crews
But the below £100,000+ plus evo saw fit to use 3

 

[frank]

this is a discussion about a catchtank on a k11 not an evo 3 ffs, your pics/diags you posted probably date from the 70,s, whereas the CG was designed in the early 90,s.
the pcv system on the CG sucks the blowby fumes out at 10 psi of vacuum during idle, and fresh air is then sucked down the back side of the cam cover and onto the middle of the cams (i,ll have to edit this post as i go because this old lappy keeps crashing !)
here,s pauls pic that shows the cleaner gallery where the fresh air enters the head, and the dirty gallery where the fumes have been sucked out.
nissan applied sealer on that baffle plate so that the pcv was only drawing fumes from the wire gauze near the piston skirts

Ffs. Start again
That fresh air then travels downwards past the chain and 3big drainholes in the head, and replaces the air that is being sucked out of the primary oil trap near the pistons.
This system is so efficient that on a healthy engine that does,nt burn oil owners can get away with not topping up their oil for literally years.
so fitting a catch can to a healthy engine cant catch oil that is,nt being consumed anyway, a healthy engine is only burning water vapour and blowby/combustion stuff.
on the other hand, on an engine that is burning oil a catch can will trap a small percentage of crankcase oil (about 1% going by pauls capture-to-burn ratio)
fitting a catch can to a healthy engine will however remove the oil scrubbing effect near the pistons, and will allow the water vapour and combustion stuff to swirl around inside the engine, eventually venting out the cam cover into the can and condensing into that oily water you guys are finding
this circulation of fresh air in - vapour out only happens while there are vacuum conditions in the inlet mani, highest on throttle lift then idle etc, at about 1/4 throttle onwards the pcv valve closes and pcv circulation ceases (same when boosting)
here,s a pic of the primary oil trap fwiw

 

[pollyp]

ok drawn afew diagrams.
here's my PCV plumbing

Below Boost
When the inlet manifold is under vacuum and off boost such as during normal low load driving or coasting with the throttle closed, the vacuum pulls open the BOV, clean fresh air (blue) is sucked from the air filter through the turbo/IC/BOV/MAF and through the closed throttle.

but it also gets sucked up through the catch can, into the PCV breather port (blue arrow),

through an opening in the middle of the cover, over the cams and down towards the crankcase via the timing cover and oil drain holes.

at the crankcase it mixes with all the blowby, oil and water vapours coming from under the pistons (red)
this soup then gets sucked through the wire gauze at the crankcase breather where most of the heavy big oil droplets condenses and gets filtered onto the gauze to drain back down to the sump.

the remaining fine lightweight mist of oil vapour (purple) travels up the crankcase breather,
through a sealed route in the rocker cover (notice the heavy build up of oil vapour deposits coming from the crankcase over the years),
some of the mist may condense on the cooler outer walls but there's no drain hole so it just gets baked on by the heat over time,
through the 1-way PCV and down into the inlet manifold after the throttle butterfly to join the low pressure airflow.

Above Boost
When the inlet manifold is boosted at or above ambient 0psi, the +ve pressure shuts the BOV, clean fresh air (blue) gets sucked from the air filter through the turbo/IC/MAF and through the open throttle.

The +ve pressure tries to enter the PCV but since it's a 1-way valve it cuts off the flow from entering the crankcase (like shutting off the kitchen extactor fan whilst deep frying).

With no vacuum extracting any crankcase fumes through the crankcase breather, the pistons are still leaking more blowby past the rings (red), especially from the increased induction boost & combustion pressure.

This extra crankcase blowby pressure has to go somewhere with the least resistance, whether its via some weak crank seals or stem seals or out the open PCV breather port.

if the PCV breather port ain't blocked, the blowby enters through the middle opening in the rocker cover (red arrow), the cooler exterior skin of the rocker cover condenses some vapours (but just like my waterfall mesh filter metaphor above, it can only capture a limited amount per flow rate.
faster blowby flowrate = less time to condense onto cover walls = less vapour captured per litre)

the small amount of condensed vapour can drain from the enclosed rocker cover down onto the camshaft area via this drain hole

 

[pollyp]

youtubed bout the PCV and found these helpful videos.

this talks bout what blowby does


when frank mentioned that some members had disconnected the PCV vacuum line and plumbed catch cans to the rocker ports and the cans had also vented straight to atmosphere, what they've essentially done is convert the crankcase into a crude 1st-generation breather tube.


here's a good description of the modern PCV. interesting to know that the PCV check valve was designed to prevent backfire getting to the flammable crankcase and that the PCV tube is restricted for a reason.


some PCV symptoms

 

[h701micra]

Brilliant diagrams Paul. Well worth the wait.
Proves my point perfectly

That photo of the evo 9 (not 3) was an example to prove their use in high end motorsport, where people know what they're talking about, with similar PCV systems as the CG

That's me finished on this subject.

 

[frank]

 

[pollyp]

I can play the facepalm game lol

thx andy.
I think this threads all explained out

 

[h701micra]

View attachment 34400

Of all people on here, I expected you to be the least childish

There's nothing wrong with being wrong about something.
You agree with Paul's diagrams and explanation that explains exactly what I've been saying, contaminants get caught in the catch can, yet say I'm wrong haha

 

[h701micra]

For those that wish to

 

[r-reg-sr]

its not childish,its human reaction we all got and azzydot my homeboy so lets keep the funny remarks aimed at sir chris phahaha i always do ,battle ship boy bullet proof

in my case(low power n dying pishrings it would be wasting my time/weight catching stuff in a tank,better of lift throttle body and swabb up evy 2 munt.,,,,,till,,,,,then im'a turn up timing and improve my ryming and blast more braps out the gaps,,,,,,,,,,did you honestly read that?

 

[h701micra]

its not childish,its human reaction we all got

And we all have self-discipline too, to accept where we're wrong
In your case maybe not so, but on engine like mine that has been cleaned it. I intend to keep it that way by keeping the crud out the airway

did you honestly read that?

This is brilliant

 

[r-reg-sr]

sinister cat,,,,,say,,,,,,,,,,,,,,,

,,,,,,,,,hi 5 i give up all in one

 

[davyboy]

All very interesting I thought, just several points of view.

 

[r-reg-sr]

All very interesting I thought, just several points of view.

pfffft,,,,,,,,if you say so

 

[davyboy]

I thought so, I am a believer though that if the manufacturer put it there......it serves a purpose.

 

[r-reg-sr]

very indebpth all partys valid points,points all round

 

[r-reg-sr]

homebru stoke the fire i must say make some chemical reactions,,,,,,,,,,,,,,,,,happen.......brrrrrrzzzzzzzzzTT

 

[drand]

I have been away and missed the fun of this thread first time round, but it got me thinking so humour me:

I am going to put in a group a airbox so I need to do something with the outlet on the cam cover that goes to the factory air box. I had planned to route it to atmosphere via a catch tank (but retain the PCV system). But why can't I just tee it into the PCV-to-mani pipe like so? what's the best option?

 

[pollyp]

that will cause both ends of the crankcase vents to vacuum against each other and basically cause a high crankcase vacuum. it's no different to simply blocking off the PCV breather port #8.

this vacuum will of course suck the existing vapours out the crankcase BUT there's no fresh air allowed to clear the crankcase area.
instead, the vacuum could either encourage even more blowby n vapours to leak past the rings and still end up contaminating the oil in the crankcase, or outside air to be sucked in through the seals

 

[drand]

Thanks pollyp. Yes I've just gone over what I wrote in my head and realised why that was a silly question (#8 lets clean air IN, not combustion gases out.) I was about to edit it and realised you'd got there first.
So I think I just need to provide clean air in on #8 and job done.

 

[--alpina--]

Bloooody hell, what a topic this turned out to be with action packed info and some heated over the edge discussions, am currently in greece an soaking the sun, over here there are no respect for cars specially for micras out here!! Wan-ers....ok back to catch can topic!! Ill buy one for an engine dress up and if it does what ive read well at least i have it all connected.

Cheers

J

 

[frank]

heated over the edge discussions

J

aint that the truth J, and the reason i hav,nt logged in for a while, and cant be arsed anymore (shouting and name calling gets us nowhere)
the reason i "like buttoned" pauls pics is because i run the same system myself, the only difference is pauls blowby/ring issue, (mine produces zilch, even under boost), hence his small amount of clean oil in his catchcan, no water or black sludge (ie, its just crankcase mist that has vented out of his breather because its not being passed through the 2 oil separators)
another reason was that it shows the downward flow in the crank case (not upward) and confirmed all i,ve been saying from day 1, about the other members that are running catchcans

when frank mentioned that some members had disconnected the PCV vacuum line and plumbed catch cans to the rocker ports and the cans had also vented straight to atmosphere, what they've essentially done is convert the crankcase into a crude 1st-generation breather tube.

bye all

 

[h701micra]

I didnt see any name calling and shouting personally
Debates like this are good as a source of information for future reference, to see both sides and make up their own mind.
I myself have seen the positive effects of a catchcan and have heard the praise of them from people who know much more than anyone here about engine building, therefore i'll stand by their experience and knowledge. Included many links in my posts for people to read such literature
Another point to note is how a catchcan is plumbed in, what type it is (cheap ones dont work), where it is in the line etc etc. These will all have an effect on the end result, but there's a reason there is sludgey build up in the intake. That's the last I'll say on the matter

 

[--alpina--]

I think sometimes a great disccussion on a topic such as this is great and helps to loosen tension to enble one and other to understand personal vews and also experiances even thou its only a small cylindrical canister with two pipes coming out of it !! Hope there was no bad feeling between you guys cos were here to hear each others views on the catchtank and it hs been an experiance to read withsome heat

So lets elaborate,exactly what doesthe catch tank do?? Hehehehehehehe. (joke)

J

 

[Low Rider]

This thread has run its natural course.

Thread closed.