crank ventilation blow by..

**S2central.net** · 11 February 2009, 23:22

There is a surprising amount of oil mist that collects at the bottom of intercooler and you can feel the mist inside of the turbo hoses - pretty nasty / stupid (so-called environmental) design that makes our engine ingest dirty air, raises the charge temperature, increases chance of knock, adds to other nastious oxides from the impure combustion process, reduces MPG and it hurts performance.

Oh but it would be so evil if we all let our cars vent crankcase gasses to atmosphere... Only last weekend I melted an entire iceberg by my own carbon footprint. What a load of balls...

If it weren't for the smell of oil vapours I would just vent the lot to atmosphere - a catch tank / cyclone is the way forward.

**s2_bo** · 11 February 2009, 23:26

lol..
Im with you on that one Paul

**A80Avant** · 12 February 2009, 08:02

i got a catch tank,simple one from ebay,with a mesh type divider,which i also found that it is sold from forgemotorsport as well.It is a 500ml tank,and i will mount it next to the left headlamp in front of the opening for the main radiator.

I hope that wont create any problems with air coming into the radiators since this is not a problem when people are using the reverse inlet manifold and the bit intercooler hose is in the same way.

I ordered fluorosilicone hoses from sfs and forge and i hope they get here in time to add this on the car,before i leave for greece for a week.
I have decided to take the hose that goes in from the back of the motor block(top one) and bring it to the tank.Then i will take the tank's outlet down to the bottom of the motor,and add a KN breather filter to it.I will have some length from the breather hoses so i will try to bring it as back and low as possible so as to avoid having all those oil vapour smells.

However im starting to think that these 500ml tanks are too small for this engine!!! hehe
on the other hand 1lit tanks probably wont fit anywhere...

JP · 12 February 2009, 20:27

Here's one I've always been curious about. An engine has never got a perfect seal on the piston rings which results in blow by. Anything that blows past the piston rings results in the crankcase pressurising. This is then acentuated on a forced induction car where there is even more blowby due to the higher pressures of the combustino cycle.

Now if you were to install the 2nd ring on a piston upside down you would have an engine that smokes forever and ever as the shape of the 2nd ring is designed to push out under the force of the combustion cycle. Turning it upside down in effect causes the 2nd ring not to work and oil will pass by like no mans business. This is pretty much the same problem that is had when the engine cannot breath properly and there is too much crankcase pressure. So VAG routed the breather system back into the intake utilising the vacuum caused by the engine under acceleration to relieve crankcase pressure to ensure the rings to seal better. In the later years on the 1.8t they introduced an electric crankcase evacuation pump to reduce crankcase pressure. The late American V8's utilise a belt driven evacuation pump to relieve crankcase pressure. Early v8's that vented to atmosphere they upgraded for racing using a crankcase evacuation system utilising a one way pcv valve using the exhaust gases to relief crankcase pressure. Race cars utilise a dry sump system where the dry sump pump acts as a crankcase evacuation system.

So why are we going backwards and removing the engineering that was put in place to make our rings seal better and for longer by venting to atmosphere either with or without a catchtank? As the minute you create positive pressure in the crankcase the 2nd ring stops working and the blowby is acentuated.

Just my 2p

**A80Avant** · 12 February 2009, 20:50

see this is something i was thinking about myself.

The fact that the turbo is actually creating a vaccum and so 'sucks' the blow by,was initially my concern regarding the use of a catch tank and the fact that there is no vaccum there to do the same thing.

So does this mean that the piston rings will be damaged much faster that way?

**A80Avant** · 12 February 2009, 20:52

and if so,is there any easy way to install a crankcase vaccum system that would still 'suck' the blowby but at least NOT in the intake system?

**S-Express** · 12 February 2009, 20:59

A lot of old diesel cars use a belt driven vac pump to power the brake servo - can't see why this couldn't be incorperated? Probably pick one up for a £ at a scrappy!

**A80Avant** · 12 February 2009, 21:10

here is a part of a post i found regarding the ventilation.

Open Breather Ventilation
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This method is adequate for ventilating crankcase gasses in turbocharged/supercharged cars because the extra blow-by will force its way through any filter quite easily. You want to make sure you provide as many sources as possible to allow the pressure to escape with ease.

For H, F, and D series engines you can use the stock PCV line(excluding the PCV valve), Breather Line, and tap an extra 1-2 ports in the valve cover if wanted. You can attach a filter directly to the line or connect them to 1or2 catchcans with a breather filter on top.

You want to place the catchcan in the highest possible location you can locate in your engine bay. This will allow the catchcan to collect blow-by gasses without consuming excessive oil and allow a drainback line to easily flow oil/gas mixture back into the engine(if you choose to use this feature).

The sole purpose of a catchcan in an open breather system is to "trap" oil and blow-by gasses so they do not contaminate your engine bay and the environment. The surface area in the lines and the catchcan facilitate this. Increasing the surface area by using steel wool or other means will certainly help capturing these gasses but will also restrict them from escaping. The best compromise is to use a baffled catchcan such as one Moroso manufactures.

-----------------------------------------------------------------------------------
So basically it says that on turbocharged cars,the boost is actually pushing the blow by,so if your breather system is not blocked in anyway,you shouldnt have any problem.Right?

On the other hand,people who already using catch tanks,do they have problems with piston ring failures?

Finaly i believe the only easy solution would be to actualy fit the catch tank between the PCV system and the inlet of the turbo,thus keeping some vacuum there still doing the sucking, while also at least get rid of most of the muck possible that is being created...

would that be a better option?

**vagrallye** · 12 February 2009, 21:48

the best thing to do is use a catch tank as an OIL SEPERATOR and keep it under vacuum aka the origonal system , the "fumes" will be drawn out keeping a steady crank pressure/vacuum but the oil will remain in the tank or drain back to sump

on the later 1.8t engine the factory setup actually drains back to the oil filter housing, the pipework actually sepperates the fumes and oil, its not perfect but it is better, improve on that by using a "aftermarket" seperator that drains back to sump or oil filter housingor even the lowest crank breather and you have a good system that maintains correct crank pressure

**A80Avant** · 12 February 2009, 21:56

hmmm,
i think i will try that for starters.Only problem now is that there is not much room to fit it in,and if i choose the location i had thought,the tubing wont be enough.Otherwise if i manage to fit it in the new position,it will be perfect...if it fits...

**newsh** · 13 February 2009, 23:22

Originally posted by vagrallye

the best thing to do is use a catch tank as an OIL SEPERATOR and keep it under vacuum aka the origonal system , the "fumes" will be drawn out keeping a steady crank pressure/vacuum but the oil will remain in the tank or drain back to sump

This is EXACTLY the way I explained to him to do it 2 or 3 weeks ago..

What happened to the plan? go back and read the thread again.

**Jamo** · 13 February 2009, 23:30

Originally posted by newsh

This is EXACTLY the way I explained to him to do it 2 or 3 weeks ago..

What happened to the plan? go back and read the thread again.

Ditto I remember saying the same thing in the thread

**A80Avant** · 14 February 2009, 00:01

yes i remember you saying that Newsh,but then i also remember you saying that leaving them to atmosphere was just as good.So at the time,thought that id rather not have ANY fumes going back into the turbo.

BUT,on that thread noone had ever discussed the possibility of engine wear and damage because of the lack of vaccum from the turbo inlet.

I know i had the 2 options.Went for the latter, then someone pointed this vaccum issue out.

Apparently after some googling, and suggestions, it seems that venting to atmosphere is NOT causing any problems to the engine,so lon as the tank and hoses dont get blocked or something...

**Jonas_R** · 14 February 2009, 08:08

Just a quick comment, I would not mount the catch tank close by the left head lamp where it will get much colder then inside the engine bay.

I remember once where I was driving to Germany ca. 400 km and it was snowing and rather cold. My catch tank was filled up completely when I got there duo to the blowby condensating to a oil/water mixture. Now after that I installed a level sensor, just to be sure, but it has never happened again. On the other hand I have not driven 400 km in the snow after that

Anyhow my point is that the catch tank will see much colder temperatures out in the front and this might be a problem for you.

Mine is setup wenting to atmosphere through a catch tank with a baffle inside.

crank ventilation blow by..

crank ventilation blow by..

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