300 24v turbo technics breather , crankcase ventalation

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boomtings

Active Member
Joined
Aug 23, 2009
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210
Location
London
Car
95 e320 cabriolet ,93 300te_24v Turbotechnics
Hi all.

The breather setup in my m104 3.0 estate is looking old, pipes are aged and the mio filter is also not looking in good condition.

I've found a thread on a Audi forum about their breather setup and was thinking of using their one way valve and pcv valve to rebuild my system.
https://forums.quattroworld.com/s4s6/msgs/22506.phtml

I've also seen bmw valves which appear to have an oil catch and return to crancase built in.
But from what I understood these systems are sealed and don't allow fresh air in

Here's a picture of my current system. Sorry it's not the best picture.

http://fastrcmodels.co.uk/M3rcs/IMG_20140119_231532.jpg

I know that the small connection on the rear of the mio filter is suppose to connect to the inlet manifold via a one way valve.

My rocker cover is connected to the mio filter which then exits to a T connector which appear to be connected to the crankcase near the water pump before going to my airbox.
Does my interpretation seem correct?

What I'm unsure of is that I thought the rocker cover pipe was primarily for pulling air into the engine to replace air that is pulled from the crank.

All other turbo technical systems I find pictures of appear to only vent a single connection.
If anyone understands my attempt to describe the set up and can offer any advice I'd appreciate it.
 
http://www.w124performance.com/service/w124CD1/Program/Engine/104/01-0400.pdf shows the layout of the crankcase breather for various flavours of the m104. What you've seen on other TT examples might be eplained by this if they were all based on the m103?... http://www.w124performance.com/service/w124CD1/Program/Engine/103/01-0400.pdf

I've no idea what TT did to the breather system but from your description/the pic i'm guessing they may have just rerouted things through the mio-filter* and added some one way valves due to the induction changes/binning the standard airbox?

I'd probably be robbing the setup from a modern turbo car too and can also incorporate an additional air/oil seperator into it if wanted/needed to do the same job as the mio-filter i.e. filter crankcase fumes entering the inlet under vacuum

* Basically a PCV valve with an inline filter
 
Thanks hotrodder :bannana:just what I was looking for.
 
Based on the Mercedes CFI diagram on the 1st page of the 01-400 PDF , it seems to me that I should refit the original crankcase to manifold pipe (part 7 in diagram) but with a one way valve installed.

This should take care of breathing under part load conditions where manifold vacuum exist and the valve will stop the crankcase pressurising under boost conditions.

The rocker cover pipe can go straight to my airbox where under boost conditions, air will be pulled into the air box by the airflow into the turbos. Obviously put a catch tank in between. Under idle conditions it will allow fresh air into the engine.

It seems to me that Turbo Technics cut pipe7 and combined the rocker ( direct to mio filter} and crankcase vent (via the T-connector) so that they both breath through the manifold at idle and through the airbox under boost.

From the merc doc ,the only thing I don't understand at present is how the standard crankcase breather behaves under full load conditions. Whilst gasses escape from rocker cover what is happening between the crank and manifold connection.

Is it safe to just put a Check valve here without an alternative exit available. Or should I fit a PCV here and vent to airbox?

Any comments are appreciated.
 
Assuming you have a TurboTechinics install on an early M104 3.0-24V with KE-Jet.

Pix of my M103-12V breather system which should be similar.
You can build your own "catch can", very inexpensive with a filter/drain used on small air compressors.
I had it installed for a while but remove it as I have zero blow by.








 
From the merc doc ,the only thing I don't understand at present is how the standard crankcase breather behaves under full load conditions. Whilst gasses escape from rocker cover what is happening between the crank and manifold connection.

I'm thinking (alright, guessing!) that the 2mm restriction drilling (item 8) might result in a kinda venturi effect when under full load i.e. when/if the pressure in the inlet manifold is higher than in the crankcase airflow through the manifold may still 'pull' fumes from the crankcase or at least due to the layout not actively pressurise it. The wording in the pdf suggest the later although they may just be referring to bulk flow

Given the restriction at #8 i'd be inclined to plumb things the way that TT did personally... bypasses the restriction and a Tee is less likely to get clogged/bug out than a PCV valve

Just be thankful that MB included a well designed air/oil seperator and breather, i make some bits for a guy that tunes Renault Alpines and apparently the stock set up on the PRV V6 is barely adequate before you start tuning 'em. I made him these for a twin turbo conversion he's building

PC040201.jpg

and he asked for the small dia tube as a 'just in case' scenario for the dipstick tube- apparently even a fresh build with good leakdown numbers is known to blow the dipstick out when you feed it some boost. Hopefully it won't be needed as i modified his valve covers too- very crude compared to the m104
 
Inlet manifold is always under varying vacuum, which draws crankcase vapor and mixes with manifold inlet air.
Intake never reaches atmospheric pressure unless the engine has a turbo.
Under boost inlet manifold is under pressure so you need a one way valve to prevent the crankcase from being pressurized.
The crankcase under boost vents to the air intake box that feeds the turbo(s)

Ed A.
 
Thanks Hotrodder and Ed for the replies.

Final questions :

What can be used to replace the actual MIO filter?
my case is ok but i seem to be missing the internals.

Im probably overthinking , but I cant help but think that on TT setup the open path to the airbox must effect the pull from the crankcase/rocker to manifold under idle.

regards
 
Thanks Hotrodder and Ed for the replies.

Final questions :

What can be used to replace the actual MIO filter?
my case is ok but i seem to be missing the internals.

Im probably overthinking , but I cant help but think that on TT setup the open path to the airbox must effect the pull from the crankcase/rocker to manifold under idle.

regards

The purpose of the red mio filter is to prevent contaminated air from entering the intake under vacuum while the one way valve in series with the mio filter stops boost from returning to the crankcase via the cam cover.
Under boost you are pressurizing your crankcase which would cause the turbo oil returns to be less efficient and eventually damage the turbo bearings.

The path to the airbox doesn't really do much more then a vent/pressure relief under boost.

The MIO filter is about impossible to find and very costly if you do find one.

In the USA many use a fuel filter like a Fram G3 in line with a PCV valve.
Common on modified small block Chevy engines.
You can also replace the MIO with an inline filter that is used on air powered tools.

In-Line Filters | Filters | Pneumatics

Ed A.
 
Thanks Ed I have a clear idea now.:thumb:

I found this brilliant 19 page PDF on engine breather systems.
breathersystemrs.pdf
 
It's simple if you break it down...

-You want a filter in the path to the intake so you don't draw in stuff that can contaminate or gunk up...
Stock air boxes which draw from the PCV have a filter in them.

- You don't want boost to return to the crankcase as it could disrupt the gravity oil return from the turbo(s)
A one way or even a PCV valve can achieve this.

Ed A.
 

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