Modifying the Crankcase Ventilation System

[sirzepp]

BMW motors are designed to run at a slight vacuum. It has bothered me that mine has not been doing this ever since I put my turbo kit on. Though the compressor inlet provides SOME vacuum, it's not up to OE spec, and I've been having oil consumption issues to boot. Since I don't have money to build a motor, and mine seems fine right now(good leakdown and compression), I have been slowly eliminating tertiary oil consumption issues. Though the lack of crankcase vacuum is a minor issue, it was something to do...and I bought a catch can too...so I wanted to install it as well(and provide it with proper vacuum when the engine was not in boost). Here is what I did:

I made it my mission to return the crank case ventilation system on my car to fully functional as designed AND add proper valving for a turbo system.

I have succeeded...after much effort and much outside help(thanks Jim and Kevin!).

Here are some pics:


Below is the lower part of the modified crank case breather line. I took a page out of the Eurosport book and cut the OEM line. I threaded brass barbs into the ends of the OEM line and connected them with an appropriate hose.


The upper part of the line.



Here is a SUPER blurry shot of the OEM CVV mounted in it's new location. I threaded a brass 90 degree barb into the 'nipple' where the CVV used to attach to the manifold(or in this case...the Eurosport M50 adaptor). It is now 'remote' mounted further forward and upward of it's old location, with a hose running from the brass barb to the Mckinney racing catch can on the front left side of the engine bay(behind the headlight housing).



Here are some shots of the modification I made to the Eurosport adaptor plate. This is the line that feeds the CVV air back into the intake. The line hooked to this barb comes out of the catch can, through a 'T' fitting(more on that later), through a brake booster check valve(from a 1981 323i), and into the intake.


Here you can see the brass plug installed in the old CVV location on the OEM plastic plenum(that is, in turn, mounted to the Eurosport adaptor plate).



More pics of the modified adaptor plate. The 90 degree barb is installed in a hole that comes plugged from Eurosport.



Here is a LITTLE better pic of the new CVV location. I fashioned a rough aluminum bracket to hold it in place...and used the OEM M50 fuel line stand-off to mount the bracket under the runners.



In this pic you can barly see the forward part of my rough bracket, the modified breather line, and the lower part of the CVV.


Here you can see the catch can hoses, the 'T', and the check valve. The "T" connects to another line, through a check valve, and into the Technique Tuning turbo inlet(at the 'stock' kit location). Basically, whent he manifold goes positive pressure, the check valve pictured here closes, and the check valve in the line to the turbo inlet opens...allowing the crank case to breath while the manifold pressure is higher than ambient. When pressure returns to 0 or lower, the check valves reverse, and stock CVS function(and crankcase vacuum) is restored. Attaching the 'atmospheric circuit' to the TT stock location will provide at least SOME vacuum...and that's why it was used.


Here is the check valve on the atmospheric circuit. It is a PCV, and will soon be replaced by another OEM BMW brake booster valve like the one pictured above(there was only one OEM brake booster CV in stock locally, and I wanted to get the car running tonight).



Another picture of the line routing with the modified breather line in background.


Engine bay as it currently sits.

[SiGmA]

Excellent work. I am a fan of dual vents for sure. Or just a single exhaust check valve.

[Sykes1330]

very nice work also was having this as a problem with my turbo m3 also and gives me a understanding to fix this problem! great work and very nice m3!

[sirzepp]

Thanks guys. This was definitely harder than I thought it would be...going in. I LOVE designing crap like this, unfortunately, I wasted an entire day and a half on a concept that was ridiculously complex(Think Rube Goldberg). When this idea was suggested(by lohe) it was the RIGHT way to do it.

[Depape]

Nice right up! I was planning on doing the same thing.

Any reason you went this way over a single exhaust vent? I'm guessing you didn't want to tap into your exhaust.

[Shuasha]

Wow, I really like the two way system. I might integrate something similar into my cars.

[328iJunkie]

Interesting...

[SiGmA]

Originally Posted by sirzepp

Thanks guys. This was definitely harder than I thought it would be...going in. I LOVE designing crap like this, unfortunately, I wasted an entire day and a half on a concept that was ridiculously complex(Think Rube Goldberg). When this idea was suggested(by lohe) it was the RIGHT way to do it.

Heh a day and a half! I came up with basically the same thing in a matter of minutes, and then decided to just route it to the exhaust. But I love your documentation, thank you very much for that, it should help others in the future

[Mad Dog 20/20]

Originally Posted by sirzepp

Basically, when the manifold goes positive pressure, the check valve pictured here closes, and the check valve in the line to the turbo inlet opens...allowing the crank case to breath while the manifold pressure is higher than ambient. When pressure returns to 0 or lower, the check valves reverse, and stock CVS function (and crankcase vacuum) is restored.

Definitely a worthy endeavor. Well done.

I wonder about the check valves though. How do they work?

Assuming its just a one-way check valve, I understand how the one leading to the mani will close when it see pos pressure, but how does the one to the turbo inlet know when to open up (or is it not just always open, as it never sees pos pressure - in which case why have it there at all?).

It seems like you would have to know/measure the amount of vac created at the turbo inlet when the manifold goes pos pressure, and then use a valve at the turbo inlet that is designed to open only above that vac threshold.

[sirzepp]

I'm actually not sure about how much crack pressure is required for these valves. I DO know they are designed to work in a brake booster, so it's minimal. I 'think' the main point of the atmo circuit is to let the crank case breath(and not build pressure). In that case, it'll be more about the crank case pressure opening the check valve to the compressor inlet as the positive pressure from the intake closes the other valve. If that's how it's actually working, I'm OK with that. The vacuum at the turbo inlet is probably minimal, as there is no venturi effect, only a bit of accelerated air. If I put the line RIGHT before the compressor...say a few millimeters(would require drilling and tapping the compressor housing), I'm sure I'd get more vacuum(turbine engines see significant pressure drop at the compressor inlet...which is why we have cowl anti-ice...BUT...the inlet is also a venturi...just like the compressor inlet on the turbo...so...again...I'd have to tap the housing to truly see vacuum...it's not worth it...the atmospheric circuit is really just to make sure the crank case doesn't see positive pressure during boost).

As far as 'why'...I don't know for sure...I just thought this was a more elegant, albeit complex, solution(I really like the OEM ventilation system, and there is no way an exhaust is going to provide the vacuum of the intake manifold...and the vacuum is what I was looking for to make the CVV(and air/oil seperator) function as designed). I really, really don't want any oil in my intake, and the CVV + catch can should help with that...especially since my motor is old...and probably has more blowby(even though leakdown is in spec).

[Mad Dog 20/20]

Again, nice job. I think the issue is a real one. One of the first things I noticed when I hooked-up my SC kit was that the CCV system was pulling almost zero cc vapor. I immediatly put a catch can in and also ran a "krank vent".
Its a one way valve that actually creates a vac, so that when the pre-sc intake tube is not generating adequate vac (which as you indicated is prolly almost always), the krank vent will generate some. It actually works - when disconnected from the intake tube, you can put your hand in front of the valve and feel the cc vapor being vented at a good rate.

http://forums.bimmerforums.com/forum...ght=krank+vent

[SiGmA]

I wonder if it would be a good idea to add vacuum to my catch can and put one way valves on the hose to the exhaust and to the manifold. It couldn't hurt and would be rather easy to do.

[BadBoostedBmwM3]

Nice write-up.... BUT, I always thought that the turbo provided efficient vacuum?? I guess not...

[So Live]

Originally Posted by SiGmA

Heh a day and a half! I came up with basically the same thing in a matter of minutes, and then decided to just route it to the exhaust.

WOW the ALL MIGHTY SIGMA chimes in!! Nobody cares...


Nice write up OP and a cool way to go about it. Great work! Keep us updated on how it works out for ya (with a few more hours)

[sirzepp]

Originally Posted by So Live

WOW the ALL MIGHTY SIGMA chimes in!! Nobody cares...


Nice write up OP and a cool way to go about it. Great work! Keep us updated on how it works out for ya (with a few more hours)

Thanks! And, FWIW, I didn't take any offense to his comment...I chuckled actually, because my first design was so God awful complex(the result of countless hours of cruise at altitude with nothing to do but talk to the First Officer or draw pictures in my head of a crankcase ventilation system).

Originally Posted by Mad Dog 20/20

Again, nice job. I think the issue is a real one. One of the first things I noticed when I hooked-up my SC kit was that the CCV system was pulling almost zero cc vapor. I immediatly put a catch can in and also ran a "krank vent".
Its a one way valve that actually creates a vac, so that when the pre-sc intake tube is not generating adequate vac (which as you indicated is prolly almost always), the krank vent will generate some. It actually works - when disconnected from the intake tube, you can put your hand in front of the valve and feel the cc vapor being vented at a good rate.

http://forums.bimmerforums.com/forum...ght=krank+vent

Freaking awesome. Wish I had seen that earlier. We should put that in the F/I FAQ, because this is an issue and that is a great solution.

I like having the stock air/oil separator, but that's only a minor advantage, and when you take into account the 'plug and play' factor of the krank system(and the fact that it's pre-designed)...I think that system is better than what I have.

I like what I did, but that krank system is very, very cool.

Actually, I wonder if those krank vents would work in lieu of my check valves(?). Perhaps that is the reason you pointed them out? I'd have to look at one...might be overkill...but would certainly be more robust than the check valves.

[mazur]

What the hell is all that adapter plate about? Are S52's really that different than S50's when it comes to the ICV?

[sirzepp]

The adaptor plate is for all the 'crap' that gets mounted to the stock S52 manifold. The OBD 1 manifold does not have provisions to mount the crap...so Eurosport built a nice adaptor plate. Of course, just using the 'hose' method works as well(to adapt the M50/S50 manifold), but you lose the air/oil sep and the solution is not nearly as nice(it's cheaper, though).