DIY Low-side PCV installation (E89 Z4)

[fmorelli]

At 30k miles my Z4 was likely due for a walnut blast. I have a BMS OCC setup, but I had understood the high side of the system is not what seems to cause most of the oil fouling issues on these DI-based heads. I initially set out and bought @Rob@RBTurbo low-side external PCV kit as a jump-off point. It's well put together, like anything else I've received from Rob. The catch can is not included with Rob's kit; he recommends the Mishimoto with 50-micron filter - hard to go wrong with that quality choice. There are alternative copies of that can from China at a fraction of the cost - I have one of the knock-offs and can report the quality is very good.

That said, in the end, @barry@3DM and I decided to do some different things. We retained the external Toyota/PCV adapter that came in Rob's kit along with the threaded plugs for the head, and rolled our own with the rest of our setup.

• Given low-side can accumulate oil with possible frequency, I wanted an easy way to check catch can fill levels without unscrewing the can and creating a mess. As well a simple way to empty it. We went with a dipstick-based can, to which I also added a petcock-based drain so it can be emptied without disassembly.
• We ran -6AN hardware and pushloc for no other reason that we prefered the hardware. No practical benefit here, just choice.
• We also ran a check-valve inline at the intake, just to prevent any vacuum leak or delay. Likely unnecessary, but that's how we did it.

One can see the full parts list on my build sheet on the Current Configuration tab (scroll down to Low-side PCV System line). I'll share some photos and info in the coming posts.

Filippo

 

[fmorelli]

First I'd like to quickly point out that, after 7k miles of pretty spirited driving, the amount of oil in the high-side catch can was minimal. Almost not even worth draining.


Once we pulled the valve cover, our first step was to tap and plug the PCV return holes. On the factory PCV system, the low-side return feeds through the valve cover, which has runner which dumps to a passage in the aluminum head over each intake runner. The valve cover feed dumps around cylinder #5 and feeds out to #6/#4 and then #3, #2, and #1 respectively. It's not surprising that the amount of residue per intake runner corresponds with the observed ordered. Nonetheless our hope was that plugging this system up and a few other things would keep us from going back in for another walnut blast at a later date.

When tapping each hole we wanted to catch as much aluminum thread debri as possible. It is aluminum at the end of the day, so not the worse thing to fall into the intake, but nonetheless. We put a bit of lithium grease on a paper towel and shoved it in the intake, which seem to be effective at capturing the swarf from cutting the thread. A bit of loctite and the 10-32 plugs sealed up the holes.

We then went through the blasting process. This is covered ad nauseum, but I thought a few quick photos might provide an idea of the before and after on a 30k mile motor. Note the car was bone stock for the first 23k of its life. In this photo Barry's manning the blaster wand.

 

[fmorelli]

Once the head was prepped, we worked on getting the intake set up for the vacuum return. RBTurbo's kit comes with a nice solution with single outlet for the external PCV system. For those looking to run both external PCV and appropriate sized vacuum feed to a Tial BOV, I would give serious consideration to BMS Adapter. This was not available when we undertook this work.

We decided to use some Russel/Vibrant -6AN hardware to connect everything up. On the intake side I wanted the lowest plenum location for the PCV line to attach. My think was that gravity is my friend and anything which may help oil not end up in the head intake runners and valves is a benefit. Our location is well below the throttle body point more commonly used. The chosen location also worked well with routing lines, installation and removal of the plenum. The plenum has a perfect location that looks as if some BMW engineer was thinking the same way. Something was meant to be install where we were going to introduce the external PCV line. Pretty simple: drill the pilot hole, expand to fitting size with a step drill, clean up, and install the fittings with blue loctite.

 

[fmorelli]

On to the catch can. Given the possibility that low-side can was going to see reasonably frequent oil accumulation from the PCV, we wanted to think through a practical solution. The first thing I don't like about the common catch can solutions used with the N54 is that one needs to unscrew a catch can to figure out if it needs to be dumped. The second thing - unscrewing the catch can, should it be full of oil, could be a spill scenario. Frankly the canister setups are not ideal.

WeI found a catch can that met the basis for solving all this. There are plenty of photos, and most of them are self explanatory. Just a few summary points. The catch can has a screw-in filter area that allows one to install whatever filter one desires. In our case, we bought a sheet of 50-micron mesh. We also wanted the unit to seal well, so gaskets were cut from grommets for both the dipstick and top plug (teflon tape for the top plug is likely a superior choice in hindsight). Finally we sourced a petcock, and fit to the bottom of the can, allowing us to empty the oil without opening up the can.

 

[fmorelli]

On the benefits of the E89 enginement compartments is space. And layout. And did I mention space? We decided to mount the catch can on the driver-side firewall - plenty of room, easy line routing, easy access including underneath when the can needs to be drained. I fashioned a simple aluminum bracket, which mounted to factory studs off the firewall. Mock up with cardboard got us in the zip code, and then adjusted the aluminum bracket work once we fitted everything together. On the back of the catch can, I tapped the mount holes for the M4 bolts, which allowed us to mount the can to the aluminum bracket.

 

[fmorelli]

Final assembly. Not much to say here. Note the Check valve installation just before the 90° elbow into the intake plenum.

 

[fmorelli]

That's it. Here's hoping to less if ever need to walnut blast again, and a reduction is the likelihood of pesky timing corrections which seem to correlate the PCV system ... at least from our point of view. Who knows ... anyway, please feel free to comment or ask any questions. Thanks as usual to @barry@3DM who has as much sweat into this car as I do. My photo Exemplar In Residence is @martymil - I'm not at his level but hopefully the photography is improving

Filippo

 

[NoQuarter]

Well done. I really like my dipstick style can as well. I need better hoses though, mine are too stiff.

 

[Jeffman]

Very nice!
But just wondering if the plastic zip ties on the hoses to the check valve will hold up to the heat during a track session. (?)

 

[fmorelli]

Good question. They are mil-spec cable ties with stainless lock, rated to 185° F. I'm not expecting issues where they are, but I'll certainly check them out. For some reason I was just not interested in putting zebra clamps there, and the check-valve is barb not push loc. Maybe I'll go to a heat stabilized nylon zip tie when the car comes back apart for turbos, and push another 50-100° F headroom.

Filippo

 

[martymil]

Love the Z4 engine bay, I wished I brought one instead of my 1m sometimes due to the vast engine bay room it has.

That engine bay will look killer with a FF style manifold.

So easy.

 

[fmorelli]

Don't tempt @martymil ... got my backlog for this year hanging over my head. Maybe next year

Filippo

 

[martymil]

A freshly painted vtt rocker cover same as your car and a fully polished manifold, any car show you enter will stop people in their tracks.

I know every time I enter one there is a small crowd around mine.

 

[NoQuarter]

Related content: https://bmw.spoolstreet.com/threads/dual-catch-can-why-you-want-to-do-it.3136/

 

[Erichale77]

Very clean engine bay Filippo. Looks good aside from that red vacuum line that should be blue like the rest. My OCD is going nuts. Lol

 

[Panzerfaust]

Once again, excellent work by you and @barry@3DM . Our ideas for the low side are very similar, except I went up to -8AN line with hose clamps rather than your (beautiful!) -6 colored hoses and I use the TB connection rather than manifold tap. I definitely agree that running a check valve between the can and intake is a good idea and have been running that way since I went external.

What are your plans for the high side? I just finished my full PCV setup that I (personally) think is the best all-around setup for a twin turbo car by doing a DIY version of the VS breather setup but use check valves and the flapper to maintain vacuum under no/low load while still venting all CC pressure from 3 sources if it builds up - this allows my turbos to drain properly thanks to maintaining the PCV side and yet I dont get any smells because it only vents under boost. I made a detailed post on my IG along with a video of the rough version of my setup that I can copy and paste if you or anyone else is interested. My thinking was that vacuum is definitely necessary for the low side but under boost it's most important to make sure you have no positive pressure and the vacuum caused by a pre-turbo inlet is negligible compared to the pressure that can build up so I wanted to play it safe.

 

[E92-Ghandi]

Great write up, i have a smilier setup for the external PCV but i don't know why i cant use the same style catch can, i'm using 2 entries and one outlet.
If i use the one entry and one outlet after stating the car for couple of minutes, i can hear a strange sound as if a vacum leak from under the car.
Next i installed the new BMS adaptor with a check valve and the car starts smoking, went back to the old setup and it's back to normal with no smoke, using the the original check valve on the throttle body.

i have ACfabrication PCV delete on the valve cover, -8 line to the catch can inlet, -8 outlet then reduced to -6 to the T on the valve body check valve.

 

[Panzerfaust]

Since my (low side) setup is very similar to @fmorelli setup and theres still PCV system questions daily, I figured I'd go ahead and share my complete solution that includes reasoning behind what I did. It's a straight copy+post from my IG so I apologize if anything is redundant from what's been mentioned.


Finally made the perfect PCV setup for upgraded turbos (@mmp_engineering 1K turbos in this case) and relocated inlets, plus an explanation as to my planning behind the setup:
Low side: @vargasturbo -8an PCV fitting to -8AN hose with a @toyota 2jz PCV valve mounted in-line vertically before the CC (cant see it in the video), to a @Mishimoto CC, running to more -8AN hose with a VTT 0/100PSI check valve in-line (post-can, pre-TB to prevent the can from becoming pressurized + as safety from the PCV valve ever leaking) down to the VTT TB connection.

High side: 100% DIY based on the @VaderSolutions setup but some slight tweaks so I can maintain vacuum on the low side. Stock CCV flapper is in place but has -10an hose running to one port on a baffled high-flow CC with breather filter, and then -10AN hose with another VTT 0/100 PSI check valve in-line (open flow direction flows towards the CC) to a -10an fitting in the head port. And then the VTT oil cap breather for safe measure.

This setup allows you to maintain vacuum while not in boost + keeps the intake ports clean from carbon buildup due to the CC and check/PCV valves, so any blow-by from the low side is caught and cant be pushed back into the crankcase due to a pressurized can or malfunctioning PCV valve. The high side allows full vent-to-atmosphere from 3 locations (flapper to breather can, head port to breather can, oil cap breather with check ball) to stop any positive pressure buildup and allows the turbos to drain properly and prevent smoking. The VTA can with stock flapper in place, plus the check valve between the head and can means the engine will pull controlled amounts of vacuum solely from the atmosphere while out of boost like BMW intended the system to function. The oil cap breather opens at 0.5 PSI so *if* any positive crankcase pressure still builds it has another vent.

 

[BrazyN54]

What size fittings did you use to adapt an fittings on the catch can?

 

[fmorelli]

What size fittings did you use to adapt an fittings on the catch can?

If you're referring to my setup, you'll find all the parts listed in the spreadsheet that is referenced in the post.

Filippo