Center post? mmmm....not sure what part that is on the catchcan I have.

 

Might as well ask why Mini is using a plastic corrugated tube that A: Massively increases the tube wall surface area, B: Massively increases the chance of it failing at one of the corrugations as the plastic ages and embrittles...

If you can tell the difference if you suck through 2 feet of 1/2" vs 3/4" diameter pipe you are a better man than me

I would suspect that the design and quality of the catch can is way more critical to the performance that the smooth wall pipe connecting it.

 

and collapsing...

 

The flow resistance is not a consequence of 'friction' but volume movement -- the narrower diameter walls "push back" hence the phrase "backpressure." Imagine for a moment if you used small diameter coffee stir straws for the inlet and outlet tubing -- the resistance to flow would be near the same as blocking the port and there would be near zero flow though the catch can. As the radius of your tube decreases, the resistance to flow increases for both gases and liquids.

The innards of the PCV valve shown on other threads in the NAM forum, show ports and passages that help meter flow rates and the direction of flow to the intake or boost ports. MINI clearly opted to place a plastic 3/4" tubing for the rear port -- the reasons? who knows, plastic is lighter and is less permeable than rubber to trap oil fumes, who knows -- but the diameter and length of tubing chosen by MINI affect flow resistance (i.e., backpressure) and crankcase evacuation rates (i.e., turnover rate at idle or partial throttle on the highway). This evacuation turnover rate is particularly important in the turbo engine when the throttle plate snaps shut after hard acceleration between shifts to relieve trapped crankcase pressure. So a large 3/4" ID tube likely sufficed that balance. My take is that the rear port helps by partially relieving crankcase pressure along with the front port when the pressure is excessive. When the rear port is blocked off, the front port takes the brunt of the pressure, but the PCV meters that flow rate with a plunger valve. If the catch can assembly adds further backpressure to the increased gas volume trying to escape the front port (if the rear port is block), then there is no alternative escape port for the pressure except through seals.

Is your rear PCV port plugged? Excess crankcase pressure will find a path of least resistance for relief and may not manifest immediately (which was my case until the rear main seal kept weeping), or no symptoms may ever appear, as I have read in many NAM accounts. All of this might be due to the variants of PCV valves available for the N14 from the discount distributors. It is not clear why all the MINI N14 turbo challenges are not universal.

 

I would hope the picture answered that question

Maybe I misunderstood but surely if the PCV system is working correctly either its venting to the vacuum side, or its venting to the high pressure side, so if I dont see how the large diameter vacuum side hose can be in play as a reservoir for excessive positive pressure. Vacuum side pressures are a lot closer to atmospheric, maybe 0.7-0.9 bar, so restrictions to airflow are less problematic. GTT have clearly given this a lot of thought and are one of the main advocates out there for having dual cans on N14 minis. If they are happy to use smaller diameter tubes on the vacuum side then I'll go with that.

 

The reason to use larger diameter tubing is to keep the velocity low. Temperature and velocity have a significant affect on the precipitation rate of the oil and aromatics suspended in the PCV discharge. Larger diameter tubes combined with a larger volume, baffled oil catch cans will perform better. Placement of the OCC should also be considered. Preferably install it in a location where it will be least subject to heat soak.

 

...but not in a location where water in the can or lines would freeze during operation....my buddy has that happen in his Mazda and it was a mess when the crank pressure found an alternate place to evacuate.

 

Lol. I bet. I've seen motors with worn rings and restricted PCV lines blow the dipstick out... oil went everywhere. Seen it cause valve cover leaks as well. Luckily our main seals seem to hold up pretty well. All in all it's really not a bad design from the factory. Just wish they had used the centrifugal separator and crank case return line I've seen on some BMW models.

 

ya his dipstick blew out and oil was everywhere. A LOT OF OIL. Now it was like -30 F in Minnesota when this happened. But hey...it's one the reasons manufacturers just made life easy for themselves and routed that crap back into the intake rather than collect it and worry about moisture freezing, having to drain catch cans etc. Direct injection is very problematic even though it brings lots of other bennies.

I salute Toyota for going with port and direct on its new motors. Injectors are cheap and rarely fail.

 

Here is my first CC install with 3/4 PVC hose and the OEM connectors pulled out of the OEM crap plastic tube. Those 3/4 lines are fricking enormous for such a small engine bay.

I used a short section of 15/32 PVC hose to properly seal the generic Chinese CC nipples which I think are 5/8ths. I had 2 old plastic OEM PCV hoses so I used the shallow angle (not right angle) connectors to make the connections on top and below.


15/32 hose under the 3/4 to create a seal.

OEM PCV plastic hose

I used 2 of these shallow angle ends.






Here is the connection under the intake manifold.

you can see the shiny new clamp onthe 3/4 hose connected to the intake manifold.

 

Well done!

After 1 month or so (if you can remember), let us know if
1) You smell oil vapors escaping through the rubber hose pores after 1 month of driving.
2) the tubing remains robust and does not collapse under vacuum after several heat/cool cycles
3) the catch can is robust (i.e., does not leak) after experiencing boost pressures through the intake manifold without a non-return one-way valve between the Can and the intact.
These pieces of information will provide broad information about this setup.

In my set up (shown earlier in this thread), after 20 miles of highway driving (never shifting into 6th gear--cruise speed 70+ MPH (4000 rpm)
with "some" 1-mile WOT pulls up to 5500 rpm to fully engage the PCV system at both ends),
I could smell strong oil vapors coming through only the silicone tubing section I added to navigate an awkward angle (circled in top photo)


Eliminating these vapors was my main goal.
So, I shaped a short piece of PEX with heat gun and replaced the silicone section. No more smell.
MINI's use of plastic tubing (rear PCV valve) and the high-density rubber(?) tubing (front valve) likely retained these odors.

The plastic tube is perplexing. Someone mentioned earlier in this thread about ridiculous corrugation -- I agree, the ridges create unnecessary turbulence.
I won't go into the physics describing the minuses of corrugation in a PCV system, but at least the OE tube was relatively short.
Also, if a solvent cleaner is sprayed through the plastic tube to clean the injectors,
then the plastic's strength is compromised along with flexing the tube to get the connector released from the PCV valve.

Especially with the original air box.

BTW: your photos show characteristic weak points of the MINI construction in addition to the PCV system; the battery cover mended with duct tape is familiar.
Accessing the battery without breaking those fragile "hinges" through the slightest opening is as delicate as doing laparoscopic surgery through a small incision.

 

Sure, I'll let you know when she is back on the road. I'm using real PVC specific tubing so it should not collapse like the OEM line did.

If it works without any vacuum leaks etc I'll install the second catch can.

You sure your oil smell isn't coming from all the other places these POS cars leak oil from?

 

I agree; my car used to leak seemingly from everywhere until I unplugged the rear PCV valve port AND removed the frit filters from the catch cans. Now it does not leak at all. Best of all, the intake valves are tan and dry, not oily. This is likely a combined effect of OCC's and Meth Injection.

I sniffed the rubber hoses as one sniffs the bouquet of a fine cigar -- up close and nearly personal, and the odor certainly came from the hoses, making me retch.

The PEX pipe has eliminated a years-long challenge. Formerly wrapping the rubber hose in FiberFix wrap helped reduce the odor but not as completely as the PEX retrofit.

 

Why was your rear PCV port plugged?

 

This is one of the suggested workarounds discussed on several N14 engine MINI threads that reduces the excess oil entering the manifold that will foul the intake valves and wreak crazy havoc (slowly happening from 2010 to 2019 to my car with MINI plastic tubing). The resulting excess crankcase pressure with rear ports plugged is reported to escape solely through the front PCV port, so several owners put the OCC on the front port.

I think for my car, the single escape path was not sufficient to relieve the crankcase pressure satisfactorily over the long run (others have experienced more positive results). For me, oil leaked from the rear main seal and oil filter housing and later from the valve cover over 1 year (mid-2019 to mid-2020) with the rear ports plugged. Note: engine and cylinder head were newly replaced at the time.

Opening all of the PCV ports with OCCs connected with rubber tubing at the time solved the leak issues over 2 years (mid-2020 until now).

I know there are plenty of flaps, plungers, passages, orifices, and a diaphragm in the N14 PCV "valve," and I don't think either works as a binary function -- on at WOT boost, off at closed throttle -- they likely assist each other.

I wish I could look at the partitioning coefficients between the front and rear ports from 0 to full boost pressure that (I think) MINI BMW Peugeot used to engineer the PCV of the N14.

Many of the differences reported among owners' mods of their PCV system could fundamentally result from different driving styles or different versions/tolerances of the PCV cover they purchased.

 

Plugging a PVC port is nuts. NEVER would I consider it.

The Mini PCV system is a turd. Dear BMW, please call Toyota for engineering assistance.

 

Food for thought for N14s...
https://www.gtt.uk.com/the-big-r56-c...p-proper-cure/

 

Good info. Thanks.

 

I finally have time to look at this thread on a larger screen.
LOL! -- This made my day and was truly very funny!Seriously:
Yeah, intuition suggests that the 1/4 inch difference would be difficult to discern until I cracked open my old flow dynamics book to review.
The reduced diameter is noticeable regarding the flow rate and balancing backpressures between the rear and forward PCV ports. Exhaust manufacturers use larger bore (often only slightly larger) tubes to balance efficient exhaust flow rates and backpressures for optimal engine performance. Using a smaller diameter tube (even 1/4 inch) and over a longer length (as done for the catch can setups) will affect the flow rate and backpressure in an exhaust. This is why it is recommended to install larger exhaust pipes when a larger turbo is used (see Milltek) -- you need to exhaust a higher volume of air per minute through the exhaust pipe.

Not knowing the cubic feet of air moved per minute (cfpm) BMW used to proportion the front and rear PCV ports of the N14 engine, it is difficult to compare the effects of a longer, smaller diameter tube attached to either PCV port on engine performance without proper measuring equipment – but for sure, the flow rates will be significantly different from the factory rates and the backpressure created by the smaller diameter and longer tube will be greater than factory.
--------------------
I agree that the OCC is critical. For each orifice in the OCC that has a smaller bore than the feed tube, the cfpm will drop off at the exit tube. The can will intrinsically introduce backpressure because it must have a stationary substrate (wool, perforated plates, etc.) that will condense oil vapor to be effective. Fritted filters, while well-intentioned to capture oil vapors, will also noticeably drop the cfpm at the exit tube – and the back pressure to the crankcase pressure will increase -- your car's computer will likely make adjustments to the timing to offset the changes, and all will be "well," but I need to see the flow values at each port measured by MINI/BMW over a broad boost/vacuum range. Any YouTubers out there wanting to measure the flow rates of an R55/R55 N14 PCV valve at each port at 1) rapid boost during acceleration and 2) cruise with the factory tubing?

If the UK GTT has these pressure/flow curve data and would post it, that would be extremely helpful to determine what is overkill and what is sheer luck in OCC design.

 

Originally Posted by keduMINI View Post
Is your rear PCV port plugged?

At quick glance on my phone, I thought your picture was oriented as portrait relative to the engine configuration (back of engine to front), but it is clear now. Clean setup. The ~115 degree splay of the inlet outlet ports helps with directing the tubing.

 

Where can I get two 3/4 inch metal barbed fittings for the second catch can install? My local home Depot only had plastic and they were way too long.

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