Who's running a catch can?

Ron

toner123

i guess the real question is, do we really need to have one? Like what are the Pro's and Cons of it

Nixlimited

No cons other than extra connections and a marginal amount of extra weight and space needed. Pros are less oil coating the intake tract as well as the fact that the vapor that is burnt off in the combustion chamber allegedly lowers your effective octane rating i.e. tends to promote detonation. That's what I was told at least on my old STI. I would be very surprised, however, if NA cars collected the same amount of oil as FI cars. The increased pressure of the FI tends to cause more blowby and more junk ending up in the intake tract. With that said, factory turbo cars come without catch cans so it may be overkill.

Note: I also had two lines on my STI and I ran twin cans rather than 1.

toner123

seems like a mod I should do then. Modme could you give us a DIY since I am familiar with your style and used your TT Diy to install mine into my Z

wstar

I posted a DIY when I did mine, over here: DIY - Oil Catch Can (w/ M370 + Batt Reloc). Mine's specific to my setup though (M370 intake manifold, and an empty battery compartment as a convenient location - may as well use the battery compartment heat shielding to promote vapor condensation in the can), but there's some general notes and ideas there too if you read through it.

All in all, doing your own catch can install is pretty simple once you understand where things hook up, you just have to decide where and how you'll mount/attach it.

I would think in general you'd be right about FI getting more blow-by, seems to make intuitive sense. But that just puts more blow-by into the crankcase, which is mostly fuel vapor. From there you're venting the crankcase through the PCV valve, and the crankcase shouldn't be at abnormal pressure, and most of the rest of the vapor is oil vapor from there. It may be that the rate of catch can condensation is mostly driven by crankcase pressure/airflow, which shouldn't vary much for FI vs NA.

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wstar

Oh and the primary Con, IMHO (and the reason factory cars never come with a catch can): it's another maintenance task you have to keep up with. If you don't dump out your catch can on time (on our cars, seems like once an oil change would be fine most likely, maybe twice if you're paranoid), the can could eventually fill up too much.

If it filled completely, or even filled far enough that the fluid can creep up the sides to the level of your outlet hose in a high-G corner, you could suck the liquid contents of the can into your intake. The condensed oil vapor + whatever else is thicker and greasier than your normal engine oil.

Imagine pouring 1/4 cup of thick greasy oil straight into your intake in one shot, while the car is at high revs pulling through a corner or whatever. At the very least I'd think you'd get some bad knock for a couple of seconds and have a mess to clean in your intake manifold, but there could be worse consequences. I don't plan on finding out

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modme

Actually, crankcase pressure/airflow are completely different from NA versus FI. In NA, you will never reach positive pressure inside the intake manifold. During WOT, pressure in the manifold will drop down to zero, the PCP valve will close and crankcase air will vent minimally through the crankcase vent.

However, in FI, your manifold pressure will reach up to 12 psi or whatever boost level you are running during WOT. So now the PCV valves close, but you have significantly more pressure venting from the crankcase vent to the air intake piping. How much oil vapor is blown through during this process, I am not sure.

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wstar

Yes, that's basically true. Given positive manifold pressures from FI, I wouldn't be surprised if some of your crankcase venting ends up exiting the fresh air inlet tubes under hard acceleration as well (as you'll be building crankcase pressure from blowby, but the positive manifold pressure will keep the PCV valve forced closed). I doubt the factory puts one-way valves in them (which aren't a great idea), so you might want to experiment with canning those as well.

Another thing could affect all of this on NA cars is your driving patterns I guess. Engine braking produces more vacuum than idle or steady-state driving (faster rate of PCV system flow), whereas hard accel (WOT) produces almost no vacuum (slower rate of PCV system flow). If you use engine braking a lot, you could be scavenging from the crankcase at a higher average long term rate.

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Maila87

Guess that experience from 350Z or any predecessor engine will help. Is catch can really so important for our cars which don't have direct fuel injection?

Carbonization is really painful on AUDI engines with FSI (Fuel Straight Injection) , or TFSI (Turbo FSI). My old 2.0T FSI with 82 000 km's on the clock didn't have any issues. But on other hand, there is owners in US which experienced problems after 1000 miles! Even RS4 are really sensitive and catch can should be factory fitted, due to liquid which looks like mud in catch can cas

BTW: Due to no big fuel quality difference and huge price mine 2nd hand TT used 95 RON fuel instead factory recommended 98 RON

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-->2005-6 Nissan Micra 1,3i CVT 72PS Red MY 98 -->2006-8 Nissan Almera 1,5i N16 96PS Red -->2007-8 Skoda Fabia Combi 1,2HTP 3 cylinder 60PS Green -->2008-11 AUDI TT 2,0TFSI FWD S-tronic 200PS Red MY06 -->2011 Nissan 370Z manual White Pearl