Engineer here

1. The engineers at honda and toyota definitely know their stuff. The reality is, this is a budget vehicle, the cheapest in Hondas US lineup. When working on vehicles, my goal is to make the vehicle what the engineers would have wanted it to be, if there were no budget or time constraints.

2. There is no such thing as a perfectly designed PCV system. In the ideal combustion engine, you would intake oxygen molecules, nitrogen molecules, some choice hydrocarbons, and nothing else. Anything else that comes in the intake valve is a compromise. PCV recirculation systems are an emissions compromise that is inherently bad for the engine ("stuff" in your intake manifold) but good for the trees.

This brings me to point number 3, has anyone investigated a PCV delete? Just an oil catch can to an air filter, and plug the PCV inlet. Obviously won't fly for those of you in California, but would work elsewhere.

EDIT
Pretty sure if we could find a Honda engineer, they would give the catch can a thumbs up.

 

So you are saying that plugging the inlet to the manifold and venting the PCV to a catch can with the breather attached would in theory work and not change the idle or tuning of the engine?

 

Not sure, cars less than 20 years old are new to me, but unless they adjust the input from the MAF to account for the small amount of gasses that goes in there.
anyone know the flow rate through the pcv system?

 

Watching with popcorn. Ive had a lot of questions regaurding catchcans that this thread has done a great job of summing up. Thank you CyclingFit for drumming up this post.

I have an idea that the catch can is (maybe) safer,given the little i understand about how maf tuning works, than the pcv delete for longevity.

 

Let me start by saying, I have never had the valve cover off of a GK car. I have to assume if a hose is going from the air intake before the throttle body, and into port on the valve cover, this is fresh air being introduced into the crankcase. Introducing fresh air into the crankcase is common on newer engines. What I do know is this is what people are calling metered air. Metered air is air that has passed through the MAF sensor and the computer has accounted for in some way.

So, without trying to expand too much..... if you closed the port on the intake manifold, there is still vacuum in there. The fresh air supply line that is just before the throttle body and supplying fresh air into the valve cover (crankcase) could be exposed to vacuum in some situations, thus reversing the flow of air and you still pulling fumes, mist, and condensate, but this time from in front of the throttle plate. NOT GOOD.

This design is counting on vacuum in the intake to draw fresh air through the engine. I will share a picture of what I understand to be the fresh air supply line.

Notice this is coming from fresh air between the MAF and the throttle body. This clean air gets to travel through the heads oil passages, down the oil return galleys of the block, and into the oil pan crankcase area. Along the way it will get mixed with fumes, mists, and condensate. The closed vacuum side that in some cases includes a catch can, then pull or vacuum suck the now dirty mix toward the intake for recycling. Hopefully our catch cans will get most of this. Personally I prefer the system intact because it is doing what it was designed to do, which greatly increases our oil life. It prevents odors under the hood and into the cabin.


Disabling the system would be very risky because of potential reversal of fumes back toward the throttle body side.
Disabling the system would eliminate the vacuum that we rely on to keep the crankcase clean of gas, fumes, mist, blowby, condensate, etc..

 

This was shared on the forum and I do have a link in my original post, but only for reference.

This is to explain why this is not the correct way. Intake vacuum is pulling and causing flow to match the red arrows. The only way to pull air is to provide air, so normally fresh air induction starts where I marked the yellow X and then goes over to the valve cover. (see post above and red arrow). In the case of this system, they are pulling poorly filtered air through this expensive catch can that is being used incorrectly. If this car was idling in front of you and you put a plastic grocery bag over that filter, it would suck the plastic bag around the filter. There is not air coming out like this owner believes..

 

Aha, I was not aware of the fresh air system, thank you for educating me

This makes PVC delete, while not impossible, probably way more complicated than it's worth, especially when the simple catch can seems to be giving good results.

Your answer does tell me that the MAF accounts for air into the pcv, and it's a substantial flow rate. To delete the PVC, you could take the crankcase fresh air line you mentioned and route it straight to the intake manifold, and set up a 12V air pump on another line of filtered but not MAFd air to push fresh air into the crankcase, which outputs to a catch can and then air filter. (Separating the two systems entirely and keeping the MAF/tuning happy, no different than a high flow air filter)

I don't actually care to delete the PVC system this much, just exploring the idea for fun.

 

I posted this in the other thread, but the installation in this picture is 100% wrong.

 

I brought in your 20 year quote because I think some old school knowledge is trickling into the equation. And because you are just having fun pondering the idea, I have a link down below.

If this was a college course in PCV, I think I am working in the 300 level courses. Certainly not ready to graduate or move on to a masters....

This https://www.enginelabs.com/tech-stor...up-horsepower/ may be closer to a 400 level course This goes into detail about understanding how many inches of vacuum are being pulled and the vacuum's ability to effect engine oil pressure, oil inside bearings, and oil on cylinder walls. In racing applications there is a sweet spot for building HP.

Enjoy!

 

A. 2015 Fit LX
B. 30,000 Miles On Odo
C. 6 Spd/MT Transmission
D. Catch Can Type = Inline Air Compressor Filter/In Line Water Moisture Trap
E. About 5ML caught after 339 miles, pics below
F. Driving style = 90% Mpg Friendly, 10% Heavy Footed





Though everyone should be running 0w-20, I just wanted to share that I personally pref the "high mileage" variety. I read somewhere it has conditioners for our rings.





Note:
I will be uninstalling the "catch can" just for a week or so, while I troubleshoot why I am losing top end power. At this point, its unclear if its due to the catch can or the throttle body spacer. Once its all sorted out, I plan to ether reinstall this catch can, or may go with something bigger and less restrictive (assuming, the source of my power loss is indeed ... a restrictive inline moisture trap)

 

For sure.

I wanted it to come up in this thread so we could be very clear as to why it is wrong ... The hardware being used is so nice looking and smooth, I really don't want anyone to think they should copy this design.

 

That does look pretty restrictive, does it have a filter elements that's getting clogged?
I notice most of the catch cans I see keep nice wide air passages

Thanks for posting actual numbers!

 

Update: 8/1/2018
Thread adapters arrived. I really did not like that the hoses touched the body. The engine rocks and the body does not. This means moving parts would touch non moving parts.... I am a little frustrated with myself for not patiently waiting for lower profile brass fittings or dropping the big bucks on the super nice black aluminum fittings. I ended up using a bushing to make what the store had larger and fit into the thread adapters. I will likely still order what I want, but spending $10 today was easier than spending $40 for black aluminum fittings.

Except for color clashing, this now looks much smoother... again, making me anxious to get the other low profile black fittings.

 

UPDATE:

with the catch can off of the car, my power is restored. I can confirm, it was indeed restrictive. in a few days I plan to take off the Ruien/Heinmo catch can off of my prius engine and giving it a test on the gk5

$29.99 (theres a cheaper version, without the breather port up top)

Rick will be pleased, as it does say "OIL CATCH CAN" on the top

 

Really surprised noone has sprung for one with a sight glass
https://www.ebay.com/p/Oil-Reservoir-Catch-Can-Tank-Kit-Breather-Filter-Baffled-Aluminum/581788670?iid=192432829330

Edit, fixed broken link

 

I attempted to get no port and ordered this one, but so many of these bulk items, it shocks me they even get the color correct. Mine came with the port on top.. LOL. $24.99 free shipping. But as shown in my OP, it took some clean up.
https://www.ebay.com/itm/111389799564

 

I have one, it's just big so it's a problem of where to mount it.

 

Update 8/2/2018: Also in OP - I am super tired from a long day, so I'll come back and tidy up this post.

Okay.... I think after a week of people with posts, chatting with others in PM, and now making what could be my final change. Here is what I have done.

I have now added stainless steel wool to my system. A lot of it.... All of this research has told me there has to be something to cause agitation in the flow of air and help 'catch' the oil. As it is caught it can grow into a full drop and move to the bottom of the can because of gravity. This is pretty much the definition of coalescing. I also changed the routing, which may startle some people, but I really believe this is a super great move by me.

If you have been following what I have done:
>> Most startling thing someone may notice is that I have air going into what some people see as the exit.
>> The hose with air leaving the can is now on the top. I really only did this to give me plenty of space between that fitting and the washer fluid reservoir. The hole on top of these shares the exact same chamber as the hole that has the plug in it.
>> The reason I am bringing air out of this side of the can is because this side has the baffles. I am using the baffles to help ensure I don't let any steel wool out of the can.
>> I have completely filled the can with the scowling pads that are shown in the pictures. This required two pads.
>> Why is the can full of wool? Because I didn't want air to simply fly across the top of the pads. I am hopeful this forces air through them. They are very coarse so they will not cause resistance.

As usual, captions are under each photo.



The 3 pack of scrubbing pads, $2 at Target.




Two scowling pads = Full Can!




Moved the intake manifold hose to the top of the can. Some cans are labeled in a way that makes this the "IN" side. I am using it as an out.




Picture take to document clearance to the washer fluid reservoir. Also the hoses are lightly zip tied together to give them more support.




A view to show the amount of clearance for the non factory items.

Just as with all the other times... Thank you for following along.

 

I recently installed a catch can in my other car (1997 GTI VR6), however I have no considered one for the Fit as of yet.

One reason that they are not equipped from the factory, aside from being an added cost, is that they must be emptied and maintained, and many people can't be bothered.

There are only benefits to be had from adding one, though. My only recommendation is to keep the sizes of all the tubing and fittings as close to OEM as possible. The PCV system on my VW uses all 3/4" hoses and fittings, which makes routing and space an issue, but I did not want to restrict the air flow.

 

Interesting setup, do let us know the outcome after a few hundred miles. I too like your idea with the 90 degree elbows. I do not foresee a major issue with the straight connectors that it came with. I dont like the steel wool idea despite others saying it will help collect the oil mist into drops. You have effectively increased the maintenance interval for the catch can by reducing the capacity of the reservoir. If anything having a larger reservoir creates a lower pressure valley to which the oil mist can collect at the bottom of the can. That is the intended function. So far I've traveled 50 miles of mostly highway, and there is nothing in the catch can yet. car drives great with the added mod.

Cheers



Whole setup