Well, I saw no reason that oil should go into the intake... so routing a hose from the catch can to the intake seemed counter-productive. Plus adding a breather on the end of the catch can is easier.

Mazda did this to burn off the excess oil... but by putting it into the intake where they did, it coats many essential parts. They realized this design flaw and changed the route on the '06s and newer, and issued the TSB on how to fix 04s and 05s that were having problems.

Your intake is for clean, filtered air... there is no reason to have the oil vapors in there.

 

Ok, another question - any idea how many people have done this? Is it common - are there many problems? $100 to get it done isn't a big deal but I don't want to mess with something that I don't really have to...at the same time - I have seen oil in my intake - trying to assess pros and cons of doing it (biggest con in my head being the dealer may void me if something were to happen to my 8)

 

I found a neat one on the 'bay - it even said 'MazdaSpeed' on the side!

I took the car for a reflash and the tech started giving me grief for 'engine mods' then he came back later and apologized - "oh, sorry man, didn't see it was a Mazda part - that's OK...."

S

 

Well, i chose an expensive can (45 bucks for a stainless steel welded can) and the other parts were about 10 bucks. So it is cheaper than the TSB. I think it is common on the forced induction 8s when oil "blow by" is an issue and on the '04s and '05s where even slightly over-filling the oil (or overfilling improperly) can lead to oil in the intake... which leads to a dirty Mass ar flow sensor causing rough idle and typically the car will run rich causing poor MPG. The oil can build up on the throttle bottle butterfly valve, also bad. And, what happened to my car. Rare, but pretty severe, covered the SSV valve in the lower intake causing it not open at idle causing my call to stall unless I had one foot on the gas at all times.

Some say that they will never over fill their oil... but, if you have dual oil coolers on an MT, its more difficult to get all the oil out of the car during a change. The design of the filler neck can lead to oil going through the hose if its filled too quickly or just runs down the front of the filler neck and into the hose.

With me, and the aggravation of not knowing why my car would run great and then stall all the time was worth the 50 dollar catch can.

In terms of the dealer... with my installation, you remove one bolt and the catch can is free... disconnect the hose from the filler neck, remove the cap on the intake and re-attach your stock hose and mazda will never know. I think you could have it off and back to stock in 5-10 min.

 

Whoa..... so all I need to do is put "mazdaspeed" stickers on my mods and the warranty will be fine? Sweet!

 

There can be problems down the road with excessive oil in the intake.
Just ask Vyndictive about that.
Here is a thread where we had to fix his stuck SSV due to oil sludge in the intake manifold (start at post 30):
https://www.rx8club.com/series-i-trouble-shooting-95/rpm-dropping-%3D-engine-stalling-162200/page2/

No real "cons" by doing this, just run a line from the oil filler neck to the catch-can.
The pros would have to be: Cleaner air filter, doesn't mess up the MAF and IAT sensors, no oil sludge on the throttle body valve, no oil sludge on the SSV valve.

That is crazy Stealth.
I think its funny when he saw "Mazda" on the side, it was suddenly OK.
I don't care if you use a beer can, its the same concept.

 

Best tip I've EVER seen or read about!

 

To backtrack a bit.

On the 2007 and newer RX8's and maybe older ones.

THERE ARE TWO OIL FILLER NECK NIPPLES. One in the front and one in the back.... When you take the line out from the back - cap it or you will leak oil onto your engine when you fill it up. Ask me how I know?

Just put a vacuum cap on it - no need to run two lines to your oil filler neck.

 

Do you happen to have a pic of this? I'm curious.

 

My car is at the shop ATM... but if you feel behind your UIM to the oil filler neck (plastic piece) feel all around the back toward the firewall you will feel a nipple (there is a stud there too; but the stud is NOT the nipple.)

 

What is that little guy supposed to do exactly? I would say you don't need it.

But, if I had to guess - keyword: guess. It would go on the line from the catch can back to the intake. The intake is under vacuum, the oil filler neck really isnt.

 

Did it come with directions?

Think Vyn has it right though.

Maybe the website of the maker or wherever will have a clue?

 

Honestly, I'd leave it off and just not run the catch can back to the intake. Just put a breather on the catch can.

 

I've been thinking about that piece... upon closer inspection, does it have a 1 way valve in it or anything that controls the flow? Perhaps since it was a universal can there are some cars out there that place a sensor in the lines. . .

Post some pics of your final install: I think it would be good for people to see other catch can setups so they know they have a lot of flexibility with this mod.

 

When you get it installed, post the pics in this other thread!

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/catch-can-pics-163702/

Could also give you other places for possible install.

 

What is the different between returning filtered hose back to intake or venting it with breather?

 

Can't fine one anymore.

 

The intake creates vacuum pulling air from the filler neck, through the catch can, and back into the intake... Although the process should get blow-by oil to stop in the can, there is still a chance (small) that oil vapors can end up in your intake.

I see no positive reasons to run it back to the intake at all.

 

bump.
tiny question, I've been thinking...
besides legal reasons, is there any reason to just not vent directly? no catch can. just a breather filter.

 

Nope.

It's just that at high velocity, the gas carries out some oil foam/droplets, which will dribble unless drained somehow.

S

 

My opinion would be that if no catch can and you had significant blow back or even just over time, you would probably end up with an oil soak breather filter and then that would/could start dripping everywhere.

 

I see the catch can really as a means to keep oil out of the intake on the chance that somehow your oil gets overfilled. Putting a breather on the end, while it has the potential to be really messy and cause other problems, it does keep the oil out of the intake.

If you don't want the catch can floating around, you could always follow the TSB and run the new line to the maintenance ports.

 

If you let your catch can get overfilled you then have runoff.

If you don't and all you have is a breather w/o an overflow then your oil no longer has a place to go. No reason to run it back to the throttle body if you have an 04 but there is a reason to have it run somewhere.

There really are worse things than oil in your intake and a stuck SSV.

But as long as you never overfill by more than your catch can and you always check your catch can to be sure it's clean before every oil change you should be fine.

 

Well, if you let your catchcan get filled to the point where its running back to your intake, you really deserve getting oil all over the place...

I guess you could argue that it is a good thing to run it back on the chance that your catch can gets overfilled and runs it back to your intake, but I would rather see the can run to the bottom of the engine bay and dump onto the road (although very illegal, it is unlikely that it would ever happen like that.)

 

Jeez, you let it ever get that full, you have serious issues don't you?