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Discussion Starter · #1 ·
Hey all,
As many have done, I've got a small little breather filter on the driver's side PCV tube. In my setup, I've got a 392 intake (but have yet to purchase a CAI), so I'm still using my factory 5.7 airbox. I bought a little Air Raid filter that clamps onto the port just under the oil filler tube... pretty normal stuff... instead of plumbing a hose back into my stock airbox port. Obviously, when I get an actual CAI, there wouldn't even be a port to plumb it into, hence the reason everyone puts on a little breather filter there.

However, I've noticed that immediately after a big throttle release, there's a very noticeable oil smell in the cabin, and I'm certain that's blow-by coming out of that little filter (which would normally go right back into the airbox in a factory setup).

My question is: how many of you notice the same thing who have done a CAI? Just trying to think about if I have a more severe blow-by issue than most. I haven't yet checked the plugs. Car does have 102k miles.

Thanks in advance,
J
 

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The Bacon Hauler (‘12 Cop Charger)
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Hey all,
As many have done, I've got a small little breather filter on the driver's side PCV tube. In my setup, I've got a 392 intake (but have yet to purchase a CAI), so I'm still using my factory 5.7 airbox. I bought a little Air Raid filter that clamps onto the port just under the oil filler tube... pretty normal stuff... instead of plumbing a hose back into my stock airbox port. Obviously, when I get an actual CAI, there wouldn't even be a port to plumb it into, hence the reason everyone puts on a little breather filter there.

However, I've noticed that immediately after a big throttle release, there's a very noticeable oil smell in the cabin, and I'm certain that's blow-by coming out of that little filter (which would normally go right back into the airbox in a factory setup).

My question is: how many of you notice the same thing who have done a CAI? Just trying to think about if I have a more severe blow-by issue than most. I haven't yet checked the plugs. Car does have 102k miles.

Thanks in advance,
J
When the engine is operating at Max torque output, the PCV valve will lose its mind and slam closed, thereby forcing the blow to gasses that would flow through the PCV and into the intake instead go thru that make-up line to the air box. That’s normal-ish behavior, if not necessarily desirable.

However, if you spend a lot of time at WOT, that behavior will tend to leave oily deposits on the top side of the stock air filter and on the inside of an aftermarket CAI intake tube. Again, normal-ish, even if undesirable.

Since you just have those gases exhausting into the engine compartment, it stands to reason you would smell oil vapor after an episode of WOT that saw the engine producing Max torque (~6000 RPM?).

Tge only thing I can think of to mitigate that in your setup would be to run an engine oil with a lower NOACK value. The lower NOACK indicates less susceptibility to evaporation, for lack of a better phrase, and thus less likely to end up as oily vapor in the PCV blow by gasses.

But that’s gonna be a diminishing return at best, and there may not be an oil that meets the engine’s certification requirements while having a different enough NOACK to make a difference in this way.

So, you may just have to live with it for now, in other words...
 
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Discussion Starter · #3 ·
Thanks, Nuke! Approaching it with a little bit of science, I like that! I've been using for the last few oil changes the Royal Purple HPS formula because it seems to have a high level of zinc. It'd be an interesting experiment to see if different oil would alter that behavior, but honestly I can't say I'd be down for testing that :). Guess I'd just like to hear if others experience the same sort of thing in setups where there is no return line to the airbox. FWIW, I do have a catch can, and the PCV valve is functional, so I feel pretty certain it's exactly what we're describing -- at full throttle, and PCV slapping shut, that blow-by has gotta go somewhere, so it's blowing out of the breather filter (instead of the closed airbox). I suppose I can run a heater hose back to my airbox and see if I notice it (I assume the phenomenon will be gone), but that's why I'm posting -- just because I'm hiding it doesn't mean it's not there, and I'm concerned my engine's level of blow-by is greater than it should be.
Cheers,
J
 

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The Bacon Hauler (‘12 Cop Charger)
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I suppose one possible option would be to avoid WOT operation, but I don’t personally consider that a viable option.

For me, a day without WOT is like a day without oxygen.
 

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The Bacon Hauler (‘12 Cop Charger)
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Another option just occurred to me for controlling the odor of oil vapors coming from your engine bay after WOT. But I’ll qualify it now by saying it’s surely more trouble than it’s worth...but if you really wanted to, this would work!

1) get a miniature inline air compressor filter like this:
Electronic device Technology Electronic component Cable Electrical supply


2) plumb that in place of the current breather element, orienting it so the air flow through it goes from outside engine thru it and into engine (since that’s normally how the fresh air line flows - from air box into engine).

3) put the displaced breather element on the incoming side of that mini air filter (which temporarily becomes outgoing during the behavior in question).

So basically, you would be adding a homemade catch can onto that fresh air line, and moving the breather element you have there now onto the end of the catch can.

This would double filter the air normally flowing thru the line and into the engine, and during the WOT Max torque operation, it filters the air being blasted out of the engine thru that line.

The mini filter will catch and hold most of the oil droplets of any air blasted out of that line, thereby reducing its oily aroma to any olfactory senses in close quarters of the engine bay. 🧐
 

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Discussion Starter · #6 ·
Another option just occurred to me for controlling the odor of oil vapors coming from your engine bay after WOT. But I’ll qualify it now by saying it’s surely more trouble than it’s worth...but if you really wanted to, this would work!

1) get a miniature inline air compressor filter like this:
View attachment 1005195

2) plumb that in place of the current breather element, orienting it so the air flow through it goes from outside engine thru it and into engine (since that’s normally how the fresh air line flows - from air box into engine).

3) put the displaced breather element on the incoming side of that mini air filter (which temporarily becomes outgoing during the behavior in question).

So basically, you would be adding a homemade catch can onto that fresh air line, and moving the breather element you have there now onto the end of the catch can.

This would double filter the air normally flowing thru the line and into the engine, and during the WOT Max torque operation, it filters the air being blasted out of the engine thru that line.

The mini filter will catch and hold most of the oil droplets of any air blasted out of that line, thereby reducing its oily aroma to any olfactory senses in close quarters of the engine bay. 🧐
You should market that ;)
 

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The Bacon Hauler (‘12 Cop Charger)
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You should market that ;)
Back when I had my 2011 Challenger I actually put one on it. I even went to the trouble of painting it Toxic Orange to match the body color.

It looked good enough and worked well enough, but I can’t see it being a profitable venture to produce. I probably spent 20 or so hours of labor and sprayed it with another $20 in paint, not to mention the $25 cost of the part to begin with.

Id have to charge $1000 apiece to make them worth my efforts to produce...either that or get better at making them, but I’m a very poor painter, so I don’t see that happening any time soon 🤔
 
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You should market that ;)
It's a poor mans version of an oil catch can. I too made my own for my previous Mustang (3.7 V6) using a water catch for an air compressor. Not hard at all to do. If you can install a CAI, you can screw on a couple of brass fittings to this water collector, then some rubber tubing, and clamps to install inline with the fresh air line.

Or spend money to buy one (oil catch can) that is basically plug and play.
 

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Discussion Starter · #9 ·
It's a poor mans version of an oil catch can. I too made my own for my previous Mustang (3.7 V6) using a water catch for an air compressor. Not hard at all to do. If you can install a CAI, you can screw on a couple of brass fittings to this water collector, then some rubber tubing, and clamps to install inline with the fresh air line.

Or spend money to buy one (oil catch can) that is basically plug and play.
Again, not trying to "turn down" the blow-by (yet), just trying to see if others have noticed the same issue when the PCV line is venting to atmosphere. Although, I like all the backyard ingenuity!
J
 

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All engines will create oil mist (crankcase blow by is the older term). My new Mustang starting at 200 miles would fill a small air compressor water collector jar (home made collector) at its first oil change (approx 6000 miles).

Oil catch cans, or home made equivilent, prevent this oil mist from building up behind the air intake flap of the throttle body (butterfly valve). Some say this build up can cause sluggish response or a drop in performance/fuel economy. There are special cleaners to spray this buildup off of the throttle body. Don't use carb cleaner, as the throttle body flap has a speacial coating on it.
 

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PCV systems are like having a controlled / metered "vacuum leak" in order to relieve crankcase blow-by and capture those gasses and burn them by introducing into the intake stream.

There's a spring to control the valve and under lower vacuum (WOT, high engine loads) the valve closes down to avoid further drops in vacuum levels and and avoid an over-lean condition and improve power under demand.

and during those conditions, crankcase pressures can rise. Having the breather on the fresh air side can allow it to vent gasses and you'll notice some odor.

I have the Mopar CAI (Shaker) and I've never noticed any stains on the filter, nor any oily residue on the hose. I have to remove the fresh air PCV supply hose to clean the filter (did the 40K cleaning of the filter, which is done every 20K).

as the miles build up, of course there's going to be more wear on piston rings and valve guides so more blow-by will happen as well
 
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