A few of questions:

1. How much of that “2 to 3 ounces” was oil? How much was water?

2. At what volume should we be concerned? Three ounces after 500 miles seems excessive and could be an indication of a bigger issue in the engine.

3. Where is your catch can located?

4. Two port or three port catch can?

 

Does running a Catch Can keep the pistons clean and shiny?

I had not heard that.

 

Hello,

I'm with AllenK4 and have never understood the catch can attraction. If you are worried about detonation / knock, that is why we have knock sensors and knock reduction built into the operating system within the powertrain control module.

I don't like catch cans for the same reason that I don't have an electric dog polisher. Its just not necessary.

Rick

 

For those who are against the can, I have 2 questions:

1) are you boosted?
2) if yes, how are you venting the crankcase?

 

I tried the boosted thing without a can and had a 1 way valve installed between the intake and pcv because I have the badly designed valve covers and had a ton of oil in the factory intake. First time I hit boost the valve was such a restriction that oil dib stick blew out and shot oil all over the headers smoking and making me think I blew my stock SBE. Since then I've had a can I see considerably more than 3-5oz but its 98% water and I attribute it to the humid climate.

 

I am boosted and vent mine to the atmosphere with a filter on each valve cover

 

I can't answer that question, what I can say is... through the years I've pulled apart many performance n/a engines, running the highest pump octane (non e85) available and could still read the piston "std or over bore" stamping. These were mostly late 60's & early 70's SBC, BBC, Pontiac and a couple AMC 390's. These engines PCV system's are quite inefficient compared to today's engines and didn't ingest blowby, they more or less spewed and leaked more blowby in the atmosphere.

A lot of 50's & early 60's cars had a blow by tube that simply dumped the blowby underneath the vehicle onto the street. At every stop light or intersection there was a huge oily & greasy spot where cars would stop waiting for the light. Talk about no traction at stoplights! Most here are to young to have seen those huge oil slicks on the pavement and would have a conniption just seeing that... I'm sure some are triggered just reading about it.

Piston with carbon buildup from my two year LQ9 build with only 11,000 miles (no catch can).



The old blowby dump tube on a early 60's small block. If it had a reservoir it would make an efficient catch can lol. You can see where the tube oozed oil on the floor just sitting there!

 

Your equation is faulty as far as the effect on octane from oil mist goes. You would have to know how much oil comes out of the crankcase during operation where the octane rating of your gas is needed. So how much of that oil gets into the intake at WOT, 3800 to 5500 rpm pulls, and how much time do you spend driving in these conditions. Maybe most of that 1-1/2 oz comes at full throttle?

My point is that you can't assume that the oil escapes the crankcase at a constant miles/ounce ratio, and have to consider only WOT high rpm usage.

And as stated above, this mainly applies to forced induction with wide ring gaps. Have you ever noticed on monster trucks, because you can see under the engine, how much fumes blast out of their downward pointing crankcase vents? It looks like a small rocket engine.

 

Same here, I just drilled the factory oil fill cap and put metal filter media inside it and a air filter on the outside to keep out dust.

 

Mike,

I’m not sure it matters when the vapor is introduced into the intake, but I am willing to listen and learn more.


Most of what I have read indicates that blow by increases with Boost and RPM.

EDIT. CORRECTION. THE PCV IN MOST VEHICLES DOES NOT VENTILATE THE CRANK AT HIGHER RPM’S. IT F7NTIONS ONLY AT IDLE AND WHILE CRUISING AT LOW RPM’s

EDITED ABOVE.....I have read; PCV systems do not return much to the intake system at lower RPM.

So, I would s that most of what ends up in the catch can gets there during Spirited Driving.


Ring gap is an interesting question. I bet most of the guys reading the forum are running lower boost levels, with stock ring gaps.


I am still unclear how to determine the change in octane that could be caused by these amounts of crankcase vapor being introduced into the intake system.

Is there agreement that introducing these small amounts of the non-oil liquid component back into the intake has little effect?