I see catch cans mentioned here a lot and I'm wondering what they do and do I need one? I have a 07/C6/Z06
Thanks.

 

The environmentalists didn't like the nasty oil fumes that come from internal combustion engines where the rings don't seal the pistons perfectly so a small amount of gas blows by into the crank case from where it must be vented. Originally the fumes were just vented. Then it was noticed that dumping these fumes into the engine bay oiled the entire bay with the fine oil particles that were picked up. So a filter was added to strain some of them out and drain back into the crankcase. This worked fine for 50 years or so until the 70's when the government decided to get involved and say this was unacceptable.

The result was Positive Crankcase Ventilation (PCV). The fumes were collected and vented into the engine intake to be burned. That's not a bad solution but now, instead of a small amount of oil particles being sprayed around the engine compartment or under the car, a larger amount (because the filter was eliminated) is dumped into the intake manifold. When most of it gets to the cylinders it is burned but oils doesn't burn as cleanly as gasoline so you get more deposits than you would without PCV.

So, along comes the catch can. The catch can is just a filter in a can that goes between the crankcase and the intake manifold. You disconnect the PCV hose, connect it to the catch can and install a second hose back to the intake. Instead of dumping the oil fumes into the intake you filter most of them out and collect them in a container (can). Once a year you empty the container.

Is it needed? That question has been asked and answered many times and my opinion is - it certainly doesn't hurt and will help keep the engine internals cleaner. But will a cleaner engine run any differently than a dirty one? Probably not enough to notice until you get 100K miles of oil in the engine. The harder you run the engine the more blow by you will get so a race car will see loss of performance sooner but changing spark plugs will probably eliminate most of the deposits that would be detrimental. Most people will probably never notice the difference.

So do you need it? Most people would probably say no but I have one because they are relatively inexpensive and I like the idea of keeping my engine clean. Besides, I open the hood and a car buff sees a catch can and says "ooohhhh, cool" while someone who doesn't know gets it pointed out and a long dissertation so that I can impress them with my vast knowledge.

Here is what I collect in about a year and 5K miles -

 

Thanks for the reply, greatly appreciated

 

Thanks Ft Morgan, best description I have seen yet.

 

The only reason I do not run one is it will not pass emission testing in California.

 

I don't race and I only get on it once in a while. After i installed my EE catch can I get a decent amount of oil at the bottom of the can every couple of months (about the same as in the pic a year) If all this oil went into the manifold/engine it can't be a good thing, so I'm happy I installed mine. Not too expensive and fun to work on the car!!

 

Thanks for the explanation.

 

 

Wel done, FortMorganAl

 

Good explanation FortMorganAl! One additional note is that when oil vapors get pulled into the combustion chamber on decelleration (high vacuum) it can degrade the octane in fuel causing knock retard.

BTW: GM improved the PCV system in the C7's, I wonder why?

 

When purchasing a new car in CA, residents do not pay for a smog certificate for the first 6 years. After six years, bi-annual smog checks are required.

Did your car fail the visual inspection? My 2008 will require its first smog certification next registration and I have a EE catch can. If needed, it's a 15 minute fix.

 

Ft. Morgan's post should be turned into a sticky note that can be referenced every time this subject comes up. Very well done!!!!!!

Can you write-up a similar one about Nitrogen vs. air in tires, oil change frequency and where to park? Then we can have all the bases covered.

 

Mine inspection is due end of 2014.

I just do not want ot mess with it. Not real mechanical inclined. although I suppose someone could walk me through it with installation.

I'll have to inquire into this to see just what is involved with removal for inspection. I know it is not major but as I said not real inclined.

 

Great discussion and write up. My only question now is how to deal with my Dad's position that burning a little oil is a good thing - keeps the top end lubricated

 

I don't know that it's necessarily a good thing, but the very small amount of oil in the OP's pic won't hurt anything either.

And yeah, great writeup.

 

Ok, what about just using a filter on the oil filler cap? Is it the same as a catch can? BTW my engine is supercharged.

 

Not needed unless you track the car or its heavily modded and see lots of high RPM's on a consistent basis. You can certainly run it on a stock car, street driven it's not going to hurt anything and they are not that expensive.

 

Not too much of the above...s it fits me fine....

 

Great explanation Al.

Mine's about half-to-three quarters full when I change the oil after a 'normal spirited' driving season.

 

Thanks to all who complimented me on my verbose dissertation. I thought I was just being my usual long-winded self.

Relieving the crankcase pressure is relieving the crankcase pressure no matter how you do it. The disadvantage of a simple filter is that there are still some oil droplets going to get past the filter and you are going to be dumping them into the engine compartment. Also you won't pass an inspection with the PCV system completely disabled so that the vapor vents through the filter. If you don't disable the PCV the filler cap filter is normally going to be sucking air rather than venting.

But you did bring up a good point about forced injection. The purpose of FI is to raise the pressure inside the cylinders which is going to cause more blow by so I would always get a catch can when I installed any kind of FI system. And CAI is NOT FI.