8th Generation Honda Civic Forum banner
1 - 20 of 23 Posts

·
Registered
Joined
·
1,895 Posts
Discussion Starter · #1 ·
Ok so what's the effect of having or not having a catch can, will it do harm if you don't have one or is it just simply there to "catch the oil"

I don't have one on the car but I don't drive it that much anyhow, just like some info on the benifit whether I would need one asap or not. Thanks
 

·
Registered
Joined
·
8,668 Posts
M. Bison got it right.

in stock form it works like this: VC is connected to the intake to draw in fresh air. PCV is connected to the left side of the IM. under vacuum the pvc is opened(sort of a check valve, but it requires a certain amount of vacuum to open) and the IM's vacuum draws in the blow by (vaporized fuel and oil)which then gets sucked into the combustion chambers and burned off. Its smog equipment.

short term it messes with the AFRs, long term results in deposits on the pistons and rings.

those deposits can eventually result in hot spots and cause knocks/pre ignition.

with boost instead of just vacuum we screw up the way it works in stock form. while in boost the PCV stays closed and now all that blow by can only escape through the VC, into the intake, through the turbo/sc, and then into the IM. Same thing happens when we just run a inline catch can.

ideally we want only air in the IM and we want the crankcase to be able to breathe as good as possible. thats why most of us have drilled the pcv and installed a breather can to the VC and PCV.

breather can is a very simple device but all it needs to do is have some sort of baffling or steel wool to slow the fumes down enough to allow them to condense into a liquid form so they can collect at the bottom of the catch can instead of blowing out the filter...coating the engine bay and stinking up the place.

and that class is how a catch can works
 

·
Registered
Joined
·
4,011 Posts
Nick nailed it on the head.

It should also be noted that a catch can from the valve cover seems to be the most popular place to catch oil vapor. But it's next to useless on our cars. Our valve cover has an internal oil baffle and next to no oil ever makes it out of that opening.

If you run a catch can, run it between the PCV valve and the intake manifold. Tons of blowby comes through this way.
 

·
Registered
Joined
·
8,668 Posts
Nick nailed it on the head.

It should also be noted that a catch can from the valve cover seems to be the most popular place to catch oil vapor. But it's next to useless on our cars. Our valve cover has an internal oil baffle and next to no oil ever makes it out of that opening.

If you run a catch can, run it between the PCV valve and the intake manifold. Tons of blowby comes through this way.
It might be because of stupid amount of boost but I am currently catching tons of fuel vapors, enough to have to drain my ghetto fab catch can every 500-700 miles.

i frogot to mention that inlines don't catch all the vapors so you will still get your im coated and vapors burnt in your combustion chamber. breather can on both is ideal. they can both be routed to the same can too.
 

·
Registered
Joined
·
1,895 Posts
Discussion Starter · #7 ·
great info, so any recommendations to which catch can i should buy
 

·
Registered
Joined
·
4,011 Posts
In reality, most mass produced catch cans (from Greddy, etc) won't do as good a job that a custom can would simply because they don't have any baffling to catch the actual oil in the vapor. But something is better than nothing.

The ideal setup would to be to drill the PCV out, have the vapor flow to a can with a breather attached, and cap off the nipple to the intake manifold. So zero blowby has the chance to enter your motor.

If you get a regular can off eBay, etc. make sure to get something small because there's not alot of room in our bay to mount anything.
 

·
Registered
Joined
·
4,011 Posts
True, that's what I did.

 

·
Registered
Joined
·
4,011 Posts
Nah, just the PCV. I check my valve cover vent hose every one in a while and it's dry as a bone.
 

·
Registered
Joined
·
8,668 Posts
I talked to Dave from SSA about catch cans. He brought up a really good point that frogot to mention in that previous post. For us turbo guys one really bad short term problem of not running the proper breather setup is a pressurized crankcase. If the crankcase actually pessurizes then the oil drain won't be able operate properly and damage to the seals can result.

on a side not, it was either import tuner or modified magazine that dyno'd a car with and without a cc and the cc netted 4 whp, chew on that.
 

·
Registered
Joined
·
8,668 Posts
its pretty easy to do. just remove the pcv and use a drill press to drill out the guts or a punch and hammer and beat the guts out (hehe)
 

·
Registered
Joined
·
676 Posts
I see that the ebay catch cans are inline. Where can I get a catch can with a breather for both the pcv and valve cover?
 

·
Registered
Joined
·
8,329 Posts
1 - 20 of 23 Posts
Top