Oil catch can pros & cons

BriinumsBo

New member
1.so it doesnt matter if i dump the oil or not?
2.and if the catch can is tight and the tubes ar short, its ok to have catch can?
3. what about recirculating blowoff valves? they give pretty big pressure back into PCV and the other tube (EGR?)

its not that i didnt understand, you just said about more different things on each sentence and i just wanted for you to explain more each of them :smokes:
 

WarTowels

Active member
On a related note, what are the effects if the tubing on your catch can is higher than the crankcase?

-Towels
 

ironpanther

New member
klue":10kg5lid said:
since a race engine usually has a considerable amount of blow by building pressure in the crankcase, this must be overcome to produce power and conquer the pumping loss. when the engine is under high rpm conditions/load the port vacuum becomes high and can easily pull the excess pressure created by the blow by gas. this is turn reduces the pumping loss created by the pressurized block. -> this gives you the performance gain.

if you have the pcv connected in the exhaust with a properly designed stem to creat a vacuum you can get the same effect as running the pcv to the intake(except you dont have to deal with the residues)

my problem with the catch can is that they hamper the flow of the pcv.

as for the sealing of the rings-> it is my understanding that the vacuum that a good operating pcv system produces helps to oil control ring effectively under loaded conditions.

Klue I have to argue your comment about excessive blowby. Any engine, commuter, or race will perform the best being built to the higest tolerances afforded and thus having the least amount of blowby.

Yes I can see the increased vacuum decreasing pumping losses but overall you are not getting a net gain because the engine still is doing the work to create the vacuum. That is simple first law of thermodynamics(output energy is never greater then input). A block breather would actually give you better performance because you are not recirculating blowby gases which displace good cold air and gas going into the engine.

The exhaust concept sounds sound with proper setup. That would include a free flowing exhaust and a check valve to manage the exhaust pulses.

While a catch can may decrease the velocity of the air in the PCV system, if you are using a check valve between the catch can and intake, you will both eliminate that issue and any possibility of problems with bypass valve dumps.

Towels, regarding tubing height it will not affect the performance but considering you are dealing with airflow things like length and sharp bends will greatly affect the performance.
 

gt4rcdude

New member
I have to agree. The rings seal by pressure differential. The difference between the pressure in the cylinder and the block. Lowering the block pressure a few inches of mercury probably won't do much.

A friend of mine ran his PCV line into his exhaust on his airplane. You have to fabricate it in such a way as to create a vacuum using the exhaust pulse and velocity. He made a small venturi in the exhaust pipe and welded a fitting at an angle just down stream of the smallest part of the venturi. No check valve required. It worked great. Not a good plan if you have a catalytic converter downline. Emissions may be affected too since you'll be burning oil.
 

BriinumsBo

New member
so is it ok to use oil catch can? im not using a breather filter for the can, everything is sealed tight! its ok filter out the oil? (its absolutely not needed for valves and rings?)
 

gt4rcdude

New member
It can't hurt, it may help. No harm, no foul. Best oil runs in an engine, not through it. Not counting two strokes. I've run one for 12k miles with no ill effects.
 

klue

New member
BriinumsBo":c1w7kn4a said:
1.so it doesnt matter if i dump the oil or not?
2.and if the catch can is tight and the tubes ar short, its ok to have catch can?
3. what about recirculating blowoff valves? they give pretty big pressure back into PCV and the other tube (EGR?)

its not that i didnt understand, you just said about more different things on each sentence and i just wanted for you to explain more each of them :smokes:

1 dont use the oil from the catch can its garbage, the additives are destroyed.
2. if you want to use one, use the biggest hose you can, with nothing smaller than that diameter in the whole system(short and sweet, minimal bends)
3. i dont recirc bovs, and i dont use egr.(no comment)
 

klue

New member
ironpanther":g47k2xmf said:
klue":g47k2xmf said:
since a race engine usually has a considerable amount of blow by building pressure in the crankcase, this must be overcome to produce power and conquer the pumping loss. when the engine is under high rpm conditions/load the port vacuum becomes high and can easily pull the excess pressure created by the blow by gas. this is turn reduces the pumping loss created by the pressurized block. -> this gives you the performance gain.

if you have the pcv connected in the exhaust with a properly designed stem to creat a vacuum you can get the same effect as running the pcv to the intake(except you dont have to deal with the residues)

my problem with the catch can is that they hamper the flow of the pcv.

as for the sealing of the rings-> it is my understanding that the vacuum that a good operating pcv system produces helps to oil control ring effectively under loaded conditions.

Klue I have to argue your comment about excessive blowby. Any engine, commuter, or race will perform the best being built to the higest tolerances afforded and thus having the least amount of blowby.

Yes I can see the increased vacuum decreasing pumping losses but overall you are not getting a net gain because the engine still is doing the work to create the vacuum. That is simple first law of thermodynamics(output energy is never greater then input). A block breather would actually give you better performance because you are not recirculating blowby gases which displace good cold air and gas going into the engine.

The exhaust concept sounds sound with proper setup. That would include a free flowing exhaust and a check valve to manage the exhaust pulses.

While a catch can may decrease the velocity of the air in the PCV system, if you are using a check valve between the catch can and intake, you will both eliminate that issue and any possibility of problems with bypass valve dumps.

Towels, regarding tubing height it will not affect the performance but considering you are dealing with airflow things like length and sharp bends will greatly affect the performance.


i dont need that thermodynamic mumbo jumbo. It works, thats all that matters to me.

you dont need a check valve, the turbine controls the pulses enough

and yes the engine must create that vacuum weather you use it or not is up to you.


-> dont get me wrong catch can is great, its keeps the intercooler clean but my greddy can needed some heavy mods to get it to work effectively.

BUT, there are better ways to control blowby ie: exhaust. you dont need no fancy tubes on ventrui's, just look at the design of the pcv nipple that tucks into the intake tubing. basically a short pipe cut at a angle(to generate the vacuum from the pressure differential) placed in the exhaust stream, where its still hot and at maximum velocity.
 

bridge47

New member
How did I miss this debate? You all make some good points. Hot Rod mag did dyno testing on PCV routed to exh. some years ago. No venturis b/c exh was very free flowing and it pulled vacuum. Can't remember exact #s but it was around 500hp small block and there was definitely a gain. I think their recommendation was that it was not worth it at OE power levels/street driving.

My experience with venting valve cover line to K&N filter (no check valve I know) is that oil gets dirtier faster but I change it often anyway. Also noticed hesitation from no boost to boost b/c, I thought, that was some unmetered air that ECU was counting. I'd be willing to try catch can if I get her back on the street. Probably a Moroso one, just because.
 

Kcman91gts

New member
Hey , speaking of catch cans , i was wondering if anyone could possibly provide some insight as to whats happening in my engine ... i know my valve seals are going because im getting a shitload of carbon build up around the tip of my tailpipe with some slight liquid / condensation

but in my catch can , sometimes its a slight foamy brown , other times its a mix between black and brown and sometimes looks like pourly stirred coffee .. and even sometimes it has actual water in the bottom with the oil floating on the top.

now some of my friends are saying it could possibly be coolant leaking past the headgasket into my combo chamber .. others are saying possibly excess fuel considering it usually smells like fuel when i dump it out (heavily)

this also started to happen on my other engine when i first installed my catch can and shortly after the engine blew .. (oil pump went)
 

BriinumsBo

New member
BriinumsBo":3jkw5axh said:
smog7":3jkw5axh said:
hmm, I am surprised that nobody has mentioned that the 3rd gen 3sgte came stock from the factory with an oil catch can... I doubt toyota engineers are idiots..on a side note, i'm eventually going to go with a diy catch can like this:
http://www.celicatech.com/forums/showth ... 634&page=1

any links of the 3g catch can? are drivers told to clean them?

gen3 catch can (type of).
no idea why there is additional catch can.


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