oil catch cans & the pcv valve

dark_knight

dark_knight

Member +
now now, before you take my head off for starting ANOTHER thread on oil catch cans, hear me out first, at least :)

on most (high performance) setups, i see that modders plumb both breathers off the rocker cover to a catch can. on others, i see only the main breather (one without the pcv valve) plumbed to the catch can and the pcv valve hose left in stock position - leading back to the intake mani.

ok, here's why i bring this up; the reason for having a catch can in the first place is to ensure the intake track stays clean and oil/sludge free. if the pcv valve hose is left in place then some oil will still make it to the intake mani when the engine is ticking over since that's when the most blow-by makes it through. now i know for emissions reasons etc, this is the reason toyota did it that way but from a modders perspective, isn't it pointless to have a catch can and only tap from one of the breathers..? i guess those who do perhaps do so because:
a) the catch cans they have only have one inlet..?
b) budget maybe..?
c) they see no need to..?

just thinking out loud..
 
ianmcintoshi

ianmcintoshi

Member +
LOL ive just had a huge discussion over on uksc about this. Your right mate, the correct way to fit a catch can is inbetween the pcv valve and the intake... simple :)
 
starletgtturbo1

starletgtturbo1

Member +
i dont think there is a thread to explain how to do it right thats why so mayny people do it wrong. to much arguing about whos wrong and whos right.
 
dark_knight

dark_knight

Member +
here's how i'd base my plumbing:
a) follow the correct air path/track, while
b) observing crankcase pressurization concerns, and
c) ensuring that it's legal so that the car can pass its MOT (for you UK folks) :)
 
dark_knight

dark_knight

Member +
custom oil catch can: concept

@Skalabala: true, and since i started this thread, i should share how mine is set up; using an old fuel filter that i fabricated & modded. in mine, both breathers from the rocker cover converge at a y-junction and vent into the catch can. the exit port on the catch can then vents to the atmosphere somewhere beside my transmission housing on the left side. i've retained the pcv valve in the stock position.
 
H_D

H_D

Member +
I use my oil catch can as a breather tank to keep my rocker cover clean...i used to have a breather on its own but would find little bits of oil residue building up on the rocker cover
 
G

GP82

Member +
Skalabala said:
i wonder if sump pressure comes into play somewhere for some reason
Click to expand...

Sump pressure? If you mean a vaccum in the crankcase, you need this vaccum to help the oil going through the turbo oil return pipe to drain back down to the sump.
 
G

GP82

Member +
spacecraft said:
in mine, both breathers from the rocker cover converge at a y-junction and vent into the catch can. the exit port on the catch can then vents to the atmosphere somewhere beside my transmission housing on the left side. i've retained the pcv valve in the stock position.
Click to expand...

To operate the pcv valve you need a vaccum to it, like the factory setup. How you have described your setup means there is no reason to retain the pcv valve as it is a one way valve. It evacuates the crankcase pressures on vaccum so off boost and below 0 InHg and closes above 0 InHg on positive pressure.
 
scot-ish

scot-ish

Member +
and the reason a catch can is fitted, is a power mod..... because the oil in the intake causes a reduction in the octane number of the fuel for combustion = less power produced from the same specific capacity of fuel. :teach:
 
P

Paul_JJ

Member +
scot-ish said:
and the reason a catch can is fitted, is a power mod..... because the oil in the intake causes a reduction in the octane number of the fuel for combustion = less power produced from the same specific capacity of fuel. :teach:
Click to expand...

Yeah but it will be closed when under boost......
 
P

Paul_JJ

Member +
spacecraft said:
ok, here's why i bring this up; the reason for having a catch can in the first place is to ensure the intake track stays clean and oil/sludge free. if the pcv valve hose is left in place then some oil will still make it to the intake mani when the engine is ticking over since that's when the most blow-by makes it through. now i know for emissions reasons etc, this is the reason toyota did it that way .
Click to expand...

80% of that stuff coming out of it is unburned petrol, so let the fucker burn again. You keep forgetting that when there is a vacuum it sucks out oil that stuff....
 
dark_knight

dark_knight

Member +
stock pcv valve

@GP82: you are right, but the only reason i have left the pcv valve in place is because i don't have the parts nor the tools to fit one of those screw-type hose connectors to the port the pcv valve goes on my rocker cover and still running the stock tmic so space under there is a little cramped. saving up money and some time to do a full fmic transplant and rocker job a little later.. :D
 
dark_knight

dark_knight

Member +
breathe in.. breathe out

while tinkering about my engine bay this weekend, i decided to gut my pcv valve (it actually broke off in my hand as it was quite brittle - i even had to pick out a couple of plastic bits that fell back into the rocker cover) and plugged the breather hole. now only using the secondary breather which vents to the atmosphere via a catch can. will give it a few more miles and check out the can for deposits. i do a lot of cold morning starts and a short trip to work. i believe there is no harm whatsoever in doing this as breathing can't be thaaaaaaaaaat heavy to warrant the secondary breather not being sufficient.

i guess this is one of those stings that can never really be closed.. :D
 
You must log in or register to reply here.
Top