http://twinturbo.net/net/viewmsg.aspx?forum=technical&msg_id=908813

 

Found this link posted by lymon a while back while searching but wondered if anyone had some further thoughts. From reading the thread it seems duffman had a few reservations (and clearly im not clever enough to know whos right..)

 

Just ask as my pcvs need changeing and was wondering about taking this route..

I have been thinking about this myself and was wondering about a catch can set up still using pcv valves with the catch cans after the pcv valves and the openings plugged on the plenum but im not sure on it myself hopefully andy will be along soon to inform us

Just hope that it might save having to keep swapping the bloody things! Mine really need doing as the smoking at idle is more obvious now the weathers getting cold

Just hope that it might save having to keep swapping the bloody things! Mine really need doing as the smoking at idle is more obvious now the weathers getting cold

Really not that bad a job mate!-just get all new hoses with the valves! ;)

my main worry is that i think that the pcv system works via the valves with manifold pressure as well to keep them closed and moving them to a catch can means they might open more..thats what im not sure on.

I would like to know more about this can you use any catch can? what are the advantages-disadvantages from this mod?

pow to the top still would like to know more about this one as my plenum is off

The way I see it,you don't need the pcv valves!-didn't even have em' years ago!!.

So if it was me,I would blank off the pcv mount holes and connect the rocker box breathers into a tank,job done!-anyone know different?(ducks!) :wack:

The way I see it,you don't need the pcv valves!-didn't even have em' years ago!!.

So if it was me,I would blank off the pcv mount holes and connect the rocker box breathers into a tank,job done!-anyone know different?(ducks!)

Eh up me duck!

thats pretty much what I am planning to do.

I take it that its also safe to get rid of the water pipes to the plenum too??

Your thoughts on that Daz???

And anyone else.

Stillen have a solution to the PCV problem, some details here :- http://home.swipnet.se/e-solutions/StillenPCV.html

PCV valves are required on turbo cars to prevent the inlet compressing the crank case under boost conditions. Under normal cruise conditions, the inlet is actually in vacuum. This vacuum is used to purge the crankcase of any blow by gases (combustion gasses that get past the rings). Without this the oil becomes contaminated and loses its lubication properties. The idea of a catch can is to seperate the oil vapours from the blow by gasses to prevent the oil being fed into the intake. Let me think about this some more and I'll get back lol.....

so two tanks one for each side connected to the rocker box breathers and plug the rest then?

Not as simple as that since the standard system works in both directions, depending on whether the manifold is in boost or vacuum ;)

 

Still trying to suss it out LOL I will be back

cool andy ill wait for you to work it out then :D

andy

I have been thinking on this and need some info if you have it

 

PCV valve works using vacuum, boost, spring pressure and crank pressure.

 

When at idle i take it the vacumm and crank pressure isnt high enough to crack the spring break and the valve stays shut.?

When on boost the boost manifold pressure along with the spring pressure is high enough to keep the pcv valve shut ( higher than crank pressure).?

When at higher than idle rpm and on vacuum the crank pressure and vacuum is enough to crack the spring and let crank gasses into the inlet.?

 

Is the problem that removing the pcv valve you lose the vacuum which sucks the crank gasses out?

Basically, yeah.

 

Under vac conditions, the PCVs are open, drawing from the back of the rocker covers, through the crankcase, feeding with clean air from the turbo inlet pipes.

 

Under boost conditions, the PCVs are closed, and any excess blowby gasses are blown into the turbo inlet hose.

 

The PCV hoses to the turbo inlets are the 2 way part, the PCV hoses to the plenum are through one way valves (PCV valves).

 

The condition of the system under boost conditions is not ideal as you are not feeding clean air through to purge the system, simply venting any excess pressure in the crankcase to the intake.

 

Does that make sense?

yeah i was trying to work out what happens when the valves fail , obviously the springs stick or fail and the valve sticks open all the time and allows gasses at idle through when it shouldnt.

 

The only way I can see to get a catch can to work is to keep the pcv valves with a catch can before the pcv valve solely for the purpose of cleaner air through the inlet....another solution to the pcv valve thing is to refit new ones remote from the plenum to make them easier to get at.

Or use the aiv pipes on the exhaust as a source of vacuum instead of the plenum...

What about this sort of set up andy..reckon it would provide enough vacuum?

 

 

Not really since both ends of the system are at the same pressure. See how difficult it is? :D

yeah you need a higher vac at the rear end

Of course you could put some kind of vac pump on it - shouldn't draw too much current....

Feckin' turbo cars! :wack: If you need to have the 'hoover' effect,I suppose you could use disc valves in-line,at least you can put these in an accessible place! :)

One thing that you also have to remember is that if you're taking air from the 'metered' side of the airflow meter it must be returned to the intake again

Eh up me duck!

thats pretty much what I am planning to do.

I take it that its also safe to get rid of the water pipes to the plenum too??

Your thoughts on that Daz???

And anyone else.

Plenum bypass is a simple job Pete,worth it too! :duffer:

you know what im thinking,

feck this recirc sys

lets run all the crank vents to one catch can and supply a load of vac to it

benefits : no dirty gas in the intake, full crank gas cleaning even on boost

 

just cant find enough vac to do it properly

 

was thinking of trying to T into the inlet pipes working out the flow with the diameter of pipe as the tubs should create enough vac but worried about passing the old gasses through into the tubs and loss in power and worried about the old gasses getting compressed causing det.....any ideas