Catch Cans? whats the deal

[armbrusb]

I spoke to AVO and they said to run hoses from both rocker covers to the catch can. They said that I should block off the vavle on the plenum and plumb the can back to my intake(before the turbo). So they've said the same as you. I'm pretty happy. Thanks.

Out of interest what is the purpose of connecting the rocker cover to the intake plenum via the valve?

[Steve]

You shouldnt need to block off the line from the plenum to the rocker cover. This is for pcv whilst not on boost - as there is a vacuum drawing the air from the rocker cover. when on boost of course, the plenum is pressurised and then the catch can takes out the oil prior to return to through turbo.

Having said that, cant see that it would hurt redirecting your PCV through a catch can.

[Steve]

I just looked at the add - it states that their can prevents oil being returned to the inlet - if you got oil, you got a warranty claim:)

[grepin]

I guess it should still be worth while blocking the route through the PCV valve as on Vacuum you could be sucking in crap through your plenum. A small point. However if you dont have an after market ECU (retune required) you will loose your light load tuning and induce stalling etc.

I had an interesting conversation with BOOSTD who has posted info on this subject under the banner of some other conversation (I havent seen it) stating he has done this. The results were better idle and a huge increase in fuel economy. He also was picking up much more shit in his catch can. Quite possible condensation/sludge mix that would normally be sucked into your plenum on initial start up.

My 2 cents

[Steve]

grepin, how did BOOSTD block his hose off?

[grepin]

He explained that he put some screws in the PC valve so it wouldnt open. Personally I tried it by using two blanks that are obtainable from most auto shops. This is where I realized it wont idle so set it back to origonal. However next tune I will set it up again. I got mine from Roccas. Of course it doesnt look legal. I have also heard of jamming a ballbearing in the hose large enough not to go in the plenum of course. This will maintain the legal look.

Is your car in? Cant wait to check it out on return from Darwin. I have heard Evan is not the quickest so it might not be ready. However small price for quality.

[DennisRB30]

The hose connects to the PCV valve on the plenum so the vacuum it creates makes airflow through the engine. This is to suck away the harmfull gasses that can build up in the sump and cause acidic residue that contaminates the oil. The PVC valve is a one way valve so it can only flow from your rocker cover to the plemum, when there is pressure in the plenum the valve closes, so the crap can be redirected through the catch can. In this scenario the valve will do its job of cleansing out the harmfull gas but when you are booting it the gas will go through the catch can and not enter the engine. I would do it this way otherwise you are not preventing your oil from being contaminatd. In my opinion this will increase the life of the engine over the long term.

The gasses won't do any harm to the engine when they are being burned under light throttle. The only time the gasses cause lost power and produce pinging is under load. Since the PCV will close then its not an issue.

[grepin]

Where do the harmful gases come from when not on boost? Something I forgot to mention before for the guys with idle problems you may be sucking air through your catch can via PCV when on Vacuum. However these are all only theories and am now interested in persuing this harmful gas problem. So is the whole reason of the PCV to remove harmful gases or does it have other roles. Oh by the way catch cans are the go. Not to be a thread hijacker.

[JimX]

Originally posted by lowlux

VPW mailorder,  there in epping but deliver to your door and yes they come with brackets but there kinda crappy so im making better ones also i had to go buy some hose and some fittings but that cost me like $20,  and the catch can was $90 soooo its all good alot cheap than the cusco ones

Lowlux, it took me awhile to find because searching on "catch can" or "separator" didn't turn anything useful up. But it seems to be the "Aluminium breather tank", with part number VPW-36108. Is this what you have? The price is also $140, not $90 At that price (plus freight) I think I might tend towards a Cusco or custom job.

[DennisRB30]

The harmfull gasses come down past the rings as combustion bypoducts and fuel etc, these mix and react with the oil and contaminate it.

It is not for pollution control (even though listed as part of emmission equipement) Having this gas vent to the air is harmfull to the environment so it is burned in the engine. There is NO NEED for a PCV system for the redirction of this gas back into the engine. By simply connecting the rocker cover hoses back to the intake before the turbo the gas emmisions will get sucked back into the engine and the EPA will be happy.

PCV stands for positve crankcase ventilation, ie forced ventilation of crankcase.

I am in the process of drawing up catch can system that won't cause idle probs with a PCV valve and will filter the gas at all times. I will post it when done.

[DennisRB30]

This took me ages to draw up, take a look and tell me what you think. It uses one way valves to stop idle probs and to ensure that only clean air is sucked into the engine. I think it has many benefits over any other system I have seen.

[Belly_up]

Ok here's a question, not related to any particular setup mentioned here, but just in general. Why, instead of venting the blow-by to the atmosphere, or plumbing in between the afm and the turbo, don't we plumb the gas back into the airbox (for those of us who still have an airbox)? that way the air gets filtered by a nice big filter, and the air still goes through the engine, so no EPA problems?

Is it because the low-oxygen blow by will affect the afm? or is there another reason?

I know this was how my old carbied magna was plumbed from the factory.

any ideas?

Belly_Up

[DennisRB30]

The fact is you can't filter out the used air as it has already been combusted. The filter simply can't absorb it.

To get picky, the gasses have already been measured by the airflow metre so by plumbing back before the AFM it will be measured twice making it run richer. It would also clog up the filter quickly and coat the AFM hot wire in oil, not good.

You will find that the Magna had the hose connected inside the round filter holder. The gasses don't go through the filter they just go straight down the carbie.

[browny]

What about this:

[Steve]

Greg the car goes in on wednesday fingers crossed.

DennisRB30, on casual look, it appears that the plenum could draw air from the breather?

Belly_up, the only problem would be the number of filter elements you would go through - and that the AFM might get dirty.

In days of old, cars just had the pcv going into the rocker cover and was vented to atmosphere through the oil filler cap, with ony a vague attempt at filtration. The pcv just stops the crank case from being pressurised by blow by. Without it it would cause all sorts of problems from blowing out dipsticks to possibly blowing seals.

I dont believe it would be essential to have the gasses go through the plenum - it appears more an attempt at emmissions control to me?

Would love to know more about this, because if by blocking off the pcv to the plenum and forcing the gasses though the catch can, it would still comply with emissions criteria. If that means improved economy all the better.

I really cant see a downside to this approach. Anyone?

[Belly_up]

Nah the magna definately ran the blow by through the filter, but it had bit of a deflector and little bit of foam to semi-filter it, kinda like a mini catch can.

we don't want to filter out the used air, we just want to take any oil etc out of it.

But i think you might be right about it making it run rich, i guess it would just depend on how significant the amount of blow-by actually was.

[Steve]

Magna is NA - if you plumb the rocker cover to the air filter, you would be getting forced blow by - the same stuff that gets caught in the catch can:)

When I am talking about old cars, I mean the pre emission, eg pre 74 ish?

[turbomad]

Dennis your idea while good is not legal because of the filter going to atmo, Browny you've got the right idea except all those hoses running under the bonnet will look terrible.

This idle problem associated with blocking the PCV valve, could it be fixed by adjusting the idle control unit, perhaps we need to let in more air to compensate for the lost air not coming from the PCV valve anymore?

[Steve]

Hmm, and there is a air bleed screw on the AAC vavle too.

[DennisRB30]

Read all the text I have written, it explains the opperation.

The plenum is supposed to draw air from the breather so the crank case is cleared of harfull fumes by positive crankcase ventilation. But it only does it under light throttle, when you boot it, the PCV closes and the air goes out the filter (or back to the intake depending on how you hook it up, again read all the text)

If you read the text it explains the benefits of having the blowby go out of the filter and it tells you how to hook it up without the filter if your worried about it being legal (but your engine will suck in blowby, but at least it will be cleaned by the catch can)

Not having a PCV won't make gaskets blow etc if there are hoses comeing out of the rocker cover, the pressure just comes out of the hoses. I explained what the PCV system does, its to clear the harfull gasses by displaceing them with clean air.

The whole idea of my system is that the PCV system still opperates on light throttle, but under heavy throttle no fumes go into the engine.

I urge you to read the text I have written with the pic.

Browny, your system does not use positive crankcase ventilation. The gasses have to make there way into the catch can under there own pressure at all times. The PCV valve does nothing but suck in the fumes that have come out under there own pressure. The outcome would be the same if it was not ther at all as it does not replace the fumes with clean air.