mtcookson

iTrader: (2)

As we all should know, when you run boost its smart to remove all of the hoses that normally vent the crank case. Running them open atmosphere at the least keeps you from making positive boost in the crank case. Better yet would be to hook up an external vacuum pump to those hoses to remove gases from the crank case which can usually increase some power.

Now, my thought is the effects of not removing them.

If you remove some of the hoses and leave at least one on, this usually causes a vacuum leak as the engine sucks air through the crank case still but sucks air through the open vents allowing an effective vacuum leak.

Now if you leave them all on this, as I said, causes you to pressurize the crank case which can cause a loss of power. I was talking to a guy with a boosted Maxima tonight about it and he asked me if the boost leak he is noticing could be due to having them all hooked up and having a leaky valve cover gasket.

I had never thought of this before but it makes complete sense since there can be a vacuum leak by having some hoses vented and some not.

Basically what I'm geting at is, if some of you guys had ever experience boost loss, had those hoses hooked up still, and have some oil leaking from the valve cover that could be the reason to your boost loss...

Thoughts on this??

DA-MAX

iTrader: (10)

I'm 50/50 on undertanding what you are saying, but you mean if you leave the breather hoses connected....thus pushing pressurized air into the crankcase from ie-one of the IC pipes?? wouldn't that put more stress on the crankcase baffles as well as the valve cover gasket being that the air is being forced in rather than drawn in via vaccuum?? because aren't the baffles sort of like one-way valves(when used in an OEM setup)?

slimer

iTrader: (13)

i just have one of those stupid spectre filters on mine. is that a boost leak? i dont have anything pressurizing my crankcase.

DA-MAX

iTrader: (10)

it shouldn't be a leak, because I was always under the assumption that the valve cover baffles acted as one way valves allowing air to be drawn in under vaccum, but not out...maybe I'm wrong, someone correct me if so

slimer

iTrader: (13)

thats what i thought tool. i mean too.

mtcookson

iTrader: (2)

i've always heard that you want to unhook them so that you don't pressurize the crankcase from boost getting in there

subs1000w

i would read this thread it should answer all your questions even though its about mustangs but there still turboed

http://www.turbomustangs.com/forums/...&highlight=pcv

95turbo gxe

iTrader: (25)

Yeah Im thinking on just putting all the vent line together. Then run one line between the Maf and TUrbo. No vacume leak and it still vent and even better under Boost. If anyone uderstands me let me know what you think of doing it that way.

P.S my Maf is on the non charged side.

DA-MAX

iTrader: (10)

basically as long as the vent line doesn't see boost you are fine

Jeff92se

iTrader: (82)

You hook the breather lines to the non-charged pipes. Thing is you have these vapors running though the turbo compressor.

95turbo gxe

iTrader: (25)

Hey is was wonding about the IACV. How about running boost to it. Maybe I should move it to. Right before the turbo but infront the MAF. what do you think?

DanNY

iTrader: (14)

why not use an oil catch can?

95turbo gxe

iTrader: (25)

yeah did not think of that. BUt is that a big deal. With the pvc vaule would they go through im so confused

Boosted Maxima

Ok guys this should Clear up some confusion.....

PCV valve Can see boost leave alone it is a one way valve only open when vaccume is present. When boost is present it shuts and does not pressureize the crank case.
YOU MUST HAVE THIS PCV HOOKED UP!!!!

The two stock vents (one per valve cover) should just get a small breather put on each. K&N or specter whatever. They filter the air getting pulled by the PCV

The Tube that go's to the IAC Idle Air Controll valve can be hooked up to boost. I've tried it before the air cleaner and open to the engine bay...neither worked because the MAF has to meter the air that controlls IDLE.

Your Brake Booster can see boost. it has a one-way valve similar to your PCV that only lets Vaccume in. So that system stays unchanged.


So if your tubes going to your valve covers are hooked up anywhere on the boost side it's realy not helping push up the pistons
~Scott

mtcookson

iTrader: (2)

the only thing is, if you leave the pcv hose on and filter the other two vents you'll cause a vacuum leak.

95turbo gxe

iTrader: (25)

Yeah im still confused. Well could we install pvc vaules on the other tubes. May sound dumb but im trying.

Broaner

iTrader: (10)

The PCV has been known to fail/reverse under boost. I say put breather filters on the breathers(I guess 3rd gens have two). I also say run the PCV to a oil catch can. It will need to be emptied periodically but it means there is no boost leak. The brake booster has a possibility to reverse under boost but it doesn't really matter cause the only time your braking is off of hard boost. My current setup leaves me with two vacum attachments on the IM; Brake Booster and FPR.


What exactly is the purpose of PCV? How do gases get into the valve covers?

subs1000w

exactly

i just have my pcv open and have the port caped off

Boosted Maxima

If you leave the PCV line unhooked and just have vents on eather valve cover your asking for trouble!
All the blowby especialy on boosted cars getting past the rings.. all the condensation that evaporates when the engine warms up and all these toxic gasses and moisture can't get out!!!!
The PCV draws the toxic vapors and moisture out of the engine through the vents in the valve covers and burns it. It is a controlled vaccume leak and the ECU already knows it's there and the MAF accounts for it. I have not had a issue with the stock PCV at all. With it working Oil lasts longer (less contaminates) and there is less drag on the engine due to crank case pressure.
Why do you think the serious racers use a big vaccume pump run by a belt to take all the crankcase pressure out? Less drag on the engine.... Better ring seat by not having pressures below it and it takes out the harmfull gases.
With out the PCV your defiantly shorting the life of the engine.
If you want a catch can for the oil vapors.. great! Oil drawn into the combustion chambers can cause detonation.. so the less the better there.
~Scott

Brad92SE

iTrader: (9)

This thread is confusing.... The way I understand it, the only two options are leaving all the hoses connected or disconnecting them all. As Mark said, having a breather on the valve cover and leaving the PCV line hooked to the intake pipe (after the MAF) would cause a vacuum leak. Now with the PCV disconnected, I would think crankcase pressure would still be able to escape, since the PCV valve doesnt see any positive pressure, with the only drawback being that there is no vacuum, so the air in the crankcase could not be drawn out as efficiently. However, isnt that the way the old muscle cars in the early 60's did it? The pressure in the crankcase should be able to escape reasonably enough so as to not cause problems.

Jaz Catch Can

Now, with something like this, how exactly would we hook it up? I assume the line from the PCV (would we even need the PCV anymore?) would connect into one side, but where would the other side go? Would that be hooked up back into the intake before the turbo (thereby before the MAF)? Or could that side just be plugged?

Broaner

iTrader: (10)

That is what I'm wondering. Why do we even need a PCV? What is so different about the rear VC that it needs this stupid BS one way valve? The front only has a breather and everything is fine. What gases is the PCV pulling out?

mtcookson

iTrader: (2)

the best way to do it is to setup an external vacuum pump to it with the oil catch can as that is said to actually increase some power on cars by getting the pressure out of the crank case.

Brad92SE

iTrader: (9)

So in this case, would the catch can just be vented to the atmosphere, with a breather hooked up to the valve covers?

mtcookson

iTrader: (2)

if i understand it all correctly you'll want the valve cover breathers to be vented and have filters on them, then with the pcv hose run that to the oil catch can and from the oil catch can to the vacuum pump. the catch can would need to be without a filter so that the vacuum pump can suck the air through the crankcase to get rid of the pressure and gases and such.

DanNY

iTrader: (14)

good lord...that's A LOT of plumbing for a PCV and from what you're saying...either i don't understand it or it just doesn't make sense to me.

mtcookson

iTrader: (2)

yeah, it definitely would be a lot of plumbing but it seems as though most of the time you can get some power gains from it and on top of that it keeps oil from getting into your intake.

subs1000w

if you run a electric vacum pump i wouldnt think you would need a oil catch can

ive also heard that 03/04 cobras run an electric vacum pump so maybe that could be used

mtcookson

iTrader: (2)

yeah, i was thinking about that... most likely its all dependent on the pump you get. i'd be absolutely sure the one you buy can handle oil going through it.

Boosted Maxima

Your getting the idea...

Let me re-state in a different way what I said in the last post.

Reasons for PCV (or) Positive Crank-Case Ventlation

1) After combustion of every revolution of the engine there is "blow by" or gasses that go past the rings down into the crank case. These gasses have no where to go.. are very hot and have alot of contaminates. If they are not pulled out they get mixed with the oil making it contaminated.
2)When the engine cools condensation forms on the inside of the block/heads ect. Think about how much water comes out the tail pipe when your cars warming up! It's the same inside the engine and that moisture has to come out!!!
3)With pressure on the bottom side of piston rings they don't seal as well.
Racers extracting ever last HP will put a vaccume pump on the engine to get negitive pressure in the Crank case to get the rings to seat better. They'll drive a 5hp vaccume pump to gain 50hp with the rings seating in the cyl.

If your PCV system is working properly you should be able to take the vent's off and put your hand/s on them for maby 5=6seconds when you take your hands off there should be a breif suction of air rushing into the valve covers. This is telling you that it's pulling air through the inside of the engine correctly.

To answer the question on electric pumps.. that's fine.. One/two vents then hook up the pump to another valve cover port to the bottom side of a catch can then hook up the top side to the pump. The can won't allow oil vapors/water to ruin the pump as fast.GM makes AIR pumps for emmissions if Ford does that's a idea too.

Back in the Muscle car days they didn't know that blow by hurt the oil and performance as much as we do now. My 72 Chevelle had one! They had to know fairly early....
I'll stick with the simple PCV doen't cost me any power or drivabilty problems.
I think one of my old College books had a good diagram of a PCV system and maby some info... If I find it I'll Scan it and send it to Mark...
Have a good saturday~Scott

Broaner

iTrader: (10)

Very informative. Thanks for that. I have a question though. If a properly working PCV increases power and reduces contamination how does it work w/ no vacum. I don't know exactly at what point the vacum in the manifold reaches zero but I think its just after opening the throttle. So, if one of the ideas is to increase power its not going to work much if any at redline. The vacum the manifold sees is zero; no? Please help clear up this confusion.

Brad92SE

iTrader: (9)

At zero vacuum, any excess pressure in the crankcase would still be able to escape, they just wouldnt be able to be drawn out. It would be like open-air venting the pcv, essentially. If the pcv is still hooked up when you are boosting, wouldnt that cause problems as the valve would be closed, and the gas buildup would have nowhere to go?

mtcookson

iTrader: (2)

if the other valve cover ports are vented then you wouldn't have to worry as the pressure should escape through those.

Brad92SE

iTrader: (9)

Would it be more efficient to just disconnect the pcv hose all together in this case then? The gas wouldn't have to travel all the way back up to the valve covers. I know that the engine wouldn't pull any air from the pcv valve then, but since you are boosting more than 50% of the time anyways, that vacuum should have little effect on how much blowby is in the crankcase.

95turbo gxe

iTrader: (25)

ok I took the vaule cover hose off and plug the intake pipe and my car does not blow smoke out of the tail pipe no more. I thought the whole time I had my drain line done wrong or I have had three bad turbos. I have the pvc line still hooked up and everything seems to be fine and no vaucum leak idels fine thanks.

Boosted Maxima

It's true that at wide open throttle you would be getting very little benifit from the PCV system.
That's why the guys run a vaccume pump to their cars to get the benifit at WOT.
We don't spend that much time at WOT. Well ... maby we do
Boosting causes more blow by than Nat. Asperated due to more cyl pressure.

Brad... Your welcome to stop by when this DAMN SNOW STOPS!!!!
~Scott

Chris Gregg

iTrader: (59)

Just thinking about this thread. I understand that the PCV is to assist in venting exhaust gases. I don't see how a filter to fent the front valve cover causes vacuum leak. At idle, the front VC is pulling in fresh outside air via the intake, the issue then is that it is metered (as said before). Simple enough. Therefore, under vacuum (at idle)and with the front VC filtered, you are drawing into the intake through the PCV, unmetered air. Would run lean at idle, but don't know if really significant. With the filter, the heat and gases would still have an escape and be forced out by the movement within the crank case/cylinders.
Now, how to hook up a vacuum if you want to pull it out instead of filter? I have an idea. How about using the Charcoil canister up front? Run a line from the VC (valve cover) to the canister. Keep a line that is supposed to be for vacuum always at vacuum by connecting to non charged piping of the intake (preturbo) and after the MAF so that it is always metered? Please share your thoughts.

slimer

iTrader: (13)

wouldnt that create a lot of extra hose? a lot of people (broaner for one) are trying to keep their setups as simple as possible.

it would be like the recirc hose that people have to use when they use the z32 maf on the non charged side though.

Boosted Maxima

Ok.. dug up that information on the PCV system with pictures and all. I sent them to Mark maby he'll bail me out for the thousanth time and a half..
~Scott

Brad92SE

iTrader: (9)

Scott, in that material you sent me, it said that the PCV valve closes at idle under vacuum, and under 0 vacuum (WOT), the valve is open fully. If that is the case, wouldnt it be a bad idea to pressurize the PCV? That would pressurze the crank then, right?

Boosted Maxima

You know what.. the book is actualy WRONG!
When at idle and cruze where the vaccume is strongest is where it pulls the most and when at WOT it's the least! Typo... but it's correct in all the areas where it states what happens with out the system.
Come put your hands over the vents in my valve covers it'll give you a hellava suck job at idle. Can I say that in here
~Scott