I'm a little confused. When adding a blower (centrifical style), I've searched the archives and found that you is to get rid of the PCV system. But on various factory turbo cars, they have a PCV valve.

There is an anti backfire device in the PCV valve to keep boost out of the engine.

Is it better to just run engine breathers?

 

With the ATI kit, you still use your PCV, you just vent it to the atmosphere, insted of back into the plenum

later
larry

 

no, thats not the answer. first off i have been wondering about this problem with my car. unless i am reading this wrong, venting the pcv to the atmosphere is no pcv at all. the breather(think of it as "air in") when disconnected from the valve cover will not hinder the flow of air into the crankcase to refill it as the pcv valve (think of it as "air out")does its job, a job posible because of vacuum- also creating a slight negative pressure within the crankcase keeps oil from wanting to migrate out everywhere it can. now take that vacuum and make it a positive pressure-boost-well its going to enter the crankcase via the pcv line and thru the breather line 5 psi on the gauge is 5 psi in the crankcase-NFG-what i have been fiddlefu-kin around with is a check valve on the pcv line (just a power brake booster inlet valve) which seems ok sofar although the seal is not as leakproof as i would like-boost is still getting by-but the breather is another story to solve i was thinking a p.brake ck.valve installed the other way maybe. i am unwilling to give up the bennies of a functional pcv system-and will also take any ideas anyone has to make a functional setup-O.E. turbo\s.c. motors all have some type of setup which works. i want to have one working on mine also.im confused too on this

 

I by no means am a engineer, just a broke a$$ diesel mechanic, but, my understanding is that the PCV (positive crankcase ventilation) is just there to allow the pressure that is built up in the crankcase, by the motion of the pistons and blow-by, a place to go. and it does(like you said) aid in keeping the oil in where its supposed to be.

I check my PCV hose all the times for signs of oil, and so far have found nothing, i still have the stock PCV valve in the valve cover.

So I guess I'm confused about what your asking?

later
larry

 

There should be no problems keeping a PCV on your cars-just make sure it is in good operating condition and does not blow through under boost.

One suggestion though-most stock PCV valves dont do a good job of keeping boost out,especially when they get a little dirty.I replaced mine with one that ATR sells which positivly stops pressure from entering the engine.I've run 22-28psi through this valve with no problems.

Steve

 

hello-hey tta850 is there a website or phone # for that valve so i can get me one too? was wondering how the breather was addressed on your motor? did you plug the fitting on the t-body? and just draw air in from atmosphere thru a k and n type breather on the valve cover opposite the pcv? im running an ac delco factory replacemnt pcv and i cant get a reliable seal-even when blowing backwards thru it-so it sounds as if the valve you describe is the ticket-thanks, frank maniacc-is your routing per ati instructions? with the manifold vac. fitting plugged off? if so then you dont really have a functional positive crankcase ventilation system. the vacuum from the engine is the key for it to function. without that it really is just an old fashioned breather system with a pcv valve actually hindering its ability to move air in and out of the c.case. also i think that the pcv setup(when routed per ati instructions) is what keeps the ati kit(s) from being a 50 state legal system.

 

Yep, my are routed the way the manual says. I guess my question now is why would i need to change PCV set-up to one of those aftermarket valves, is it just for emissions? or is there some other benefit that i'm not seeing?

this is the reason that i'm here is to help my knowledge grow!!!

later
larry

 

right on-me too i am of the opinion (thats me, only)dont everybody get hostile-that a motor that will see duty like probably 90% of us here use them-benefits greatly fromthe use of a functional pcv system-mainly for me its the fact that oil leaks and i cant get along and a little neg.pressure inside the motor is just whats needed to ensure leaks dont happen-not sayin that it will fix leaks but it will prevent oil from being forced out everywhere-i have seen plenty of motors w/o pcv and most suffer some form of drippage el nasty-o. pcv works great w/ a vacuum in the manifold drawing air out of the c-case-metered by the valve. now introduce boost into the plenum and it will pressurize- thru the breather and the pvc vacuum line-the crankcase.hence the deletion of the system w/ati. so we are loking for a way to have it work and draw out during no boost conditions and also isolate the crankcase from pressure during periods of boost. so ive been playing w/ck valves so i can keep oil inside and shiny outside.trial and ummm....SEEYA for now

 

grumpygreaseape and anyone else interested the valve is from Applied Technologies and Reserch(ATR) and they call it their positive action check valve.As far as I know it is something created by one of their customers back in 1993 and they started making and selling it.

Their part number is CV101 for the valve and you can contact them at 864-972-3800(phone) or 864-972-4900(fax).The price is $19.95 which sounds high but it uses a spring loaded valve with a high temp Viton seal and in the 4 years I've never had to replace it-I just move it from car to car over time and it still seals great.

Steve

 

that all sounds great w/the PCV but under boost it is not doing its job and being performance enthusiest ,under full throttle is when that vacuum is very important to your rotating assembly
and not being supplied which is why some people run an alternate vacuum source (converted smog pump or other pump,
header collector scavengers,ect)
not only does that vacuum under full throttle keep oil off the
spinning mass but things also operate w/less friction under a vacuum.

 

normally aspirated motors-dialed properly wont see but maybe an inch of vacuum at full throttle so i dunno the typical rpms tpi motors see the benefits of c.case scavenging you describe would be marginal at best. most time isnt spent at wot but somewhere below that and just after the start of boost-(the second the manifold transitions from a vacuum to boost)are the operating range im talking here. just need a way to keep from blowing out the seals over time and also retain the benefits of pcv. ati's way is a cop out as far as i can tell-look at all the vortech kits-check out syty.org-them things run 2 pcv valves one for normal and one for boost. later

 

Boost guages go on the manifold.
PCV lines should be hooked to a place where there is never a loss of vaccume, even under boost. On Carbeurated engines, you hook them to the carbeurator. Under boost conditions, the carb still maintains alot of vaccume.

On Fuel injection, usually, whereever your brake vaccume line is connected, should be consistant vaccume. Unless its on the manifold of course... Doh... Find a place above the manifold to hook your PCV.... If it exists. Usually TBI has lines coming from the throttle body itself for things like that, but im no expert on TPI... Look at anything BEFORE the manifold that might be a vaccume line or a "possible" vaccume line (check if its just capped off)

heh you can always ditch the Fuel injection and get a roots style blower and hook up your PCV to the back of the carb like Im doin.

 

OK, maybe I can shed some needed light here, (I hope).

First a little on the valve.
The ATR valve is probably a good idea. If you do use a stock replacement valve, replace it often, as the seat and disc must be clean to seal. Don't be too concerned if a fresh stock type valve leaks a little if you blow back through it with your mouth. Unless your a Hollywood hooker, you cant blow as hard as a supercharger or build as much boost pressure. The manifold boost pressure will help close the valve firmly, and if clean it will seal, if it has carbon build up it may not. There are lots of stock turbo systems running any where from 7 PSI to 15 PSI or more using regular PCV valves. The ATR unit would seal better I'm sure, especially at higher boost levels and probably last much longer between needed changes. I don't know, but it may be made so it can be cleaned and the rubber seal can be replaced.

Now for the PCV system function:
Our stock naturaly aspirated systems have the valve installed between the drivers side valve cover and the manifold.
The other valve cover has the breather hose attached. This hose goes to the throttle body on TPI cars, and to the air cleaner housing on carbed engines. Either way, the breather hose is connected in the intake tract in front of the throttle blades, but behind the place where air is drawn into the intake duct from the atmosphere.

when at idle, or part throttle (high manifold vacuum conditions) The PCV valve is open and is "sucking" on the drivers side valve cover, drawing air through the crank case, through the other passenger side valve cover, through the breather tube, picking up air from the T body (TPI) or air cleaner housing (carb). The crank case air pulled through the valve into the manifold is then burned in the engine. If There is an intake backfire the PCV valve closes due to the manifold pressure. The breather side is not pressurized because the breather tube is on the atmosphere side of the throttle blades and the energy has an easier way out through the intake tract to the atmosphere.
Now, at wide open throttle, the system still funtions, although in a different way. At wide open throttle there is little manifold vacuum, so not much air is drawn through the PCV valve. There is a lot of air moving through the intake tract though, and there is some vacuum there in relation to the crank case. This draws crank case air back through the breather tube opposite to it's part throttle flow. This crank case air is drawn past the T body and into the engine to be burned. So at either part throttle or full throttle the crank case emissions are still burned. They are just introduced into the intake manifold in two different ways depending on throttle position, manifold vacuum, and intake air velocity. This is refered to as a "closed system"

If you remove the breather hose from the passenger side valve cover and T body (or air cleaner housing) and replace it with a filtered breather on the valve cover but leave the PCV valve and hoses on the drivers side, then you have a "partly closed system". At idle and part throttle, air is drawn in directly from the atmosphere, through the breather. It is still pulled through the crank case and PCV valve into the intake manifold, by manifold vacuum. However at wide open throttle, There is not enough vacuum to pull air through the PCV valve. The crank case emissions are just released under crank case pressure through the breather into the atmosphere. Not smog legal. If you also remove the PCV valve and hoses and replace them with a filtered breather, you have a completely open system that always vents under preassure to the atmosphere. Way not smaog legal!

Now for forced induction:
The PCV valve side stays the same and functions the same way as it does on a naturally aspirated engine.
The one end of the breather tube stays in the passenger valve cover. The other end must be removed from the T body though, and the port in the T body must be plugged up. The end of the breather hose removed from the T body must be installed upstream of the blower, or turbo.
It is often tapped into a port on the intake bell of the turbo, but anywhere in the intake duct between the inlet of the turbo or blower, but before the opening to the atmosphere. Mounted in this location the system will funtion exactly as a naturally aspirated system does.
If the breather hose where left connected to the T body, the crank case would be pressurized by the turbo or blower. You could install a check valve in the breather hose, but then it would not draw crank case vapors out and into the intake tract when at wide open throttle (bad), and the crank case would be pressurized by blow by (very very bad), so a check valve in the breather tube is a no-no. It is a good idea to replace the small diameter breather hose with a larger diameter hose (at least 1/2" ID. 5/8" or 3/4" would be even better. Also the closer it is installed in the intake duct to the inlet of the turbo or blower the more efficiently it will function.
You can also just run a partially open system, (like Maniacc) or a fully open system, or you can use a vacuum pump or exhaust venturis to scavange the crank case but those are not smog legal if that is an issue.

While I'm at it I may as well clear this up:
originally posted by Kingtal0n:
Nope, doesn't work that way. The PVC valve only needs to be hooked to manifold vacuum. The breather hose is never hooked to manifold vaccum but should connect the crank case to the intake duct after the air inlet from atmosphere, but in front of The throttle blades (naturally aspirated TPI & carb or blown with draw through carb). For blown TPI, or blow though carb, The breather hose must be attached to the intake tract before the super/turbocharger because they are pressurized yes, even the carb is pressurized.

 

IROCKZ4me,very nice post.Hit the nail on the head and described exactly the way the PCV system in an a TTA(or GN)where the PCV hose goes to the throttle body and the breather hose goes to the inlet bell of the turbo.

The only thing is,on a forced induction application I would use a partially closed system rather than a closed system to help keep oil from entering the intake track under boost.Probrobly the first thing people do to the turbo buick motors is pull the little tube off the turbo and plug it while putting a little breather on the valve cover.

Steve

 

originally posted by TTA850:
Yep I think your right, that's done by many. Probably the most common back yard mod besides an aquarium valve on the actuator hose. LOL It works perfect for most, but it doesn't always work best for everyone. I have a buddy that did the partly open system to his, but he autocrosses his car, as well as drag racing and normal street driving. It was fine for street and strip, but at the first autocross after installing the breather, he found that it wasn't much good for that. since his breather port was on the front side end of his valve cover, and the stock internal breather baffle isn't very good at all, the hard cornering and braking washed oil up there and it came out of the breather and got all over his turbo and downpipe. We all thought he blew something when we saw the giant smoke cloud.
When he stopped and we investigated and found it was just oil coming out of the breather it was pitched. We made up a system similar to stock, but with larger diameter hose, and a small oil sepperator/trap in line. I had made up a similar setup for my IROC-Z (my valve covers have no internal breather baffles). The Buicks (with stock valve covers) need the oil trap more though than a SBC due to the postion of the breather port on the valve cover. I like a set up with a good oil trap at the valve cover or inline and the breather hose mounted in or near the inlet bell because the high velocity air flow there helps scavange the crank case through the breather port at wide open throttle. I wouldn't run it at the bell without a good oil trap though, (I'm not good friends with detonation). If I weren't using a trap (but I would be) I would probably install the breather hose into the intake duct in a place with less intake velocity, and where oil could not drain to the turbo/supercharger inlet (like at the air cleaner housing on a Buick turbo car) You would lose a lot of the scavenging effect that way though.
A partly open system is definitely the easiest and cheapest to set up though and is more than sufficient for most.

 

Cool,I've never had a problem but then again I never autocross. Could you describe a good oil trap?I'd like to know what has worked for you,I'd like to put the breather tubes back on my stock cars but not unless I know I'm not gonna get oil up in the intercooler

Steve

 

right on irocz4me but i think kinktalon is correct though in regards to the presence of vacuum (albeit very little at wot) beneath the butterflies in a carbureted draw thru(roots) application because the boost is happening somewhere about the mid section of the blower as the air fuel travels down to the cylinders. am i correct? seeya

 

The roots type set up is what I refered to as a "draw though" carb system grumpygreaseape. The PVC valve still only needs tied into a manifold vacuum source for these as well, and the breather tube for a closed system just needs to be somewhere on the atmosphere side of the throttle blades. You could run the PVC to the carb adapter plate on the blower or the base of the carb (as long as it isn't ported vacuum) and the system would still function correctly, but you don't have to. You could also just use a partly closed system with a filtered breather. On a "blow through" system, where a centrifugal supercharger or turbo is pressurizing the carb the PCV still just needs tapped into manifold vacuum but the breather hose must be inline before the turbo/supercharger. That is the main thing.

 

You can buy them prefabbed from racing parts suppliers, made of plastic or aluminum with 2 hose fittings (in and out) or with just one hose fitting and a filtered breather on top. The ones with a filtered breather on top can also be modified to work as a dual hose unit just by replacing the breather with a hose going to the intake duct.
You can also make them out of a prefabbed aluminum or plastic puke tank. I made one from a plastic "Jaz" puke tank once. It had one grommet and hose fitting in top of the tank (for the hose from the radiaor), and one petcock in the bottom of the tank (to drain it). I just drilled a hole in the side of the tank about 1 1/2" from the bottom and installed a grommet and fitting there for the hose from the valve cover, and ran a hose from the top fitting to the intake bell.
If you want to fab up your own from scratch it's pretty easy.
Basicaly all you need is a small canister of some kind that is pretty much air tight. It should have a larger cross section than the breather hoses you are using. This is to reduce the velocity of the air as it passes through the trap so the oil won't get carried on with the air.
Install a petcock in the bottom to use as a drain.
install a hose fitting in the top. You can use a hose coupling nipple and a grommet, a bulk head fitting, or weld a threaded bung in if you use metal for the canister. This hose will go to the bell.
Install a fitting near the bottom, but leave some room for collected oil. An inch or two should be enough. Run the hose from the valve cover to this fitting.
This is usually more than sufficient to trap the oil, but if you want more you can install baffles in the trap. Just don't cut down the cross sectional area inside the trap, you want reduced velociy there so any oil will fall out of the air. Put the baffle near the top of the canister. You could use one of the MR G baffled breather grommets for the top fitting. If you do use one you will need to clean up the slits in the bottom of it with a razor blade , or utillity knife. The slits in the baffles are mostly filled in with casting/molding flash and aren't worth crap right out of the package. If you make the can out of metal you can weld some baffles near the top, just leave the main area of the can open. You usually don't really need baffels though if you are not autocrossing, launching really hard or something that would cause the oil to climb the side of the can. It should be checked and drained as often as needed to keep it empty or nearly so. There is rairly more than a few drops at most in it though, unless you never drained it, lol. Hard braking is what seems put the most oil in the breather tube in a Buick turbo motor with stock valve covers, or at least with the stock breather location on the valve cover. My buddy used to have to drain his between each round at the autocrosses, before he got aluminum heads and the valve covers for them.

 

Hey IROCZ,

While your answering everyones questions, can you help me with mine..

Why is my vac/booste gauge going from 20lbs vacume at 2,000RPMS, to about 0lbs booste at around 5k??

The gauge is connected to the back of the plenum (where the fp regulator was, and the FP regulator is "T" connected to the accesory fitting).

-- Joe

 

originally posed by Anesthes:
Joe, If I understand what you are asking, it is "why is your gauge not measureing boost levels above atmosphic presure?"
Your gauge is showing 20 (probably inches of mercury or HG, not pounds) of vacuum, but drops to 0" and shows no boost at all? In other words it's only showing vacuum and no boost, relative to atmospheric pressure, right?

 

I connected the PCV valve to a home made header collector scavenger.

( click to enlarge )


I ran a hose from between the air-filter and supercharger inlet to the 'air inlet' on the passenger side valve cover.

I have not measured the crankcase vaccum but it seems to work.

 

that looks like an EGR valve to me... but i may be wrong.

 

anesthes,

I take it you are just sitting there revving up the engine and not seeing any boost, am i right?

You will not see any boost, unless you load the engine in some way, like on a dyno, or sometimes a poor mans dyno (hold the brake as hard as you can, and mash the gas pedal) you should start to see alittle boost this way. But is not recommended by me in any way, shape, or form!

Get out on the road, goto WOT and hold it till you see boost.
My D1sc starts producing boost approx 3000 rpm's

later
larry

 

It is a check-valve. I took it from one of the stock exhaust manifolds.

 

Hi,

Thats what someone else told me -- perhaps even you in the past, well I revved it to like 5500 in 2nd gear, with traction and it stayed around 0..

Weird.

-- Joe

 

Have you tried a different gauge, to test? Your gauge may be damaged and only showing vacuum.

 

Guess I can test it with the blow gun set to like 10psi.. Oh well.

Thanks!

-- Joe

 

Guess I can test it with the blow gun set to like 10psi.. Oh well.

Thanks!

-- Joe