I replaced my PCV valve last year and noticed there was oil seeping past the PCV grommet. On boosted engines you want the PCV valve acting as a check valve to stop boost leaking into the crankcase.
Under boost, the PCV should be closed (or a check valve installed inline) and any blowby gases/crankcase pressure generated will reverse flow and go OUT the inlet pipe connected upstream on the turbo/SC. There should be a slight vacuum there to draw them out.
If the PCV is not closing off flow, you've got boost passing into the crankcase that will blow oil past seals and gaskets. In my case I had pressure/oil coming past the valve cover grommets (obviously the wrong or bad PCV).
I'm pretty sure I had an AC Delco Grand National PCV valve before I replaced it with some other brand. It seems AC Delco has discontinued all PCV valves for older turbo applications. eg: Grand National, Turbo Sunbird and even Typhoon/Syclone.
Of the aftermarket junk for those applications I found - you could blow through the PCV both ways (more in the "working" direction). I think the manufacturers are just using a "close enough" PCV valve to fill the gap.
Perhaps the PCV valve from 2014 Cadillac XTS with 3.6L twin-turbo would work. But I have't been able to find one listed to see a picture of the thing (too new - not available yet?)
I went and got a 1995 Toyota Supra 3.0L twin-turbo PCV valve from a Toyota dealer PN 12204-46020 for $17. It's a strong steel/brass piece. Opens in the "working" direction, and a "dead stop" in the other.
You need a PCV valve grommet with a smaller hole. HELP! PN 42332 does the job. The valve fits the stock PCV valve elbow just fine. Blow-through into the crankcase is stopped.
A few other potions (not researched, but just a thought) may be from one of the turbo eco-tech engines, from the SS Coblat, SS HHR i believe, as well as the top end solstice and sky.
Option 2 may be looking at the turbo Small Block Chevy or the 90* v6 aftermarket community to see what PCV they use and see if it is adaptable.
make sure it's installed after the o2 sensors, and that you have a catch can to prevent pulling oil into the exhaust.
I notice these two points for the evacuation system you used: 1. Cannot be used on vehicles with mufflers 2. Summit crankcase evacuation systems are designed for drag race use only
These may just be emission based concerns....any thoughts?
AFAIK, PCV valves are one way valves for the suction direction only. If they flowed both ways why would they be called a valve? You are not running in boost mode most of the time so I wouldn't worry too much about continuous crankcase evacuation.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 07-19-2014).]
I notice these two points for the evacuation system you used: 1. Cannot be used on vehicles with mufflers 2. Summit crankcase evacuation systems are designed for drag race use only
These may just be emission based concerns....any thoughts?
1. The idea is that gas velocity will en-train the crankcase gasses and pull them from the the angled tubes, should still work fine with mufflers as long as they aren't super restrictive. similar to how a carburetor works.
2. Setup as a crankcase evacuation system, probably best left to the track, but as a PCV system, it'd probably be fine on the street.
You could always run the suction for the thing to the low side of the turbo, where there is never positive pressure. On my XR4Ti, there is an oil separator on top of the valve cover that keeps the big stuff from being sucked into the turbo. On my old 8v Saab there was a separator inside the airbox, so that big stuff accumulated there and the small stuff was filtered by the air filter. There are plenty of turbo cars out there to draw inspiration from - and virtually none of them have a "conventional" PCV valve like GM was half-assing with in the '80s. Personally, I think a catch can filled with steel wool connected to the low side of the turbo should work great. That's how I plumbed my Saab track car, and it's never given a problem.
[This message has been edited by thesameguy (edited 07-18-2014).]
In a misjudgement I made (penny wise pound foolish), I ordered an aftermarket PCV valve for a 1995 Toyota Supra 3.0 Turbo from Rockauto. The brand was Intermotor.
I saw this thread, thought I might get lucky with an aftermarket part, but no. Real POS, I could blow through it the wrong way just as much as the stock (or stock replacement) Fiero PCV valve.
Then, I decided to head to my local Toyota dealer. I tell the parts guy that I have a "1995 Toyota Supra 3.0 Turbo", he asks if I have the 2JZ engine, then I reply "I suppose so", and then he looked at me funny.
$19.62 CAD (taxes included) and a week later, I have the Toyota 12204-46020 PCV valve in my hands (plus a spare one, for an additional $19.62). I blew into the PCV valve to simulate boost, and it didn't leak.
The purpose of this message is to corroborate fierosound's findings.
I have yet to test the fitment of the PCV valve with the grommet and elbow.
[This message has been edited by pmbrunelle (edited 04-26-2018).]
On my turbo 2.2 ecotec , there is no PCV valve, just a hose fitting on the valve cover. There are internal baffles that prevent the oil from getting in to the hose that I have routed to the fresh air side of the intake. I think all the 4 cyl ecotecs are the same. I don't have a catch can and do not see oil in the hose. I think the tighter tolerances of newer engines prevents pressure buildup in the crankcase.
On my turbo 2.2 ecotec , there is no PCV valve, just a hose fitting on the valve cover. There are internal baffles that prevent the oil from getting in to the hose that I have routed to the fresh air side of the intake. I think all the 4 cyl ecotecs are the same. I don't have a catch can and do not see oil in the hose. I think the tighter tolerances of newer engines prevents pressure buildup in the crankcase.
Possibly true. But we're not talking about piston blow-by.
We want a PCV to be closed when the manifold is under pressure when being boosted by either a turbo or s/c. Otherwise you will lose some boost as that pressurized air will will blow through the PCV into and pressurize the engine's crankcase.
If you installed a turbo on your Ecotech you likely need to do something similar.
The PCV line goes to the non pressurized side of the intake. So no buildup of pressure in the crank case is possible. I have been turbo for 10 years now and have not had any problems. Some people just put a small air filter on the vent fitting but I like the fumes to be drawn in to the engine.
[This message has been edited by wftb (edited 04-27-2018).]
The PCV line goes to the non pressurized side of the intake. So no buildup of pressure in the crank case is possible. I have been turbo for 10 years now and have not had any problems. Some people just put a small air filter on the vent fitting but I like the fumes to be drawn in to the engine.
The only non-pressurized location would be upstream of the turbo.
On the stock V6 the valve cover toward the passenger cabin has a tube to the rubber tube connecting to the TB for fresh filtered air. The valve cover on the trunk side has the PCV that routes to the intake manifold so engine vacuum can pull the PCV open and draw the fumes into the engine.
Item 10 is fresh air to engine tube.
Of course, when my s/c is producing boost and the intake is pressurized, the PCV needs to act as a check valve which is why I needed a good one. My "fresh air" connection is after my air filter but ahead of my s/c.
[This message has been edited by fierosound (edited 05-01-2018).]
So you either re route your PCV lines so they both go in to your intake after the air filter but before your supercharger or find a PCV valve that will close well enough to prevent the pressure buildup. From my experience with PCV valves over the years most of them are cheap pieces.So maybe you will find a good one maybe not. The PCV valve will still function if it draws air from a source other than your intake manifold. The air in the intake before your supercharger is under vac anytime the engine is running. The other thing you could do is incorporate a brake booster check valve after your stock PCV valve. The booster check valve holds up very well against boost.
Originally posted by wftb:find a PCV valve that will close well enough to prevent the pressure buildup. From my experience with PCV valves over the years most of them are cheap pieces.So maybe you will find a good one maybe not.
Uhhhh, the subject of this thread is a PCV valve that closes under boost...
...a PCV valve that Toyota felt good enough about putting on a production turbo car.
quote
Originally posted by wftb: The PCV valve will still function if it draws air from a source other than your intake manifold. The air in the intake before your supercharger is under vac anytime the engine is running.
Anywhere that's upstream of the throttle body won't be under vacuum. So it won't positively ventilate the crankcase. But fumes should be able to passively wisp into the intake tract and still be consumed... just not positively.
fierosound's throttle is downstream of his supercharger, so the air coming into his supercharger will never be under vacuum. But a PCV hookup between the throttle and supercharger as in a typical roots blower type arrangement should work well, I think, and avoid boost.
On my car, since I will be using water/meth injection, oil contamination is a big risk. Good crankcase ventilation will be important for my Fiero.
The air in between the air filter and the throttle valve might not technically be under vacuum but the air is constantly being drawn in one direction towards the throttle body whenever the engine is running. So if you vent your PCV valve there it will be more than a passive vent. My point is that you can do this with your stock PCV valve and have adequate crankcase ventilation and not have to buy a different PCV valve.
------------------ 86 GT built 2.2 ecotec turbo rear SLA suspension QA1 coilovers on tube arms
At the top is a modified (just shortened, the ends are original) stock Fiero 2.8 PCV assembly, for reference.
Either elbow works in either position (intake manifold or PCV valve).
The elbows also fit well over a 3/8" OD cupro-nickel brake line. A plain deburred end results in a tight fit with either elbow. No clamp would be necessary.
I'm not sure which elbow is preferable. The Dorman 46024 is made of a stiffer rubber.
The Dorman 47029 is more supple; it stretches a lot more when attempting to pull it off a fitting. Could this result in tearing when I go to service/disassemble the elbow down the road?
I will read online reviews to see what people have to say regarding these parts' respective reliabilities.
The Dorman 46001 may also be a candidate to be evaluated.
EDIT: The Dorman 46024 has awful reviews on amazon. Splitting after weeks or months. 47029 and 46001 don't have much data. I guess no reviews is better than bad reviews?
I am planning on tossing all three of these elbows into the valley of my daily driver's Vulcan 3.0.
After 2 months, hopefully one of them will still be serviceable...
[This message has been edited by pmbrunelle (edited 05-05-2018).]
I placed these two elbows on the engine of my daily-driver Ford Ranger. Both elbows were slipped onto a piece of 3/8" OD tube. Dorman 46024 Dorman 47029
After 4 months of daily driving with the Ford, here is the result:
The elbow on the left was cracked. The elbow on the right (Dorman 47029) looked fine, so I chose to use it on my Fiero build.
I have two summers and about 12000 km on my Fiero since the rebuild, and the elbow has been holding up fine.
I recommend the Dorman 47029.
[This message has been edited by pmbrunelle (edited 07-19-2021).]
I ran a turbo for a few years and had the stock Fiero PCV valve. It is designed to work on vacuum and its seems to block pressure and pass vacuum. What ever it did, the boost came up fine and there were no problems. The breather seemed to eliminate any positive crankcase pressure that will occur in boost mode only. An engine with a turbo or supercharger only runs in boost mode for maybe 10 seconds at a time, if that. No ill effects were seen on my engine.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Late to the party but was going to make a new post for my question, but here seems as good a place as any.
I plan to run a PCV system on an NA motor (LZ9) with both valve covers feeding a catch can and then a breather line going to right before the throttle body. This would normally be the fresh air port for a stock setup, but also allows venting when the PCV is closed. I plan to use no PCV valve in my setup since I am not going to supply the system with any strong manifold vacuum.
Any issues with this setup or suggestions? From what research I have done this should be sufficient, but I do not know if I will be missing out on power from applying vacuum to the crankcase in a stock setup. Though it seems to not be true vacuum since there is a fresh air inlet on one valve cover in a stock setup. I do not want to run any breather filters as they seem to get gunked up quickly and start leaking at seals from the inevitable pressure build up. Catch can will be large for maximum oil extraction.
I think you don't want to do it that way. The more efficient PCV approach is to have a vacuum port and a fresh air port, so that the vacuum side draws fresh air though the crankcase and back into the intake. So in your example, you would want one valve cover (after your MAF, if equipped) ahead of the throttle body for fresh air, and then a valve-equipped valve cover behind the throttle body for max vacuum.\
FWIW, proper PCV can help make power... keeping the crankcase under vacuum means that pistons aren't also pumping air around. On boosted motors, which have potential for significant blowby, PCV is critical.
[This message has been edited by thesameguy (edited 07-20-2021).]
Originally posted by thesameguy: I think you don't want to do it that way. The more efficient PCV approach is to have a vacuum port and a fresh air port, so that the vacuum side draws fresh air though the crankcase and back into the intake. So in your example, you would want one valve cover (after your MAF, if equipped) ahead of the throttle body for fresh air, and then a valve-equipped valve cover behind the throttle body for max vacuum.\
That's pretty much a description of PCV on most factory cars since the 60s.
What reasons motivate you to deviate from the standard configuration, zkhennings?
quote
Originally posted by thesameguy: FWIW, proper PCV can help make power... keeping the crankcase under vacuum means that pistons aren't also pumping air around. On boosted motors, which have potential for significant blowby, PCV is critical.
Unless you have a fancy setup like ericjon262, normal PCV doesn't keep the crankcase under vacuum at WOT, because there is no manifold vacuum.
There is no manifold vacuum at WOT, that doesn't mean there is no vacuum anywhere. For example, on my Saab and my XR4Ti the suction for the PCV is on the inlet side of the turbo. There is sufficient vacuum there for proper PCV function.
[This message has been edited by thesameguy (edited 07-20-2021).]
The stock setup does not use a normal PCV valve, it is a solenoid controlled by the ECM normally and I will be running Microsquirt. I could use another factory PCV valve (which is why I was looking at this thread originally) but I do not really see the benefit of putting the PCV system under vacuum at idle, and it's not true vacuum regardless because there is a fresh air source.
I do not necessarily want to put the system under true vacuum as I have seen that that can lead to sucking dirt in from around the various gaskets in the motor, it is great for a racecar but not necessarily a street car, even though it makes more power.
Since at WOT when the most blow by is created the intake is barely under vacuum, and in a boosted car the PCV would seal and it would just be evacuating to a pre-boost intake location, then I don't really see how having a PCV valve helps improve performance.
Seems like most people are successful with having breather filters on the valve covers or on their catch can, with the caveat that they get easily clogged so you have to check and clean them often.
Therefore I have come to the solution that I will vent both valve covers to a catch can that will have a line going to the intake pre-throttle body. The moving air should have a slight pressure drop for a light suction action, and it is no different in performance to a factory setup at WOT from my understanding. It will not be pulling vacuum at idle like the factory setup would, but it still can vent freely and out of both valve covers instead of just one of them.
If I was going to incorporate a PCV valve I would possibly need 2 catch cans if I really want to keep oil out of the intake because when the PCV closes, the venting is reverted and it vents through the fresh air inlet, so I would need filtration of some kind on that side as well.
The only information I have that would bias me towards including a PCV is that without the crankcase getting refreshed with clean air, it can cause acidic oil buildup from oil vapors condensing in the motor. I have not seen this actually happen to anyone though in my research. If there is any benefits of the PCV system I am unaware of I would appreciate that input.
It would not be challenging to incorporate a PCV valve, I just would like to keep dirty octane reducing oil out of the intake.
I could also go with the exhaust based evacuation system, though I would provide the motor with a fresh air source to prevent sucking dirt through seals. But since simple breather filters seem to work for most people who keep them clean, I think the simplest solution would be the original one I proposed with 2 vent lines going to a catch can which then goes to the intake pre-throttle body.
The idea of POSITIVE crankcase ventilation is that you have a vacuum source on one valve cover, a fresh air source on the other, and filtered air is constantly (well, most of the time when you're not at WOT) flowing through the engine, keeping the oil and crankcase clean.
Due to the fresh air vent, you don't have an actual vacuum in the crankcase (because air spills in from the fresh air vent). It wouldn't make sense to have no fresh air vent, because then the PCV would be sucking from a closed chamber, and there would be no constant airflow.
The idea of breathers connected together and going towards the intake tract allows the crankcase to relieve its pressure, but it does not provide constant air circulation. Early Mustangs had road draft tubes, and I did read on a forum about one guy who changed over to PCV, and he noticed that his oil was no longer black when he did his oil changes.
With a normal PCV setup, if you are concerned about oil being sucked into the intake manifold (though the PCV valve) potentially reducing the octane, well that should only happen at part-throttle when the octane requirement is low. At WOT, when you need high octane, there is no vacuum, so there shouldn't be any oil sucked through the PCV valve.
On my Fiero, I have the Supra PCV valve between the intake manifold and a valve cover, but the fresh air inlet (on the opposing valve cover) has its own dedicated K&N breather filter. It did drip oil sometimes, but I installed a sock to prevent the dripping: https://allstarperformance....ather-sock-all36208/ I've never needed to clean the sock yet; it has not yet become saturated with oil. It would have added more complexity to route the fresh air inlet back to the air filter canister, and I didn't want oil fumes to be routed there at WOT... in large part because I didn't want the blow-off valve to open and blow a bunch of oily mist throughout the engine bay.
The exhaust-based system with a fresh air vent at least accomplishes the goal of circulating fresh air (sometimes) through the crankcase.
You can implement your breather plan without positive ventilation, but you're basically going back to pre-60s tech.
In essence the oil may get dirtier from not evacuating the crankcase while also supplying it with fresh air. I imagine that could have negative performance effects over time.
Maybe I will retain my scheme of only feeding it to the intake pre-throttle body, but put a breather filter on one of the valve covers with a one-way valve so that instead of solely relieving crankcase pressure, the system will provide a fresh air source as well that the crankcase vapors cannot revert through.
My only issue with doing it the way that you have accomplished it is that at WOT where the most vapors will be produced, they will have to exit through the breather filter which could eventually get clogged and cause the crankcase to pressurize. Have you had any issues with this?
Originally posted by zkhennings: In essence the oil may get dirtier from not evacuating the crankcase while also supplying it with fresh air. I imagine that could have negative performance effects over time.
That's the gist of it.
quote
Originally posted by zkhennings: Maybe I will retain my scheme of only feeding it to the intake pre-throttle body, but put a breather filter on one of the valve covers with a one-way valve so that instead of solely relieving crankcase pressure, the system will provide a fresh air source as well that the crankcase vapors cannot revert through.
Pre-throttle body you'll get vacuum from the air filter restriction. The vacuum increases as airflow increases. So that setup will suck the most oily crankcase vapours at WOT... and you were concerned about the octane reduction due to oil. Octane matters most at WOT, but not at idle.
quote
Originally posted by zkhennings: My only issue with doing it the way that you have accomplished it is that at WOT where the most vapors will be produced, they will have to exit through the breather filter
Yes, that's what it does.
quote
Originally posted by zkhennings: which could eventually get clogged and cause the crankcase to pressurize. Have you had any issues with this?
I have observed a hint of crankcase pressurization when I found the dipstick popped out of its hole (perhaps raised 1 inch) a few times, though it did sometimes that with the stock 2.8 as well. However, it seems like the rubber on the original dipstick shrank, and it was no longer making contact with the dipstick tube. So, I made a small sleeve, and that gave the dipstick enough friction to hold:
The main issue I've had with the breather has been oil droplets (related to WOT, not calm driving) escaping the breather and landing on the valve cover. Originally, I had a smaller breather (perhaps 2" dia, 1" long). I switched to a larger breather (3" dia, 2" long), and the air/oil velocity slowed down enough that the pleating could catch the oil without it flying right through. For good measure, I also increased the diameter of the breather's inlet tube (in conjunction with a larger valve cover grommet), again to slow down the air blast.
The oil was stopped by the pleating, but then it would drip down onto the valve cover, so then I added the sock. So far I'm happy with this setup.
The breather filter hasn't gotten clogged, and it doesn't look like it would happens. Air filters in general don't completely clog, but I'm not driving through mud or anything.
Personally, I think a catch can filled with steel wool connected to the low side of the turbo should work great. That's how I plumbed my Saab track car, and it's never given a problem.
