Vacuum assisted PCV scavenging

[HCP2311]

Is it necessary for the 1FZ-FE?

A little context, ill explain more than I probably need incase I label something wrong. The Valve cover has two PCV hoses: One to the intake plenum, plumbed with a 1 way valve. (Exhaust side) The other is open between the valve cover and BEFORE the throttle plate. (Intake side)

My understanding is that one allows metered air INTO the crankcase and the other pulls air OUT of the crankcase and back into the intake plenum for burning. However, BOTH hoses are pulling vacuum??? Which really isn't surprising considering there isn't a way one valve on the intake hose, but obviously this worked for 30+ years until the engine was rebuilt & reassembled recently.

I found a picture of a RHD 80 that someone had routed the intake hose over to the base of the air filter box, but there wasn't any explanation as to why, but I wondering if its because theirs was also pulling vacuum on both hoses? I guessing this would solve the problem since the vacuum is probably less at that location that directly in front of the throttle plate. Except that now that engine would be getting unmetered air. Right?

So, I'm thinking about installing a K&N PCV filter on the intake side of the valve cover and a filtered VTA catch can on the exhaust side of the Valve cover. My question is does the 1FZ-FE NEED vacuum assist in scavenging the crankcase or will the crankcase vent naturally?

 

[azusa]

One of the hoses are for the PCV, the other one is the breather. How much vacuum do you have on the breather side? What brand air filter do you have?

 

[HCP2311]

One of the hoses are for the PCV, the other one is the breather. How much vacuum do you have on the breather side? What brand air filter do you have?

I didn't measure it but more than the PCV hose was pulling. The filter is a WIX 42159.

 

[azusa]

Picture of the breather and PCV, if everything's plumbed correctly and the filter is flowing you should not have any vacuum on the breather hose.

 

[HCP2311]

Well I've already plumbed it for VTA, but it was an identical set up to the pictures in the front of the FSM on here.

It seems to be breathing fine with the VTA, oil pressure ranges from 10psi up to about 60ish on hard accelerations. The VTA solved my issue I was trying to solve which was figuring out why removing the oil cap with the engine running made it die. The vehicle is still running lean. I adjusted the VAF and that helped some but not completely.

 

[smritte]

My question is does the 1FZ-FE NEED vacuum assist in scavenging the crankcase or will the crankcase vent naturally?

Yes and no.

To understand the answer you need to understand PCV and why its important.

Here it is put very basically.

As your piston compresses and fires, some pressure push's past the rings (blowby). This does two things, pressurizes the crank case and induces burned and unburned fuel into the oil. The oil also collects moisture overnight. These contaminants form acids as well as cause other issues.

The PVC system is tied to vacuum from the intake and isolated with a check valve (most common design of the three). The other side is tied to filtered air. Normal driving the check valve is pulled closed by engine vacuum. This is so you don't have a vacuum leak.

Acceleration causes the blow by gases to increase, raising crankcase pressure. At the same time, engine vacuum drops. This causes the check ball to roll away from the intake side. The intake side will have a lower pressure than the fresh air side. The blowby gasses will (mostly) go to the intake side (least resistance) and get pulled into the intake to be burned in the combustion cycle. Filtered air will get pulled into the crankcase and replace the contaminated air inside.

Now.....
Worn out engines will normally have more blowby. This will cause an increase in oil being pulled into the intake. Some people fix this with a catch can.
Very high compression, forced induction will normally cause more blowby. Again with the catch can.
Stuck open PCV check ball will normally cause a constant vacuum leak. This will pull more oil fumes, run rough and clog things. You will also notice oil loss
Disabling PVC and adding a filter will allow most of the pressure to be pushed out but will do nothing for the gas contamination and will make a mess of the valve cover.
Stuck closed PCV check valve will cause the pressure to find a way out. Oil fumes will get pushed into the inlet side and can cause oil to be pushed out from the crank seals.

That's the basics on PCV. When my engine had 250k, I had enough blowby to consume about a quart of oil every 5k. The blowby wasn't too bad but I had traces of oil inside my intake. 5k on the engine rebuild. I bumped the compression slightly and have no noticeable oil in the vacuum side as well as no more oil consumption. This is why I don't need to add in a catch can and have no reason to add one.

As you can see the answer to your question was yes and no.
Yes it will work without a pcv but, it wont remove the contaminants caused by blowby and moisture.

 

[azusa]

Edith: badly gummed up pcv would not pull any vacuum. If you tee into the breather side, you should hardly see any vacuum.Your PCV could be gummed up inside holding the ball away from the PCV housing, this will create more vacuum in the crankcase. The PCV valve is metered vacuum, if you're using an aftermarket PCV valve it could have the wrong metering.

 

[HCP2311]

As you can see the answer to your question was yes and no.
Yes it will work without a pcv but, it wont remove the contaminants caused by blowby and moisture.

Why not install a catch can with a vent on the pcv line? Wouldn't that solve the contaminate issue? I have noticed that at operating temp and idling some crankcase vapors escape through the PCV vent I've installed on the breather port, but above 1500rpms the flow switches directions and starts pulling air into the crankcase through the filter.

Edith: badly gummed up pcv would not pull any vacuum. If you tee into the breather side, you should hardly see any vacuum.Your PCV could be gummed up inside holding the ball away from the PCV housing, this will create more vacuum in the crankcase. The PCV valve is metered vacuum, if you're using an aftermarket PCV valve it could have the wrong metering.

I did replace the Valve with a Wells 6P1156. I couldn't get any noise out of the factory one so I decided it was stuck open. The breather definitely had vacuum on it, the PCV also had a vacuum, but a much more moderate amount. There was also a dirt dauber living inside the pcv hose, obviously I removed it and fed some compressed air though the nipple in the plenum and it seemed to be clear.

 

[smritte]

Why not install a catch can with a vent on the pcv line? Wouldn't that solve the contaminate issue?

Unless your talking about oil getting pulled into your intake, NO. The contamination is from the blowby into the crank case and moisture from the engine cooling down.
The PCV pulls the gasses from the crankcase. If you have enough blowby to warrant a catch can, you either have poor sealing from your rings (worn out/improper build), super high compression or sometimes turbo/supercharger with a high amount of boost.

some crankcase vapors escape through the PCV vent I've installed on the breather port

Just so I understand what you did, you disabled the PCV (intake side) and added a breather vent?

above 1500rpms the flow switches directions and starts pulling air into the crankcase through the filter.

If you did actually remove the pcv, how is a pressurized chamber, that increases in pressure due to load, is turning from a positive pressure to a negative pressure?

If you didn't remove the PCV system and just added a breather, that's how it works. As I mentioned in my original post, the slight pressure you see coming out of the vent you added, will eventually deposit oil on your valve cover. The original factory breather caps had chambers built in to help with this but still deposited oil on the valve cover. I think they went away from this design in the mid to late 70's. The little filters people put on their valve cover was from this era.

 

[HCP2311]

Unless your talking about oil getting pulled into your intake, NO. The contamination is from the blowby into the crank case and moisture from the engine cooling down.
The PCV pulls the gasses from the crankcase. If you have enough blowby to warrant a catch can, you either have poor sealing from your rings (worn out/improper build), super high compression or sometimes turbo/supercharger with a high amount of boost.


Just so I understand what you did, you disabled the PCV (intake side) and added a breather vent?


If you did actually remove the pcv, how is a pressurized chamber, that increases in pressure due to load, is turning from a positive pressure to a negative pressure?

If you didn't remove the PCV system and just added a breather, that's how it works. As I mentioned in my original post, the slight pressure you see coming out of the vent you added, will eventually deposit oil on your valve cover. The original factory breather caps had chambers built in to help with this but still deposited oil on the valve cover. I think they went away from this design in the mid to late 70's. The little filters people put on their valve cover was from this era.

This is the current set up. I'm waiting on a elbow to change the red hose and I'm trying to decide if I should try attaching the Catch Can to the plenum for scavenging.

The original problem was when the engine was running and you removed the oil fill cap the engine would die. What I tracked down is that the breather hose (Now just the KN filter) was pulling significant vacuum on the crankcase in addition to the PCV hose pulling vacuum. (Now the red hose). If I blocked the breather nipple in front of the throttle plate the engine would idle just fine. Maybe a SLIGHT change in idle tone. There was trace oil present in the PCV line to the plenum and also oil present in the breather hose to the throttle body.

I was expecting the breather hose to alternate between slight vacuum and slight pressure depending on RPMs but all it ever did was pull a strong vacuum regardless of RPMs. The engine runs lean regardless of the PCV changes.

(EGR was missing when I got the vehicle and the extra wiring isn't finalized yet.)

 

[smritte]

breather hose (Now just the KN filter) was pulling significant vacuum on the crankcase in addition to the PCV hose pulling vacuum.

Answer

Stuck open PCV check ball will normally cause a constant vacuum leak. This will pull more oil fumes, run rough and clog things. You will also notice oil loss

What you did will work as I mentioned in my first post. What it will not do is remove the blowby contamination. How much difference will that make? No idea. If you pull a sample of your oil after about 5k miles and send it out for analyzation (Blackstone Lab), you will find out whether or not your causing an issue. I know, people do this all the time but I'm very OCD about how my vehicles are set up. I'm not trying to say whether or not you should modify it, that's all your call.

My knowledge and experience is due to a lifetime of building, racing, three decades as a master diagnostic tech and two decades of an automotive technical trainer for a manufacture. What that means is I try not to modify things I don't understand.
Your system will work as it is. My original post was me going into teacher mode so you would (hopefully) understand how the system works and answer your original question.

 

[HCP2311]

Answer


What you did will work as I mentioned in my first post. What it will not do is remove the blowby contamination. How much difference will that make? No idea. If you pull a sample of your oil after about 5k miles and send it out for analyzation (Blackstone Lab), you will find out whether or not your causing an issue. I know, people do this all the time but I'm very OCD about how my vehicles are set up. I'm not trying to say whether or not you should modify it, that's all your call.

My knowledge and experience is due to a lifetime of building, racing, three decades as a master diagnostic tech and two decades of an automotive technical trainer for a manufacture. What that means is I try not to modify things I don't understand.
Your system will work as it is. My original post was me going into teacher mode so you would (hopefully) understand how the system works and answer your original question.

I appreciate the explanation and It answers my question really. I'm going to try plumbing back in to PCV vacuum and leave the breather open with the filter and if it doesn't cause a lean condition. I'll keep it that way.

 

[smritte]

Earlier today, I was pondering this. What would be nice is if the catch can had a small vacuum pump built in. That would actually solve may issues.
Now to figure out if there's a market for that.

 

[HCP2311]

Earlier today, I was pondering this. What would be nice is if the catch can had a small vacuum pump built in. That would actually solve may issues.
Now to figure out if there's a market for that.

Honestly when I think about it, we already have vacuum in that area. There is probably a way to tap in to it. I'll update here in a few days if plumbing the catch can back in to PVC causes a lean condition with that breather filter on. I want to say it will, but it may be such a small amount of new air that it doesn't make a difference.

 

[smritte]

Some vehicles run an orifice type pcv. No check ball, just a small metered leak. If its small enough to be compensated by the PCM, that design works too.

 

[ppc]

The original problem was when the engine was running and you removed the oil fill cap the engine would die

Not a problem. That in itself is normal functioning for all 1FZ-FE motors.

 

[HCP2311]

Not a problem. That in itself is normal functioning for all 1FZ-FE motors.

WHAT?? really?

 

[ppc]

Removing the oil cap allows unmetered air into the engine. No Bueno on an EFI motor. Same with engine oil dipstick. Other vacuum leaks will yield the same results.

 

[HCP2311]

Removing the oil cap allows unmetered air into the engine. No Bueno on an EFI motor. Same with engine oil dipstick. Other vacuum leaks will yield the same results.

NONE of my other vehicles do this. (93 850, 04 TJ, 09 ML320, 09 XC90, 08 JK, 19 JL, 10 C30) Are you saying this is specific to the 1FZ-FE? Because I could see it, I really don't see how it could be any other way with the breather hose right in front of the throttle plate with no 1 way valve.

What STILL doesn't make sense to me is why an open breather on the valve cover doesn't cause a lean condition. You'll see in the video below there is no lean condition caused by having the breather open but the PCV still plumbed to the intake, but when I pull the catch can dipstick it immediately goes lean. I even checked the breather port on the valve cover with compressed air to make sure it wasn't clogged.

The water pump pulley has thrown in the towel, I know.

 

[azusa]

I'm assuming you're a young guy with not much experience, not making fun of you. If my assumption is correct and you are interested in learning, find the yourself City college that offers automotive training. Again not making fun of you, from your posts does not seem you have an understanding of how things work.