Catch Can or delete PCV

[CT22]

I know this is an age old debate but a lot of info I am finding seems dated so I thought I’d bring it up here.

does deleting your PCV set up by removing the valve and replacing with a breather really cause long term damage to your motor?

I hate the idea of reserculating oil back in my motor (Dark Horse). Shit I deleted the EGR on my diesel. But I’m okay buying a catch can if it’s bette long term.

but if there is no proof that long term reliability is negatively impacted by a simple delete and breather that seems like the obvious choice to me. I don’t care about the emissions aspect of it. Just long term reliability. Will it hurt my motor? I drive it often and i drive it hard. Not blown… yet. Maybe I will. And I do intend to track it.

Thanks for your input!

Sponsored

 

[Supra Killer]

does deleting your PCV set up by removing the valve and replacing with a breather really cause long term damage to your motor?

I'm not aware of any case where doing this caused damage. I can't think of how that might even even be possible. Can you share a claim here?

I don’t care about the emissions aspect of it. Just long term reliability. Will it hurt my motor?

No. Before EGR/PCV, the crankcase was vented to atmosphere (they just pissed oil vapor on the ground) so that the blow-by that passed the piston rings didn't create too much pressure inside the engine.

This is and has always been an issue of environmental concern. The 'catch-can' isn't really a pollutant, though, in my opinion because the noxious gases are still sent back into the combustion chamber. The oil vapors are not and that's the point of the device.

 

[Skye]

My thoughts...

I pulled some threads on the debate of using a can versus venting.

Some owners will have unique applications with venting that does not involve the PCV valve and system. I'll set this category aside, as it often involves specific tuner/modder/part manufacturer recommendations.

For the rest of us, primarily street drivers, with occasional track or strip action, I'll break it into two examples.

1. Venting with no PCV system.

You've removed the PCV valve, capped the hose at the intake and the port in the valve cover. You've installed a filtered vent in the valve cover. This is one way to prevent any oil-based vapors from entering the intake system. But all the rest of the effects are negative.

- In states with emissions testing, it's an immediate fail

- I doubt any Ford dealer would see it in good light, especially if dealing with other engine-related matters

- Previously, there was negative pressure helping "suck" the rings onto the piston lands; that's gone

- Several parameters in with PCM/ECU could reach their upper ranges, with no adjustability left

- The venting filters have to be cleaned. Depending on conditions, oil may drip out and you might clean often

2. Catch Can with PCV system.

You've placed a catch can in-line with the PCV system.

- You'll have to occasionally remove the can, drain and re-install (5-10 minutes, once or twice a year)

- I get something of a window into the crankcase (see water, fuel contamination)

- Negative impacts listed in the previous paragraph don't exist

Option two, the catch can, seems like the path ahead, if concerned about oil-based vapors and the desire to keep them out of the intake

 

[Zig]

does deleting your PCV set up by removing the valve and replacing with a breather really cause long term damage to your motor?


Thanks for your input!

Not any more than removing the cats.

edit: although long term could result in ‘vapor stain’ (damage). The same stuff you would have caught via catch can is now free to waft and wisp about resting upon whichever is receptive.

 

[Zig]

My thoughts...

- Previously, there was negative pressure helping "suck" the rings onto the piston lands; that's gone

Past the valves - what happens in the opposite bank?

 

[Skye]

what happens in the opposite bank?

The primary source for the gases of interest is the underside of the pistons, what gets past the rings, all of which are part of the same cavity in the bottom of the engine.

The oil galleys from the heads to the pan are not completely full of oil at any given time; this is proven by the gases being excavated from the pan and up into the left side (if facing the car) head before entering the intake. Regarding the opposite bank, any gases top side simply take a longer route to exit.

Racing and modded applications can differ. Owners should discuss the topic with their builder or equipment source.

 

[Zig]

The primary source for the gases of interest …

Are evacuated from the engine via the valve cover?

 

[Skye]

Are evacuated from the engine via the valve cover?

So, there's a few things going on.

If you look at the top of a Gen 3 engine, you'll see two PCV hoses:

1. Right side of engine (facing car). Goes from front of throttle body to the valve cover.

2. Left side of engine. Goes from intake manifold to the valve cover. Connection has PCV valve.

The reason there are two hoses, one before and one after the throttle body is Edit: [to allow for the movement of air through the engine internals when the PCV valve is open.] vacuum. At idle, when the vacuum is highest, sucking through the PCV is like drawing closed straw, if it were not for the other hose.

Edit and clarify, next four paragraphs:

At idle, when vacuum is highest, the PCV valve is closed. Little blow-by is occurring. There is not much need for excavation. The spring-loaded PCV valve being closed prevents the conditions of what would be otherwise an open-ended vacuum leak.

As engine RPMs increase, vacuum reduces, the PCV valve opens, and the ever-increasing crankcase gases can then escape into the intake. The purpose of the second hose, in front of the throttle body, is to allow for the movement of air. Otherwise, the condition would be akin to sucking on a closed straw while attempting to recover crankcase gases.

The sucking source is from the intake manifold, where our vacuum is. Fresh air enters the right side, from ahead of the throttle body. This air enters the right valve cover and eventually meets the bottom of the engine. Now, gases flow up the left side, where they are consumed at the intake.

Pressure differentials on left and right sides of the engine allow for the movement of air and gas recovery under partial(part throttle)-to-no(WOT) vacuum conditions.

The hoses need to be top side. Having a pickup in the pan wouldn't work; I've got 10 quarts, 9.5 liters of oil sloshing around. That, and using less hose to do the same job is less expensive when I'm building hundreds of thousands of engines every year.

 

[Zig]

So, there's a few things going on.

If you look at the top of a Gen 3 engine, you'll see two PCV hoses:

1. Right side of engine (facing car). Goes from front of throttle body to the valve cover.

2. Left side of engine. Goes from intake manifold to the valve cover. Connection has PCV valve.

The reason there are two hoses, one before and one after the throttle body is vacuum. At idle, when the vacuum is highest, sucking through the PCV is like drawing closed straw, if it were not for the other hose.

The sucking source is from the intake manifold, where our vacuum is. Fresh air enters the right side, front of throttle body. This air enters the right valve cover and eventually meets the bottom of the engine. Now, gases flow up the left side, where they are consumed at the intake.

The hoses need to be top side. Having a pickup in the pan wouldn't work; I've got 10 quarts, 9.5 liters of oil sloshing around. That, and using less hose to do the same job is less expensive when I'm building hundreds of thousands of engines every year.

Doesn’t the valve close with increased vacuum?

 

[Dena]

PVC valves were one of the first emission control devices and were a required retrofit at least in Arizona along with a vacuum retard when the engine reached a certain temperature. You don't really need a PVC valve but it's one of the things that they might catch when they do an emission control check. Your dealer might also catch it if you use them for routine service as they occasionally go bad and need to be replaced.
I took it off my falcon for a while because the original retrofit was cheap and not working but I had to reinstall it so I plugged the breather tube and installed a Ford PVC valve. If you're tracking the car or pushing it hard, get a catch can. Otherwise it probably doesn't make much difference.

 

[Skye]

Doesn’t the valve close with increased vacuum?

You are right. I have corrected and updated my earlier post.

 

[HWill]

PVC valves were one of the first emission control devices and were a required retrofit at least in Arizona along with a vacuum retard when the engine reached a certain temperature. You don't really need a PVC valve but it's one of the things that they might catch when they do an emission control check. Your dealer might also catch it if you use them for routine service as they occasionally go bad and need to be replaced.
I took it off my falcon for a while because the original retrofit was cheap and not working but I had to reinstall it so I plugged the breather tube and installed a Ford PVC valve. If you're tracking the car or pushing it hard, get a catch can. Otherwise it probably doesn't make much difference.

Actually catch-cans are beneficial in daily driven cars also. I'd never say they don't make much of a difference having had them in just about all my vehicles from aftermarket, factory add-ons and custom made ones.

 

[Zig]

Actually catch-cans are beneficial in daily driven cars also. I'd never say they don't make much of a difference having had them in just about all my vehicles from aftermarket, factory add-ons and custom made ones.

Do you always start at mile zero or do you take it to the first (or some fraction thereof) oil and filter change before installing?

 

[HWill]

I have done it many different ways. I have installed them on new cars with less than 20miles, in between oil changes and during an oil change.

 

[Dena]

Actually catch-cans are beneficial in daily driven cars also. I'd never say they don't make much of a difference having had them in just about all my vehicles from aftermarket, factory add-ons and custom made ones.

A Positive Crankcase Ventilation valve isn't a catch can. It is intended to pull exhaust gasses out of the crank case. A catch can is intended to remove oil that might be in those gasses.

Sponsored