PCV Block Off Plate vs. Catch Can vs. Nothing

[IanCH]

Well, you clearly didn't know it at all so why does the hyphen matter?

 

[aaronc7]

No, it's Micro Penis Insertion

 

[jimlloyd40]

If you want to get cocky, at least get it right yourself: multi-point injection.

You are correct it's always been "point" not "port".

https://clubtechnical.com/multi-point-fuel-injection-mpfi-system

 

[jimlloyd40]

No, it's Micro Penis Insertion

Nope I'm not going to say it.

 

[IanCH]

While technically you could call it both this as they describe the same things.

But the name for our cars is multi port injection, it's what is used on the VW literature.

 

[aaronc7]

Anyways, I'm still running stock, but here's my thoughts:

OEM "PCV Plate"
- Is a true 2 way system like all modern PCV systems. During low load, fresh air is circulated thru the crankcase to extend oil longevity, remove moisture etc. Under boost, it vents to the air intake just like aftermarket systems
- It connects to a passage in the block that goes all the way down to the lower crankcase--this is where pressure is vented from. This passage has some baffling in place + good baffling within the plate itself....it does a very good job separating the oil from the air, and returning the oil to pan.
- Has been known to cause issues on track--"oil surge" in the cyl head/PCV, partly due to the fact it retains this 2 way system and the vacuum it puts into plate during engine decel, etc.
- Some reports of it physically failing in high boost builds... unknown if 30+ psi is just too much, or these are coincidences of PCVs going bad at the same time etc. It does have these rubber check valve things, and if some of those were to fail, it's likely to cause issues and boost actually pressurizing the crankcase etc.
- Catch can on this OEM system would only be catching stuff about 2% of the time when under WOT, most of the 'airflow' is routed directly to the intake valve area. But the OEM system does a great job separating the oil, kind of a useless anyways. Maybe a catch can would be useful for a track car, just as a bandaid and avoid oil getting into the charge pipes at all.

Aftermarket PCV plates
- Removes any sort of "2 way" functionality.....it is not intake manifold vacuum 'powered' anymore, more than anything it's like a vent to atmosphere breather system, but it is routed back into the air intake generally. In theory the air intake provides a little 'suction' at higher airflow....but it's not going to be much.
- Removes any sort of OEM baffling in place, and uses their own. Generally does a poor job at separating the oil and air, which is why the cans fill up so fast, even without really beating on the car. Note the distinction that the OEM system vents pressure from low in the crankcase, and effectively with these aftermarket units, its vented from the head itself. What's likely happening is oil is getting flung all around in the head from the spinning cams + crappy aftermarket system baffling = results in lots of oil making it to the can.
- Generally works better on track because that real vacuum source is removed
- Generally accept the fact that you need to empty the can often..... moreso on built motors, moreso if you drive it hard or track the car.
- If you ran this without a catch can, you're in for a bad time.
- For a lot of the big power / lots of track time cars it becomes the only solution, even if it's not a great solution.

Personally I'm keeping OEM / no catch can until I see an absolute need to do so...but I doubt it given it's a street car / I won't be pushing 40psi boost etc.

 

[aaronc7]

I've always just called it "Port Injection" until I came to this platform where everyone puts the M in front.

 

[jimlloyd40]

Whatever you call it everyone understands the meaning.

 

[anotero]

Well, you clearly didn't know it at all so why does the hyphen matter?

Smh.

 

[anotero]

Anyways, I'm still running stock, but here's my thoughts:

OEM "PCV Plate"
- Is a true 2 way system like all modern PCV systems. During low load, fresh air is circulated thru the crankcase to extend oil longevity, remove moisture etc. Under boost, it vents to the air intake just like aftermarket systems
- It connects to a passage in the block that goes all the way down to the lower crankcase--this is where pressure is vented from. This passage has some baffling in place + good baffling within the plate itself....it does a very good job separating the oil from the air, and returning the oil to pan.
- Has been known to cause issues on track--"oil surge" in the cyl head/PCV, partly due to the fact it retains this 2 way system and the vacuum it puts into plate during engine decel, etc.
- Some reports of it physically failing in high boost builds... unknown if 30+ psi is just too much, or these are coincidences of PCVs going bad at the same time etc. It does have these rubber check valve things, and if some of those were to fail, it's likely to cause issues and boost actually pressurizing the crankcase etc.
- Catch can on this OEM system would only be catching stuff about 2% of the time when under WOT, most of the 'airflow' is routed directly to the intake valve area. But the OEM system does a great job separating the oil, kind of a useless anyways. Maybe a catch can would be useful for a track car, just as a bandaid and avoid oil getting into the charge pipes at all.

Aftermarket PCV plates
- Removes any sort of "2 way" functionality.....it is not intake manifold vacuum 'powered' anymore, more than anything it's like a vent to atmosphere breather system, but it is routed back into the air intake generally. In theory the air intake provides a little 'suction' at higher airflow....but it's not going to be much.
- Removes any sort of OEM baffling in place, and uses their own. Generally does a poor job at separating the oil and air, which is why the cans fill up so fast, even without really beating on the car. Note the distinction that the OEM system vents pressure from low in the crankcase, and effectively with these aftermarket units, its vented from the head itself. What's likely happening is oil is getting flung all around in the head from the spinning cams + crappy aftermarket system baffling = results in lots of oil making it to the can.
- Generally works better on track because that real vacuum source is removed
- Generally accept the fact that you need to empty the can often..... moreso on built motors, moreso if you drive it hard or track the car.
- If you ran this without a catch can, you're in for a bad time.
- For a lot of the big power / lots of track time cars it becomes the only solution, even if it's not a great solution.

Personally I'm keeping OEM / no catch can until I see an absolute need to do so...but I doubt it given it's a street car / I won't be pushing 40psi boost etc.

Thanks for the details, very useful.
You mentioned oil getting into the charge pipes. Why does that happen, is it absolutely not supposed to, and how much is too much?

 

[aaronc7]

When oil goes thru the intake/TIP....then thru the turbo, it will get into the charge pipes and such.

Yeah some is normal.... always a little oil residue when I take my TIP/pcv hose fitting off. I didnt notice any when I did intercooler swap. It's bad because you dont want it coating the inside of the intercooler etc....a little fine mist is normal. Quarts of oil going into it is not normal (like you would presumably get if you ran aftermarket PCV without a can).

It would be interesting to see an aftermarket plate/system that uses some of the baffling thats already inside the block, i dont know why none of the kits utilize it, maybe theres a good reason, maybe just lazy.

 

[El_bigote_AJ]

I've always just called it "Port Injection" until I came to this platform where everyone puts the M in front.

It’s cause we are adding it to a direct injection setup, so now it’s multiple “points” of injection. Lol

 

[aaronc7]

I always thought it was called that as a way to distinguish itself from a single point injection system.

IE... back in the day you had carbs........... then throttle body injection............. then multi point or port injection etc.

I don't care either way, I love how a PCV plate thread went this direction lol