Is this how Positive Crankcase Ventilation works on the Z22SE?

[richard165]

Hey berto

I have an opel zafira with 128k. It's the weirdest car I've ever owned! It's like the z22se has its own personality! With the dipstick reading, pcv mods, timing chains and balance chain, (done recently btw).

After that job, 4.5l magnatec, then reset trip counter and didn't check it until the info display told me to, then i was worried about oil feed to chain or lack of.

 

[Berto]

OK, just for peace of mind I wanted to measure how much vacuum is being pulled from my crankcase at various driving conditions with the extra 3.5mm Ø post-throttle PVC line.

First I thought of rigging a spare oil filler cap with a fitting and hose leading to a vacuum gauge ...



... but as Z22SE oil caps are curiously hard to come by here around, I decided to skin the cat another way.


So I rigged a makeshift airtight plug of the adequate size, pulled out the oil dipstick, inserted the plug into the dipstick tube, lead a hose from the plug to a vacuum gauge, and duct taped the gauge to the base of my windshield. As ghetto as they come but it worked fine.


Now the Gunson gauge I used is designed to measure inlet manifold vacuum, and is graduated in inches of mercury (" Hg):



To measure the very slight crankcase vacuum that I was expecting to register beforehand, some manometer graduated in inches of water (" H2O), like a Magnehelic or a makeshift U-tube, would have been more adequate (1" Hg = 13.6" H2O). But Magnehelics ain't cheap, I wasn't in the mood for more bricolage, and all that was needed was to verify that my crankcase vacuum wasn't shooting up to some worringly high level under any driving condition.


Once on the move, the needle in the Gunson vacuum gauge barely wobbled above 0" Hg at idle or under acceleration, and only on a long downhill coastdown overrun with my foot off the throttle pedal did it move a bit closer to 1" Hg.


So no worries, as expected there's only a very slight crankcase vacuum, enough to ventilate and relieve crankcase pressure and make the rings work better, but far too low to generate problems with gaskets/seals or oil pressure.




*** For those interested in the symptoms of excessive crankcase vacuum, at about ~7" Hg of crankcase vacuum you start hearing weird whistling noises coming from the engine (that's outside unfiltered air forcing its way into the crankcase thru gaskets/seals, nature abhors a vacuum), then at about ~14" Hg of crankcase vacuum your oil pressure starts dropping down dangerously.

 

[Berto]

... It's the weirdest car I've ever owned! It's like the z22se has its own personality! ...

That's the throttle-by-wire pile of dung and the frigging way the ECU was programmed at the factory to control it. Instead of sharply obeying what you command with your right foot, the ECU operates the TB butterfly as SHE likes instead.

The end result is that you are never entirely sure what's gonna happen exactly when you press or release the throttle pedal. That destroys driver's confidence.

How happy would I be if only I could throw all this electronic bullcrap out the window and fit a good ole throttle cable to my Z22SE.

 

[richard165]

You're right, it just does what it wants, like a woman! I think we all just love to tinker with her a bit mate

I've had problems with erratic idle and egr too but i am just curious about the pcv. Its strange how it loves to drink 5w 30. My oil consumption is erratic so I'm just wondering if i can improve but as berto pointed out my oil consumption, at present, is ok.

An interesting topic.

 

[patricks]

How happy would I be if only I could throw all this electronic bullcrap out the window and fit a good ole throttle cable to my Z22SE.

.

I beleive the early z22se from USA (called L61 over there) had cable throttle with ECU to control the rest

 

[Berto]

... Its strange how it loves to drink 5w 30 ...

On a 128K miles/206K Km Z22SE like yours I'd contemplate switching to some thicker xW40 oil.

"... Certainly engines that have experienced significant ring and liner wear benefit from thicker oils. Thicker oil use results in compression increases, performance improvements and reduced oil consumption ..."

Motor Oils - Fuel Economy vs. Wear

I beleive the early z22se from USA (called L61 over there) had cable throttle with ECU to control the rest

Yeah, I should raid some american junk yard and upgrade my Z22SE from throttle-by-wire to throttle-by-cable. Like when you upgrade PCs from Windows 10 to Windows 7,

 

[Berto]

LOL this is funny , "chubacca noises" coming from a BMW with broken CCV system screwing up crankcase vacuum:

 

[patricks]

On a 128K miles/206K Km Z22SE like yours I'd contemplate switching to some thicker xW40 oil.

I wish. My engine has 560K on it Ive toyed with the idea and have even run thicker oil 5-50 and even 10-60. Uses no oil at all on the 10-60 but she doesnt like it lifters very noisy. Funny thing is i had the compression measured at 170k by a dealer and she was 170 - 175psi on all cylinders - and she maintained that all the way to 445k when i did my chains - after which compression now reads 175-180 psi on all cylinders.

PS i use windows 2000 at work (the most stable operating system ever outside linux) and i listen to vinyl lol. Hi tec isnt always better.............

 

[patricks]

Disregard just realised u were talking to richard165

 

[Berto]

... have even run thicker oil 5-50 and even 10-60. Uses no oil at all on the 10-60 but she doesnt like it lifters very noisy ....

^ Interesting. How well did the 5W50 fare? I've had good experiences with Mobil 1 5W50 on very high mileage engines in the past.

... Hi tec isnt always better.............

As Scotty Kilmer likes to say (with his Texan accent): "They put technology in the cars often just because they can, not that it really needs to be done"

 

[Berto]

... I'm getting 19" Hg of intake manifold vacuum @ warm idle on my Z22SE after the 3.5mm Ø by-pass line (without PCV valve or catch can).

Self-correction, I forgot to take this into account:

"... it’s important that you remember that the vacuum readings will decrease as your altitude increases. So if you live on top of a mountain, remember to drop 1 inch of vacuum for each 1000 feet you are above sea level."

Using a Vacuum Gauge for Engine Diagnostics

It's 3000 feet altitude where I live, so 19" Hg of inlet manifold vacuum @ warm idle should be corrected to 22" Hg at sea level.

 

[Berto]

... Ive toyed with the idea and have even run thicker oil 5-50 and even 10-60. Uses no oil at all on the 10-60 but she doesnt like it lifters very noisy ...

I'm going to experiment with a mix of Mobil 1 FS 0W40 and Mobil 1 Extended Life 10W60:

I'm starting with a 80/20% ratio, the resulting cocktail will be something like this:

Will update on the effects of this alchemy.

 

[Berto]

Couple of empirical facts.

· The Z22SE engine in my 2001 Astra Coupe takes exactly 1 litre to fill from min to max on the oil dipstick. My guess is that field remedy 1620 only applies to engines from 2002 onwards:

​

· You really want to check your oil level on a really cold engine (as in the morning after the engine has spent all the previous night stopped) if you seek a true measurement.

 

[richard165]

if i install an oil catch can do you think it will reduce oil consumption further?

i don't think that there is any sense in the rocker cover design. not enough baffling or whatever to separate oil out plus the cam breather pipe is running under a vacuum. no wonder people discover pools of oil in inlet manifold.

(at least the cam breather pipe is after the map sensor though right?!)

also how will this oil in inlet affect running of engine? could this cause an erratic idle?

 

[Berto]

if i install an oil catch can do you think it will reduce oil consumption further?

I wouldn't expect so. It will reduce oil ingestion, however (oil will pool inside the catch can, instead of coating up the intake tract and being burnt in the combustion chambers).

i don't think that there is any sense in the rocker cover design. not enough baffling or whatever to separate oil out ...

There is always room for improvement but the Z22SE cam cover design doesn't look too bad to me. I suspect that the real problem lies in the oil control rings' design.

... plus the cam breather pipe is running under a vacuum ...

Only at WOT does the cam breather see a slight vacuum pulled from the intake tract. Most of the time (idle & part throttle, everything but WOT) it works as a fresh air inlet for the crankcase.

... (at least the cam breather pipe is after the map sensor though right?!) ...

It connects to the airbox => TB pipe downstream from the intake temp sensor...

... but upstream from the map sensor, which is located in the intake manifold, #6 in this pic:

... also how will this oil in inlet affect running of engine? ...

Negligible effects on a naturally aspirated engine for the street as long as PCV system works OK and ventilates the crankcase as advertised.

... could this cause an erratic idle?

I'd expect a high blow-by ratio (from spent rings and/or defective PCV) to alter idle quality far more than any oil in the inlet tract.

 

[richard165]

hi berto, thanks for answering my question.

how is the oil coming through the breather pipe though?

it's not like it's pumped through, so that's why i assumed it was under a vacuum and sucking oil through it.

id like you to look at my car! you are clearly very experienced

 

[Berto]

hi berto, thanks for answering my question.

My pleasure.

how is the oil coming through the breather pipe though?

While driving at part throttle (say at a steady 90mph on the highway) the post-throttle plate PCV line (on Z22SE engines, just a metered orifice buried inside the intake manifold) is pulling vacuum from the crankcase, and the pre-throttle breather line functions as a fresh filtered air supply to the crankcase.

Then when you floor it at WOT, there is no longer any vacuum (or just very little) inside the intake manifold, so the post-throttle PCV line no longer pulls vacuum from the crankcase (or just pulls very little). In those conditions, crankcase pressure builds up, and the flow in the pre-throttle breather reverses direction: it no longer flows fresh air in towards the crankcase, but evacuates crankcase gasses out towards the airbox => TB pipe.

And that's when you get your throttle body stained with oily residue, at WOT.

id like you to look at my car! you are clearly very experienced

Nah, there are people here around like Vocky or Evocarlos with miles more experience fiddling with these engines than here your servant.

 

[richard165]

that explains motorway oil usage. if i take the journey to the same place using a roads instead i have very little oil usage.

thank you very much for the advice, you've clearly taken time and care in your response.

 

[Berto]

Results with "cocktail 82" (0W40/10W60 @ 80/20%):

· Cold start: No noticeable difference.
· Cold idle: No noticeable difference.
· Warm idle: Finer and less noisy.
· Engine performance: No noticeable difference.
· Fuel consumption: No noticeable difference.
· Oil consumption: ~25% decrease.


Next experiment will be on "cocktail 55", 0W40/10W60 @ 50/50%. This concoction should behave more or less like a 5W50 with slightly better viscosity index:

 

[Berto]

Results with "cocktail 55" (0W40/10W60 @ 50/50%):

· Cold start: Noisier tappets, they quiet up once engine is warmed up.
· Cold idle: No noticeable difference.
· Warm idle: Finer and less noisy.
· Engine performance: No noticeable difference.
· Fuel consumption: Slightly increased average from 8.1 to 8.3 litres/100km (35 to 34 UK mpg). Guess part of this comes from increased internal friction from thicker oil, part from colder weather than in previous tests.
· Oil consumption: ~67% decrease.