Spec vac draw for PCV's?

[Schrade]

Is there a minimum vacuum draw necessary for PCV's to keep crankcase purged?

I want to re-route the PCV purge line IN FRONT OF the air filter, and cap off the plenum PCV port. Get a port fabbed on the AF housing, so that the crankcase air gets filtered BEFORE getting burned.

I ran this idea past Marc, and Dominic, and neither was really impressed by it. one of them said something about having to clean the air filter more often, but that's not something that would be bothersome at all.

The catch can isn't something I'm considering.

When I first finished the 'Top End Resto', and ran half a dozen Closed Loop cycles, I had to break down again while looking for a dropped bolt. Seeing new oil inside the plenum, after cleaning up so much, was dis-appointing.

With grill-work of a sort on the AF housing, the vacuum draw probably wouldn't equate to the same vacuum on the plenum port.

Only question is, would it be ENOUGH vacuum to keep the CC vapors purged???

[mike100]

Marc Haibeck published a mini article that his theory is that it is a ring control issue more than a pcv mist issue. people aren't catching buckets of oil in their catch cans, yet that first qt of oil burns off as windage pretty quickly.

click here (http://www.zr1specialist.com/HAT%20Web/articles/my%20experience%20with%20LT5%20oil%20consumption.h tm)

[mike100]

so I just cleaned and sealed the pcv related tubing and concentrated on the throttle body air leak as the issue with idle. There's not much you can do with it outside of possibly restricting the line back to the TB and y-ing off the pcv tubing to atmosphere thru a small filter or something. Outside of that rebuilding the TB.

[Franke]

Schrade, I think you may end up with a little bit of increased crank case pressure too. Similar to when cars used a road draft tube for crankcase vapors and a vented cap on the intake manifold or valve covers. You definitely will have a oily air filter if you duct it before the filter.

[Schrade]

so I just cleaned and sealed the pcv related tubing and concentrated on the throttle body air leak as the issue with idle. There's not much you can do with it outside of possibly restricting the line back to the TB and y-ing off the pcv tubing to atmosphere thru a small filter or something. Outside of that rebuilding the TB.

Mike - I'm not sure what you're getting at this post; can you elaborate? (I'm not tying my hesitation investigation to oil fouling)

As far as oil blow-by, Marc and I didn't discuss that, while talking about the oil coming into the plenum at the PCV purge port. He DID acknowledge how much DOES come in there.

Franke - oily air filter? Seems to me that that's much preferred, over fouled intake, valves, plugs, and exhaust...

You HAVE TO agree???

[mike100]

Crankcase pressure is positive when you get on it and manifold vacuum isn't really sucking too hard when the throttle is open 100 percent as it approaches atmospheric pressure.

you could road draft the PCV outlet and the plenum will still get soaked in oil. I wouldn't worry about it. the only thing the pcv circuit does affect is the idle as it is a calibrated leak the system expects to see.

[Franke]

Schrade,
I do agree that it could be a problem if it is excessive. I would then look to the valve seals, rings, breather cover etc if so but I have 56k on my engine and the plugs are clean which tells me I have a good burn on whatever oil is present. I did see a little bit of oil in the plenum past the TB but I don't see a big issue there. My engine doesn't smoke so I don't have a concern. It also wouldn't pass emissions here if it did.
Do you think based on what you saw in your engine that you may have more blow by (oil build up) in the plenum than is normal for this type of engine? Perhaps the oil filters in the cam covers have disintegrated. I think Dyno expressed that in one of his posts when he removed the cam covers. Since some guys on this forum are using oil catch cans I believe the LT5 has a bit more oil consumption than say a standard design engine.
Based on how well your mill is running per your vids I don't see a problem. JMHO.

[A26B]

If you change the vacuum source from the plenum to in front of the air filter housing, you will essentially & effectively kill the PCV system. You won't have a vacuum source anywhere in front of the throttle blades.

Regarding the cam cover filters.
Under normal driving conditions, the air flow is INTO the cam covers, NOT out of the cam covers. The purpose is to allow filtered air into the crankcase, through the cylinder heads so that there will be purge air flow for the PCV system to operate properly.

The filters inside of the cam covers are for high rpm conditions, when vacuum to the PCV is low and there is little to no purge air flow of filtered air into the cylinder head. The purpose of the filter is to prevent splash oil from under the cam covers from getting up & into the aluminum purge air pipes.

If you are really worried about the oil in the plenum, a catch can is the only way to deal with it, simply & efficiently.

[Franke]

If you change the vacuum source from the plenum to in front of the air filter housing, you will essentially & effectively kill the PCV system. You won't have a vacuum source anywhere in front of the throttle blades.

Regarding the cam cover filters.
Under normal driving conditions, the air flow is INTO the cam covers, NOT out of the cam covers. The purpose is to allow filtered air into the crankcase, through the cylinder heads so that there will be purge air flow for the PCV system to operate properly.

The filters inside of the cam covers are for high rpm conditions, when vacuum to the PCV is low and there is little to no purge air flow of filtered air into the cylinder head. The purpose of the filter is to prevent splash oil from under the cam covers from getting up & into the aluminum purge air pipes.

If you are really worried about the oil in the plenum, a catch can is the only way to deal with it, simply & efficiently.

You are correct sir about the filters. I stand corrected. what was I thinkin?

[Schrade]

That sheds light on the PCV system SOURCE air there Mr. J; also explains why the cam cover pipes were clean on the inside BEFORE Top End breakdown in Nov...

Still wondering here if there's improvement possible...........

??? The PCV-to-plenum inlet is RIGHT UNDER the TB primary butterfly???

Hmmm...

[Schrade]

You are correct sir about the filters. I stand corrected. what was I thinkin?

Doesn't matter WHAT you were thinkin' there Franke...

Matters only that you're THINKIN'. And readin' it. http://www.zr1.net/forum/images/icons/icon14.gif

Thinkin' is ALWAYS good. It's when stuff comes to ya'...

And I wish some of you guys would read and feedback on the other post #218 in the Throttle Hesitation thread.

_____________________________________________

...and I'm still thinkin' on PCV oil pullin' through the burn...

Marc acknowledged that a LOT of oil does come through the PCV.

The plenum has a depression right at the PCV inlet port, where the oil collects (Primary butterfly location of course has a little to do with that). And isn't the Charcoal Cannister purge port right next to PCV port? Do the fuel vapors facilitate vaporization of the oil?

Is Duty Cycle of CCP longer and more frequent in LT5, that other GM mills?

If one uses lighter viscosity oil, then oil is gonna' more readily vaporize, and more readily pull from the crankcase, through PCV - correct?

An ACCURATE oil level is imperative too, since too much oil gets foamed up by the crankshaft spinning through it???

__________________________________________________ _

Do oil catch cans have to be emptied?

If so (or even if not), could a check valve be integrated into the can, to allow the accumulated oil to be purged through CCP?

Could CCP Duty Cycle be re-coded to accommodate this???

[Dynomite]

Here is what I am thinking :D
Just Do It. But in this case Do Not DO IT :sign10:

PCV System TIPS (http://www.zr1.net/forum/showthread.php?p=184606)

Do use an oil catch can :thumbsup:

See item#5. LT5 Added Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html#post1579114180)

Details for Oil Catch Can Installation (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html#post1581665524)

Say Schrade........tell Daryll (GC) I am in Kauai Hawaii today. He is always wondering where I am. :D

[Schrade]

2. Crankcase Area.
The Crankcase is vented upward through the two large "L" hoses connecting the Cylinder Case vents to the Injector Housing Ports located under the Plenum. This allows the piston ring Blow By to be vented to the Injector Housing.

Does ring blow-by go through the burn, to exhaust?

Hawaii. Pffft...

Not enough Global Warming in SD???

http://zclub.net/forum/images/smilies/extras/toetap05.gif

[Dynomite]

Does ring blow-by go through the burn, to exhaust?

Hawaii. Pffft...

Not enough Global Warming in SD???

http://zclub.net/forum/images/smilies/extras/toetap05.gif

Ring blow by goes into crankcase and then to plenum via PCV then burn then exhaust.
10 below zero this morning in SD ........70 in Kauai Hawaii. ;)

[bradley]

what I have found with my 2 cars if I run the oil level right at the add line .I burn about 1/2 qt in 3000miles . when I first got both cars I ran the oil level all the way up and had to add oil about every 1000 miles . jmho

[Franke]

what I have found with my 2 cars if I run the oil level right at the add line .I burn about 1/2 qt in 3000miles . when I first got both cars I ran the oil level all the way up and had to add oil about every 1000 miles . jmho

I was wondering the same thing as I used to do that in my other vehicles for that very reason but since some newer cars have oil level indicators and warranty stuff I stopped. I don't think my 90 has a oil level indicator in the crankcase or does it?

[bradley]

my 90 doesn't but my 92 does . filling the way I shared I have never had the low oil level light come on in the 92. I have cked it to make sure it still works . I have been changing the oil in both my zr1s this way for almost 120k miles. yes I drive both cars as much as I can .lol what I do when I change the oil is put in 7.5 qts start her up for 20 seconds . then the next morning add what ever I need to to bring it up to just above the add line . usually it isn't very much at all maybe 1/3 qt

[Schrade]

Experimentation and new stuff ! Looks like a summation of just about every one of my posts there Mr. P! http://www.zr1.net/forum/images/icons/icon14.gif


Performance is quantifiable, sound is more subjective.

Performance wise, Marc suggests the Corsa with headers, sans cats, if allowed. The package delivers performance gains w/o resonance (I'm told), but they do have a "tinny" sound that some like and others do not.

The 3" Magnaflow system gives a nice, deep tone w/o resonance. However, the resonator chokes down the inlet to a single ≈ 3" perforated tube running the length of the resonator. Furthermore, there are several abrupt(!) choke and sudden transition points throughout the Magnaflow system (6 on the right side, 5 on the left) (which I believe any flow dynamics expert will tell us is NOT conducive to performance. FWIW).

The B&B has evolved from a pretty much wide open 3" cat-back with significant drone in the 1900-2200 rpm range, to a more restrictive system and "lesser" drone.

Pete, ever experimenting to get the most hp, is running a modified version of the earlier B&B system with Watson headers, and now using the NPP valves to control in-cabin drone. (The word is he can now carry on a conversation since installing the NPPs. Others too have gone that route and agree). Nobody is going to convince Pete that a Corsa is better for performance.

Experimenting goes on. I'm a Warrior (at least in my mind and I try to be:p) which means I'll put up with a little racket if there's hp to be made.*
* or tune to improve upon

I've watched the FBI efforts with great interest, and I believe the gurus have come up with what I consider the best of both worlds - to date at least:

The system that impresses me is the headers (SW or Watson), sans cats, SW type X pipe, no resonator, the Dynamax 17228 muffs with the NPP type gate affixed to one of the two active muffler outlets.** It is a true 3" system from the header collectors to the muffler inlets for least restriction and max performance, and the valve on one of the muffler outlets reduces resonance to a very tolerable level. What's not to like???

I'm not sure what Marc's setup is, but I don't believe it is a Corsa. And, I know he likes quiet for normal driving and has a pair of the Flowmaster dual outlet muffs on the back with 4-bolt flanges on the inlet side so they can be easily removed at the track. A variation of that is to install cut-outs just behind the differential which is perhaps an alternative to the NPP and perhaps just as effective.

Fact is, all of them are a compromise in some respect. Sound, vs. performance, vs. cost... Always room for more experimentation - and new "stuff"!;)YUP - always room for improvement... You are correct Sir!

======================

So to get back on topic here, and not boost my own thread :p...

Problem is oil fouling the burn. Objective is filtering the oil / fumes, sans the 'old' way (catch can).

PCV SOURCE air comes in from IN FRONT of the TB butterfly.

PCV purge is BEHIND the butterfly.

With 2 LARGER vacuums 'feeding' (??? :confused: ) the cam covers ([I]and another vacuum besides, pulling EVAP), and one smaller vacuum PURGING PCV, WHAT'S THE NET VAC DIFFERENCE???

And how much vacuum is necessary to maintain purge?

If only a nominal amount is necessary, then we REDUCE the source ports, move the purge up front of the air filter, and increase the line size enough to maintain pressure differential.

Thoughts? Opinions? More ideas here?




Always thinking; experimenting ... ;)