Postive Crankcase Evacuation

Start by reading through that, so you will better understand my opinions on PCV Modification do's and don'ts.

The article mentions that increased mileage on the motor will lead to increased piston blowby. It doesn't mention that increased cylinder pressures also lead to increased blowby. Which means in the best case scenario, you've got at least one factor that leads to increased blowby and two if your motor isn't freshly rebuilt.

Why is that so important?

Because blowby gases contain a bunch of nasty stuff, from unburnt fuel to hydro carbons from the combustion process itself. At best, the combustion process has burnt all of the fuel and you only end up with nasty soot mixing with your oil...that's OK right? No.

Blowby is the #1 reason your oil is black when you change it. So even with the motor running naturally aspirated and the stock PCV System working at 100% you STILL get lots of blowby mixing with the oil. So much so that it turns totally black long before you are scheduled for a change. The oil cleanliness factor determines how fast your bearings wear as well as ALL the other lubricated surfaces in the entire motor. Sounds important when you think of like that huh? It is. Oil isn't changed because it's worn out...it's changed because it's contaminated.

Remember that we:
1) Just increased the cylinder pressures across the board by adding a turbo.
2) If your motor isn't fresh then you're already venting blowby into the oil.
3) If the tune isn't perfect you're adding increased blowby, in this case it's in the form of unburnt fuel. Adding boost requires the tune to be rich in order to not suffer from knock. Most consider this the "safety margin". It isn't bad in itself because it's necessary for most daily drivers. However, if the tune isn't perfect, you're pumping fuel into the oil.
4)Cranked up the load / temperature of the entire motor causing further oil breakdown.

Knowing that, do you still want to take the stock system and weaken it? By that I mean any system or modification to the system that removes vacuum from the crankcase. Obviously we don't like the blowby gases being fed back into the intake manifold. It coats everything with carbon sludge and reduces the effective octane ratio of whatever fuel you'rein using. The next few things are idea's that don't work as well as the stock system. Yes they bypass the recirculation back into the motor, but at the cost of ruining your oil.

Having the valve covers vented to the atmosphere doesn't PULL blowby gases from the sump, it allows them to vent. The venting takes place when the sump fills up with vapor or the heat causes the vapor to rise on it's own. Doesn't sound very effective huh? That's because it isn't.

Having the PCV valve connected to the intake pipe pre-turbo doesn't PULL blowby from the motor. There is NO VACUUM before the turbo. When the turbo is spooled up it does pull quite a bit of air, however, when you're on boost you're also creating the most blowby. You also have to run an air / oil separator in-line so as not to have oil and carbon coat your entire intake tract. But wait, doesn't that just let the gases go back into the intake anyway? Hmm...

Those are the two most common setups that don't work. There are many other options that people have tried, but the fact remains. If you remove vacuum from the sump, you add crap to the oil.

What are our options then?

How about anything the mind can come up with, so long as the sump sees some type of vacuum related evacuation.

I like to keep things simple. So I choose to improve the factory system. I mean why not, it works and it's already in place. What parts can be improved? Well the PCV valve isn't designed for boost, so lets start by either adding an extra check valve that doesn't allow boost to creep past or swapping the stock PCV valve for one that's designed for boost.

The stock air / oil separator isn't ever changed. So lets add a air / oil separator in-line. One that allows us to monitor how much blowby we're actually removing and has changeable filters. I recommend the filters from Home Depot that they use for air compressors. Cheap and easy to install = win. In two simple steps we just increased the effectiveness of the stock system.

Another thing I do is swap oil filters in between oil changes, to cheap and to easy not to do.

Not enough? Want to remove the gas from going to the intake entirely?

You can run a vacuum pump. They can be had in the junkyard for about $40 from any older GM V8. They can be installed where ever because the pump is electric. Simply run an air / oil separator between the PCV valve and the pump and your done. Now you have vacuum even under boosted conditions. You can also buy aftermarket systems that go all the way to $550.

The other thing you can do is run a header mounted evacuation system. They are under $100 but only pull blowby when you're under a load. When idling there won't be enough exhaust flow to create the venturi required to pull the blowby. I also can't say without speculation what rpm and load would be enough to start the venturi effect. I'd use this method combined with the vacuum pump if I wanted the best of both worlds.

Questions?

WD

This is what I am familiar with.
Your Constructive Criticism of it could also be applied to the factory system though. Without higher RPMs or WOT you don't have a ton of vaccum either... so I think the Exhaust pulling method is best because it creates vacuum and also still has to travel through the Catalytic Convertor for those who are environmentally conscience.

I'm probably going with the GM Vacuum pump. I've read that if done correctly it actually put enough vacuum on the sump that it stopped a rear main seal leak. That's impressive for a $40 pump and some heater hose...lol.

Combine the 2 and you'd be golden

I'm just running a breather, and you KNOW how much work I put into my motor... Plus the fact that I kept stock compression (actually probably HIGHER, since it's built to closer tolerances)... I could probably use this.

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Here's the Summit Racing Header Mounted Kit, $39 for the whole kit, minus 5/8's hose.

Let me dig up the part numbers for the Electric Pump stuff.

WD

Pretty basic setup

That is the pump I'll probably use though. I'm hunting for a few alternatives right now.

Got a link that sells those pumps new?

WD

here's the way i did mine to improve my stock PCV system.
http://forums.nicoclub.com/zer...06595

i like the exhaust gas set-up since it would have vacuum during boost when the PCV closes. Vacuum pump would be really nice too.

I've been really busy but i will take pictures of my setup collecting blowby gas to prove that this really works.

http://www.summitracing.com/pa...large

Thanks!

http://cgi.ebay.com/ebaymotors....m245

also here is a site that I read on the subject. It has some good info, some not applicable to our setups but good none-the-less:

http://www.dragstuff.com/techa....html

Modified by ace0073 at 6:30 PM 8/26/2009

You seem to have done a lot of research on this but the good thing is i think you finally understand the how the PCV system works. I remember giving you info about my set-up and i guess you ignored it so i didnt care to help...but i guess now you KNOW!

Don't mistake what I'm saying. The system will work fine if you add a air / oil separator and a new check valve to the stock setup.

The people that are adding an exhaust mounted evac system and wiring up vacuum pumps should be quite able to tune the car themselves. Or at least they are aware that when you change things on the motor you need to verify the timing and AFR's.

If you're wondering how much of a change this will cause simply unhook the vac line coming from the PCV valve and plug it. Check you AFR's and base timing. Tune accordingly.

WD

now with the vacuum pump, would it be long lasting on a daily driver? i was thinking of making it run with the check vavle, so it would kick on at idle and WOT(tied in to the TPS). the rest of the time just use the check valve method. maybe i am wringing my brain too much?
this pcv is no joke, the tuner shop i went to for some welding told me to vent it atmosphere...

If running the vacuum pump would a catch tank with baffles and packing be enough to protect the pump?

Modified by koukiKA240 at 3:24 AM 8/29/2009

Quote, originally posted by trackslut240 »

this pcv is no joke, the tuner shop i went to for some welding told me to vent it atmosphere...

To be fair though, that will prevent the RMS from blowing out... because the 'mini' filter becomes the path of least resistance.

It just won't increase oil life.

Did you read the part that said THERE IS NO VACUUM BEFORE THE TURBO? You can't source something that isn't there. Vacuum is created by a force pulling air against a restriction. You have air being pulled through the turbo but there is no restriction on the other end to cause the vacuum.

Does that help?

Quote, originally posted by trackslut240 »

WD thats an awesome explanation of the whole PCV mystery. thanks any links to getting the check valve coz i looked one up on mcmaster carr, which seems to do the job well. http://www.mcmaster.com/#about...e3ue8 the valve i thought of is 7775K61 for $11.97 1/8" cracking pressure .3 psi, also the lowest Cv(Cv factor (coefficient of volume) is the amount of water (in gpm) that will pass through a fully open valve at 1 psi with 1 specific gravity (60° F).) just need you inputs, thanks now with the vacuum pump, would it be long lasting on a daily driver? i was thinking of making it run with the check vavle, so it would kick on at idle and WOT(tied in to the TPS). the rest of the time just use the check valve method. maybe i am wringing my brain too much? this pcv is no joke, the tuner shop i went to for some welding told me to vent it atmosphere...

I don't know if I'd use the valve in your link.

I know for a fact that the PCV from the 87 Buick GNX will work very well and it's only $3 and available at any Autozone

Buick GNX PCV Valve

You can either ADD that one inline or replace the stock one with it. I'd add it in

WD

+1 for Sticky!!

When my engine is out in a few weeks I'm planning on installing a check valve and a home depot filter.

so thanks for the alternative makes my life easier.

I was just messing with you, I like to give all our Northern members a hard time The staff guys we have up your way catch hell in the Mod forum

Quote, originally posted by Chris28 »

Wait, so that Buick PCV valve is a check valve?

A PCV valve IS a check valve. All it does is allow liquid or gas to move in one direction. Any reverse flow closes the valve.

WD

Looking forward for your pictures.

I may be completely off on this, still getting a grip on this PCV business.

Actually, I have the same question.

So WD, what's your opinion on removing the PCV system and plug those holes in regards to the risk of boost leak?

http://www.ka-t.org/forums/vie...f5ca7

Or just lose the PCV system entirely like I described above. Worrying about a "possible" boost leak isn't worth not having crankcase evacuation. Don't believe anyone that says different, they simply don't understand.

WD

WD, thanks for your input.

I have pics somewhere of the last time I cleaned mine, it was a tar like substance that smelled like burnt fuel and oil nasty as f***.

I know it works better cause I had the line kinked due to a hasty engine install, my oil lasted only 1500ish miles before I felt the NEED to change it....
500 mile mark normally the oil has turned and it now stays that golden color longer.

Glad a thread with research and info has landed, dont let it fall off the front page maybe people will find it

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r.i.p. Dad I miss you
06/14/54~04/18/09
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r.i.p. Lee
09/01/89~09/28/06

WD

It does have some flaws to it, but it gets the job done.
it has ups and downs.
The thing has no filter which was a plus when I cleaned it ,a little dawn in both sides ,rub a little and its sparkly clean again. But the design is to let the oil drip out of the bottom, fine and dandy on a air line for tools and what not but not so hot as its a vac leak, thats when you put the plug on.The leak is minute but there as you can hear a clear hiss unless its blocked..

I'll go snap a shot, I didnt clean it with my last oil change so it should be dirty still.