Crank Case venting solutions for FI..your thoughts???

Ok, this is something I have never really seen anyone talk about in length so here it goes.

On a stock car we all know how the crank case gets it ventiation. You have a tube going from the valve cover to the TB to get a vac. source and to help burn off some of the oil vapors coming from the motor, and we have a PCV valve that is looped into the intake manifold.....blah blah blah blah so on and so forth.

Now once you had a forced induciton to the car the PCV system is pretty much worthless since you are pressurizing the intake system of the car. The TB line can not be used or it will pressurize under the valve cover and more times than not the PCV will just pop out of the intake. So what do you do?

I know in ATI's kit they just have you put a breather on the valve cover, plug the TB line, and run a line from the PCV down to the intake side of the blower. Thats all fine and dandy but how good does it work? And the only other problem with that is that it sucks oil all thru the intake system and if you do have a somewhat loose built motor your going to just coat everything in a fine mist of oil....and if you have a blow thru MAF, your going to coat it as well.

Now most drag guys use a header Evac which can create tons of vac., Hardcore road race guys more often than not use a Dry Sump....so they have their problems covered.

So what about us street guys that still want to screw around on the race track? Header evacs suck to much oil to use for 20mins on a road course, dry sumps are pretty pricey and not really needed for the occasional trip to the track.

So here's what I thought up and put on the car. I have a converted LT1 AIR pump being used as a vac. pump and it is pulling from the stock PCV location in the intake (without the valve) there are two breathers in the valve covers with small baffles on them and the TB line is blocked off. So this techincally isn't going to pull a hard vac. on the motor but should keep the crankcase clean, correct?
Some pics of the motor....
http://a9.cpimg.com/image/DD/AC/22210269-3455-02000141-.jpg
http://a8.cpimg.com/image/DC/AC/22210268-4ec4-0200014B-.jpg

Keep in mind this is a brand new motor and I have yet to get into the boost with it, but I got under it to do a second oil change after 150 miles to keep it clean and there is a fine mist of oil all under the front of the car (the vac. pump is mounted under the battery). I'm thinking about putting a catch tank on the car to keep it clean, but is this normal? Should I even have it on the car at all? I do notice if it isn't on I do see some slight smoking from the valve cover breathers once it is warm but nothing major.

Thoughts, ideas, solutions? Normal?

I tried using the LT1 air pump, but it wouldn't pull enough vacuum to do anything. Next I plan to try an actual vacuum pump off a Ford or Caddy.. I already have a vented catch bottle to vent the pump to.

Currently, I have breathers in both valve covers, and a check valve on the PCV hose. The PCV mainly works at idle, since at WOT you don't have much vacuum. Seems to work ok, but I still have a small leak on my oil pan.. although I think that is coming from the return line fitting.

Pan-evac systems don't work too good with mufflers, just enough back pressure to make them pull more oil than vacuum.

There is a list of donor cars for the vacuum pumps on my tech page...

http://www.turbomustangs.com/forums/showthread.php?s=&threadid=6083

there is an option.....he did post an update post and said that the pump pulled 15" of vacuum but that was on the bench and not on the actual motor

maybe give him an email and ask him if he had a chance to put it on the motor yet

Originally posted by 1LEThumper
Ok, this is something I have never really seen anyone talk about in length so here it goes....

There was an informative, semi lengthy thread a couple months back. Don't recall if it was here, adv. or tech though. Do a search. BTW, the AIR pump is virtually worthless.

Well if the AIR pump is worthless, they (local shop) did something to it to make it work better because it does pull, and it pulls enough to get an oil mist after driving for an hour or so.

Hey Anthony

I did a lot of reading on this topic and I concluded based on the opinions of some apparantly informed folks that the LT1 air pump would not be enough of a vaccum. texlurch has a great explanation on the topic, you check it out yet?


my thread on this topic.
http://web.camaross.com/forums/showthread.php?s=&threadid=146563&highlight=vacuum+pumps

telurch excellent page
http://camaroz28.cardomain.com/member_pages/view_page.pl?page_id=199561&page=9

I actually tried the F-body AIR pump on mine. I plugged the PCV valve, and hooked the suction side on the pump to the rear of the pass valve cover. I also have a catch/breather tank on the outlet side. When I fired it up, it immediately started smoking out of both tailpipes. I pulled the hose off the valve cover, and hooked a vacuum gauge up, it was only pulling maybe 3" of vacuum. You need around 12 to make any difference. Here is what my hookup looked like:

http://images.cardomain.com/member_img_a/190000-190999/190723_102_full.jpg

Ignore the breather on the valve cover, that was removed.

Now, 1LEthumper, on yours you said you still have the breather and PCV hooked up, so you are not pulling a vacuum per say, just sucking the oil and air out of the valve cover.

The whole idea is to create a vacuum in the crankcase, and to do that you need a sealed system. If it is vented, you are just basically pulling some air thru, and with it the oil mist. That is why you run a catch can with a breather on it, and drain it occasionally.

And the AIR pumps are designed to push air, not pull it, so they are not that efficient. I am still searching for an electric vacuum pump, so don't give up yet!

:cool:

What are the technical reasons for creating a vacuum in the crankcase?

The way mine is run, is that it has 2 open breathers in the valve covers, and the vac/AIR pump is pulling from the stock PCV location just thru a fitting. I knew it wasn't going to pull a vac. on the crankcase, I was just trying to help circulate air thru the motor untill I figured out how I was going to do it with out hurting anything. I just figured this would simulate how it would work with the PCV pulling from the intake side of the blower and the valve cover breather that ATI puts in the kits....correct?

The main purpose (correct me if I'm wrong here) is to get the air out of the crankcase letting the pistons move up and down easier so they do not have to fight the air pressure in the crank case as they move up and down. Correct?

What about using a vac. pump off of one of the Mod motor'd Cobras? Also how do you tell whats good and bad as far as Vac. readings go, and should it suck some oil when it does run all the time?

One other question, do you even need one on there or can you just block the PCV and run the 2 breathers and still be fine on a FI car? Granted you'll loose a little bit of power not having the vac. pump but would it do any damage to the motor??

Originally posted by 1LEThumper
The main purpose (correct me if I'm wrong here) is to get the air out of the crankcase letting the pistons move up and down easier so they do not have to fight the air pressure in the crank case as they move up and down. Correct?

No, that is a fallacy. Cuz, as one piston goes up, one is coming down. IF that idea had any merit, which it don't, one piston would offset another. The intent is to remove any pressure to assist/improve compression ring seal.

What about using a vac. pump off of one of the Mod motor'd Cobras? Also how do you tell whats good and bad as far as Vac. readings go, and should it suck some oil when it does run all the time?

Idea is to prevent pressure buildup in crankcase (from ring blowby) when PCV doesn't function, ie at WOT. IOW, picks up where PCV leaves off. BTW, may be fine/ok for drag racing, but I wouldn't recommend a sealed system on the street. That is not the intent.

One other question, do you even need one on there or can you just block the PCV and run the 2 breathers and still be fine on a FI car? Granted you'll loose a little bit of power not having the vac. pump but would it do any damage to the motor??

Wouldn't recommend disabling PCV.

Ok...so the only reason to have a vac. pump is to have something working during WOT? Just a question then if you have breathers on a stock motor are you not getting rid of the vac. all together then since you just opened the system?

Also on a FI car, the PCV isn't going to work when its under boost since its a one way valve and when it gets boost, it can't really do much. I can't see the inlet side sucking enough to over power the boost in the intake manifold, right? I know some of the factory turbo cars like DSM's have a PCV system but I'm not sure how they work.

Ok so whats going to be the best bang for the buck setup for a FI car? The way ATI had it set up it just didn't seem right to me. Plus it just blew oil all over the inlet pipes.

Originally posted by 1LEThumper
Ok...so the only reason to have a vac. pump is to have something working during WOT? Just a question then if you have breathers on a stock motor are you not getting rid of the vac. all together then since you just opened the system?

It will certainly generate less vacuum than a fully sealed system.

Ok so whats going to be the best bang for the buck setup for a FI car? The way ATI had it set up it just didn't seem right to me. Plus it just blew oil all over the inlet pipes.

As noted, I prefer a non sealed system, IOW, more passive. Texlurch has endorsed a more dedicated system that is sealed and obviously draws more. He obviously has had good results, so no way can I state that his is not the better approach. My personal view, is that it is a little extreme for daily street use, that's all. So, now you have a choice, as to how effective you want your system to be. Some experimentation could be conducted to determine if sealed is noticeably more effective than a modified non sealed system, with a restriction in the line, in lieu of the non restricted free flow oem style.

Originally posted by arnie
There was an informative, semi lengthy thread a couple months back.

http://web.camaross.com/forums/showthread.php?s=&threadid=82357

GOOD Reading.

"The oem system is not a sealed system. It draws in metered air from TB. The breather would
replace the TB as a source of incoming fresh air."

Hows this work? The motor can't suck in its own air thru a breather. And I thought that was the hole point of that line was to suck out of that vavle cover.

ok, so then what is a passive system on a FI car?

Originally posted by 1LEThumper
Hows this work? The motor can't suck in its own air thru a breather. And I thought that was the hole point of that line was to suck out of that valve cover.

ok, so then what is a passive system on a FI car?

If I understand the ? correctly, the oem system is not intended to hold a given amount of vacuum in the crankcase. The blowby and mist are drawn out the PCV in the cover, and replaced with fresh air from TB or a breather. If too much pressure builds up in the crankcase, it starts pushing out the pcv till the vacuum isn't able to stay ahead. It then closes the one way valve. The pressure then continues to exit out the breather/TB, which is ordinarily, the intended inlet.

If enuf vacuum can be generated in the crankcase, ring seal is improved to the point of diminishing blowby. In reality, the more passive oem style of blowby elimination, with an auxillary pump, is less effective in generating appreciable vacuum, to improve ring seal a noticeable amount, even if it were a full time system, without some form of restriction in the fresh air inlet. For the MOST benefit in ring seal improvement, now we are where Texlurch is at, a fully sealed full time system.

Thanks, Ken. Don't you guys sleep nites?

You have to remember, in my case anyhow, that my car is far from a daily driver.
And since the LT1 AIR pump didn't work, here is where I am currently at so far as breathers...

Plugged stock air line on TB.
Breathers on both valve covers
inline check valve on the PCV hose (I used one off the power brake booster, since it is 3/8 and fit the hose)

The PCV works at idle and high vacuum, once the motor goes into boost, it closes and I rely on the breathers to vent the crankcase pressure.

The idea of the vacuum pump is to increase power due to better ring seal, and also less pressure in the crankcase working against the crank, rods and pistons. It isn't a crutch for too much blowby.

For a daily driver I would try running what I have now.. it doesn't draw any more oil into the intake then the stock system did, and cures the problem of boost pressurizing the intake thru the PCV valve. Or you could leave the airpump on, but vent it to a breather tank.. and also try one of the seperator type breathers that the Mopar ran (which comes in the Pan-evac system everyone sells)

That just made me think of another question. Does the stock brake booster have a check valve in it? I've never heard anyone talk about it, so does it get pressure blown into it when the car goes into boost?

So then I can just use the pump to draw air thru the motor and keep the breathers, its not really creating a vac. but more or less just simulating the stock PCV system since it is drawing out of the PCV hole, correct?

Wonder why ATI wanted to pull it from the inlet side of the blower and all of the other little lines they wanted hooked up.

Originally posted by arnie
Thanks, Ken. Don't you guys sleep nites?
Didnt you know i'm a robot?

Originally posted by arnie
If I understand the ? correctly, the oem system is not intended to hold a given amount of vacuum in the crankcase.

The OEM system is to remove gasoline vapors from the crank-case so the motor doesnt blow itself up. I've personally seen it happen on higher milage motors that sit and Idle alot. The rings dont seal as well at idle and vapors get into the crankcase, eventually fire gets past the piston rings and boom! blows the valvecovers off.
I was going to do the A.I.R. pump thing when i had my motor out a few months ago but that thread that was just linked to discouraged me from it.

Been reading, and i am interested in this subject. So my setup does 20" of vacuum at idle. Is that good or bad? No vacuum assist as far as i know...

Originally posted by 1LEThumper
That just made me think of another question. Does the stock brake booster have a check valve in it? I've never heard anyone talk about it, so does it get pressure blown into it when the car goes into boost?

OEM put one there, so if functioning/not removed, will prevent boost from being blown into it. However, do not know strength of check valve.

So then I can just use the pump to draw air thru the motor and keep the breathers, its not really creating a vac. but more or less just simulating the stock PCV system since it is drawing out of the PCV hole, correct?

Correct! There is little question generating a measureable vacuum in the crankcase with a semi or fulling closed system (as Texlurch is advocating) will benefit ring seal. The system you subscribe to will depend on how you prioritize improved ring seal. With an electric auxillary vacuum pump ( in lieu of mechanical pump) it would be easier to set it up to operate at WOT only. Part throttle can be handled with the oem PCV system, seeing improved ring seal would not be a major concern when engine is generating vacuum in the intake tract. Yet, at WOT more priority could be given to ring seal. Check valve on fresh air intake side to close when exposed to a certain vacuum level, anyone?

Wonder why ATI wanted to pull it from the inlet side of the blower and all of the other little lines they wanted hooked up.

Not familiar with ATI setup. :shrug:

Been reading, and i am interested in this subject. So my setup does 20" of vacuum at idle. Is that good or bad?

Measure how much is being generated in the crankcase. Ah, the vacuum we are referring to, is that in the crankcase itself, not in the induction system. As far as your ? is concerned, that is about right for an oem type cam.

Originally posted by arnie
One other question, do you even need one on there or can you just block the PCV and run the 2 breathers and still be fine on a FI car? Granted you'll loose a little bit of power not having the vac. pump but would it do any damage to the motor??

Wouldn't recommend disabling PCV. [/B]

Arnie, why wouldn't you recommend that? I am running one breather and I just capped off my PCV, so far it feels the same, but I am wondering now if maybe I shouldn't.

Originally posted by Burn_Out
Arnie, why wouldn't you recommend that? I am running one breather and I just capped off my PCV, so far it feels the same, but I am wondering now if maybe I shouldn't.

Unless you are running a dedicated vacuum pump, what would you gain by deleting the PCV valve? It is there to suck crap out of the crankcase, whether blowby residue or oil mist, or any other crap floatin' around. The breather won't do anything other than relieve any pressure buildup. AFAIC, the PCV system would do the job more effectively. If you are concerned about contaminating the air/fuel charge, :shrug: unless you are experiencing excessive blowby, I don't see it as a noteworthy factor.