Crankcase evacuation }{ PCV, header evac, vacu...

[Fire67]

Im finally getting the details ironed out for my new combination... I know I do not want to run the stock PCV system because of the oil in the intake. Harold at Port Pros recommended an evac system of some sort over the use of breathers for several reasons.
Basically I know I want to keep negative pressure in the crankcase, but how?
What would be the best and at least affordable route?
Im looking for personal experiences and the pros and cons of each possible route.
Here's what I know, any info you guys can fill me in on would be great.

Vacuum pump evac systems are available with either engine driven (big $$$) or electric pumps. The electric versions are said to be problematic and both are capable or pulling too much vacuum and disrupting the proper operation of the oil pump. Which means you'd need some sort of vacuum regulator or release valve.
Either way, a pump setup will be out of my budget

The header mount evac systems use oil separators in place of breathers on the valve covers, and a check valve threaded to a tube in the header. The thing is Ive heard they will contaminate the exhaust system with oil and shouldnt be used on a street car. But Moroso has a street version of the oil seperator/breather, but doesnt go into details as to whats different.

Then there's always the catch can idea with the factory pcv system. This I dont like because the catch cans Ive seen only seem to catch some of the oil, while the rest still goes into the intake...

Anyone have any input, ideas?
How about filling me in on your setups?
Thanks in advance

[94m6hardtopz]

for a wet sump system on a street car there are a couple of schools of thought,

1. that you want a crankcase pump to keep the pressure down for good ring seal. you have to be careful on a wetsump system though. if you run more then about 10" of vacuum in the crankcase you will have oiling problems. crankcase pumps were really designed for dry sump setup.

2. the other school is that you do want some crankcase pressure to help 'push' the oil into the pump. you can avoid over pressure by using several breathers to keep the pressure down but not eliminate it totally. 2 people that propose this school of thought for wetsump systems is David Rhere (Rhere-morrison racing engines) and Job Spetter Jr. (turbo people). when Job Jrs car was running 7s on 10.5s years ago i saw that motor setup in person. it did not have a pump on it, just breathers. and that car was making over 1500hp from 330ci.

[1bad2k2ta]

fire67 said:

Im finally getting the details ironed out for my new combination... I know I do not want to run the stock PCV system because of the oil in the intake. Harold at Port Pros recommended an evac system of some sort over the use of breathers for several reasons.
Basically I know I want to keep negative pressure in the crankcase, but how?
What would be the best and at least affordable route?
Im looking for personal experiences and the pros and cons of each possible route.
Here's what I know, any info you guys can fill me in on would be great.

Vacuum pump evac systems are available with either engine driven (big $$$) or electric pumps. The electric versions are said to be problematic and both are capable or pulling too much vacuum and disrupting the proper operation of the oil pump. Which means you'd need some sort of vacuum regulator or release valve.
Either way, a pump setup will be out of my budget

The header mount evac systems use oil separators in place of breathers on the valve covers, and a check valve threaded to a tube in the header. The thing is Ive heard they will contaminate the exhaust system with oil and shouldnt be used on a street car. But Moroso has a street version of the oil seperator/breather, but doesnt go into details as to whats different.

Then there's always the catch can idea with the factory pcv system. This I dont like because the catch cans Ive seen only seem to catch some of the oil, while the rest still goes into the intake...

Anyone have any input, ideas?
How about filling me in on your setups?
Thanks in advance

My system may not be unique, but it is different, and may give you some ideas.

The stock LS1 PCV system has a tube that connects to the rear of the driver's side valve cover, goes around the back of the engine, connects to a barb on the rear of the passenger's side valve cover, passes through the PCV, then into the intake. Then there is a barb on the front of the passenge side valve cover that goes directly to the rear of the throttle body.

The LS6 PCV system has a barb at the front of the valley cover just below the intake slightly to the passenger side of the intake. The PCV connects there, then goes directly to the intake.

What we did was use the stock LS1 PCV system as a pressure relief system. It hooks up just like stock, but instead of going to the PCV, it goes to a catch can. I have an LS6 valley cover so we used that for the PCV only put a check valve between the PCV and where it connects to the intake to prevent boost from being forced back into the crankcase. The front barb on the passenger side valve cover is currently capped off, but I plan to run that to the catch can, also. From the catch can, another hose exits and runs to the hat on the supercharger, providing a vacuum source to evacuate the crankcase. There is also a drain valve in the bottom of the catch can. To date, I have not collected a single drop of oil in it. The catch can contains some copper mesh like scouring pads you clean dishes with.

Before we did this, I blew the dipstick out.......not pretty. So, I zip-tied tied it down to the A/C hose until we made the change. Haven't had any problems with the dipstick, but I still want to run the extral hose to the catch can as described above. You will still generate some positive crankcase pressure, but it will not be excessive, so you don't have to worry about blowing dipsticks, seals, etc.

Hope that helps. Good luck.

[Fire67]

96M6hardtopz:
I definitely wont be running a vacuum pump... Too much hassle and/or too much money either way you look at it.
I may end up going with breathers if all else fails, I just dont really like the smell you get in the cabin from them.

1bad2kta:
Does your catch can have an air filter? Or just hose fittings?
The reason I ask is because if it has an air filter, your vacuum source mentioned would then be a vacuum leak right?
The engine builder basically told me that having vacuum in the crankcase would promote ring seal and help build power by lessening the crankcase side pumping the pistons have to do.
I guess I was hoping that someone would chime in saying that there was a good header style evac system that wouldnt let oil into the exhaust...
I'm doing some more searching, trying to find out about these "street" valve cover breathers for the moroso header system. I wonder whats different about these?

[1bad2k2ta]

fire67 said:

1bad2kta:
Does your catch can have an air filter? Or just hose fittings?
The reason I ask is because if it has an air filter, your vacuum source mentioned would then be a vacuum leak right?
The engine builder basically told me that having vacuum in the crankcase would promote ring seal and help build power by lessening the crankcase side pumping the pistons have to do.
I guess I was hoping that someone would chime in saying that there was a good header style evac system that wouldnt let oil into the exhaust...
I'm doing some more searching, trying to find out about these "street" valve cover breathers for the moroso header system. I wonder whats different about these?

Mine is a closed system, no breathers. Ideally, a slight vacuum is desireable, however without a pump, it is almost impossible in a boosted application. Any header evac system runs the risk of dumping oil into the exhaust system. For race only applications, this is not all that bad, or even on the street if you don't have to worry about emissions, but this could wreak havoc on O2 sensors and cats (longer term). Does your D1SC setup have the hose that runs from the PCV to the s/c intake hat? If so, you could run a combination of the header evac and the catch can. This would give you two vacuum sources.

[Fire67]

You know, I never thought of doing it that way... Maybe I can run the pcv on the side of the manifold to the SC intake through a catch can, and then do the header evac system also...
Interesting... Now my gears are turning.

[94m6hardtopz]

youll still get oil mist on the blower impeller. i would either run an exhaust evac or breathers. you get oil in the air/fuel charge and youll be building a motor all over again after it detonates.

[1bad2k2ta]

94m6hardtopz said:

youll still get oil mist on the blower impeller. i would either run an exhaust evac or breathers. you get oil in the air/fuel charge and youll be building a motor all over again after it detonates.

This was a concern of mine, also. The guy who designed the system is not only a mechanical engineer, he is one of the premiere ZR-1 experts in the U.S. and he is no rookie when it comes to this sort of thing. The catch can has a large amount of the copper mesh in it for any oily vapor to condense on. If any of this vapor were to contain any significant amount of oil, it could be detected, as you said, on the blower impeller. It would also likely collect in the intercoolers before being introduced into the cylinders. We are monitoring this at the catch can and the impeller. As I stated earlier, there has not been so much as a drop of oil in the catch can. In actuality, this is safer than the factory PCV system which takes oily vapor and routes it directly back into the intake without the benefit of the condensing catch can/intercooler circuit.

[Fire67]

94m6hardtopz said:

youll still get oil mist on the blower impeller. i would either run an exhaust evac or breathers. you get oil in the air/fuel charge and youll be building a motor all over again after it detonates.

That I cannot allow to happen. That manifold pcv port is pretty well baffled, and with a catch can... I thought itd be pretty clean air before it gets to the intake. Maybe your right though, there's alot of vacuum on the intake of the blower, so the air/oil would be rushing through very fast and probably isnt likely to get separated by a catch can.

It seems every route possible has drawbacks on a supercharged motor.

Would a coat of oil on the inside of the exhaust have any adverse affects on my muffler, or anything else for that matter? Im not worried about emissions, I dont have cats, and I'm sure I could install the tubes after my O2's.

[1bad2k2ta]

fire67 said:

Maybe your right though, there's alot of vacuum on the intake of the blower, so the air/oil would be rushing through very fast and probably isnt likely to get separated by a catch can.

Not true. While the air flowing through the s/c intake tube is significant at WOT and high rpms, the vacuum drawn through a 3/8" hose, the catch can, and PCV is by no means "rushing". A couple of months ago I participated in a dyno day. I wanted to see how much pressure was in the crankcase at WOT. On the second and third pulls, we took the cap off the front barb on the passenger side valve cover and connected a 3' rubber hose. At WOT a slight steady stream of smoke came out. This was pure ring blowby. If the vacuum from the s/c intake through the catch can was significant, this stream of smoke would not have been there, it would have, in fact, been a negative pressure rather than a slight positive pressure.

[94m6hardtopz]

the intercooler would probably catch it even if it did get past all the filters. ill stick with breathers though.

[1bad2k2ta]

94m6hardtopz said:

the intercooler would probably catch it even if it did get past all the filters. ill stick with breathers though.

The problems with breathers are that if mounted on valve covers, they tend to spit fine dropletts of oil everywhere, and at no time is the crankcase under vacuum regardless of where they are mounted. I was originally going to go this route. In fact, in the picture to the left, or up top, you can see one on each valve cover. For me, the closed system provides the least drawbacks and keeps the crankcase under vacuum except at WOT where a slight positive pressure is present.

[Fire67]

Thanks for hashing through this with me guys!
I've got alot to think about, including the packaging of whichever system I go with...
I definitely want negative pressure in there as much as possible, without breaking the bank.
The header evac setup seems like it would be as good as an intake evac setup, but cheaper. Especially if I can baffle the pickup points enough to keep the raw oil out of the exhaust.
Allthough, the raw oil would do great at keeping the pipes and muffler from rusting on the inside
But if it'll require catch cans to keep the majority of the oil out, I'll just buy one and go the intake evac route.

[94m6hardtopz]

1bad2k2ta said:

94m6hardtopz said:

the intercooler would probably catch it even if it did get past all the filters. ill stick with breathers though.

The problems with breathers are that if mounted on valve covers, they tend to spit fine dropletts of oil everywhere, and at no time is the crankcase under vacuum regardless of where they are mounted. I was originally going to go this route. In fact, in the picture to the left, or up top, you can see one on each valve cover. For me, the closed system provides the least drawbacks and keeps the crankcase under vacuum except at WOT where a slight positive pressure is present.

according to david rhere not making vacuum in a wet sump street engine is not a bad thing.