pcv for performance.

Ok... so am I wrong, or are most guys that are running a lot of boost also running an open to atmosphere type PCV system? I have been trying to run a closed system on a 16v +t conversion, and it seems that everything I try just doesn't work... Is there anybody using a closed system that is proven to be effective? Last thing I tried, was a open 5/8 hose(no flame trap/restrictor) from the oil separator box to a ebay catch can, then to the pre turbo inlet pipe.... only thing I got was about a 1/2 quart of oil in the intercooler and intake track!!!! and the ebay catch can had nothing in it!!!!! what gives. would have been better to just leave it alone. any help please?

Did the 'catch can' have baffles inside? A lot of them are just boxes with two inlet/outlet ports and one drain, and they do nothing in terms of seperating the oil from the vapor. I'm working on a design that's based off intake designs on drag racing boats, as they use acceleration of air in a high pressure zone, then a 180deg bend to help shed moisture onto foam(I'll use sst wool). If it works for water, it will work for oil, so I'm going in that direction and will post pics when finished. So: Run one with baffles, not just the open can style.

Problem I hear about venting to atmosphere is you're losing crankcase vaccum which apparently helps with sealing a motor. Of course this is just off what I've read. I've never vented to atmosphere.

At wide open throttle there's no "vacuum" to be applied to the crankcase anyhow with a traditional PCV set up. You only get vacuum at closed/light part throttle conditions. Even less so with a boosted application. The benefit of pulling a bit of vacuum in the crancase is simply that it reduces the work the pistons do pushing air out of the way on the BACKSIDE of the piston. More vacuum in the crankcase equals less air to push around which frees up a bit of HP. But only if you can create some vacuum under heavy throttle open scenarios. For that you generally need a vacuum pump set up.

To the OP - you need the oil traps/seporators to knock the oil out of the crancase vapor. Even if you vent to atmosphere (solves oil in intercooler) you're going to make an oily mess wherever you vent unless you knock out the oil. Removing the factory baffles hurt you in this case.

^ The PCV pre turbo inlet provides plenty of vaccum. Should be pretty close in relation to the boost you're seeing on your gauge, according to some engineers here. Pre turbo = vaccum proportional to boost.

Anybody drill out the intake nipple a little for a little more pull on an older engine?

atrokz said:

^ The PCV pre turbo inlet provides plenty of vaccum. Should be pretty close in relation to the boost you're seeing on your gauge, according to some engineers here. Pre turbo = vaccum proportional to boost.

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I've wondered about that. Do you have something that illustrates this? Have you tested it?

scotti said:

Anybody drill out the intake nipple a little for a little more pull on an older engine?

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Which one? Just one of the ports?

Anyone ever check out the nipple off the stock oil separator? It's tiny internally.

atrokz said:

Did the 'catch can' have baffles inside? A lot of them are just boxes with two inlet/outlet ports and one drain, and they do nothing in terms of seperating the oil from the vapor. I'm working on a design that's based off intake designs on drag racing boats, as they use acceleration of air in a high pressure zone, then a 180deg bend to help shed moisture onto foam(I'll use sst wool). If it works for water, it will work for oil, so I'm going in that direction and will post pics when finished. So: Run one with baffles, not just the open can style.

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^^This. I just got one from ebay and will be modifying it. The ports are just as you said, just ports. No routing into the can itself and no baffling.

I'll be opening up the ports for 1/2" NPT fittings and one of them will be attached to a copper tube with perhaps a double 180? bend with soldered plates for baffling.

I'll post pics in the "more crankcase ventilation thread"

turbojose said:

Ok... so am I wrong, or are most guys that are running a lot of boost also running an open to atmosphere type PCV system? I have been trying to run a closed system on a 16v +t conversion, and it seems that everything I try just doesn't work... Is there anybody using a closed system that is proven to be effective? Last thing I tried, was a open 5/8 hose(no flame trap/restrictor) from the oil separator box to a ebay catch can, then to the pre turbo inlet pipe.... only thing I got was about a 1/2 quart of oil in the intercooler and intake track!!!! and the ebay catch can had nothing in it!!!!! what gives. would have been better to just leave it alone. any help please?

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Did you get one of these?

Ursan said:

I've wondered about that. Do you have something that illustrates this? Have you tested it?
.

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We didn't graph it out or use gauges, but basic logic defines that there will be an increasing vacuum as the vacuum through the airbox increases when the turbo increases it's rpm. It will reach a limit, and the returns will diminish, but there will indeed be more vacuum at boost than at idle. I should find a vac gauge I don't mind getting oil vapors in to show numbers.

Ursan said:

^^This. I just got one from ebay and will be modifying it. The ports are just as you said, just ports. No routing into the can itself and no baffling.

I'll be opening up the ports for 1/2" NPT fittings and one of them will be attached to a copper tube with perhaps a double 180? bend with soldered plates for baffling.

I'll post pics in the "more crankcase ventilation thread"

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Do it. I gotta stop by my old shop to get it done. Already have a few plans sketched out. Thinking of doing either a spiraled tube feeding off the inlet, with gradually increasing holes on the outside ID of the helix, or, a baffle formed from sheet metal going: Large area - small area - Large area - smooth long 180 bend up - gradually smaller area. They both should separate moisture well using both condensation and centrifugal force, so it just depends what materials and tools I'll have at my disposal.

I believe if you're developing any significant vacuum on the suction side of the turbo the inlet system is far from optimal. Logic doesn't dictate that as boost builds, so will vacuum on the other side of the compressor. Compound turbo set ups illustrate this quite well. The compressor takes the fluid stream at a certain pressure - and compresses it to a higher pressure. Start with a lower absolute pressure (e.g. - vacuum) and you'll get a lower pressure on the other side of the compressor. If you have a restrictive inlet (classic case is a clogged air filter) you'll start to get vacuum at the inlet -- and reduced performance.

I believe the fundamental problem the OP is facing has to do with no oil traps or baffles to knock the oil out of the vapor stream. Crankcase pressure is what's forcing the flow out --- not a significant 'pull' from the inlet side of the turbo. But - it's just an opinion.

fwiw - I've played around with alternative crankcase ventilation scenarios over the decades. Other than venting to atmosphere or having it hooked up to the intake (with a check valve for boosted set ups) everything I've tried has resulted in the same result the OP got. Oil from the engine showing up in places I didn't want it to show up --- outside the crankcase. Usually, in my experimentation, which included connecting it upstream of the intake or power adder, all I succeeded in doing was elevating crankcase pressures thus forcing oil out of the crankcase and past the front and rear crank seals.

OP needs to get his crankcase vapors to slow down and turn a few corners so that the oil will drop out.

OP if you've got multiple quarts of oil in the intercooler..... Time for something different!

My Turbo six vents to atmosphere.... via the standard vent. Very little crankcase vapors under boost in mine.

"Very little crankcase vapors under boost in mine." Good cylinder seal. With more boost (or dynamic compression) usually comes more blow-by and the resulting higher crankcase pressure.

M.H. Yount said:

I believe if you're developing any significant vacuum on the suction side of the turbo the inlet system is far from optimal. Logic doesn't dictate that as boost builds, so will vacuum on the other side of the compressor. Compound turbo set ups illustrate this quite well. The compressor takes the fluid stream at a certain pressure - and compresses it to a higher pressure. Start with a lower absolute pressure (e.g. - vacuum) and you'll get a lower pressure on the other side of the compressor. If you have a restrictive inlet (classic case is a clogged air filter) you'll start to get vacuum at the inlet -- and reduced performance.

I believe the fundamental problem the OP is facing has to do with no oil traps or baffles to knock the oil out of the vapor stream. Crankcase pressure is what's forcing the flow out --- not a significant 'pull' from the inlet side of the turbo. But - it's just an opinion.

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I'll hook up a vac gauge when I can to test it, but I do believe there are more cfms of air as higher rpms are reached. There has to be in order for air to be compressed "more". Same as a turbine engine. As rpm speeds increase, higher volumes of air are injested. I guess we'll know as soon as I test it. Either way, yes, baffles to some degree are needed in the CC. I'll go the condensation via pressure differentials route to achive cleaner vapors.

Interesting discussion!

I'm researching the same topic at the moment and have yet to decide which route I'll take with my car.

Regarding the vacuum in the intake (pre-turbo), I can say this much: On my old 850 Turbo with only a K&N filter of unknown age (PO installed it) and otherwise stock at 16 psi, I saw only 1.5-2 inHg in the turbo inlet at full boost/RPM.

I don't think it's so much a measurable vacuum caused by the engine/turbo that "pulls" the vapors from the PCV hose on the stock setup, but the vacuum-created venturi effect of the air rushing past the PCV inlet at a 90 degree angle. Same concept as the PCV venting into the exhaust--which may just be the best way to do it if you don't have to worry about emissions.

Speaking of using centripetal force to separate out oil and water from the crankcase vapors, I had an idea about this..

What about using a fuel cooler as a catch can to help separate out the oil and water? Ya know, the small canisters with several coils of tubing inside, designed to be surrounded by ice water to cool down the fuel post pump..

Just thinking out loud here.

Ursan said:

I'll post pics in the "more crankcase ventilation thread"

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Click it

Ursan said:

Did you get one of these?

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No... I actually got the 14.99 one... serves my right!! I have seen many with different prices, I was just hoping someone is using something or doing something that definitely works... I hoping to not pay and pay and pay until I get it right. Isn't someone using something that just works.

The way to get vacuum preturbo is a restrictive inlet system. I've posted this before, but with my 4 inch intake , 25lbs of boost pushing 70lbs of air/min, I logged less than 1 inch vacuum. With the gm vacuum pump I saw like 3 inches under full boost.

I think we see a low pressure draft, not vacuum.

Nathaninwa said:

The way to get vacuum preturbo is a restrictive inlet system. I've posted this before, but with my 4 inch intake , 25lbs of boost pushing 70lbs of air/min, I logged less than 1 inch vacuum. With the gm vacuum pump I saw like 3 inches under full boost.

I think we see a low pressure draft, not vacuum.

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That's what I thought.

My pre-turbo intake:



Is just a couple of 45? bends. The MAF is just at the radiator support and the filter is tucked up behind and inside the bumper C-channel.

I've never gotten any vacuum there.

I was able to get "some" when I drilled a 1" hole and installed a grommet. Then I took a 3/4" copper pipe with a 45? hash cut into it facing in the direction of the turbo which causes a slight venturi. Not a lot of vacuum, but certainly more than before. (1" at best)

Nathaninwa said:

The way to get vacuum preturbo is a restrictive inlet system. I've posted this before, but with my 4 inch intake , 25lbs of boost pushing 70lbs of air/min, I logged less than 1 inch vacuum. With the gm vacuum pump I saw like 3 inches under full boost.

I think we see a low pressure draft, not vacuum.

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That's definitely the better way to word it. Maybe a pump setup is really best.