Sealing the crankcase

[shoz123]

I don't know if this is the proper forum for this post. If not please move it.

On my '97 and '93 Ford Taurus SHOs there is a secondary intake valve butterfly arrangement. This opens at a higher rpm for more power. The runners in the intake are tweaked for low end power and this opens the second intake valve to the intake manifold and adds power up high.

This butterfly assembly is called an Intake Runner Manifold and gets carbon-ed up badly from the oil ingested through the PCV system. Plus the Surge tank part of the intake fills up with oil.

Recently I have added a catch can between the oil separator between the heads and the PCV valve on my '97 and have been collecting the condensate before it is sucked up into the engine.

I have found that the mixture is ~50/50 mix of oil and water. I now seal off the fresh air intake part of the PCV system and have noticed that the water condensate is almost eliminated. Plus I have 10" Hg of vacuum on the crankcase on the '97 and ~2" Hg on the '93.

Any comments?

 

[TheLoneRanger]

Shoz, I don't think it's a good idea to close off the intake air on PCV systems. The engine needs the fresh filtered air to circulate and help remove crankcase gases. The PCV system is also designed to use metered air, and closing the intake throws off the metering. This is what's giving you the high crankcase vacuum in the 97.

Unfortunately, carbon build-up over time is a fact with PCV systems. It can't be eliminated entirely, but good engine maintenence will reduce it to a "normal" level. Make sure the oil splash guard is in place where the PCV tubing goes into the valve cover. It sounds like you're getting too much oil into the PCV hose, so I would stop it at the source, rather than try to filter or condense it out.

Oh, and I wouldn't worry about the water condensate. It won't hurt anything, and a little water vapor induced into the intake manifold will help to control detonation. WWII fighters used water injection at high power settings for the same reason. They didn't want "pinging" when they went after a bogey.....

Just my two cents.....

 

[Shannow]

I agree, I think that with the closed system, you have a "vacuum", but are not necessarily purging the combustion leakage/residues from the sump.

I'd also be worried how the crank seals like that sort of DP over a long period of time, rather than the 1/4 mile sprints that an evacuated sump is generally used for.

 

[Drew99GT]

Exactly, even with a catch can, you still need a fresh air source for the engine's vacuum to suck out crankcase vapors, or you'll end up with real high vacuum in the crankcase. That means the vacumm from the induction where the PCV hooks to the intake, won't be allowed to actualy suck out vapors from the crankcase. Catch cans are a wonderfull thing because the still allow positive crankcase ventilation but won't gum up your intake tract.

 

[shoz123]

But wouldn't the blow-by gasses provide some flow? There are still gasses being drawn out as evidenced by the condensate I collect from the catch can. Also with the crankcase under a partial vacuum the lighter most volatile contaminate components will be more readily be pulled from the oil.

It is my feelings that the added water from the atmosphere, when mixed with the oil, will actually cause more gunk to be drawn through the PCV valve.

 

[TheLoneRanger]

Hi Shoz. The best way to think of the PCV is as a "balanced" system. It's designed for a specific flow into the engine intake at all rpm's, and the PCV air intake helps to meter the flow. Under certain conditions (such as low rpm/high load), the crankcase gases will actually flow out of the intake air side of the PCV. As an engine ages and produces more blow-by, more gases will come out there, because the intake manifold metering is not enough to control the greater gas volume.

I would look at a better baffling system for your PCV, since you're getting excessive oil into it. Or maybe the baffle in the valve cover has come loose?

 

[shoz123]

I could spend $500 on a crankcase vacuum pump. Which is a proven HP producer. Instead if I do as I have done I can maintain 7-10" Hg on the crankcase and reduce the amount of oil passing through. I do not consider my blow-by excessive. The motor only has 15K on it. I am trying to stop ingestion of oil through the PCV system because of coking issues on the secondary intake butterflies.

I understand how PCV systems work very well. My 3" TB will suck up plenty of air to run the motor and needs none from the PCV system to run correctly.

quote:

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I would look at a better baffling system for your PCV, since you're getting excessive oil into it. Or maybe the baffle in the valve cover has come loose?

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The flow is not out of the valve cover but into it normally. The PCV system pulls it's gasses from in between the heads through an oil separator.

 

[TheTanSedan]

There is a product out there with which I have no experience, but you may wish to have a look: it is called the Condensator, out of Canada.

 

[Shannow]

shoz,
I'd be careful pulling serious vacuums in a street engine. (I've done it too to see what the difference was).

It's a proven horsepower producer, I agree. But the engines that it's typically used on run a few miles a quarter mile at a time, of at most, a couple hundred miles in an afternoon.

Your engine's seals are designed to keep oil in, and dirt out. With maybe a slight DP one way or the other. Running high DP could shorten their life considerably.