PCV Catch Jar Question - Page 2 - Fuelly Forums

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Old 11-13-2006, 12:27 AM   #11
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Quote:
Originally Posted by repete86
Really? I was under the impression that it reduced emissions because the gas being sent back into the engine is cleaner. It's essentially taking some oil that would be sent into the engine to be unintentionally burnt with gasoline out of the mix so that what goes back into the injector is clean gas.

How does it negatively alter my emissions?

This is how it works.

The PCV (postive crankcase ventialtion) is a system that attempts to improve emisions that would normaly be vented to the atmosphere by reintroducing them back into the intake to be burnt.

Inside the engines crankcase (everything below the compresion rings) there is oil mist (windage) and blow by (compression that has leaked past the rings).
These have the effect of presurising the crankcase area.

This in turn would create leaks at the seals and gaskets , so the engine degigners must make a vent system to keep the crankcase presure low.

In the old days they would just vent to the outside air.

Since this unburnt gas and oil mix is not good for the environment they decided to send it back to the intake to be consumed in the combustion chamber., hence the PCV emissions system.

This provided the needed venting and effectively controlled the emisions.

Alterning thePCV system and changing to an oil catch can will increase emisions and violate EPA laws.
If you catch the oil then you must dispose of it somehow , this waste is polution.
If the top of the oil catch can is vented to the atmosphere you may still catch the oil but not the gas fumes.
This too is polution and a violation of EPA laws.

If the vent on the top of the oil catch can is plumbed back to a vac line then it will introduce those fuel gasses back into the intake., but this fuel is unmetered and wont improve FE.

If it did ,, then worrn out engines that make lots of blowby would be superiour FE machines , but of course, we know thats not true.



PS ,, the only time an oil catch can could possible improve FE is on a realy nakkered engine.
A poor engine which was attempting to burn its blowby waste could foul the spark plugs causing only a partial burn of the intake charge thus dropping engine power which in turn would need more GO pedal.- Meaning less FE.
On this engine an catch can or just venting the crankacase to the atmosphere could improve FE by allowing a more normal combustion.

Of course it would be a lot smarter to rebuild the dying engine instead.
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Old 11-13-2006, 12:55 AM   #12
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Quote:
Originally Posted by theclencher

I see catch cans possibly keeping the intake a bit cleaner and possibly reducing plug fouling (but that shouldn't be a problem on a good engine anyway) but beyond that I don't know.
Exactly rite
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Old 11-13-2006, 07:19 AM   #13
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Quote:
Originally Posted by repete86
In 30 miles, the bottom of it is already filling up..
For sure you have significant ring/bore wear.

Before adding the catch can did you notice a large amount of oil in the air filter ?

I bet you did.

In a good engine there should be NO oil in the air filter housing.
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Old 11-13-2006, 08:10 AM   #14
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A properly set up catch can (at least by this method) does not vent to the atmosphere, just to clear things up. Some people do, but I did not.
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Old 11-13-2006, 11:05 AM   #15
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Mine doesn't vent to the outside air either. The PCV system still goes from the engine block to the intake manifold, but between the two there is a chamber that allows the heavier gasses like oil to condense and become liquid again while the gasoline goes back into the manifold. At no point does this go back into the atmosphere. The gunk captured by the catch can will be recycled along with regular used motor oil.

There hasn't been any carbon buildup on the filter yet. It seems like with any older car though, this is pretty normal for a few thousand miles until the system is cleaned out.
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Old 11-13-2006, 10:56 PM   #16
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Quote:
Originally Posted by repete86

There hasn't been any carbon buildup on the filter yet. It seems like with any older car though, this is pretty normal for a few thousand miles until the system is cleaned out.

?Carbon build up? ? . there wont be any.
You can get oil mist combining again into oil residue in the air filter housing but not carbon.

?until the system is cleaned out?
The PCV system is not like a rubbish storage device that will then deposit it into the oil catch can after its fitted.

The rate that the pick up can will fill at depends on a few things.(including driving style , brand of oil etc)

Vertical scores or deep scratches on the cylinder wall usualy will show with a consistant rate of oil loss.(into the can)

Vertical scratches on the rings will like-wise show consistant oil loss.

Other ring problems , chipped faces , loss of tension , general ring or piston ring groove wear , or sticking rings may work with minimal oil loss at some times and then at other times a lot of oil loss.
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Old 11-13-2006, 11:10 PM   #17
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I've seen carbon on the filter on a car that I owned in the past. Something was wrong with the throttle body and carbon was getting to the air filter for some reason. After a few thousand miles of it, my mechanic found it during an oil change and the entire back of the filter was black. I was going to change the filter about 200 miles ago, but when I took it out and took a look at it, it was still in good condition, so I left it in. The back of the paper was still pretty white. No oil mist is making its way to the filter.

I haven't had it in long enough to know if it's going to fill at a constant rate, but I will in a few days. I need to drive alot for my work, so I'm taking a look it whenever I get to a location. I drove about 120 miles today and it seems to me that it's filling a little slower, but I'll know for certain after a few more days of driving it around. I am aware of what the PCV system does though. When I said "clean out" i didn't mean the PCV system, but the whole engine interior. If this oil isn't being run into my injectors to be burned the engine should naturally clean its self out (especially with the acetone that I've been adding). The carbon buildup inside the engine will at least slow down because this oil isn't being burned any more.

I don't think that there are any significant problems with the cylinders. I still have good compression and drive it enough to know that it's running fine.
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Old 11-13-2006, 11:32 PM   #18
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Quote:
Originally Posted by repete86
I've seen carbon on the filter on a car that I owned in the past.--- I am aware of what the PCV system does though. When I said "clean out" i didn't mean the PCV line, but the whole interior. If this oil isn't being run into my injectors to be burned the engine should naturally clean its self out.--
You cant get carbon in the air filter.
You can get black dried fuel (crrap) burped back to the inside of the air filter element if the engine backfires.
You can also get dried oil residue which may also look carbon-ish on the outside of the air filter element but this is most likely just dried oil (crrap) from the emmision lines.
But it is not carbon in the same sence as what is found in the exhaust ports of the engine.
Carbon requires that oil (or oil based product) be burnt , and I dont think theres much oil burning going on in your air filter element housing .--do you?

?If this oil isn't being run into my injectors to be burned the engine?
The oil (blowby waste) NEVER goes through the fuel injectors.
It is reintroduced in 2 places depending upon throttle position , either at the air cleaner element housing or to the inlet manifold.
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Old 11-13-2006, 11:49 PM   #19
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Quote:
Originally Posted by onegammyleg
You cant get carbon in the air filter.
You can get black dried fuel (crrap) burped back to the inside of the air filter element if the engine backfires.
You can also get dried oil residue which may also look carbon-ish on the outside of the air filter element but this is most likely just dried oil (crrap) from the emmision lines.
But it is not carbon in the same sence as what is found in the exhaust ports of the engine.
Carbon requires that oil (or oil based product) be burnt , and I dont think theres much oil burning going on in your air filter element housing .--do you?

?If this oil isn't being run into my injectors to be burned the engine?
The oil (blowby waste) NEVER goes through the fuel injectors.
It is reintroduced in 2 places depending upon throttle position , either at the air cleaner element housing or to the inlet manifold.
The old one didn't backfire, so I guess it was dried oil getting to the housing, and since I don't have any oil on my air filter on this car, it's obviously taking the second route back and going into the engine. The PCV catch can takes much of this oil out. I don't like oil burning in my engine. It's bad for emissions. Believe it or not (though this could just be placebo effect), the engine seems to be running a little quieter and smoother now with the catch can.

Also, and I know how much everyone here hates tank to tank comparisons, I think that this may have been responsible for my city driving mileage going up to 32.2 on this tank rather than the 29-30 norm. I'll see if the trend continues.
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Old 11-22-2006, 05:05 PM   #20
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Cool

It's not the oil from he PCV system that causes the problem of messing up the intake tract. That problem is causes by EGR. A light coating of oil is nothing, but the clogging of passages, and orifaces with carbon is the actual problem.
I hate to stay it... But as a mechanic, racer, engine builder, and tuner. Catch cans are completely stupid. They are balked at, as they should be. They do not solve a problem. They *mask* it.

If you want to get rid of the fact that small quantities of oil are sucked through the engine. Pull your valve cover<s> off. Anyplace where there is a breather hole attached, (Keep in mind that most engines use both a PCV going to high intake manifold, AND an open breather hose going to pre-throttlebody vacuum) shield this area from oil that flies about via the valvetrain. Most properly designed engines () will already have mostly shielding, and need little modification. Oil not only flies directly to the breather hole, but it also is shot on the valve cover wall, and runs down it at a high rate of speed. This is where most directly shielded engines fail.
  1. Clean the valve cover of oil with acetone
  2. Cut, and bend metal strips to cover said passages, while allowing for vacuum the ability to suck ambient gasses from the crankcase
  3. Weld, braze, or JB weld your pieces on the breather
Congratulations. You've now actually *solved* a problem. instead of simply trying to cover it up.





You also get other benifits, such as replacing valve cover gasket<s> that are common to leak in many instances. You see the condition the engine oil, and maintenance is on the engine. Many engines have other maintenance proceedures can be done at the same time by a gneeric home mechanic.
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