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Old 09-12-2006, 10:54 PM   #1
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pvc oil mileage?

i finaly got around to making a PVC filter catch can thingy for helga. used http://www.crxmpg.com/pcv.html

my queston is my filter looks just like the last pic in that thread only after 80 miles. does that mean my engne is more warn out than svoboys? he said that pic was after sevral hundered miles. could helgas heart be wearing out?
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Old 09-12-2006, 11:03 PM   #2
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I think it just means your engine is letting oil slip by. Worn out rings perhaps?

At least the catch can is doing it's job.
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Old 09-12-2006, 11:48 PM   #3
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Hi Diemaster

The oil being catched in the can is from oil blowby.
Blowby is oil vapors that come from inside the engines crankcase.
They are casued by compresion leaking past the compresion rings (usually 2) on the pistons.

Some engines will create a little blow by even when new depending upon the surface of the cylinder bore and the finish and material of the rings.

Unless allowed to escape , blowby will presureize the crankcase causing oil to leak through or break gaskets, so they must vent them somehow.
In the old days blowby was just allowed to escape via a vent tube from the block , but then they discovered that it wasnt too good for the environment and it allowed the oil to drip on the roads , which isnt good either.
So then they designed PCV , ?postive crankcase ventialtion?.

The PCV system allows this airborn oil to be consumbed in the combustion chamber.
If an engine doesnt a normal amount of blowby it is no problem for the engine to consume, in fact , a little oil may lubricate the upper cylinder area and improve engine and valve life.

If you are getting a lot of oil in your can , then it is likely that you have engine wear problems.
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Old 09-13-2006, 05:46 AM   #4
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Does it use oil between changes? When I first put mine on it was like that I thought that I was going to have to empty it every 500 miles but it seemed to slow down. I just dumped it at 1500 miles and it was half full (it's only about 1.5 oz). I'm not using oil and I running synthetics.
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Old 09-13-2006, 06:20 AM   #5
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Hi zpiloto

If an engine is making a considerable amount of blowby you can rest assured that you are getting crankcase dilution as well.
The fuel in the air that would normally be compressed that is getting past the rings will go into the oil.
So it may indeed look like you are not using oil , but in fact you are.
In real bad cases it can look like you are getting more oil added (rising on the dipsick) over time but its really just liguid gas in the oil.

A normal engine will use a little oil between changes.
If it looks like you are not using any , then you probably have crakecase dilution from worn rings.

PS , depending on the exact bore or ring wear an engine may start to use oil , and then stop , then start using it again - quite randomly.
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Old 09-13-2006, 09:47 AM   #6
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Quote:
Originally Posted by onegammyleg
Hi zpiloto

If an engine is making a considerable amount of blowby you can rest assured that you are getting crankcase dilution as well.
I'm sorry I should of said I don't have to add additional oil between changes. I guess the question is what is a considerable amount of blowby. Mine fills pretty quickly but the whole container I'm guessing only holds about 4 oz of fluid. So even if you dump it every 500 miles it still not a lot of fluid. What is your experience with the fill rates of catch cans and what would be excessive?
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Old 09-13-2006, 05:53 PM   #7
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Quote:
Originally Posted by onegammyleg
The PCV system allows this airborn oil to be consumbed in the combustion chamber.
If an engine doesnt a normal amount of blowby it is no problem for the engine to consume, in fact , a little oil may lubricate the upper cylinder area and improve engine and valve life.
I'm under the assumption that the PCV catch device will prevent carbon and "gunk" deposits from building-up in the intake manifold, injectors, and cylinder bores. I'm not an expert on combustion dynamics, but would the small amount of blow-by already lubricate the upper cylinder rings, walls and valves, and then be collected? Furthermore, does fuel not have lubricating characteristics?

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