Positive Crankcase Vents

Competition engines and ancillaries - general discussion
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cantfindausername
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Joined: July 19th, 2006, 6:07 pm
Location: Crawley, West Sussex
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Positive Crankcase Vents

Post by cantfindausername » July 22nd, 2006, 8:42 am

This is something that I have always been unsure of,and that is which is the best way to have a Crankcase Vent set up.

The standard PCV set up on my car (Toyota MR2 Turbo) is to have the it feeding back into the intake pipe just before the turbo. A common assumption on the MR2 scene is that this is due to emmissions etc.

Now, most people complain of having an oily build up from this, coating the inlet to the turbo, and generally throughout the intact tract. Some people fit oil catch cans into to the PCV line and then carry that on to the intake pipe, others fit a breather/filter to it and have it venting to atmosphere.

So my question is this:- Is it better to have the Crankcase gases pulled through using the intake pipe method (with a catch can to "clean" the gases) or would there be sufficient pressure for the crankcase to vent itself i.e using the breather/filter method?

Thanks,
Ant

- just realise this is probaly in the wrong section. Sorry :oops: please move accordingly

SteveNZ

Post by SteveNZ » July 23rd, 2006, 2:02 am

The intake is not designed to pull the gasses out. It is fed back to the inlet for emissions and most probably simplicity also.

The later 3SGTE engines have a box fitted in the crancase breather tube from factory. I assume this is an oil seperator, at least thats what it looks like to me. However there is no drain plug.

Do not just fit a filter to the breather, the oily mess will come out all over the engine and if there is an engine problem it will push out oil everywhere. A catch tank is the best idea. You can fit a filter to the tank or feed it back to the inlet if you prefer. Make sure the spigot sizes and tank capacity are adiquate.

cantfindausername
Posts: 306
Joined: July 19th, 2006, 6:07 pm
Location: Crawley, West Sussex
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Post by cantfindausername » July 23rd, 2006, 9:15 am

Thanks Steve. You're right in what you say about the later Revision 3 onwards engines having the catch can, but no drain facility.

I have an aftermarket catch can that I used to run on the engine before I took it apart. My set up was PCV -> Catch can -> Vented out to the atmosphere.

I think I will go with the idea of re-fitting the catch can but with a filter on it somewhere away from the main block. I think I will also fit a drain facility to the catch can as it would save having to remove it so often.

Ant

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