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Crank Case Ventilation fully explained. (Naturally aspirated edition.)

Thread: Crank Case Ventilation fully explained. (Naturally aspirated edition.)

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Posts: 41-50 of 165
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2010-08-19 16:04:22
#41
Originally Posted by enohand
hmmm.....so by installing a RR valve cover on my non rrr will work & i can remove the oil catch can from the front of my block?
Already asked and answered in posts #7 and #8.
Edit: The roller rocker cover will not fit. See here: http://www.sr20-forum.com/turbo/41416-valve-cover.html

Originally Posted by enohand
would there be any issues with doing this ^^^^ & also removing the EGR stuff completly?
EGR questions like that belong in this thread:
http://www.sr20-forum.com/general-maintenance/24765-egr-delete-information.html
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2010-08-19 22:55:52
#42
you compile your ideas and research so well.
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2010-10-14 19:12:55
#43
I'm still working on this thread. I've added a great idea for crank case ventilation mods to the first page.
This method involves using an electric (or mechanical) air pump designed to evacuate the crank case while separating the oil. "Smog pumps" on older American or European cars can be retrofitted to perform this function.

Read more about it here:
::: DRO ::: Tech Section - Power from Thin Air - 1/7/05s
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2010-10-14 19:15:18
#44
For those of you looking for high flow, high quality, really good performing oil separators, here's the current cream of the crop:
MANN FIlters - MANN Provent 200

See in use on this turbo e30:
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2010-10-14 19:23:41
#45
What about on a roller rocker motor, removing the pcv valve and replacing it with a normal hose connection, then running both hoses to a catch can and then run a hose from the catch can to the plenum. This would create a vacuum under idle conditions and would still draw the air through on WOT. Thoughts?
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2010-10-14 19:49:40
#46
Ben why not run a vacuum pump?

I do this on all the race engines i touch. Then you can eliminate all the crap up the top end of the head. Most guys dont run A/C so the pump could be placed there.
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2010-10-14 19:50:38
#47
Originally Posted by mongo_tuned
What about on a roller rocker motor, removing the pcv valve and replacing it with a normal hose connection, then running both hoses to a catch can and then run a hose from the catch can to the plenum. This would create a vacuum under idle conditions and would still draw the air through on WOT. Thoughts?


If I understand what you're trying to do, I have to say it'd a bad idea. You don't want to remove the PCV check valve because it is slightly more complicated than just a simple valve. You would be creating way too much vacuum in the crank case by doing things the way you describe. Lots of vacuum in the crank case is good, but allowing the entire vacuum of the engine to suck on the crank case unrestricted is WAY too much vacuum. Also the PCV valve provides a restriction so you don't suck in enough crank case air during idle and cruising to change the air/fuel mix much. Read how the PCV check valve works here and you'll likely see what I mean.


1. At idle and under lift off deceleration conditions the intake vacuum is strong and the blow-by production low. The PCV is fully open and in this state restricts the flow path from crank case to intake manifold to a low level. This level is however still sufficient to draw all blow-by produced into the engine for re-burning. Flow travels from the crank case to the intake manifold in this mode.



2. At low load under cruise conditions the intake vacuum is moderate and so is blow-by production. The PCV sits half way open and in this state restricts the flow path from crank case to the intake manifold to a moderate level. As above, this level is however still sufficient to draw all blow-by produced into the engine for re-burning. Flow travels from the crank case to the intake manifold in this mode.



3. At high load under wide open throttle conditions pre-boost the intake is very close to atmospheric pressure and blow-by is significant. Depending on how good the breather from the crank case to the pre-throttle intake is, the PCV valve will either be closed or slightly open. If the breather is good, the PCV will be closed and all flow of blow-by will be from the crank case to the turbo inlet or equivalent. If the breather is restrictive there will be a pressure build up inside the crank case which will overcome the spring pressure in the PCV and cause it to open allowing flow of blow-by from the crank case into the intake manifold. Because the crank case is under pressure the breather will also be flowing blow-by into the intake pre-turbo or equivalent.



4. During a back fire, when the engine is off or when the engine is seeing intake boost pressure the PCV valve is closed and any blow-by is exiting through the breather into the intake pre-turbo or equivalent.



5. In the case of boost being present, the PCV is closed and sealed (or close enough to it to not worry about it) and blow-by is at an all time high. Because it is unlikely that the crank case pressure will exceed boost pressure all blow-by flow must exit through the breather. Because the breather is the only exit path it must flow well enough to prevent pressure build up inside the engine. Boosted engines typically produce a lot more blow-by and also are on average more likely to be driven hard.



It should be noted that during idle, lift-off, cruise and low load conditions that there is a cross flow of fresh air into the crank case from the breather and blow-by and fresh air out of the crank case into the intake manifold. This is because the PCV is drawing more gas than the engine is pushing past the rings. This style of setup is more than adequate for the vast majority of vehicle users running naturally aspirated and low boost engines in a normal non-abusive way.
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2010-10-14 19:51:55
#48
Originally Posted by Autech
Ben why not run a vacuum pump?

I do this on all the race engines i touch. Then you can eliminate all the crap up the top end of the head. Most guys dont run A/C so the pump could be placed there.
Absolutely. That's actually the latest diagram I've made and just posted a couple minutes ago.

I have two more major methods to post and then I'll get to the turbo guys.
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2010-10-15 02:00:18
#49
still waiting on the turbo edition!!

Great read, I think I understand everything but I did have a question about running blow through and the hose that ran from the intake, before the TB and after maf, to the valve cover. I know you don't want this anymore because you will pressurize the crankcase. I have it running back to my turbo intake, which means air is once again being measured twice and I'm losing some of the air that the maf is reading??

Fired the car up the other night for the first time after dropping it in and didn't have any of the catch can lines hooked up. I can definitely understand how this all works after seeing the smoke that rolls out of those things when the motor warms up. Guessing fuel/oil vapor...wish I had a video of it, it would make a great addition to your thread.
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2010-10-15 02:28:20
#50
Originally Posted by nsusammyeb
still waiting on the turbo edition!!
Yah I know I'm getting to it. Sorry. :o

Originally Posted by nsusammyeb
Great read, I think I understand everything but I did have a question about running blow through and the hose that ran from the intake, before the TB and after maf, to the valve cover. I know you don't want this anymore because you will pressurize the crankcase. I have it running back to my turbo intake, which means air is once again being measured twice and I'm losing some of the air that the maf is reading??
No big deal. That's how the DETs are done from the factory. You're doing great with that setup.
Edit: Okay I may have been wrong about that. I think your MAF placement is problematic. Yes you double-meter air, and you also run the risk of contaminating the MAF with oil. The factory setup has the recirc done after the draw-through MAF.
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