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Old 10-24-2010, 06:02 PM   #1
MrZone
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Default Q for engine guru - engine "breathing"

I am very interested to hear some opinion on my "worry"..

I have a build engine (2.0L JDM v8 head w/ 2.5 USDM STi block with forge pistons). Very mild engine and running only 300whp. It is recently build.

I am venting the block and head via the Grimmspeed AOS. I have begin to wonder if the AOS is providing enough breathing for the engine (as both head and crank are routed into AOS then breathing out of 1 outlet - PLUS - the engine is also pushing some amount of air up the oil filler neck).

I am very tempted to vent the head and/or the crank to atmosphere (capping both line with a K&N crank vent mushroom filter).

I understand the side effect of oil everywhere and environmental issue, etc. But is it better for the health of the engine?

Is there a way to "measure" the internal pressure of the engine? Maybe I am just worrying too much?

Any opinion will be very helpful and appreciated.
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Old 10-24-2010, 07:04 PM   #2
Patrick Olsen
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How do you know it's pushing air up the oil filler neck?
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Old 10-24-2010, 10:31 PM   #3
iana
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lol grimmspeed AOS. that is all
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Old 10-25-2010, 12:41 AM   #4
Murphdog
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Do you track the car at all. I'm running 25 psi on a 35r and on the street for DD the Grimmspeed worked perfect. I ran into issues at the track when turning high speed corners and running high boost I would get oil from the valve covers sucked into the seperator and pushed through the turbo inlet. I ended up going to the Crawford V2 and all my problems were solved. But I'd think at your power level you will probably be fine. Grimmspeed makes great products and for a street car or mild build I think their A/O is one of the cleanest and nices out there.
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Old 10-25-2010, 01:08 AM   #5
MrZone
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I only do those once a year lapping day... running around 18psi boost.

There are some amount of air coming up the oil filler neck - I notice the air when I am at idle and putting my hand over the oil filler neck.

Any method of ensuring I do not have excessive pressure build up internally? Venting to atmosphere... any thought?
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Old 10-25-2010, 01:14 AM   #6
Pacemaker
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Air out of the filler neck is normal, smoke in the other hand would be bad.
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Old 10-25-2010, 02:05 AM   #7
Murphdog
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Yup air out is normal, smoke is bad. I cant see any real down side to venting to atmosphere other than what you said before about the mess and enviroment issues. But if your intercooler is clean and oil free I'd leave it how GS recomends.
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Old 10-26-2010, 10:45 AM   #8
MrZone
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thanks guys. The GS AOS is fine.. I am oil free from middle line (AOS -> Intake).

My biggest concern was the engine might not be venting as efficiently and sufficiently as I am worry the AOS is creating a bottleneck in terms of properly venting the head and the crank.

Reason for my concern were two areas:
* both HEAD and CRANK are now piped into the AOS with only a SINGLE outlet
* the AOS is also venting the air coming up from the oil filler neck

Am I thinking too much?
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