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Old 05-02-2008, 12:04 AM   #1
tico915007
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Default Benefits of a Breathable oil cap

I feel like an idiot but here it goes.....This is a 2007 STI mods are HKS catback and Cobb Intake. Maybe someone can help, yesturday I was adding some oil to my car was missing half a quart. To make a long story short i was in a hurry and i left the oil cap sitting on my intake manifold for about 24 hours unoticed obviously. While i was driving the car i was amazed to how much it pulled it had its initial jump but instead of staying consistent after 5,000 RPM it kept pulling like a champ. Thinking i was going crazy i took my buddy for a drive and he said my car felt faster and this morning my Girlfriend asked me if i did something else to make my car faster...... I finally notice my oild cap was off check my oil lever and it was fine. My question is does running with your oil cap off release presure in the motor allowing you to inadvertly run more boost or am i going crazy..... On my car before a 2004 gto i know when people were running boost on them the got a breathable type oil cap to releave crankcase presure is this so on our car?
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Last edited by tico915007; 06-09-2008 at 11:49 AM.
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Old 05-02-2008, 12:05 AM   #2
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this is what im talking about

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Old 05-02-2008, 06:20 AM   #3
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n/m---
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Old 05-05-2008, 11:33 AM   #4
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wow. i never heard of a breathable oil cap, but i'm subscribing to see if anyone knows anything about this.
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Old 05-06-2008, 10:53 AM   #5
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This to me does make sense... Kinda.

When the oil cap is on the engine is constantly creating a vacuum, which could be like saying the engine is "pulling itself", which creates a constant vacuum. You may notice on some high-powered Chevy motors that the valve covers have breathers (usually have K&N style filters on top of them.) The picture you provided with the filter that replaces the oil cap... I just don't like that idea, plus the design scares the crap out of me. (What is holding it on?!) Air filters block most of the airborne debris, but never 100% so who knows what is getting mixed up with your oil.

Anyways, removing the oil cap eliminates the vacuum in the crankcase which in turn allows the engine to move more freely. It would be like going from a shirt that is a little snug to one that is a size or two bigger.

Last edited by magnum2066; 05-06-2008 at 10:59 AM.
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Old 05-06-2008, 11:09 AM   #6
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This is the first I've heard of the breathable oil cap. I'm interested in learning more on it and what applications can utilize it.
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Old 05-06-2008, 02:16 PM   #7
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Wouldn't this kill the vacuum needed for the assisted brakes (or is that vacuum created from some thing/place else)?
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Old 05-06-2008, 02:29 PM   #8
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we have something similar to that on our cars its plumbed to the intake...
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Old 05-06-2008, 04:16 PM   #9
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Quote:
Originally Posted by prometheum View Post
we have something similar to that on our cars its plumbed to the intake...
Yeah, and there is always a vacuum on that end (suction intake), and the PCV valve (one way check valve) on the other end of one hose.

I just remember auto-x'rs running out vacuum and the pedal getting hella heavy (then plowing into cones soon afterwards) as the stories went.
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Old 05-06-2008, 07:46 PM   #10
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Eliminating vacuum in the crankcase has nothing to do with the brakes. Two completely different systems.
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Old 05-06-2008, 07:58 PM   #11
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Quote:
Originally Posted by magnum2066 View Post
When the oil cap is on the engine is constantly creating a vacuum, which could be like saying the engine is "pulling itself", which creates a constant vacuum. You may notice on some high-powered Chevy motors that the valve covers have breathers (usually have K&N style filters on top of them.)
my 1.9L ford escort had exactly that. It came factory with a line plumbed into the intact tract behind the filter, and was replaced along the way with a mini k&n style filter. (held on by hose clamps, it wasn't moving!)
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Old 05-06-2008, 08:06 PM   #12
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Quote:
Originally Posted by magnum2066 View Post
Eliminating vacuum in the crankcase has nothing to do with the brakes. Two completely different systems.
correct the master cylinder is plumbed directly to the intake manifold on the driver's side
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Old 05-06-2008, 08:12 PM   #13
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There is a decent amount of pressure in the crank case especially in these EJ's.

Why not tap your oil cap with a barbed fitting and run it to a catch can? (along with the other breather lines) I think I'm going to do this.
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Old 05-07-2008, 07:53 PM   #14
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isn't there a company that makes high boost pcv valves? I'm sure I've seen that somewhere.
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Old 05-08-2008, 10:54 AM   #15
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Found this related link, seems like a good read for/against:
http://www.supersixmotorsports.com/pdf/PCVBypass.pdf
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Old 05-08-2008, 11:11 AM   #16
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so i wasn't going crazy potentially this could of made my car feel "faster"...... it wasnt like it was 100 hp more just felt like the car was losser almost like i was accelarating downhill all the time
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Old 05-09-2008, 02:21 PM   #17
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ok so this is a good thing...why wasnt i aware of this before ,,,,,,,can the effect be seen on a normaly aspirated car
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Old 05-09-2008, 03:35 PM   #18
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Yep. Even non-turbo vehicles have a vacuum while the engine is running.
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Old 05-09-2008, 03:46 PM   #19
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Ya know when i get dyno'd i'm going to do that test.
This would be interesting to see.
I have 2 oil caps i'll drill one and put a breather on it and have stock as well.
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Old 05-14-2008, 01:59 PM   #20
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Quote:
Originally Posted by Chandy69 View Post
Ya know when i get dyno'd i'm going to do that test.
This would be interesting to see.
I have 2 oil caps i'll drill one and put a breather on it and have stock as well.
sounds hood let us know your results
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Old 05-14-2008, 03:00 PM   #21
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Ummmm... what about the vacuum helping the sealing of the rings?
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Old 05-14-2008, 03:02 PM   #22
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Vawy intewesting!!
http://www.speedwaymotors.com/p/1877...Breathers.html
I found this link. Does anyone know the diameter of the oil cap hole? I would be willing to buy one for 15$ shipped and see if it does any good for a RS.
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Old 05-14-2008, 07:47 PM   #23
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Keep in mind that although your car feels faster, you will get no gain in HP. The only difference would be how fast you are able to rev up. Again it reduces the load on the engine, which almost has the same effect as putting on a lightweight flywheel (or pulley). You are merely freeing up more power to the wheels.
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Old 05-14-2008, 07:56 PM   #24
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There you go!! There's part of the next Periodic Review Of Nasioc video
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Old 05-14-2008, 10:58 PM   #25
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Quote:
Originally Posted by magnum2066 View Post
Yep. Even non-turbo vehicles have a vacuum while the engine is running.
ALL

repeat

ALL

internal combusiton engines are, for all intents, vacuum pumps and create vac as a function of their functioning

FI engines just change where they are creating vac when on boost compared to off boost operation.
They ALWAYS suck air in at one end and force it out the other end while in operation.
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