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Old 05-15-2008, 12:06 AM   #26
Mechie3
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I'm not sure of the benefits, but I know that for the street prepared autocross classes you're allowed to change the oil cap, but the rules don't permit the fitting of a breather. This leads me to believe that, at least in some applications, there is a potential benefit. Whether it's making power or freeing up power (which pretty much has the same effect) it's worth someone with time and the proper measuring tools to do some tests.
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Old 05-30-2008, 02:34 PM   #27
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I am actually almost done making this...

I used a metal mesh breather filter from Spectre 11.99

A cheap oil cap from Kragen Auto... 10.99

1.5" long of hosing ... 1" think with a inlet of about 3/4" Got it for free cuz it was soo small hahah

I am going to bore a hole in the top of the oil cap. Then the breather slips into the top of the hose, clamps down with clamp. The bottom of the hose (inside the oil tube) will be fitted with a mesh washer for a sink, inverted. Last protection will be a mesh screen below that. Pics to follow soon...

I will report the results.. Could be fun...cost me less than $25...

Last edited by bue car; 05-30-2008 at 03:24 PM.
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Old 05-30-2008, 03:00 PM   #28
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very interesting...

keep us informed!!
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Old 05-30-2008, 03:15 PM   #29
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will do!

not going to lie but the set up looks pretty friggin sweet

I hope the height is not an issue...
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Old 05-30-2008, 11:02 PM   #30
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bue car...have any pics of your setup, wanting to do this myself.
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Old 05-31-2008, 05:08 AM   #31
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wow i never knew that.
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Old 06-01-2008, 02:00 AM   #32
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I can think of no benefit at all that a free breathing crankcase would help. Years ago crankcase gases were simply vented to the atmosphere via a downtube under the car. Beginning somewhere around '70 anti pollution measures were fitted to engines. One was a PVC valve. This stands for Positive Crankcase Ventilation. With this system gasses in the crankcase were sucked into the intake manifold and these gasses were then run through the engine and out the exhaust. The crankcase does not create vacuum or pressure, in fact it doesn't create anything. It is simply a chamber that houses the crankshaft, oil, bearings, connecting rods, etc.

So why does it need ventilation and where are these gasses the PVC valves, including the ones on WRX's and STI's, indeed almost all engines, coming from? It is simply blow-by and a slight amount of oil particulates from all the fast moving parts spinning about. Hot gasses always slip past the piston rings, the more engine wear to the cylinders/piston rings, the more blow-by. The higher the boost and rpm, the more blow-by. This blow-by gas goes into the crankcase and needs to be vented in some manner. Todays engines, at least unmodified ones, run everything including blow-by gases from the crankcase through the intake system, through the engine, through the catalytic converter and out the exhaust.

A filter on an oil cap or on the PVC hose serve the same purpose, they let the crankcase gasses be vented to the atmosphere outside of the engine. HP gain, I doubt it. Hwy61
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Old 06-01-2008, 03:11 AM   #33
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Quote:
Originally Posted by hwy61 View Post
I can think of no benefit at all that a free breathing crankcase would help. Years ago crankcase gases were simply vented to the atmosphere via a downtube under the car. Beginning somewhere around '70 anti pollution measures were fitted to engines. One was a PVC valve. This stands for Positive Crankcase Ventilation. With this system gasses in the crankcase were sucked into the intake manifold and these gasses were then run through the engine and out the exhaust. The crankcase does not create vacuum or pressure, in fact it doesn't create anything. It is simply a chamber that houses the crankshaft, oil, bearings, connecting rods, etc.

So why does it need ventilation and where are these gasses the PVC valves, including the ones on WRX's and STI's, indeed almost all engines, coming from? It is simply blow-by and a slight amount of oil particulates from all the fast moving parts spinning about. Hot gasses always slip past the piston rings, the more engine wear to the cylinders/piston rings, the more blow-by. The higher the boost and rpm, the more blow-by. This blow-by gas goes into the crankcase and needs to be vented in some manner. Todays engines, at least unmodified ones, run everything including blow-by gases from the crankcase through the intake system, through the engine, through the catalytic converter and out the exhaust.

A filter on an oil cap or on the PVC hose serve the same purpose, they let the crankcase gasses be vented to the atmosphere outside of the engine. HP gain, I doubt it. Hwy61
+1

On larger engines, the crank case was kept at vacuum via intake for safety reasons, not emissions. At high temps, lube oil creates a fine mist, and if mixed with air between the upper and lower explosive limit, could pose a risk of explosion. I seriously doubt this is a problem with smaller engines. Hell, ship's propulsion diesels actually had blast doors, which would blow out to relieve pressure from a crank case explosion and then spring reseat immediately afterward before air could be sucked in to create another explosive mixture...

As far as HP is concerned: HP is related to the physical properties of the engine as well as rpm and cylinder pressure. If the crank case is in a vacuum, there would be no net "pumping" losses (if you can even call it that ) because it is acting on all of the pistons, regardless of whether they are moving out or in from dead centers I'm not sure how much a vacuum in the crank would help seating the rings on the intake stroke (the only stroke the cylinder could potentially see a vacuum IN the cylinder) any thoughts?
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Old 06-01-2008, 03:49 AM   #34
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The OP is NOT crazy.

I did the same thing forgot to put oil cap back on.
But it does abit of go, nothing crazy just "free-er". Actually the OP did a really good job, of explaining, I'm not even going to try. Don't believe it....try it

I put mine back on, afraid it would screw something up.....



SO...would anything negative happen by venting it.....
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Old 06-01-2008, 01:32 PM   #35
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Unbaffled vented systems are not allowed on a drag strip for the same reason you can't spray the intercooler. Oil or water on the track could cause unintended wheel spin resulting in a blown engine or losing control of someone's car or both. An open vent could allow oil to escape and end up on the track.

Unscrew the oil cap with the engine running. Stick a piece of paper over the opening. In a properly functioning engine the paper should flap up and down rapidly. This is due to the pistons moving up and down. Of course when one piston is moving down two things are happening. The downward/inward moving piston is reducing the volume of air inside the crankcase creating a slight increase in internal crankcase pressure, blowby gasses add to this from the same cylinder. But, this is negated by other pistons moving upward which increases the volume inside the crankcase offsetting the effect of the downward moving pistons. The upward moving piston does not however compensate for blow-by gasses.


An engine with a hole in a piston, broken rings or severe wear will cause the paper to flap in an abnormal manner and a severely worn engine, the kind that blow a lot of oil smoke will have constant air blowing out the oil fill cap indicating serious wear or other problems and time for a rebuild. The only areas of vacuum on an engine occur when the pistons are in the intake position, moving downward with the intake valve open. The crankcase is sealed from this vacuum (PVC valve line exception) but the intake components are under a vacuum condition due to the pistons sucking in air and fuel. This vacuum is least at WOT and non existent with a turbo or supercharger, both of which replace the vacuum created with pressurized air. Your boost gauge is connected to the intake system reading either vacuum or boost.

The OP needs to pay a visit to a dyno, My money says no increase in HP. Venting won't hurt anything but in many engines you will blow oil out the opening so baffling and a filter are necessary. At 7,000 rpm there is a lot of oil particulates flying around inside the crankcase. I doubt they are explosive in a regular car engine, never heard of one blowing anyway and in a high performance engine, including a Subaru boxer running 20+ lbs of boost the engine will be tuned on the rich side to keep things cool.

Of course some unburned gasses are going to bypass the piston on the compression and power stroke so theoretically if there was something to ignite this mixture it might be possible for an explosion to occur. Never heard of one though. 6,000 hp dragster engines.....that is another story. Same for huge marine engines. I'm not sure about these but if the engineers added spring loaded blow out vents then they did it for a reason. Hwy61

Last edited by hwy61; 06-02-2008 at 02:03 AM.
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Old 06-01-2008, 01:40 PM   #36
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Above posted twice for some reason. Deleting second post. hwy61

Last edited by hwy61; 06-01-2008 at 06:01 PM.
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Old 06-01-2008, 03:54 PM   #37
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pics will be uploaded today!

iwill be doing a 80 mile run today and post physical results

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Old 06-01-2008, 05:38 PM   #38
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please do! what all did you need to do this? what filter? clamp? hose?
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Old 06-01-2008, 08:39 PM   #39
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Default my set up...

Here is the side view. On top is the Spectre MeshBreather...11.99



This has a 3/4 inch rubber tube extending down...

I fit this into a 1 inch hose...about 1.5 inches long.

then i set the clamp that came with the filter around the neck.

Then i bored a hole in a cheap oil cap...10.99

to bore the hole i used the drill bit that you use to cut door knobs with... not sure of the name...

use a 1 inch

Then needle nose pliers to pull the tube through...

bottom view:

inside the tube i squeezed a screened washer found in kitchen sinks...

On the first run, the car feel like it looses a little torque. .. I plan to run a 40 mile freeway stretch i will post tomorrow as i dont have a comp at home
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Old 06-01-2008, 08:49 PM   #40
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nice work man, looks very clean
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Old 06-01-2008, 08:50 PM   #41
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This is friggin' interesting! And I clicked on this thread because I expected the OP to get flamed. I'm in for the long haul on this one, I want to see where it goes.
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Old 06-02-2008, 01:04 AM   #42
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Ok after my post yesterday I did some thinking and searching....

The crankcase pressure is actually METERED AIR. So one thing to look into is how much is it changing the a/f.
I discussed this with a few suby friends too, and one of them said you might possible get more blow-by since the crankcase pressure is being released. dunno how you'd test that though...
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Old 06-02-2008, 02:09 AM   #43
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Quote:
Originally Posted by bue car View Post

Then i bored a hole in a cheap oil cap...10.99
" I don't want to hear you boys say anything over 50 cents is "only" or "cheap". Dad, about 1965..

I like your "can do" attitude blue car. It's how you and the rest of us learn things. Important things. How about this test for all the boys and girls here. Take an oil cap and install a vacuum line through it, thread it under the hood and into the cockpit where it needs to be hooked to a nice boost gauge. Make a number of passes with the engine under load, different RPM, etc. while a buddy makes a written record of what is happening with the pressure/vacuum inside the crankcase. Make him pay ya for the fun and for science too. Hwy61
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Old 06-02-2008, 02:17 AM   #44
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Quote:
Originally Posted by Nicklz View Post
Ok after my post yesterday I did some thinking and searching....

The crankcase pressure is actually METERED AIR. So one thing to look into is how much is it changing the a/f.
I discussed this with a few suby friends too, and one of them said you might possible get more blow-by since the crankcase pressure is being released. dunno how you'd test that though...
Are you sure about that? I don't think so at least not in an amount that is significant.

Actually your crankcase is totally separate from the intake system ( except for the PCV valve). The by-pass valve does release metered air back into the intake system but not into the crankcase. Air in the crankcase is an entirely different matter and in itself has little I expect to do with metered intake air. But it is constantly sucked out of the crankcase by the vacuum created in the intake via the PCV valve but does not pass the MAF sensor. I don't know how to test this either.

What I still want to know is why there would be any increase in boost pressure per the thread title? Hwy61

Last edited by hwy61; 06-02-2008 at 02:28 AM.
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Old 06-02-2008, 01:30 PM   #45
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The oil cap is too tall the first way. I took the clamp off the pushed the breather all the way in...fits perfect. The small bulge created from pushing the breather into the hose is enough to seal the air. I will post pics soon of the set up again and in the car... i am at work and cant do any uploading...

So on the free way


Sounds nice. The car ran smooth...no CEL's. I notice that below 2000 rpm if you are driving slow...the car feels like a heavy sedan. The go just isnt there..is almost like the pedal is soft.

Now when you open her up...well thats another story

She flys hahah The pull is slightly smoother...as well as the shifts

The i did the 5,500 rpm launch....



My best launch yet..

The car sounded rather happy to launch at that rpm this time...and no bucking / deep drop in rpms from dropping the clutch...

the best part... no oil traces AT ALL on my set up. I wiped the inside of the cap after each run..city driving, freeway (80 mph) and launching. Each test resulted in no oil on the underside of my cap.

So far i may just keep this set up...
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Old 06-02-2008, 02:17 PM   #46
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So i wasn't crazy lol. very happy to see it actually worked.... how does your hood close now does it clear it just fine
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Old 06-02-2008, 02:31 PM   #47
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Originally Posted by tico915007 View Post
So i wasn't crazy lol. very happy to see it actually worked.... how does your hood close now does it clear it just fine
the hood clears fine when you remove the clamp. With the clam..does not fit. You can slam it down, but the right side stick up a little...and i was not about to go 80 on the freeway with my hood slightly open...
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Old 06-02-2008, 03:07 PM   #48
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Amazing what a vented oil cap will do!!!!!!!!!!!!!!

Low speed, makes the car feel like a heavy sedan.
The shifts are smoother.
The pulls are smoother.
The car sounded happy.

Now about that 5,500 rpm launch. I'd like to hear your exact launch technique. What did you think about the vacuum/boost gauge hooked to the oil fill cap to record what is going on?, and........what exactly in the operation of the engine do you think is creating more boost and better performance with a vented oil cap?
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Old 06-02-2008, 03:45 PM   #49
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Ahh I didnt say more boost or hp gain..

I said on a physical test, if you drive really slow, the car pulls slower then normal.

At higher speeds, the car feels smoother as if some pressure holding you back is gone...

The best way to describe it is if you put a axle back on the car...really there is no hp gain per say...1~3 max, you do feel a 'slight difference' in the pull ect...

As for the launch... very very slight feather before dropping the clutch...I rolled forward for about a split second... to be honest, i have not seen our cars launch this clean ...even all the youtube drag videos arnt this nice lol

Not saying i am good at launching
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Old 06-02-2008, 05:09 PM   #50
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Quote:
Originally Posted by Nicklz View Post
The crankcase pressure is actually METERED AIR. So one thing to look into is how much is it changing the a/f.
Quote:
Originally Posted by hwy61 View Post
Are you sure about that? I don't think so at least not in an amount that is significant.
from the previously posted link (http://www.supersixmotorsports.com/pdf/PCVBypass.pdf)

"Its important to note 2 significant issues:
1) The crankcase ventilation airflow is metered since the vent tube is located after the MAF. Because the airflow
is metered, it must make it into the intake manifold to assure that the air/fuel ratio is correct."


Since no one else seems to be able to data log, I will.....measuring boost, AFR and acceleration with/without the oil cap on isnt that hard.
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