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Old 03-02-2012, 10:29 AM   #1
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Anyone removed AOS & Used hoses/breather tank

Looking to see if anyone has done this for a Boxster race car. It is regularly done in
in BMW's....

Thanks for you response!

-Chuck
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Old 03-09-2012, 12:49 PM   #2
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How do you get the oil back into the engine?

Our engines continue to puke the oil.. which means draining the breather box after every session.. which means refilling the oil..

I was just looking at several BMW race cars this past weekend at NASA event.. the fast guy's are all dry sump.


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Old 03-09-2012, 02:33 PM   #3
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This is an honest question because I really don't understand.

Why do Boxster engines puke more oil than any other engine?

Surely if the Breather tank is mounted high enough then the puked and churned oil that is spewing up the new breather hose will return by gravity once it has settled down. Breather tanks are meant to capture oil vapor and condense it and i can't see why we couldn't do the same on a Boxster - except in spec Boxster where we aren't allowed to.

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Old 03-09-2012, 02:38 PM   #4
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Porsche pulls a vacuum on the block to keep things from leaking and to make some power by offsetting the piston movement pumping action.

Go to a puke tank situation and block off that vacuum line to the AOS and watch what happens It will leak from every seal possible

2.5 cars? 6200 rpm? not needed. Box-S 7200? Needed. The piston size on the 3.2/3.4 is MICH bigger, which means more pumping pressure from the back side of the pistons.


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Old 03-09-2012, 02:41 PM   #5
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Your GT3, pulls oil from the tank so fast, it creates a vacuum on the block and keeps the engine from leaking everywhere. Porsche Motorsports made 8-10more hp by changing the rear main seal on your GT3 engine.. you know why? That seal let the engine breath. The vacuum from the oil tank was so great, that it actually caused the rear main seal to collapse!!

We have no mechanical vacuum on the Boxster engines..



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Old 03-09-2012, 02:44 PM   #6
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Now, that being said.. drag racers for years have used a belt driven vacuum pump to pull upwards of 20inches of vac on the engine at high rpm (non dry sump engines)

GT3 = dry sump
9X6 = wet sump
9X7 = wet sump

Want to run a breather can? Go to a belt driven vac pump and adjust the suction side of the pump so it does not pull too much vac on the engine causing seals to collapse.


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Old 03-09-2012, 03:04 PM   #7
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Quote:
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Now, that being said.. drag racers for years have used a belt driven vacuum pump to pull upwards of 20inches of vac on the engine at high rpm (non dry sump engines)

GT3 = dry sump
9X6 = wet sump
9X7 = wet sump

Want to run a breather can? Go to a belt driven vac pump and adjust the suction side of the pump so it does not pull too much vac on the engine causing seals to collapse.


B
Hmmm. That may be a little more complicated than I had in mind.

Thanks for the explanation regarding vacuum. Was not aware of this. Isn't that the reverse of the old fashion PCV (positive crankcase ventilation) that so many of my early cars featured?
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Old 03-09-2012, 03:18 PM   #8
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Bingo @PCV

Porsche has known for a long long time that pulling a vacuum on the engine was a good thing. Most european car companies do this, it wasn't until the late 90's the "merican" car companies figured it out.

PCV's pull vacuum on the engine, but it was not what we call "plenum or port vacuum" it was a simple line from the PCV to the air cleaner.

New LS GM engines have a version of our AOS on them.

12k RPM VW drag engines will make 3-4hp *more* with a belt driven pump


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Old 03-10-2012, 08:54 AM   #9
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Quote:
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How do you get the oil back into the engine?

Our engines continue to puke the oil.. which means draining the breather box after every session.. which means refilling the oil..

I was just looking at several BMW race cars this past weekend at NASA event.. the fast guy's are all dry sump.


B
Thank for your response!

In my BMW racer we'd get a teaspoon per race/session... setting it up as I described and the BMW has what they call an air/oil separator, (that I removed), that seems to serve the same function as the AOS. So, if I do this in a 2.5 motor, how much might it "puke" per session and is there lost hp?

By the way in NASA GTS-2/3 most BMW's ran an after market pan baffle and 1 quart more oil... no dry sumps that I was aware of...

-Chuck
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Old 03-10-2012, 09:51 AM   #10
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Hi Chuck!!

Just run the AOS. I sat on the original rules committee that put BoxsterSpec together. I have traveled the country running the 2.5 cars since Nov. of 2005. I have replaced a total of 2 AOS at track events since then.

The 2.5 car's have close to NO issues. A forum member here "Topless" has his OE 1997-98 horizontal AOS still in his car!! The very first versions had a horizontal diaphragm, the newer versions have a vertical diaphragm. Topless hits at least 10-12 events a year and is by no means what we deem "a back marker"

The real issue with our AOS? (on 3.2 and up engines) they cannot drain the oil back into the engine fast enough as they fill up. This is why it gets through the diaphragm. Porsche solved the issue several years back on the 996 3.6 engine, then a newer fix for the CaymanS engines.

Are you the new owner of Goodies?



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Old 03-10-2012, 09:57 AM   #11
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This is straight out of my arse, but I believe ALL inline engines have less of an internal air pressure issue versus a horizontally opposed engine.

FYI: new AOS's are $93. Keep a spare with you, or look for me at the track

I'll be up for the THIll PCA club race and will be at the NASA Buttonwillow event.


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Old 03-10-2012, 10:26 AM   #12
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Hi Chuck!!

Just run the AOS. I sat on the original rules committee that put BoxsterSpec together. I have traveled the country running the 2.5 cars since Nov. of 2005. I have replaced a total of 2 AOS at track events since then.

The 2.5 car's have close to NO issues. A forum member here "Topless" has his OE 1997-98 horizontal AOS still in his car!! The very first versions had a horizontal diaphragm, the newer versions have a vertical diaphragm. Topless hits at least 10-12 events a year and is by no means what we deem "a back marker"

The real issue with our AOS? (on 3.2 and up engines) they cannot drain the oil back into the engine fast enough as they fill up. This is why it gets through the diaphragm. Porsche solved the issue several years back on the 996 3.6 engine, then a newer fix for the CaymanS engines.

Are you the new owner of Goodies?
B
Hi Brad-

Not new owner of Goodies....although I'll take it!! So I'll get a new AOS and be done with it! Thanks again!

-Chuck
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Old 03-10-2012, 03:01 PM   #13
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I'm all for re-inventing the wheel, but .. this is one of those times we don't really need too

Glad to see/hear that NorCal Spec cars numbers are increasing


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