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Old 05-23-2015, 05:50 AM   #1
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AOS Delete

As anyone deleted there AOS, ie blanked off the throttle body and run a pipe from the top of the AOS to a catchment tank/can.

l replaced my startermotor a few weeks ago and found a fair bit of oil in the pipe
between the throttle body and AOS, but i wasn't getting any smoke bombs while
running just the odd puff of blue smoke if reved hard at standstill and when the wife
followed me it did smoke a little but nothing major

Anyway clean out the pipework fitted a new AOS done 300 miles just checked
the pipe and there oil in there again.

Have seen posts on here where a guy had 3 duff one's straight from the box think
it was one of jake's post.

So has anyone deleted theres, if so has there been any performance loss
with the crankcase not being under vacuum


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Old 05-23-2015, 06:19 AM   #2
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What year is your car?
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Old 05-23-2015, 06:29 AM   #3
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What year is your car?
1998 with a 3.4 996 motor
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Old 05-23-2015, 06:30 AM   #4
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What year is the motor?
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Old 05-23-2015, 06:40 AM   #5
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I have stuff to do. Check this if it corresponds to your engine.

Crankcase Ventilation Valve

In some cases the ventilation valve on the valve cover that connects the crankcase to the oil seperator becomes clogged, and may cause problems for the oil seperator. If your newly replaced oil seperator is starting to fail, or you are about to install a new seperator, you might consider replaceing the ventilation valve.

Pelican Parts - Product Information: 996-107-047-51-M100
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Old 05-23-2015, 06:54 AM   #6
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I've seen that valve its on bank 4 to 6 AOS pipe did wonder what it was, can it be cleaned
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Old 05-23-2015, 07:03 AM   #7
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Piston ring tension is affected IIRC. You don't want that
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Old 05-23-2015, 08:43 AM   #8
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Quote:
Originally Posted by whitecliffs View Post
As anyone deleted there AOS, ie blanked off the throttle body and run a pipe from the top of the AOS to a catchment tank/can.

l replaced my startermotor a few weeks ago and found a fair bit of oil in the pipe
between the throttle body and AOS, but i wasn't getting any smoke bombs while
running just the odd puff of blue smoke if reved hard at standstill and when the wife
followed me it did smoke a little but nothing major

Anyway clean out the pipework fitted a new AOS done 300 miles just checked
the pipe and there oil in there again.

Have seen posts on here where a guy had 3 duff one's straight from the box think
it was one of jake's post.

So has anyone deleted theres, if so has there been any performance loss
with the crankcase not being under vacuum

The low tension piston rings rely on the crankcase vacuum to help seal the rings, eliminating that vacuum increases blow-by. If the AOS is disconnected from the vacuum source no oil will come out the top of the AOS.
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Old 05-23-2015, 08:58 AM   #9
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Originally Posted by BYprodriver View Post
The low tension piston rings rely on the crankcase vacuum to help seal the rings, eliminating that vacuum increases blow-by. If the AOS is disconnected from the vacuum source no oil will come out the top of the AOS.
Along with blow by and he loss of effectiveness for the low tension rings used in these engines, not having vacuum in the case sump will lead to increased water and fuel level build up in the oil as the low vacuum level created by the AOS helps to flash them off at lower temperatures. This will very quickly degrade any oil.
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Old 05-23-2015, 10:16 AM   #10
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Cheers for the replys lads, looks like I'll give that one a miss
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Old 05-23-2015, 12:31 PM   #11
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good reading

^^^
+ 1

Very interesting comments from BY and JFP
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Old 05-23-2015, 02:40 PM   #12
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Cheers for the replys lads, looks like I'll give that one a miss
A catch can needs to be plumbed inline between intake plenum & AOS.
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Old 05-23-2015, 10:53 PM   #13
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Something like this then.

BRUSHED ALUMINIUM OIL CATCH CAN BREATHER TANK RESERVOIR WITH 19mm 3/4" OD BARB | eBay

Should be enough room near the side intake fan to install
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Old 05-24-2015, 04:54 AM   #14
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Or something like this

OK, here's where everyone tells me I'm killing my engine. I've run this for 3-4 years now and 25,000+ miles. So far so good. I think I did it as much to try an alternative solution as I did for a cheap easy fix. But it's just a race car, so what the hey. I would not do this to my everyday driver.
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Old 08-18-2015, 06:52 AM   #15
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Or something like this

OK, here's where everyone tells me I'm killing my engine. I've run this for 3-4 years now and 25,000+ miles. So far so good. I think I did it as much to try an alternative solution as I did for a cheap easy fix. But it's just a race car, so what the hey. I would not do this to my everyday driver.
Can you elaborate on how you've plumbed this in? I am looking to delete the AOS on my 986 racer (which is getting ITBs, so no real good source to hook up the AOS vaccuum line).
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Old 08-18-2015, 12:35 PM   #16
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My "piggyback" AOS is plumbed in between the facatory AOS and the intake. I removed the plastic tube, threaded the AOS and the intake "T", adding brass hose fittings. I then mounted the piggyback AOS in the trunk and ran fuel line to connect it to both brass hose fittings.
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Old 09-29-2021, 06:41 AM   #17
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Resurrecting this post from a fellow 986 track driver, who gets the occasional blue puff of death.

Add $1000, the motor sports AOS solution seems to be overkill. Looking for a more pragmatic solution. Is your truck solution still working well? How often do you have to drain the oil from the bowl?

Much appreciated!!
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Old 09-29-2021, 08:11 AM   #18
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I run a 1 qt nuke performance catch can after disabling the stock AOS. I've added a vW regulator further down the line. This seems to work well and would cost you about $350. That said, I've deleted both my SAI and engine compartment fan to get space, so ymmv.
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Old 09-30-2021, 04:50 PM   #19
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I plumbed a $25 catch can between the AOS and intake. I wanted to leave the AOS as a regulator valve because redoing all the connections would be a pain to do. However, a good adjustable valve would only run another $25 (that way you can dial in the exact pressure you want).

I've run mine 5hie way for over a thousand miles. No issues. I've looked in there recently and have very little kerosene like residue.

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