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The Radium King · 01-24-2020, 08:07 AM

i did. i also read the links in the thread, such as this one:

https://rennlist.com/forums/996-foru...l#post14198625

where jake says:

-The AOS balances fuel trim. If the pressures are not correct within the crankcase the engine runs rich, or lean, and that means an AOS can kill cylinders, create oil consumption, and etc.

there are other threads on the issue where jake specifically says that he was unable to fix the fuel trim issue with other aos units. and this is a guy who actually builds and tests these engines, not a self-proclaimed 'porschetech' and 'porsche god' that is selling $10 licences to people to do his testing for him.

basically, what is happening is that the heat and churning of the oil in the crankcase creates vapors which in turn pressurize the crankcase. if unaddressed, this pressure blows seals, pushes past piston rings, kills engine power as it resists the movement of pistons.

this vapor cannot be vented to atmosphere by law, and is combustible given the oil content. the aos uses intake vacuum to evacuate the crankcase and reintroduce it into the intake.

the thing is, most of the vapors and pressure are happening at high rpm, while most intake vacuum is happening at idle. this is why there is a diaphragm on the aos. at idle and high vacuum, the vacuum draws the diaphragm closed and restricts flow from the crankcase. as vacuum decreases the diaphragm relaxes and flow increases.

this diaphragm flaps in and out a bazillion times and is a failure point. when it fails the intake is applying full vacuum all the time; this is why a bad aos is detectable at idle by difficulties in opening the oil filler cap due to the increased vacuum at idle.

the issue is having an appropriately-sized diaphragm. too small (or open too slow) and not enough vacuum is applied at high rpm, not enough pressure is relieved, power is lost, seals and rings fail.

too big (or close too slow) and when you come off wide open throttle all the vapors get drawn into the intake and you get more fuel (oil vapour) than expected creating an over-rev situation.

the porsche god appears to be evaluating the replacement aos diaphragms by durability and not response to vacuum (other than a few static vacuum measurements that do not give any indication of the dynamic response of the diaphagm).

having said all that it work fantastic on his car, apparently.

01-24-2020, 08:07 AM	#5
The Radium King Registered User Join Date: Apr 2010 Location: Canada Posts: 3,121	i did. i also read the links in the thread, such as this one: https://rennlist.com/forums/996-foru...l#post14198625 where jake says: -The AOS balances fuel trim. If the pressures are not correct within the crankcase the engine runs rich, or lean, and that means an AOS can kill cylinders, create oil consumption, and etc. there are other threads on the issue where jake specifically says that he was unable to fix the fuel trim issue with other aos units. and this is a guy who actually builds and tests these engines, not a self-proclaimed 'porschetech' and 'porsche god' that is selling $10 licences to people to do his testing for him. basically, what is happening is that the heat and churning of the oil in the crankcase creates vapors which in turn pressurize the crankcase. if unaddressed, this pressure blows seals, pushes past piston rings, kills engine power as it resists the movement of pistons. this vapor cannot be vented to atmosphere by law, and is combustible given the oil content. the aos uses intake vacuum to evacuate the crankcase and reintroduce it into the intake. the thing is, most of the vapors and pressure are happening at high rpm, while most intake vacuum is happening at idle. this is why there is a diaphragm on the aos. at idle and high vacuum, the vacuum draws the diaphragm closed and restricts flow from the crankcase. as vacuum decreases the diaphragm relaxes and flow increases. this diaphragm flaps in and out a bazillion times and is a failure point. when it fails the intake is applying full vacuum all the time; this is why a bad aos is detectable at idle by difficulties in opening the oil filler cap due to the increased vacuum at idle. the issue is having an appropriately-sized diaphragm. too small (or open too slow) and not enough vacuum is applied at high rpm, not enough pressure is relieved, power is lost, seals and rings fail. too big (or close too slow) and when you come off wide open throttle all the vapors get drawn into the intake and you get more fuel (oil vapour) than expected creating an over-rev situation. the porsche god appears to be evaluating the replacement aos diaphragms by durability and not response to vacuum (other than a few static vacuum measurements that do not give any indication of the dynamic response of the diaphagm). having said all that it work fantastic on his car, apparently.