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Maybe just as simple as -
Larger diameter tubing(5/8"?) with reinforced walls so it does not collapse under vacuum/looks stock/does not deteriorate with oil vapor/heat.
Use stock-looking hose clamps.(Norma?)
My installed mod got some months ago an update. The rubber hoses were replaced by PVC ones. Exactly to avoid bending and collapse of the rubber hoses in a smaller radius curve. The heat of the engine does make the rubber soft and makes it to ‘click’ inward when into a tighter bend.
The PVC tubing is also not completely the final stage of the development. It turns out to be quite fragile. I pierced recently the line coming from the oil cap when closing the deck lid. It is a ribboned PVC line. Too tight curves and the plastic will crack at the outer side, cracks in the inner side of such ribbon, as it gets hot.
Typical iteration progress with something new developed. When it is put to the real test the flats will appear.
My installed mod got some months ago an update. The rubber hoses were replaced by PVC ones. Exactly to avoid bending and collapse of the rubber hoses in a smaller radius curve. The heat of the engine does make the rubber soft and makes it to ‘click’ inward when into a tighter bend.
The PVC tubing is also not completely the final stage of the development. It turns out to be quite fragile. I pierced recently the line coming from the oil cap when closing the deck lid. It is a ribboned PVC line. Too tight curves and the plastic will crack at the outer side, cracks in the inner side of such ribbon, as it gets hot.
Typical iteration progress with something new developed. When it is put to the real test the flats will appear.
Was it the 997 that has the vent line into the oil fill tube? Would that fit the 996?
Thanks! I was looking at my old one last night trying to figure out how to get it open as I was curious to see what's inside. You just saved me some time.
The only weakest part is the diaphragm, which has to be air tight. I just don't understand why it has to be so flimsy. I'm sure it will last a lot longer if it were thicker.
I also measured the two springs inside controlling a reduced orifice (to reduce the vacuum flow to the throttle body). It's a 2-stage design. At 11" water, the vacuum intake flow is reduced and at 17" water, the diaphragm shuts off the vacuum completely.
The trouble is when the diaphragm has tears, the valve doesn't work anymore and it allows full intake vacuum to be applied to the crankcase.
Also, you can see the flows from bank 1 and bank 2 are merged on the left first, then it goes up and enter the center "cyclone cone" to generate a swirl action not too different than to the bagless vacuum cleaners.
The motorsports AOS has two such cyclone cones each dedicated to a bank so it's > two stock AOSs because it's taller and bigger overall too.
One more thought. 997 uses a smaller AOS placed in the middle of the engine but on each bank, it has a pre-AOS. I think it's just a swirl pot with no mechanical parts inside.
Perhaps if we can installl this pre-AOS on our bank 2, it will increase our effective AOS capacity. Kinda a poor mans motoraport AOS. Not sure if our stock aos bank 2 hose can mate to it. It definitely needs an adaptor plate to be installed on the head.
If my engine was off the car, I would have experimented with this idea.
the difference is the diaphragm and how the aos responds to vacuum. on decel the engine wants to idle (throttle closed) however rpms are high and lots of splashing happening in the crank case. with throttle closed not much fuel is required. further, with throttle closed there is a lot of vacuum in the intake. on an oem aos, this vacuum would pull the diaphragm closed and limit the amount of cleg (air with combustible fuel and oil vapour) drawn from the crankcase. with the aftermarket catch can, even with a third party diaphragm (i think stelan used an vw/audi unit) too much of this stuff gets past and throws off the trims.
all silk is doing is attaching the aos to the intake at a different location. completely apples and oranges.
This makes me wonder.
Would a Stelan option, or simply a catch can instead of the AOS, with the rerouting suggested by Silks setup, be a good option?
This would eliminate the high vacuum problem causing fuel trim issues with the wrong diaphragm since vacuum is seriously reduced by the fact that its connected to the air box instead of close to the plenum.
In short:
1. Eliminate AOS (once it fails).
2. Install catch can instead of it, with large fittings. 1/2 or 3/4.
3. Use air box as outlet to intake instead of close to plenum.
Catch can wouldn't fill up as fast as some race cars have noticed because of lower vacuum when off throttle.
In my case I'm talking about a 986, however it applies to 996 too I would assume.
05-03-2019, 06:42 AM
