once more ... the credits are not mine

 

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?

 

WOn the 997.2 it looks like this

On the 997.1 and 996 it can be easily made like this:

 

Does the 997.2 run under the intake or is it plumbed into it like 996? Hard to tell.
Thanks for the pics!

 

No, the pictures solely show the overpresuure protection, which is integrated in the 997.2 oil filler tube. And the mod to put it onto the 996/997.1

you should look at the diagrams to check where it exactly leads to.

for the mod it goes to the air filter box. With/without the catch tank in between.

how exactly the crankcase ventilation / AOS is connected in the dfi engines I further do not know.

 

 

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.

 

Sledge hammer would have been my tool of choice!

 

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.

Photo found on the Internet.

 

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.





https://www.autohausaz.com/pn/141913...BoCIb0QAvD_BwE

 

Good stuff, thanks!

 

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.

 

My understanding is that a certain amount of vacuum is needed to relieve crankcase pressure and eliminating the AOS is not a good idea.