"Because they say it increases flow"

This has been debated endlessly. IMO AN -16 is the way to go. The OE hoses are somewhere between AN-12 and AN-16. Lots here claim AN-12 to be just fine.
This shows the comparison of AN-16 with OE SC hose. You decide.
http://forums.pelicanparts.com/uploa...1506703175.jpg

Back in the day, VW T1 oil pumps were routinely "ported". Not rocket science, and the results are debatable. No one that does this to a 911 pump is willing to show an example, I guess.
Here is what is done on a VW pump.

http://forums.pelicanparts.com/uploa...1506704176.jpg

I would have thought that an aerated oil was fairly compressible and the restriction would need to be quite significant before the pressure changes very much.

We use Aeroquip Socketless hose installed in the heater tubes in our Rally Car and it has never been a problem.

It would be really good to measure the pressure.

With regard to porting the inlet of the pump it would be interesting to understand the reasons for doing this.

If the port is a significant restriction to flow then I can understand the logic.

If we take an engine designed for very low engine speeds and hence relatively low flow requirements, it is possible that the port design may be a limiting factor.

If we significantly modify the engine and increase the speed of the pump then its delivery will try to increase.

The port restriction will stop oil entering the pump and the pressure of the oil in the mesh of the gears will fall.

This becomes critical when the pressure falls to below the vapour pressure of the oil and cavitation occurs.

This will then pump oil vapour to the bearings which will rapidly fail.

I would agree that opening the port will fix this problem.

I am not sure that I believe a 911 pump will ever cavitate - even at 8500rpm so opening the port is unlikely to achieve very much.

I had AN-12 on my 3.2L short stroke racecar engine. Had AN-12 pretty much everywhere except for a short section of original steel oil piping that was cut up to make an adapter fitting from the engine scavenge/outlet port to an AN-12 hose that connected to the external thermostat. Had plenty of oil pressure and temperatures were good.

The downside I see to the AN-12 is the hose fittings really choke down to a small orifice. In other words if you look at the hole in a male AN-12 fitting, it's quite a bit smaller than a typical male metric "globe" fitting we see on our cars. So it is indeed a downsize from original metric hose size.

These pumps are positive displacement spur gear driven. The only way these pumps can increase their flow is by change of gear diameter, number of teeth or pump speed. What goes in has to come out minus any leakage pass the outer clearance and end clearance.

Changing the inlet size/pipe ID diameter will make no difference as long as the inlet size, flow wise is greater than the gear volume "v" pump speed. We know this is the case otherwise you would pump an air pocket and have an immediate bearing failure.

Anyone selling a modification that increases the pumps flow ability has to be changing one of these parameters. I have not seen any modification on these pumps that does any of these.

Porting work will have zero effect on flow. It may lower the work the engine has to over come to drive the pump, but flow increase will be zero. So will lowering the overall pressure the oil system runs at.

72 lbs is more than required for these engines but Porsche has historically built a lot of safety into these engines . Performance wise, as long as you see no oil starvation damage and the cam timing is not affected, you can lower the pressure considerably. For street use, leave the pressure where it was designed and enjoy.

Anyone interested to know more about the Glenn Yee process can discern some of the info from the article here

andy