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You can see here that they went through all the trouble (raised humps in RH balance shaft area) of casting in two separate passages for each circuit but they both terminate back into the girdle.
Last picture (just because Michael mentioned it earlier), is the main oil duct that runs along the RH side of the block and feeds the mains and balance shafts.
The two wires represent main bearing (and thus rod bearing) #s 1 and 2.
The pump output, after being bled and regulated, leaves the block (if you have an external cooler - and I hope you do.. ) to be cooled and the comes back to feed the main oil duct.
What Michael was referring to earlier is evident here that incoming oil back from the cooler is lined directly up with the feed passage for the #1 main journal feed (#1 rod). Although it has to travel across the diameter of the main oil duct, maybe and inch in diameter.
Next in line (and here's where MM lost me with an earlier comment) is the #2, then 3,4 and 5 (#3 really only feeds the crank thrust and balance shaft - no rod)
So Michael...., can you elaborate on what you meant by #2 being last to be filled....? I'm missing something.
Oops, T., I was incorrect in my comments on #2 oiling. Thanks to your recent posts and a review of the Porsche oiling diagram I now realize it. I typically revised the oil entry on the dry sump race engines (see pic) and my mind was stuck on that arrangement rather than the normal oil entry into the main galley. Thanks for pointing it out! FWIW, here's what I did back in the day in an attempt to improve oiling to #2 rod. Although the dry sump was definite improvement, I decided my revised oil entry location was not.
You must have as many past project pictures at hand as I do.
Every time I get a new PC/laptop, 1/2 of my new hard drive is full of files like "Files from old laptop", "pics from tablet", "old desktop fujitsu drive track car pics"...
Re. your mods, the sorry thing for me is, there's no way I think PCA is ready to allow full dry sump.
**I am thinking gutted stock pan with a perforated box bafflling, twin scavenge takeoffs, belt driven scavenge to 2-3 gallon de-aerating tank at stock battery location, fed back into the stock pump suction.**
It's that wording "stock pump must be retained" that I think is sell-able.
I think whatever I do...., I will take the bleed orifice passage back to the girdle and weld block it, with the dead end passage that's left, I'll simply vent it by drilling into the inner crankcase wall, which will allow it to bleed into the sump.
Do you think the part above with asterisks is a legit improvement worth the effort...?
The triangular hole, lower one in the above pic with the yellow wire.
This is the port mentioned by Mark above and assumed to be diverted back to the sump.
Sad to say....., no, this passage is only oil (and air) that makes it past the orifice in the end of the OPR spool valve showed above. It starts at the face of that valve, travels through the hollow valve itself and then between the valve a sleeve (1st pic) and then bleeds out of the hole of the same size that you can see in the OPRV sleeve.
The problem is....., this aerated oil is delivered right back into the girdle to re-feed the pump.
There was a purposeful intention in the design to keep these two oils separated, that can not be disputed...., they each have their own separate tract all the way back to the girdle and they took the extra measure of isolating the oil that passes through the orifice (+ air) and the pure oil that lifts the spool against spring tension of the OPRV itself - by machining in a separate passage for the good oil inside the valve bore in the block and building into the casting of the oil filter housing, a totally separate path for the oil (air) that passed the bleed orifice.
But then they terminate them both right back into the girdle....?
So basically, we have high pressure oil entering a suction tract that is under vacuum, and also, aerated oil from a bleed orifice that also enter right back into the pump's suction.
T
OK so that's quite interesting T. I went back and looked at some additional pictures. I'm guessing you stuck the white wire down the channel that is near the bottom inside edge of the OPRV sleeve right? I hadn't noticed that as a separate passageway before. The oil pan was on my car at the time or I might have tried doing what you did with the wires.
I'm trying to follow your logic about the OPRV and oil / air separation though. My 86' block uses the 3 piece OPRV design. It's just a simple piston that presses against the port in the side of the main oil galley. But like you said, the white and yellow wires both go to the same location so what's the point of creating two separate paths?
Porsche designed the block this way for a reason. We just haven't fully understood the reason yet.
OK so that's quite interesting T. I went back and looked at some additional pictures. I'm guessing you stuck the white wire down the channel that is near the bottom inside edge of the OPRV sleeve right? I hadn't noticed that as a separate passageway before. The oil pan was on my car at the time or I might have tried doing what you did with the wires.
I'm trying to follow your logic about the OPRV and oil / air separation though. My 86' block uses the 3 piece OPRV design. It's just a simple piston that presses against the port in the side of the main oil galley. But like you said, the white and yellow wires both go to the same location so what's the point of creating two separate paths?
Porsche designed the block this way for a reason. We just haven't fully understood the reason yet.
That's correct.....and if you look at your picture, inside the triangular hole, what you are seeing is the interior wall of the crankcase which is used for on of the walls of the passage back to the girdle. This is where I would vent that oil back into the crankcase and just block off the girdle from it.
This feature is built in to all the blocks, early and late....so maybe the later valve, they thought they'd just use that same passage as an aerated oil vent. The original reason could have been to keep the valve from becoming hydro locked since even though you have a -0- tolerance valve, some oil will get past it. If it had no exit, it would build and keep the valve from stroking.
This could be the same function on the second design 1 piece but then there's the bleed orifices added....?
First, understand that NO bearing will stand up to a loss of oil film. The rotating rod rides on an oil film, and it is that film that provides separation and prevents metallic contact with the bearing. Since the oil is incompressible, tremendous loads are transferred to the bearing and that's why the bearing construction is critical. The H bearing's value is in the beating it can take - but only if there is that critical film of oil.
Will the bearing survive in a low oil pressure situation (oil light comes on)? If the engine is shut down before the oil film goes away, then yes. Keep in mind that RPM, load, duration all contribute to how long the film will protect the bearing. The H bearing is far tougher than the Glyco, so it may survive a bit longer, but do try not to go there!
Hi Michael,
Can you give me the information for the rod upgrade , so i can do this in de netherlands with my car.
thanks already
You’d think that most people tracking these cars would have started dry sumping them about 25 years ago when the number 2 conrod bearing issue started to become apparent as a design weakness.
If it’s good enough for the 911 then why not the 951?
Are 951 owners just too cheap to do it right?
You’d think that most people tracking these cars would have started dry sumping them about 25 years ago when the number 2 conrod bearing issue started to become apparent as a design weakness.
If it’s good enough for the 911 then why not the 951?
Are 951 owners just too cheap to do it right?
its not good enough for 911 owners anymore. the factory engines 911 haven't been dry sumped in a decade.
Besides - dry sumping a 944 is not a cheap option. over $5k to do it right, maybe up to almost $10 if you are paying a shop to do it all. Need to give up S/C for most installs.
In addition while the rod bearing failure it is not as common as you might think.
Chris,
I think we sometimes blow these things out of proportion & they gather a momentum of their own.
You’re right, it’s now only the GT & “Turbo” branded 911 models which use a genuine dry sump system.
I’ve often felt that perhaps between using a 10w60 oil, enhanced crank case ventilation & the biggest oil cooler that you can fit, a good number of these rod bearing issues might have never happened.
05-30-2016, 06:42 PM
) to be cooled and the comes back to feed the main oil duct.
