Girdle oil passage modifications
10-13-2009, 02:26 PM
#76
Racer
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10-13-2009, 06:24 PM
#79
Nordschleife Master
Thread Starter
I believe the stock Porsche crank has an adequate drilling. I feel very confident that it can be improved upon with simple albeit time consuming techniques. I thought that I had mentioned these before but I will repeat them here. These techniques will help avoid localized pressure drops that can allow bubbles to coalesce.
The drillings in the crank intersect oneanother. Because the passages are straight and made by entering the crank from the outside there are a number of blind passages created. The edges created allow for turbulence and this will encourage localized pressure drops which will encourage air to coalesce and then be stratified in the flowing oil which would encourage further coalescing.
My suggestion is to remove the plugs and carefully thread the passage. With careful measuring it should be possible to avoid threading the entire passage and introduce sharp threads to the flow. Create threaded male plugs to just fill the passage. Index the threaded male plugs. Contour the ends of the plugs so that they change the angles and surfaces exposed to the flow to more propitious ones. A lot of work? Yes. However, someone having access to advanced machining facilities could use CAD and CNC machining.
The drillings in the crank intersect oneanother. Because the passages are straight and made by entering the crank from the outside there are a number of blind passages created. The edges created allow for turbulence and this will encourage localized pressure drops which will encourage air to coalesce and then be stratified in the flowing oil which would encourage further coalescing.
My suggestion is to remove the plugs and carefully thread the passage. With careful measuring it should be possible to avoid threading the entire passage and introduce sharp threads to the flow. Create threaded male plugs to just fill the passage. Index the threaded male plugs. Contour the ends of the plugs so that they change the angles and surfaces exposed to the flow to more propitious ones. A lot of work? Yes. However, someone having access to advanced machining facilities could use CAD and CNC machining.
Tale a look at the photo from threads past:
(1) Remove both existing plugs.
(2) Thread both holes almost to the channel intersection
(3) Make two plugs that have thread most thru them and smaller unthreaded part in the tip. The idea is to create two plugs that when screwed in, partially plug the intersecting channel.
(4) Screw on the left plug, fully in, and mark the position of the screw. Drill the tip off from the right. Unscrew the left plug.
(5) Screw on the right plug, fully in, and mark the position of the screw. Drill the tip off from the left. Unscrew the right plug.
(6) Install both plugs and verify that the position of the screw is the same as when drilled.
To someone wlike me hose only tool is a library card, this looks like a doable job for a professional. The resulting passages are still non-monotonic but at least the surface would be guaranteed to be smooth as the plug is drilled in position. I think this drilling in situ probably makes manufacturing those plugs cheaper.
I have no idea if this would improve the crank, you tell me.
10-13-2009, 09:53 PM
#80
Former Vendor
10-13-2009, 10:21 PM
#81
Nordschleife Master
Thread Starter
12-09-2012, 02:14 AM
#82
Nordschleife Master
Thread Starter
I can't believe someone actually did it!
Reading thru posts from the time I was absent, Erkka (https://rennlist.com/forums/9317325-post1.html) had linked to this writeup:
http://www.amicale928.org/forums/vie...hp?f=13&t=7951
If someone ever runs to "BW76 (walter) from close to Strasbourg", buy him a beer on me! Seriously!
Test 1
Stock
Main No air Air More air
#5 2.0 2.0 2.0
#4 2.1 1.7 1.3
#3 4.7 3.2 1.8
#2 2.1 1.4 0.7
#1 2.0 1.9 1.8
Test 2
#2 main entry with 5mm hole drilled
Main No air Air More air
#5 2.0 2.0 2.0
#4 2.1 1.6 1.2
#3 4.7 3.1 1.7
#2 2.1 1.9 1.3
#1 2.0 1.9 1.8
Mod picture here:
This one made my night. Progress.
Reading thru posts from the time I was absent, Erkka (https://rennlist.com/forums/9317325-post1.html) had linked to this writeup:
http://www.amicale928.org/forums/vie...hp?f=13&t=7951
If someone ever runs to "BW76 (walter) from close to Strasbourg", buy him a beer on me! Seriously!
Test 1
Stock
Main No air Air More air
#5 2.0 2.0 2.0
#4 2.1 1.7 1.3
#3 4.7 3.2 1.8
#2 2.1 1.4 0.7
#1 2.0 1.9 1.8
Test 2
#2 main entry with 5mm hole drilled
Main No air Air More air
#5 2.0 2.0 2.0
#4 2.1 1.6 1.2
#3 4.7 3.1 1.7
#2 2.1 1.9 1.3
#1 2.0 1.9 1.8
Mod picture here:
This one made my night. Progress.
Here are some ideas. I have obviously never done anything like that, ever, so these are just off the wall ideas.
- Bolt a plexiglass plate on the top of the girdle.
- Capture the flow on video
- Plug the points that I have marked with green.
- Drill a hole to the plexiglass at the red square to reflect the oil flow to the head, and direct it to bucket with a hose. I have no idea how much oil flows / needs to flow to the heads, so it's a guess.
- Use the bolt holes to direct the oil out of the girdle. It would be nice if you could make restrictors for those bolt holes that you could adjust. The restrictors for mains 1, 2, 4, and 5 should be the same size. The restrictor of main 3 should let more oil thru, but I have no idea by how much.
- Then see how much oil comes out of each the four holes (mains 1, 2, 4, and 5) as you vary the pressure. Also vary the main 3 restrictor size.
Also what would be very interesting is seeing on video what happens when you feed whipped chocolate milk shake aerated oil to the girdle. Does the air and oil separate in a way that just sends more air to #2 main? Instant classic movie.
- Bolt a plexiglass plate on the top of the girdle.
- Capture the flow on video
- Plug the points that I have marked with green.
- Drill a hole to the plexiglass at the red square to reflect the oil flow to the head, and direct it to bucket with a hose. I have no idea how much oil flows / needs to flow to the heads, so it's a guess.
- Use the bolt holes to direct the oil out of the girdle. It would be nice if you could make restrictors for those bolt holes that you could adjust. The restrictors for mains 1, 2, 4, and 5 should be the same size. The restrictor of main 3 should let more oil thru, but I have no idea by how much.
- Then see how much oil comes out of each the four holes (mains 1, 2, 4, and 5) as you vary the pressure. Also vary the main 3 restrictor size.
Also what would be very interesting is seeing on video what happens when you feed whipped chocolate milk shake aerated oil to the girdle. Does the air and oil separate in a way that just sends more air to #2 main? Instant classic movie.
Last edited by ptuomov; 12-09-2012 at 02:39 AM.
