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Old 03-12-2017, 04:21 PM   #139
Scooby Specialist
Member#: 260314
Join Date: Oct 2010
Chapter/Region: NESIC
Location: S central CT, New England
2007 STI
silver gray metallic

Default EJ 25 Series oiling system design and modification notes

I am going to speak to the EJ25 engine because it's what I know. A lot will be applicable to other, earlier engines. I will make the caveat here and at the end that the enlargements I've done are untested for the moment. They do follow in the footsteps of much of what's been mentioned before in this and other threads on this subject.
The majority of passages and orifices in an EJ 25 case do not exceed 13mm inside diameter (ID). Almost all passages in the case halves are cast-in using tapered core pins. Passages from the oil pump to oil filter and the return are, at the maximum, 16mm and taper down to 12mm ID. Once oil reaches its highest point in the right-hand side of the case and branches off at 90 angles to the main oil galleries it is reduced to 12mm and tapers down to approximately 8mm at the end of the galleries. As the runners go from the left and right galleries to the heads they taper from 12mm to 7mm.
The single oil feed passage into the head's galleries is a drilled 6mm ID. Internally the head's galleries are drilled to 8mm ID. The external feed tubes for the AVCS Control Valve is 6.5mm ID (8mm OD). There is a significant reduction to 2 mm ID at the Right, rear head banjo (where oil comes out of the head and through the tube terminating in a -4AN male flare fitting for feeding the turbo and the AVCS, if you have the late model heads and it has this type of tube.

Other sizes of importance and summary:
Oil Pump feed to filter: tapered from 16mm to 12mm ID
Oil filter to upper galleries: this passage tapers from 12mm to 14mm ID and reduces down to 10mm as it transitions horizontally to the left side of the case.
Left side case oil gallery only goes half way to the rear of the case (tapers from 13mm to 8mm ID)
Right side case oil gallery (tapers from 13mm to 8mm ID, from each end)
Turbo CHRA (bearing cartridge) Oil Feed (late model heads): reduction to 2mm ID
Note: on many turbos there is another reduced ID orifice fitting to which you connect the SS braided hose.
Right Head Oil Feed Line (tapers from 12mm to 7mm ID)
Left Head Oil Feed Line (tapers from 12mm to 7mm ID)
Heads entrance for oil: 6mm ID (drilled passage)
#5 Main bearing and rear thrust bearing (6mm ID feeds #4 rod journal through crankshaft journal without reduction)
#4 Cylinder, rod bearing feed line (from #5 main/thrust bearing through crankshaft)
#4 Main bearing oil feed line (feeds only this main bearing)
#4 Main bearing feed line diameter reduction (passage reduces from 6mm minimum inside diameter to a 3.5mm orifice, like #2 main)
#3 Main bearing feed line reduces to 7mm minimum ID (feeds both #2 & #3 rod bearings through this one crankshaft journal)
#2 Main bearing feed line, feeds only this bearing (6mm minimum inside diameter passage reduces down to a 3.5mm orifice)
#1 Main bearing, with reduction to 5.5mm diameter (feeds from/beginning at the front of the right gallery)
#1 Cylinder, Rod Bearing feeds from #1 Main Journal through crankshaft journal)
Crank main oil holes are 5.5mm and rod journal holes are 4.5mm.

Summary: I eliminated the bottlenecks of the cast-in tapers in the galleries and passages. I enlarged the right side gallery to 14.3mm (9/16***8221. On the left gallery I enlarged it 14.3mm till I hit the feed for #2 Main Bearing. I reduced the ID to 13mm (1/2***8221 for the balance of the distance to the #3 Main Bearing runner. Feeds from the oil pump to the filter and back to the vertical runner up to the galleries were all enlarged to 14.3mm. I drilled the runners so they were a consistent ID to the step in the journals, but did not increase the minimum exit ID to the main journals.
All large passage bends were radiused and blended. The tapered feed runners to the heads were opened to 13mm. The receiving orifice in the head was radiused and tapered to be funnel-like.
I'm not convinced that the #2 and #4 Main bearing orifices should be enlarged. So far I have left them alone. That is what one experienced builder suggested.
I removed flash, steps and obstructions in the case and heads to ease oil return flow, as has been documented previously.
All this work was done with the express intent of running an 11 mm oil pump that is ported and shimmed to achieve a hot oil pressure of 85 PSI with bearing clearances of Mains @ .0015" and Rods @ .002".
I'll use what has worked for me in the past and that is -10AN hose and fittings going to an external cooler and remote, oversized racing filter. I run a KB wet sump so I also use an Accusump.
Since -10AN is nominally .480" ID or 12.2mm and galleries and primary passages reduce down to 8mm or 10mm in stock form, I feel I now have the hose and fittings as my bottleneck. -10AN has worked successfully for me in undrilled/unmodified cases to 7,200 RPM and 395 AWD HP.
This latest full case mod is for an anticipated 8,000 RPM red line and up to 500 CHP or 400AWDHP. I have currently succesfully run to 8.5K @470 HP.
My pistons weigh 530 grams (complete) and the Manley rods 592 grams. Together, this is 14% less than stock.
I can't see a problem with what I'm doing, but I'm going bigger and doing a bit more than I see described or shown by others. I'll again use the caveat that some of these enlargement mods are untested at this date.
*To quote hotrod on this forum: "Detail work on the oil pump passages (and engine oil gallery passages) is how the high end racing engine builders keep adequate oil flow without jacking the oil pressure to the moon. Cosworth knows what their doing." NASIOC

I've now modified and used 11mm oil pumps that I have ported and shimmed as well as a 12MM oil pump in my Alpha engine where I am using an external, adjustable Peterson oil bypass valve. The bypass returns to the sump. Significant porting of the oil pump does little good if you do not address restrictions mentioned above, IMHO. The pump is capable of flowing oil through 14mm passages with little work. What you run into is restrictions in the galleries of the engine block due to tapers in the passages. If you drill these out to eliminate tapers then you can enjoy the full benefit of the oil pump porting. The pump chokes the outlet flow by 6.5% at most, when everything's stock. There are other restrictors in the case, between where the oil exits the pump and where it T's off after coming back from the filter. The outlet to the case is 14mm internal diameter. So the mismatch there is not very relevant in relationship to what else is restricted.
The return hole from the filter mount area is only about 1/2". At the first and second 90 turn in the front gallery it is 12mm (.176 sq. in.) due to the core tapers.
If you enlarge all these to 1/2" D., or .196 sq. inches, then you can more than equal the flow size restriction in the stock pump.
So, at a minimum everything should equal .2 sq. inches, regardless of shape until you get to the T. Cutting the partition in the pump's pressure chamber exit by a millimeter would accomplish that and it would end up being .225 sq. in..
The rest of the work I do, or extra enlargement, just improves flow, reduces turbulence, aeration and heat.

EJ25 Engine Oiling Diagram Key
1. Oil Filter
2. Oil Cooler or Heat Exchanger (purpose is to warm the engine oil and then cool the oil during heat spikes)
3. Oil Pump
4. Oil Strainer and Oil Pickup (in oil pan)
5. Intake Camshaft Oil Gallery, drilled 8mm
6. Exhaust Camshaft Oil Gallery, drilled 8mm
7. Right side Oil Gallery (tapered from 13mm to 8mm from each end)
8. Left side Oil Gallery and Gallery plug (tapered from 13mm to 8mm)
9. Turbo CHRA (bearing cartridge) Oil Feed line (reduced to 2mm ID)
10. External Feed line, Right AVCS Control Valve (5mm max.)
11. External Feed line, Left AVCS Control Valve (5mm max.)
12. Right Head Oil Feed Line (tapered from 12mm to 7mm) Note: heads have 6mm drilled primary feed runner to the head's cam journal galleries.
13. Left Head Oil Feed Line (tapered from 12mm to 7mm) Note: heads have 6mm drilled primary feed runner to the head's cam journal galleries.
14. Filter screen in banjo bolt (locations vary per year and model)
15. #5 Main bearing and rear thrust bearing (6mm ID feeds #4 rod journal through crankshaft) Fed by right gallery
16. #4 Cylinder rod bearing feed line (from #5 main/thrust bearing through crankshaft) Fed by right gallery
17. #4 Main bearing oil feed line (feeds only this main bearing)
18. #4 Main bearing feed line diameter reduction (reduces to 3.5mm ID) Fed by right gallery
19. #2 Main bearing feed line reduces to 3.5mm ID (Fed by left gallery and feeds only this bearing)
20. #3 Main bearing feed line reduces to 7mm (Fed by left gallery and feeds #2 & #3 Rod bearings through crankshaft)
21. #3 Cylinder rod bearing, fed by #3 Main bearing
22. #2 Cylinder rod bearing, fed by #3 Main bearing
23. #1 Main bearing, with reduction to 5.5mm ID (fed from beginning of Right Gallery)
24. #1 Cylinder Rod Bearing (fed from #1 Main Journal through crankshaft)
25. Gallery plug with pressure sensor
26. Small gallery plug (2X, hex head)
27. Large gallery plug (2X, hex socket head)

NOTE: I'm not the creator of the original drawing. It suggests that oil comes from the head's top, main oil gallery to the front journal. This is in error for an AVCS head and the external tubes for the AVCS solenoid are required as they are the only source of oil to the front journal!
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Attached Images
File Type: jpg lubrication engine copy.jpg (100.9 KB, 640 views)
File Type: jpg front T collage sm.jpg (90.0 KB, 293 views)

Last edited by Scargod; 02-12-2022 at 08:05 AM. Reason: added collage of porting on front "T" of gallery. Corrected spelling to gallery/galleries. Noted illustration error!
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