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Old 03-02-2008, 08:10 AM   #235
widebodygtr
Scooby Newbie
 
Member#: 173337
Join Date: Mar 2008
Location: Australia
Vehicle:
1990 GTR Skyline
Bayside blue

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Great thread guys, Am new to subaru engine building so don't shoot me.
I currently have a GTR skyline and have had a look at the oiling system on it that may help.
These engines have a 8250 rev limit stock and will gladly rev higher with few oiling issues.
First things are oil pickup starvation on heavy corners due to gforces(fixed by baffles around pickup
Second is over oiling to the cams(fixed by restricting oiling to the top end) cams only need minimal oiling due to slow revs and no heavy loading as associated with mains or rods.
Third is faulty oil pump drive(fixed by using a longer pump drive on the crank)
And finally drain back from the head(fixed by plumbing a -10 line from the back of the head to the sump
Now some of you are saying cross drill and some are saying don't and some of you say that it is because the oil hole is at 90deg.
The RB26 in gtr's run there oil holes at 90deg aswell and run 10psi of oil pressure per 1000revs but difference is they run full groove mains on top and bottom main bearings and numerous holes on the rod bearing bottom shell.
My engine in particular makes over 800hp at the wheels running 10,000 revs 30psi boost and 100psi oil press at max revs with no cross drilling or oil chamfers on the crank, I run .002" on the mains and .0025" on the rods.
Running larger than .002" to .0025" on the mains in a subaru engine seems a little big to me as taking into account the expansion rate of the cases you will end up with more like .003 to .0035" which in turn will lose oil pressure and also cause the crank to whip slightly
There are quite a few GTR engines that rev to 13,000 and 45psi boost with aftermarket cranks that seem to only cross drill keeping them at 90deg to the crank.
I am just a bit puzzled as to why you are so worried about centrifigal force when these engines run similar crank designs.
I think your issues are more in the feeding as stated by someone else how it feeds 2 rods of one main and also the oil hole phasing.
As for phasing there is more load on the crank about 15 to 20deg ATDC as the combustion process is in full swing as opposed to BTDC when there is still pressure applied but nowhere near as much, Having said this you need to pre empt this and time them a little earlier so as it has full oil pressure at this point
As for loosing HP with higher oil pressure, i would rather loose 7 to 10hp in knowing that my bearings are not going to run dry with the higher oil pressure, and taking into account that there are a number of 90deg turns in which you usually loose some pressure in the engine it is wise to test oil pressure at a number of locations with the last point of oiling usually the worst.
Don't mean to step on anyones toes, they are just some of my theories
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Last edited by widebodygtr; 03-02-2008 at 08:17 AM.
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