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Old 07-29-2007, 01:52 PM   #176
Homemade WRX
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Larry, how old are you?!!

I'm game and still trying to get one of my EE buddies to get the logging system done for me...mulitple sensors in the motor all with there own channel...kinda of make a time line of the air pocket in the system
maybe gauges and a camcorder will be easier.
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Old 07-29-2007, 03:55 PM   #177
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Larry, how old are you?!!
I'm a Vietnam era veteran if that gives you a clue --- late 50's.

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but wouldn't it be more accurate/beneficial to measure the oil pressure at the main gallery (specifically the main gallery that feeds number 3 main)?
It would be good to log all the engine galleries, but the most distant point should show the worst case (earliest signs of system oil pressure drop). yes in a perfect world you would log oil pressure in each of the main caps supply gallery to see if flow limitations in the combined gallery does not keep up with the oil getting thrown out of those two mains/rods.

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Old 07-31-2007, 03:52 PM   #178
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This is an interesting thread.

Not sure if it was clearly explained somewhere in this thread or not....cross-drilling means drilling a second passage in the main journals at 90 degrees to the existing passage (as in a "cross" shape). The reasoning behind this has to do with the main bearings and how the oil is being supplied to the rod journals. The main bearings for the 3 journals that supply the rods are grooved. It is the reservoir of oil created in these grooves that feeds the rods. However, if you look at the bearings you will see that the grooves are not machined the full circumference but instead at the parting line of the bearings the groove has tapered off to nothing. Therefore with a single through-drilled oil passage in the crank, when that passage is in line with the parting line of the bearing the oil flow to the rod bearings is cut off momentarily. By drilling another through-hole at 90 degrees it ensures there is a constant flow between the main journal and rod journal a full 360 degrees of rotation.

With regards to aftermarket billet cranks...many of them are line drilled tying the main journal oil passages together and therefore the rods are fed by multiple mains. Thus by drilling the mains at different orientations relative to each other the same effect is produced.

The same effect as cross drilling can be achieved by machining a full groove on the main bearings...but this reduces the surface area of the bearings and therefore reduces their load carrying capabilities slightly.

This modification is most beneficial at high rpms where oil flow is marginal at best to begin with. Additionally, the inertial loads on the rods increase exponentially with rpm and these loads have a tendency of distorting the big-end of the rod and disrupting the oil clearances. So rod quality and strength are critical for high rpm use so rod distortion is kept to a minimum.

With regards to the oil pump...all Impreza turbo models use essentially the same pump. The Spec C does not have a special pump. However, the 2.0L turbo Legacy models do show a different part number (ending in 270 as mentioned somewhere) and the pump rotor part number is different as well so its possible this pump has increased volume. I will have to order one and check the dimensions. Additionally, Cosworth is now offering a high output oil pump with similar dimensions to the JUN one but at maybe 50% of the price. According to JUN the increase in volume is 20% so I would figure something similar for COsworth.

One of the issues with the Subaru's horizontally opposed design is that oil tends to accumulate in the heads due to lateral g forces in long high speed corners. With the AVCS there is additional oil being dumped into the valve cover when the oil control solenoid is exhausting oil from the cam sprocket during changes in cam position. One thing you will notice with the engines equipped with AVCS is the second set of breather hoses that T together and feed the top of the block....I believe the purpose of this is to help redirect liquid oil back to the block (although I have yet to find any definitive info on this).

Finally....quite often we find that the cause of engine failures is tuning-related and not due to defficiencies in the engine internals. Excessive piston temps (due to either excessive combustion temps or poor ring contact) leading to piston siezure or detonation forces causing a disruption in the oil film. Excessive oil consumption, aside from potentially dropping the oil level also affects the combustion and can cause detonation in an otherwise properly tuned engine. Lots of things to consider and so many variables to balance out to achieve reliability at extreme power outputs.

For anyone seeking JDM Subaru or STi parts, Cosworth, JUN, or other stuff we do supply these parts and do in fact build a lot of custom engines for clients.

--Dave
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Old 07-31-2007, 06:36 PM   #179
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Good post Dave.
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Old 07-31-2007, 08:52 PM   #180
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Originally Posted by Dave_RalliSpec View Post
Additionally, Cosworth is now offering a high output oil pump with similar dimensions to the JUN one but at maybe 50% of the price. According to JUN the increase in volume is 20% so I would figure something similar for COsworth.
--Dave
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Dave, the -270 PN was probably a 12mm pump. the stock sti has a 10mm rotor pump

cosworth, jun, and cobb all offer a "high volume" 20% increase oil pump.

it's a glorified factory subaru, dual avcs, 12mm oil pump. that being said, I know cosworth does some internal "massaging" to their 10mm pump, and I'm sure the same drilling is done to their 12mm "high volume" pump.
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Old 08-05-2007, 11:01 PM   #181
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An interesting read.
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Old 08-09-2007, 06:42 AM   #182
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I keep coming back to the fact that the engineers at subaru are no dummies.
They have kept the cross drilled design for quite a few years now, even after the redesign of the positioning of the thrust bearing they kept the cross drilling.
If the cross drilled design is inherently flawed would they not have changed it?
Surely they would have got excellent feedback from world rally?

I was a firm beleiver that the cross drilling design was the cause of the journal failures but now I am not so sure.
He dont have enough of the altered oiling design cranks out there to get a fair amount of feedback if the bearings are fairing better. So we cant judge on those.
If the cross drilling was at fault why do we see some engines destroying bearings and not others?
Maybe the real culprit here is oil starvation at the oil pickup, throw in the variables of cornering, inconsistent oil levels between engines, quality of tune and irregular high rpm use and it may account for the failures.

We really lack calculated information on how much force is being generated against oil flow due to centrifugal force acting upon the oil. Wouls be good if someone could work this out.......

Unless I am mistaken other manufacturers such as nissan, toyota etc also use cross drilled cranks and are spinning them well over 8000rpm and have no oiling issues. Why are subaru's failing?
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Old 08-09-2007, 09:07 AM   #183
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I like dave's explanation

Turbos defy four stroke, there is no time association. Squirts of timed oil aren't enough- the milliseconds an engine tries turbine mode (hellacious tune ) they are dying until THEY DIE. Very simple. Crossthreading, and more volume was a must do for someone who took the engine that far. I personally would have higher volume on all ej engines, but that is my area going from -20s F to 100F, and very extreme changes inbetween. In fact all engines have proven sime kind of problem going through my area for just one season, that will not be found in a more ambient place. The oil delivery has everything to do with it. The greatest ever encountered personally was the three main bearing subes with a trochoid oil pump- (just keep it full). The ej, just by sight of oem is repulsive to think it is feeding more than ever on that tiny pump. Just my two cents and years of my own mechanical trials. I was hoping to read an upgrade by subaru themselves, but it hasn't happened , unless you find the odd part# doing more as in daves thread states. The miles on the engine with no faults should easily figure that out.
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Old 08-09-2007, 09:08 AM   #184
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very valid point...have the reason why for my original build I wanted to use an factory crank and see on the dyno at what point the bearings got starved...no g's and no questionable oil level. Then of course a full motor tear down to do some investigation.

As for the WRC statement, their oiling system and I'm willing to bet, crank, isn't remotely close to factory.

Now I do believe starvatoin and bad tuning to have been the cause of a lot of the bearing failures. I also believe that the flawed oil delivery and the repeating same bearings failing point to a root problem.

Last edited by Homemade WRX; 08-09-2007 at 09:13 AM.
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Old 08-12-2007, 04:30 PM   #185
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well, have some pretty cool news to share with the community...
Just got in a new EJ20 crank from the dealership. I opened the box and unwrapped it to start checking it over when I noticed something great about the main journals. They are drilled just like the spec c crank.
I took some pics and have the part number. I'll post it up later on tonight when I get home.
Wonder if this is subaru's solution to sooo many failed rod bearings. Wonder if the new EJ25 cranks are coming the same way...?
have a good one,
Micah
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Old 08-13-2007, 01:15 AM   #186
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Originally Posted by Homemade WRX View Post
well, have some pretty cool news to share with the community...
Just got in a new EJ20 crank from the dealership. I opened the box and unwrapped it to start checking it over when I noticed something great about the main journals. They are drilled just like the spec c crank.
I took some pics and have the part number. I'll post it up later on tonight when I get home.
Wonder if this is subaru's solution to sooo many failed rod bearings. Wonder if the new EJ25 cranks are coming the same way...?
have a good one,
Micah
Wow! thanks for the info Micah!

Only the main have now 4x holes (90 degrees apart) or does the rod journals also have 4?

It's a wrx EJ205 crank?
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Old 08-13-2007, 09:22 AM   #187
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yup..four holes=two drillings approx 90* apart....looked as though they might be a bit tighter than 90* apart...but close enough

yeah, EJ205 crank. I have the part number on my phone and will post the pics and number when I have time. Should be later today.

Didn't get to do it last night. Was troubleshooting AEM ignition pick up problems...
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Old 08-14-2007, 09:29 PM   #188
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Bump for the pictures Micah

Just wondering now if I should double cross drill the rod journal also like the STI spec C crank I will be using the 12mm oil pump.
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Old 08-14-2007, 09:52 PM   #189
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what about the ROD journals? How are those drilled?
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Old 08-15-2007, 12:17 AM   #190
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rod journals are the same...the main journals are now double cross drilled.

now having issues with we-todd-did-racing...time for the next server

edit and then my internet took a dump. I'll post them up later today.

Last edited by Homemade WRX; 08-15-2007 at 08:37 AM.
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Old 08-15-2007, 07:41 AM   #191
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Ok. Thanks for the info.
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Old 08-15-2007, 03:28 PM   #192
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ok here we go...the shiny crank is obviously the new one with part number on the box...the old crank pics are just for reference.







-Micah
p.s. sorry pics were taken on my phone

Last edited by Homemade WRX; 08-23-2007 at 12:43 AM.
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Old 08-15-2007, 06:18 PM   #193
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Thanks for the pics.
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Old 08-15-2007, 07:09 PM   #194
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Default main bearing shells

I have several subie short blocks to study. I have only taken a few apart. I have a 2.2 na motor that has 360 degree grooves in all the main shells. I have a 2.5 na that only has the thrust main with 360 degree groove. I haven't taken a sti short block apart yet to see. I also have a 2.0 closed deck sb that I will be taking apart. On the statement about running more clearances thats not for me. That would require more volume and thicker oil that doesn't flow as well. That approach is for drag motors IMO. Any comments will be welcome.

This is an update, on all the subies I have taken apart the block has a 360 degree groove running under the main shells so oil is ALWAYS supplied through the holes in the main shells no matter where the crank is. Maybe the main shells oil holes could be elongated in their grooves to provide more volume. I think I will cross drill my cranks anyway but the deal about the grooves in the main shells stopping at the center or part line is not why the cranks were crossdrilled. I would like to see a new set of bearings that goes with the new crank to see if the're any different.

Charlie

Last edited by charliew; 08-17-2007 at 09:28 PM.
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Old 08-15-2007, 09:01 PM   #195
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The USDM EJ257/255 has the thrust/center/front (1-3-5) bearings with the 360 grooves in the bearings...the other ones, 2 and 4, do not have grooves.
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Old 08-18-2007, 04:30 AM   #196
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The USDM EJ257/255 has the thrust/center/front (1-3-5) bearings with the 360 grooves in the bearings...the other ones, 2 and 4, do not have grooves.
Thats very interesting information.
I was doing some research on crank oiling. It seems many high revving engines use the cross drilled design for example the honda S2000 and aftermarket cranks such as TODA for nissan/honda's. If the cross drill design was so inherently flawed I would expect TODA and JUN would not be using this method.

I checked out the ACL bearings website. You can call up bearings for various engines and it shows a detailed drawing of the bearing shells. Its interesting to note that the Subaru design is not really used in other engines.
On many other engines the load bearing area of the bearing has no groove and the groove only appears to the sides of the shells where the load is reduced. Its odd that the Subaru bearings are the opposite, even after taking into consideration the boxer layout it doesnt make sense.
Subaru's use of a full grooved bearing shell is much more logical, this was not always the case.

In my opinion if you have the 4 oil hole hole type crank and full groove bearings you should be ok in that area.
That just leaves-
1- Uninterrupted oil supply to the oil pump (oil pan level)
2- Non aerated oil being sucked up by the pump
3- Adequate oil pressure/volume (maybe the 12mm pump will sort this out)
and finally.....
4- Bearing clearances.
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Old 08-19-2007, 07:32 PM   #197
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You have to keep in mind you are talking about a "system" you can't judge the merit of a feature in isolation. Cross drilled cranks are, very cheap and easy to build, and very good for reliablity for low stressed engines below their rpm cutoff. That rpm cutoff is determined by, journal diameter, engine rpm, oil pump supply pressure and volume, bearing clearances, and journal/bearing width and bearing loading. Just because a 237 hp S2000 turns 9000 rpm on a cross drilled crank, does not prove that a cross drilled crank in a 500 hp turbocharged engine that has over 2x the bearing loading, is a suitable combination.

Assuming the info I found on the net is correct, the main bearing journal on the S2000 is .784 inches wide, vs our 0.6875 wide mains (14% more bearing area). I believe the journal diameters are similar diameter so they are carrying 1/2 the load on larger bearings when compared to a modified Subaru.

As a system there are a dozen ways to solve the problem, go to wider bearings (not likely needs to redesign the whole engine), up the oil pressure and volume flow, or change bearing clearences so you have a thicker oil film, or change the crank drilling design so it is more favorable to the higher bearing loadings seen in a high performance turbocharged engine.

The cross drilled design is not "defective" it is simply is not ideal/suitable for this application in my view.

Change any one of those key secondary factors like bearing loading and you change the whole equation regarding how successful the cross drilled design is for a given situation.

Larry
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Old 08-19-2007, 10:57 PM   #198
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The cross drilled design is not "defective" it is simply is not ideal/suitable for this application in my view.
Subaru are now supplying cross drilled (main journals) cranks for wrx's with 227HP to the engine 7K rpm, like Homemade WRX told us. The spec C also uses cross drilled cranks (main and rod journals). All of this with the 10mm oil pump, so I'm stating to think we're on the right track to solve our oiling issue. It's a good and inexpensive mod to do on our build engines, adding the 12mm oil pump is not a bad idea also.

EDIT: nope I was wrong, the spec c doesn't have the rod journals cross drilled, my bad.

Last edited by Kosmic; 08-19-2007 at 11:21 PM.
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Old 08-19-2007, 11:04 PM   #199
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The USDM EJ257/255 has the thrust/center/front (1-3-5) bearings with the 360 grooves in the bearings...the other ones, 2 and 4, do not have grooves.

1-3-5 are exactly where Subaru are now cross drilling their cranks, they are the main journals that feeds the rods.

Now, why don't they cross drill the rod journals also? we know that the spec C cranks are. The diff between the wrx and spec C --> about ~100HP and 1K rpm.

EDIT: nope I was wrong, the spec c doesn't have the rod journals cross drilled, my bad.

Last edited by Kosmic; 08-19-2007 at 11:21 PM.
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Old 08-19-2007, 11:08 PM   #200
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Now, why don't they cross drill the rod journals also? we know that the spec C cranks are.
are they?...I thought it was only the mains...time to find some pics again.
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