Oil Pump Discussion

[Legacy777]

This stems from fatgc8's comments in this thread
http://bbs.legacycentral.org/viewtopic. ... 20#p328320

The jist of it was to upgrade to the 08+ STi oil pump because it is an 11mm pump and will flow more. I did some looking on NASIOC and found some old threads and some new ones with info.

First I found an old thread talking about oil pumps, and found a comment from Matt regarding the ej22t pump.
http://forums.nasioc.com/forums/showthr ... p=16811155

Specifically, I was interested in what he said about the shims. My ej22t pump only had one shim in it. Not sure if the shims varied between years....or what.

Next this thread talks about the differences between the 10mm & 11mm STi pumps
http://forums.nasioc.com/forums/showthr ... ?t=1438693

Which then lead me to this thread with info on the pressures and flow rates.
http://forums.nasioc.com/forums/showthr ... ?t=1411649

Interesting note is that the ej22t pump has a higher relief valve pressure setting than the 11mm STi pump. In those threads they talk about too much flow/pressure. I do believe you can have too much flow. So without knowing a little more info on the flow requirements I'd be a little hesitent to upgrade to the 11mm pump.

I am curioius though now about the number of shims in the ej22t oil pump. Those that have taken one apart, how many shims were in there? I am now wondering if the fact I only had one shim in there could have caused the rod bearings to be starved by oil due to lower oil pressure at higher rpms when the oil squirters kick in.

[Legacy777]

More info
http://forums.nasioc.com/forums/showthr ... ?t=1433697

[93forestpearl]

I'm on the side of the fence that believes you can have too much flow from your pump. If the 11mm pump has a lower relief pressure, there will be a lot more time in by-pass. Especially on a motor with OEM oil clearances.

Some people run looser rod bearings, so more oil flow would be needed for that.


Since you'll be keeping it under 6500 rpm, I think you'll be fine on the EJ22T oil pump.

[Legacy777]

Yeah, that's my thoughts as well. I'm just curious now about Matt's comment about there being two washers. Do you recall whether there was just one, or two washers in the oil pump?

[93forestpearl]

I haven't taken one apart, so I couldn't say.

[07Evolved]

The oil pump I just took off my EJ22T had one shim..

[93forestpearl]

I'm assuming that the thickness of said washer(s) is what counts.

[Legacy777]

Thanks for the info 07Evolved!


Dan, pretty sure the thickness of the washer is the same. The ej22t pump has a different part # for the spring, so I would assume most of the added force to increase the pressure is a result of the different spring. I'd like to get the spring rate for the spring and do the calc to figure out the actual pressure relieving pressure based on the tested spring rate.

[kimokalihi]

Shouldn't it show how many shims there are in the parts catalog?

[Legacy777]

It should....but you never know with Subaru....they like to do odd things some times.

Looking for one more person to confirm that there's only one shim/washer......anybody....one more person

[fatgc8]

I have been working on Subaru motors for a long time now and I've only seen 1 washer on the ej22t 10mm oil pumps..

[fatgc8]

If you call your local dealer the 10mm & 11mm pump are virtually the same price (at least in my area) so its kind of obvious witch one people should by. With that being said, do not buy this pump if you don't plan on going beyond 6500 rpms. I bought the pump because im revving my sti out to 8.5k. Looking at all the flow rates and how you got your bearing clearances setup, if you plan on revving your ss or tw to about 7200-7500 rpms you should buy a 11mm pump.

[93forestpearl]

Josh will still have 22T heads with HLA's, so it will be pointless for him to rev of 6500, or even 6000 for that matter.

[skid542]

^^^ Your comment is more centered around the flowing abilities of the heads and not the HLA's correct? I only ask because I plan to redline my EJ20H heads with HLA's the same as I've readlined my old 22T heads - stock rev limit.

[93forestpearl]

^^^ Your comment is more centered around the flowing abilities of the heads and not the HLA's correct? I only ask because I plan to redline my EJ20H heads with HLA's the same as I've readlined my old 22T heads - stock rev limit.

I'm not sure which is affecting it more, but either way airflow drops off significantly over 6k. It's especially bad over 6500. I noticed it on mine when I had the car on the dyno. The fuel cure was nice and smooth, but afr's tanked over 6500.

[Legacy777]

Thanks for the comment on the one washer.

I tried doing some testing two weekends ago, but my test rig didn't really work out. I'll have to see if I can come up with something else.

[Legacy777]

Well I finally got my testing rig setup for the oil pump relief spring. I tried one test rig and that didn't work. The test rig I made used a digital package scale, a wooden jig with a brass fitting, and metal rod cut to lengths: 1/4", 1/2", 3/4", 1", 1-1/4".

The brass fitting supported the spring and the wooden jig was setup so that the top of the spring was flush with the top of the board. I then inserted the different metal rod lengths, compressed the spring so it was flush with the top of the wood, and then read the force on the scale required to compress the spring the given length.

This test setup is rather crude, but the results were relatively consistent. What I was ultimately looking for was to determine whether the spring had a near steady spring constant or if it were progressive across it's "operating" window. I say it's operating window because the spring's free length is roughly 3". Based on the measurements I took, it's compressed length is 2.162". It's length when it starts relieving is about 1.834". These measurements work out pretty well with the calculations I performed and the resultant pressures.

Here's pictures of the test setup
http://main.experiencetherave.com/subar ... umprelief/

Here's a spreadsheet with the test data and calculations
http://main.experiencetherave.com/subar ... _Calcs.xls

[93forestpearl]

The spring has a little rise to it, but nothing crazy. I'm still digesting your spreadsheet.

[Legacy777]

I need to rework some of the measurements I took and scan that page in. That will probably help clarify things. I may adjust the spreadsheet a little....because yeah it is a little confusing.

[NICO]

i have 1 question, i all ways use the legacy t pump & i was going to use the new 08 pump on my motor. but then i came to thinking, i dont have the intake or exhuste controle timeing like the sti or do i have the crazy crank they use.

my question is, the sti pump need's all that extra pressure to help out with the heads and crank ??

[Legacy777]

The newer 11mm dia. pumps on the STi have more flow. They don't necessarily have more pressure. With the AVCS they need more flow to control it. Pressure doesn't necessarily need to be higher.

The turbo legacy pump has a higher relief pressure primarily due to the oil squirters.

There is a relation to flow and pressure, but that is dependent on the oil needs of the engine, primarily bearing clearances, etc.