Oil Pump O-ring Mod - Testers NEEDED

[TitaniumTT]

So here's the backstory, my last engine was a 13B-RE Cosmo motor with the stock oil pump, stock OPR, stock bypass valve and stock casting under the pump itself. At idle I would see about 15ish psi and on decel the low psi warning light would come on @ 15 psi I believe. I've seen as low as 7psi and the most I ever saw with that motor, I checked the logs, was 67 psi @ 6k+rpm. Not great but "acceptable." I use that term loosely. The pump, when I broke the motor apart was visibly scored.

The engine needed a rebuild and I wanted to really address the oil system for a myriad of reasons. I decided to go with
1) FD OPR
2) Shim the bypass with 2 washers
3) Clean up the casting under the pump
4) MAKE A POSITIVE SEAL BETWEEN THE ALUMINUM PUMP AND THE IRON MOUNTING SURFACE.

A friend of mine has a CNC mill and when I approached him about the idea, he kinda scoffed at it saying that no-one has ever done it to his knowledge and people don't seem to have problems so why bother? It didn't take long for me to convince him to try it and I sent him a stripped down and cleaned up pump. It was actually the one that was visibly scarred. There was no scaring on the pump body, just the troicoids and the pieces between them. I had a second pump on it's way to me anyway. This is what we have.

I cleaned up the casting, nothing crazy, about 20 minutes of work

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4838&stc=1&d=1237951133

And here is the pump body

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4839&stc=1&d=1237951133

And here is the o-ring installed with a smear of hylomar on the seam between the o-ring and the outside sealing surface to keep the o-ring in place and on the mating surface itself. THe hylomar cannot get into the pump.

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4840&stc=1&d=1237951133

Also of worthy note is my dual mocal oil coolers run in series with -10 line. Theres close to 15' of -10 line which should also reduce the pressure some.
http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4928&stc=1&d=1238394974

bulkhead fittings
http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4929&stc=1&d=1238395194

T-Stat
http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4930&stc=1&d=1238395194

The results, well the are RIDICULOUS. At a fast cold idle I'm seeing close to SEVENTY psi. (I'm going to type out the numbers so you know it's not a typo) At a normal hot idle I'm seeing thirty-five psi and by Two-thousand eight hundred rpm's I'm seeing over a hundred and nine psi. I have the standard 0-100psi 0-5v sender and it's pegged at 109. I don't know what my max psi is yet becuase I just don't have a sender that reads that high. One is on order. Right now my dash is throwing a "code" and readin 0.0psi which obviously causes me concern. Upon first start-up when the rpms climbed high enough the dash read 0, it's default error. I quickly shut the motor off. It took me a minute to realize what was going on. I had to open up the Motec and bring up a dial gauge that read the voltage from the sensor. With the voltage pegged I realized what was going on.

I called my aluminum chip eating friend to tell him and he was pretty surprised. However, we are not sure how much of it is the o-ring, and how much of it is the motor itself, the builder, the tolerances I used, the FD OPR, etc etc etc. It's all me, the builder ;)

Anywho, what we are looking for are people that are rebuilding motors that aren't going to change ANYTHING else in thier oiling system. We can't use my experience as an example becuase I did so much at once we cannot be sure what mod effected the pressure. For all we know the o-ring did nothing and it was the change in pump internals and the FD OPR. I doubt it. My gut is telling me that the o-ring made a significant difference but with so many variables, we cannot be sure. I have however done some research in both the FSM and with other peoples experience and it looks like my pressures are MUCH higher than other peoples with similar mods. I should also mention that the pump was actually worn PAST the FSM specs as measured with the feeler gauge. I didn't have a third pump on hand so I played musical internals until I got the closet tolerances I could. They were still out of spec though. In otherwords, the pump should've been thrown out but instead, it's making more pressure that the FSM states as minimums. In most instances, 2x the amount.

Is there anyone that wants to actually test this mod? The o-rings came in packs of 10 so you'll be getting a free o-ring. The machining we are not sure of the cost. He seems to think there won't be any interest. I told him I thought he could make a decent coin offering this service if we can prove that it significantly raises oil pressure. The first testers would pay very little if anything for the machining. It's up to him, not me. But if we could get a group of people that wanted it, I'm sure the cost would be insignificant.

So, if there's anyone who wants to try this - post up, or PM me. I'll be putting this thread in every relevant section just so it can get attention. However, if all responses can be placed in the "General Rotary Engine Related Tech Section," that would be great. Thanks guys

[j9fd3s]

very interesting! ive been using silicon on the pump/iron surface for sometime, it seems like using nothing might be ok on a NEW pump and iron, but used needs help!

[neit_jnf]

any updates? i read somewhere that judge ito uses a paper gasket in here to improve oil pressure...

[TitaniumTT]

paper gasket soaked with locktite I believe. I know Joe uses a small silk tread (cool idea).

So far the results are impressive. I'm getting >120psi >6krpm and idle is ~30 psi. Cold start idle oil pressure is around 100psi.

All this and I BELIEVE my o-ring in the front cover squeezed out too! I found about 1/3 of an o-ring lodged in the filter on the last oil change.

[neit_jnf]

what weight oil do you use? at what temps are you seeing those pressures? maybe you can go to thinner oil now for more flow and less drag while maintaining a healthy pressure!

[TitaniumTT]

I run Mobil 1 10w30. Cold start the oil is usually ~50*. I'd have to double check the logs but I'm pretty sure that the 120>6k really doesn't car about temps. 170-220* will net about 20psi @ idle

[Whizbang]

how much would it cost us to have your friend do a little milling on our oil pump housings?

[TitaniumTT]

Dunno, I'd have to ask him. We we're honestly expecting a lot more interest in this that what we've had.... A GB on them would be something to explore though so he can just crank them out.

It's also a matter of which pump you have as well. I have the higher volume one with the inlet that leads down. All the N/A ones that I've come across are perfectly circular.

I know Ejay is interested, which pumps do you guys have?

[Whizbang]

i might be getting the mazda hi performance one unless of course a turbo one works the budget better

[TitaniumTT]

Oh really. Why have I never heard of this mazda hi-perf oil pump. Do you have a PN by chance?

[Whizbang]

it appears the Turbo pump (86-91) is listed as their performance pump

#N318-14-100A

[TitaniumTT]

Ah, interesting. I wonder what the difference between the S4/5 TII pump and the S6+ pump is.

[Whizbang]

not sure. wouldnt be hard to compare. Im sure Atkins would know or easily be able to tell.

[C. Ludwig]

Ah, interesting. I wonder what the difference between the S4/5 TII pump and the S6+ pump is.


The S6+ pump has an additional cavity on the inlet or outlet side (can't remember and don't have one in front of me). The 3rd gen pump won't work on the S4/5 irons unless you port the iron to match the pump. Think it's been done but a quick search hasn't turned anything up.

There is/was a "comp" pump offered by Mazda Comp for the 12A. It has heat treated shaft and rotors. Other than that there are only stock pumps.

[TitaniumTT]

Thanks Ludwig. So just to clarify, the one that I have pictured is considered an S6+ pump correct? Does anyone have pictures of an S4/5 turbo pump?

[Rotary Inspired]

I never see below 40 PSI at idle with current engine with similar results up top. I do have a the Racing Beat oil pressure reg. Idle is 1120-1200 rpms. Car is a 10AE. Very very large extended port. I actually RTV the pump to the housing where you use the hylomar. I have never had an oil pressure issue since i have started doing this 15+ motors.

[C. Ludwig]

Thanks Ludwig. So just to clarify, the one that I have pictured is considered an S6+ pump correct? Does anyone have pictures of an S4/5 turbo pump?


Yes. The earlier pumps are entirely round without that flared out section.

Did TiTT, did you use a gasket for the front cover? With the S5+ you need to use a gasket of some sort or the white plastic ring with bulge out and press the rubber o-ring into the oil passage. The RX-8 gasket fits the earlier engines and is a metal gasket which seems to be a nice way to go.

[TitaniumTT]

I used the 13B-RE metal gasket (similar to the Renni but no need to trim) along with the white teflon piece and the o-ring. Everything pressed in all nicey nice. I have no idea why it popped out. Now that I think more nad more about it though, the there is no other o-ring to pop out of place. I hate that setup, I really do. I'm thinking about plugging that passage on the iron and reeming the iron to the side and using an NPT to -10 AN fitting on the next engine I build. Just seems like an uneccessary potential failure.

Rot Inspired - my idle is MUCH lower than yours and such it would be expected that my oil pressure lower @ idle. I'll check the logs when my laptop is up and running again to see what the OP is @ 12-1300. When my engine cold idles at that speed I see about 90-100psi

[Longshoe]

I like the idea of doing this kind of oil pressure mod but doesn't excessively high oil pressure like that cause problems? I would think you would want flow and that pressure that high is not necessarily a good thing.

[C. Ludwig]

I used the 13B-RE metal gasket (similar to the Renni but no need to trim) along with the white teflon piece and the o-ring. Everything pressed in all nicey nice. I have no idea why it popped out. Now that I think more nad more about it though, the there is no other o-ring to pop out of place. I hate that setup, I really do. I'm thinking about plugging that passage on the iron and reeming the iron to the side and using an NPT to -10 AN fitting on the next engine I build. Just seems like an uneccessary potential failure.

Rot Inspired - my idle is MUCH lower than yours and such it would be expected that my oil pressure lower @ idle. I'll check the logs when my laptop is up and running again to see what the OP is @ 12-1300. When my engine cold idles at that speed I see about 90-100psi


13B-RX3 did a good write up on what you're describing on the other site. Though it's a better setup it would be over kill in a street car IMO. Though the front cover o-ring does fail from time to time it's been around long enough and worked well enough that I don't really consider it an issue.

What I have looked for an would like to try is a copper or aluminum crush washer instead of the o-ring but I have yet to find something that is the right combination of diameter and thickness. When I mentioned earlier about the o-ring squeezing out without a gasket on the front cover, that is from experience. We found the o-ring in the cooler many miles down the road. Thing is idle oil pressure on this engine was still solid at around 40 psi. The teflon retainer had been squeezed enough (since I didn't use a front cover gasket) that it was doing the job of holding the seal. Again, I would like to try something similar with a soft metal crush washer.

[TitaniumTT]

I like the crush washer idea. Have you tried looking @ either GoodRidge or McMaster?

For the next engine I build I think I'm going to take your infered advice and skip the metal gasket, use the o-ring and the teflon piece as well and see how that works out. When this engine comes out in a month or so I'll pull the front cover, see if the 0-ring is still there. If not, replace the cover sans gasket and see if the oil pressures are any different.

I do disagree that this is not worth it for a street car. In my opinion this would be better for a street car than a race car becuase of the idle oil pressures. I would like to see oil presure @ idle consistantly be above 25psi to keep the jets in the e-shaft opened at all times. This promotes cooling of the internals more during extended idle periods which a street car sees more than a race car. Just my $.02 though.

[C. Ludwig]

I like the crush washer idea. Have you tried looking @ either GoodRidge or McMaster?

For the next engine I build I think I'm going to take your infered advice and skip the metal gasket, use the o-ring and the teflon piece as well and see how that works out. When this engine comes out in a month or so I'll pull the front cover, see if the 0-ring is still there. If not, replace the cover sans gasket and see if the oil pressures are any different.

I do disagree that this is not worth it for a street car. In my opinion this would be better for a street car than a race car becuase of the idle oil pressures. I would like to see oil presure @ idle consistantly be above 25psi to keep the jets in the e-shaft opened at all times. This promotes cooling of the internals more during extended idle periods which a street car sees more than a race car. Just my $.02 though.


I looked through McMaster online. Nothing was ideal. I tried some aluminum washers they had that I thought would be a good thickness. They were too large on the OD so I worked them over with the sanding wheel. I just tried it in a mock up and it ended up being too thick and didn't "crush" at all. Thick enough it propped the cover up off the iron. Copper might be soft enough to work in a similar thickness but I never revisited the issue. There has to be something out there that would work, it's just finding it.

Don't do the S5+ cover/iron without a gasket. What I was trying to explain is that if you do this the teflon will be squeezed enough to guarantee the o-ring is pushed into the oil passage. You can mock one up and try to see. Alternately, I would like to try another engine with just the teflon piece as a crush washer and no gasket but I haven't built an engine for myself in some time that I can experiment with.

Another idea I have had regarding the front cover o-ring is to machine the pieces for a dowel. Would work just like the rotor housing to iron joint. The dowel would support the o-ring and pretty much eliminate the chance of a blow out. Again, I've never really had an issue though with the parts properly assembled so it's never been followed through.

If you want the jets open at all times remove the check ball and replace the jet with the Weber jet or the Mazda comp jets. Easy enough. I've used the comp jets in a number of IT engines and never have any issues.

[Whizbang]

hmm once i start the PP project, ill be giving my hand in configuring something as well or at least testing some ideas.

[TitaniumTT]

hmm once i start the PP project, ill be giving my hand in configuring something as well or at least testing some ideas.

Bitchin'!

Don't do the S5+ cover/iron without a gasket. What I was trying to explain is that if you do this the teflon will be squeezed enough to guarantee the o-ring is pushed into the oil passage. You can mock one up and try to see. Alternately, I would like to try another engine with just the teflon piece as a crush washer and no gasket but I haven't built an engine for myself in some time that I can experiment with.

That's what I was getting at, no o-ring or gasket. Just the teflon piece.

Another idea I have had regarding the front cover o-ring is to machine the pieces for a dowel. Would work just like the rotor housing to iron joint. The dowel would support the o-ring and pretty much eliminate the chance of a blow out. Again, I've never really had an issue though with the parts properly assembled so it's never been followed through.

That right there is an awesome idea. I meed to look into that for the next engine IFF it continues to be a problem with this one.

If you want the jets open at all times remove the check ball and replace the jet with the Weber jet or the Mazda comp jets. Easy enough. I've used the comp jets in a number of IT engines and never have any issues.

I was told that by removing the bacll and spring (Yes they will always be open) and replacing them with the weber or MazdaComp jets, the idle psi will suffer to the point where the idle should be raised slightly to bump the pressure. This is why I shied away from changing the jets out. No-one could tell me with any certainty what the idle psi would be on a street car. Just that it would be to low for a street car idle. What have been your experiences.

Something else I was going to try was going to be removing the ball and spring but leaving the factory jet in. Seems like a nice compromise

[Rotary Inspired]

Like to hear where yours oil pressure is at that rpm. I wish I could get my idle lower but with primary ports bigger than stock secondaries it doesn't like to idle at below 1000 as well. It gets very rough and almost sounds bridgeportish below 1000

[C. Ludwig]

With the comp jets installed and an FD regulator you should see 30 psi at 1000 rpm hot which is plenty.

The comp jets and the Weber jet are pretty much the same size. The Weber jet just fits inside the stock jet. I'm not crazy about paying the same amount for another part that presses inside something in the crank shaft, so I use the comp jet. Both actually have a smaller orifice than the stock jet. I guess the idea is that with the ball and spring removed they have the same peak flow and still have constant flow.

Also, did some playing around yesterday. The oil pedestal o-rings are a good match for the S5+ front iron. You could possibly use one of those in place of the teflon o-ring/small o-ring combo and do like we do with the earlier engines that don't use the teflon piece and simply omit the front cover gasket in order to squeeze the o-ring a little tighter. The oil pedestal o-ring has a little larger diameter than the regular front cover o-ring as well so you should get plenty of grip on it.

[TitaniumTT]

Hmmmm, I like what your thinking on eliminating the teflon peice. I never did like the two pieces to accomplish the same thing that one could do. I'll try the larger o-ring and skip the teflon piece. I have an entire kit of o-rings so finding a nice sized one shouldn't be a problem. I could always just take the front iron down to Napa and size it there as well. Get the dimensions and order a ton of them from McMaster.

[Nismo]

Brian, I might be interested in testing.