Shimmed oil pump, why? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-03-2011, 06:31 PM   #1
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Default Shimmed oil pump, why?

So why would you want to get different shims on your oil pump?

Is there a reason not to get +35psi all the time?

Under what situations would you want different shims?

How does this work with the high volume pump?
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Old 03-03-2011, 06:38 PM   #2
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Stock pumps will produce the needed psi with the stock clearances in the crankshaft and connecting rods. Race motors often have much looser clearances, so to get the oil pressure to the correct level, you have to make an adjustment on the pump.

That is why you want to know what kind of clearances you will have in the bottom end before knowing exactly what kind of pump set up you will need. Also, I believe turbo oiling can rob some of that pressure as well, resulting in the need for an adjustment on the oil pump.
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Old 03-03-2011, 06:41 PM   #3
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I know about loose tolerances needing more flow, but that's why the high volume pump was produced, so that seems pointless to shim instead.

I can understand shimming for oil coolers and turbos, more lines and pressure loss, I'd forgotten about that when I posted, thanks for the reminder. But that wouldn't be more than 7psi, so I don't see the point of more.

So: Loose engine = High flow pump. Turbo/oil cooler = one shim. What's the point of more?
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Old 03-03-2011, 06:42 PM   #4
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So far as I'm aware, "shimming" in this context is done to the plunger & spring which set the maximum oil pressure.

In the stock design, the bypass is supposed to open at around 60 PSI. So when the oil is very cold, this protects the system by setting a cap on the maximum pressure that will be generated. (Too much oil pressure and your oil filter bursts.)

However, it's important to remember that this mechanism determines the maximum oil pressure. It should have no effect whatsoever on oil pressure below the bypass threshold. In other words, if you have only 10 PSI at idle, then you're going to have 10 PSI at idle no matter how stiffly you've shimmed the bypass spring. (Unless of course the whole reason you only have 10 PSI is because the bypass valve is sticking, though in that case the solution is simply to repair the plunger.)
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Old 03-03-2011, 06:46 PM   #5
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That's strange, I'd read the bypass was at 90psi when reading the original BE pump thread earlier today.

I assumed the shim set base pressure instead of maximum, that's good to know, thank you. It does seem to make shimming even more silly, though...

(Responded to my post on m.net about the LS1 IAC, Joe.)
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Old 03-03-2011, 06:50 PM   #6
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I was easily seeing more than 60psi on my VVT motor for quite some time, on a quality solid state sensor.
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Old 03-03-2011, 06:54 PM   #7
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Joe that may be partially true. I was under the impression that oil is being recirculated all the time, and that it is fully open at 60 psi. From what I understood, shims would get your idle psi to a safe operating pressure when you have a loose motor. That is why there are so many options.
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Old 03-03-2011, 07:17 PM   #8
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Quote:
Originally Posted by Nagase View Post
That's strange, I'd read the bypass was at 90psi when reading the original BE pump thread earlier today.
From the '92 FSM:




Quote:
Originally Posted by Reverant View Post
I was easily seeing more than 60psi on my VVT motor for quite some time, on a quality solid state sensor.
Ditto on my '92. If I really rev it on a cold morning, the stock OPG goes off-scale. I expect that we both have bypass valves which are sticking in their bores and failing to open when they should.


Quote:
Originally Posted by miata2fast View Post
Joe that may be partially true. I was under the impression that oil is being recirculated all the time, and that it is fully open at 60 psi. From what I understood, shims would get your idle psi to a safe operating pressure when you have a loose motor. That is why there are so many options.
While the operation of the plunger and spring is definitely an analog phenomenon rather than an on-off switch, it's not like an oil thermostat where there's a leak engineered in. If you take apart an oil pump and inspect the bore, it's pretty clear that no oil should be flowing through the bypass when the plunger is extended. If there is, then (IMO) something is very wrong. You'd have to replace the spring with the one from Hustler's novelty ******-in-a-can product to get it to depress past the bypass hole at only 10 or 20 PSI.
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Old 03-03-2011, 07:22 PM   #9
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Then why so many options?

I had a verbal conversation with the folks at Boundary, and they wanted to know what my final clearances were before they knew how to shim the pump. I do not recall the exact conversation, but that is how I remembered it.
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Old 03-03-2011, 07:31 PM   #10
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Originally Posted by miata2fast View Post
Then why so many options?
I don't know.

Maybe if your engine is set up on the tight side, you want to increase the pressure beyond stock in order to achieve enough flow. That's a question for an experienced engine builder, of which I am not one.
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Old 03-03-2011, 07:32 PM   #11
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Yeah, I posted in this section rather than in a general one in the hope that someone from BE would show up and comment.
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Old 03-04-2011, 12:38 AM   #12
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Noticed Travis hadn't been on in a few days, shot off an email...
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Old 03-04-2011, 01:13 AM   #13
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Quote:
Originally Posted by Joe Perez View Post
I don't know.

Maybe if your engine is set up on the tight side, you want to increase the pressure beyond stock in order to achieve enough flow. That's a question for an experienced engine builder, of which I am not one.
Yes, that is exactly it. So what you need to do this is the Petroff equation and a plane flow equation, and then a reaction force equation to make sure you get the proper bearing support at the lowest friction. What I usually tell people instead is that if your running a tight clearance increase the pressure, if you run a loose clearance get a high flow oil pump and maintain the stock pressure.

Quote:
Ditto on my '92. If I really rev it on a cold morning, the stock OPG goes off-scale. I expect that we both have bypass valves which are sticking in their bores and failing to open when they should.
So the stock relief valve is basically like a poppet valve. You can only get so much flow through the valve regardless of how far it opens. When the oil is extremely viscous it exceeds the valves ability to relieve more flow. The good thing is that your engine actually needs that extra pressure because of how viscous it is.

----
The only downside of running more pressure is that there is more power needed to drive the pump. There is a bit of an over limit situation where you can get bearing erosion by having too much pressure, but I wouldn't necessarily worry about it unless you are over 100 PSI all the time.
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Old 03-04-2011, 01:17 AM   #14
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If the shimming is for a tight engine, doesn't that make the high flow pump a bit useless?

I'm just not seeing the difference between a high flow pump and shims in that case, unless high flows are only for loose engines... but then why couldn't you just shim more for that?
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Old 03-04-2011, 01:32 AM   #15
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Oh no, there are actually physical limitations to the stock oils pumps. Some of the people on the boards here have used pre-VVT oil pumps with VVT engines and experienced no more then 40 PSI. Mazda sized the pumps extremely marginally for best fuel mileage and power. So if you change anything at all in the dynamics, raise the rev limit, or increase the boost pressure then you have changed the design operating condition of the bearing.

The main reason that we sell our assembled pumps in only high flow varieties is because we machine all the areas where the pump actually sits. This gets the most amount of flatness and concentric measurement out of the bore we can reasonably get. We want to produce the best product possible, and the as cast and machined surfaces aren't that great. This is especially true in used pumps were we've ween wear over .005 inches from the inside to the outside edge of the housing.
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Old 03-04-2011, 11:24 AM   #16
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my daddy was tellin me a story about his race cars one day.

and he told his friends he was putting motor X into his race car and they all said "those are oil starved with two pumps!" and he did some testing and determined that he was not having a pressure issue but he was having a flow issue so he ran four pumps and his motor did not starve and die.

or something like that.
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Old 03-04-2011, 12:27 PM   #17
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Quote:
Originally Posted by TravisR View Post
Oh no, there are actually physical limitations to the stock oils pumps. Some of the people on the boards here have used pre-VVT oil pumps with VVT engines and experienced no more then 40 PSI. Mazda sized the pumps extremely marginally for best fuel mileage and power. So if you change anything at all in the dynamics, raise the rev limit, or increase the boost pressure then you have changed the design operating condition of the bearing.

The main reason that we sell our assembled pumps in only high flow varieties is because we machine all the areas where the pump actually sits. This gets the most amount of flatness and concentric measurement out of the bore we can reasonably get. We want to produce the best product possible, and the as cast and machined surfaces aren't that great. This is especially true in used pumps were we've ween wear over .005 inches from the inside to the outside edge of the housing.
Soooo... How much oil pressure do your VVT pumps generate when oil is hot? At idle? Max psi?
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Old 03-04-2011, 04:10 PM   #18
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Originally Posted by Faeflora View Post
Soooo... How much oil pressure do your VVT pumps generate when oil is hot? At idle? Max psi?
55-65 should be typical at high rpm. 15-20 typical at idle with stock shimming. I've seen as high as 85PSI on the street/strip pumps. The problem is there are ALOT of variables that move that number up or down. The high flow pumps are capable of over 90PSI at high RPM, and some tests have indicated over 150 PSI.

Jason was the guy on here who was having problems with pressure and his VVT motor. He made a post about it some months back. There was another instance posted before that, but I forgot the originators name. It is important to size the pump with the amount of oil flow that you need. Generally the street strip pump does it for everyone. If you're deleting oil squirters you can definitely use stock sizes. If you are going with a larger then normal clearances, have VVT, and keep the oil squirters you might want to consider a high flow.

Best,
Travis

Last edited by TravisR; 03-04-2011 at 04:34 PM.
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Old 03-04-2011, 05:32 PM   #19
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Random question:

I've already got a new set of your gears sitting on the shelf, and when I tore down the pump that came on my donor '99 engine, it seemed a bit worn. Not horrible, just "a bit."

So I surf over to Rosenthal looking for new pump housings. They list two parts for 1999-2005 Miata. One is BP4W-14-100A "Through 2/28/1999 production" and the other is BP6D-14-100 "From 3/01/199 production." No mention is made of a change occurring in '01, which would have been VVT time. Moreover, the "old production" pump is $130, the "new production" pump is $250.

The parts catalogs confirm this. A change happened in mid '99 (at VIN -9301) and this pump was used at least through the end of '02 production, which is the last catalog I have.


Whiskey Tango Foxtrot?
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Old 03-05-2011, 10:21 PM   #20
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Quote:
Originally Posted by Joe Perez View Post
Random question:

I've already got a new set of your gears sitting on the shelf, and when I tore down the pump that came on my donor '99 engine, it seemed a bit worn. Not horrible, just "a bit."

So I surf over to Rosenthal looking for new pump housings. They list two parts for 1999-2005 Miata. One is BP4W-14-100A "Through 2/28/1999 production" and the other is BP6D-14-100 "From 3/01/199 production." No mention is made of a change occurring in '01, which would have been VVT time. Moreover, the "old production" pump is $130, the "new production" pump is $250.

The parts catalogs confirm this. A change happened in mid '99 (at VIN -9301) and this pump was used at least through the end of '02 production, which is the last catalog I have.


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99 year is when they changed the casting to a softer alloy I do know that. Wear in the 99+ housings is REALLY bad. We tested the housings and they were so soft we couldn't get a good reading with our equipment.

The gear thickness change has always been reported in 01. The complete pumps we sell fit on any block with a long nose crank though. We don't worry about it too much because most everyone who has a new housing and wants a billet set of gears has so much housing wear it won't work anyways. Thats not to say we don't exchange gear sets if they need the upgrade size. We have both in stock, we just have them send it back and then we exchange it.

As far as why the catalog doesn't match that?? I don't know. The oil pump lineage I know about is as follows.

So our motor line came from the protege, and the 1.6L used the original non-turbo protege pump and block. The upgrade to the 1.6L long nose crank also switched to the oil pump that the turbo protege (GTR or whatever) had. The pre 1.6L long nose blocks had a pump that was both smaller radially and axially.

The long nose 1.6L pump was carried over to the 1.8L pump all the way up to 99 when they retooled the castings to a softer alloy. For what reason? I have no idea! In 01 when the VVT mechanism was added they also increased the oil pump size about 10% to accommodate for the increased volume demand. I also theorize that they increased the volume because of the high wear the pumps naturally went through due to the softer alloy. If my thinking is right we should see pumps wearing to the point where oil pressure is a problem in the next 2-3 years. This increase in pump size could delay the housing wear problem.

Meh, the one thing I've learned about doing ignition systems in Miatas is that the progression is in no way linear. Quite frankly its pretty hackneyed! There is no telling what the actual reasons and when the actual changes occurred.
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