Rule change on oil pumps

#1

Pretty soon we’ll be into the rule change discussions, arguments, beat-downs. I’d like to suggest that we be allowed high capacity oil pumps, as long as they are enclosed within the pan and are not an attempt to create a dry sump.

Justification. The bottom line is that a high capacity pump will allow worn bearings to last longer before they have to be replaced.

Details:

Keeping bearings happy is all about providing adequate oil flow such that the “wedge” of oil within the bearing is maintained. Oil enters the bearing thru the little cut in the bearings and exits by being squeezed out the sides. As long as pressure to the main bearings is maintained, oil gets pushed thru holes in the crank to the rod bearings. Rod bearings are therefore the first to lose oil flow and the last to get it back when oil pressure is restored. Neglecting the greater stresses on rod bearings, their vulnerability to loss of oil flow is reason enough for them to fail first in a motor.

Our oil pump can maintain 60psi only at a given flow rate. When worn bearings allow oil to be squeezed out of the larger gaps easily, our oil pump can’t maintain 60psi, even with high visc oil. Pretty soon the rod bearings aren’t getting much oil because the system pressure is down to 30psi and 25psi of that is squeezing out out of the large gaps in the worn main bearings.

A high capacity oil pump would be able to maintain 60psi at a higher flow rate. So even tho oil would be squeezing rapidly out of the worn main bearings, oil would still get to the rod bearings. And that would mean that a motor with worn bearings would last longer before the bearings had to ultimately be replaced.

It’s pretty routine for someone to build a car and put a crankscraper into a motor with an unknown history. At that same time it would be pretty easy to put in a high capacity oil pump if they wanted a little more insurance.

A note on oil starvation. This doesn’t have anything to do with starvation. The rules allowing free oil pans and Accusumps have provided all the freedom people need to beat oil starvation. Having said that, a pump with dual pickups would be an oil starvation preventative measure, but I’ve not seen one that would fit the M20.

Now don’t go OT and talk about other rule changes. You want to talk about other rules, make your own thread.

#2

IF you find a high capacity oil pump for a M20 motor, let us all know. Chuck[color=#FF0000][/color]

#3

Cool, what’s the part number and we’ll all rush to purchase one. The rule will follow the part?

The committee is a commonsenseical (new word) group, and this is not a performance advantage item.

Again, the part number?

RP

ps, if you’re looking for a rules yes-or-no in these forums you’re wasting time.

#4

A high flow pump would be a great idea, but would not solve the problem. The problem is, getting oil to the oil pump. The only thing that a high flow pump will do is starve the engine bearings for oil sooner. The only solution to the problem would be remote pickups, electrical controlled and baffled, in relation to cornering load.

Don’t take this the wrong way, I believe that you have the right idea about getting more oil to the bearings, but you have to get the oil to the pump first!

But remember that the more oil psi that you have in your bearings is more drag on the motor, causing friction, and loosing horse power.

Peter Thibault

#5

Thanks Peter, but you aren’t helping…just tell him where to install the sensor.

#6

PThibault wrote:

[quote]A high flow pump would be a great idea, but would not solve the problem. The problem is, getting oil to the oil pump. The only thing that a high flow pump will do is starve the engine bearings for oil sooner. The only solution to the problem would be remote pickups, electrical controlled and baffled, in relation to cornering load.

Don’t take this the wrong way, I believe that you have the right idea about getting more oil to the bearings, but you have to get the oil to the pump first!

But remember that the more oil psi that you have in your bearings is more drag on the motor, causing friction, and loosing horse power.

Peter Thibault[/quote]

Re. the issue is getting the oil to the oil pump. We’ve talked the issue of oil starvation to death. This is a new issue.

Re. more oil pressure means hp loss. I’m not talking about higher OP, I’m talking about a pump that could maintain OEM OP at a higher flow rate. Besides, the checkvalve sets OP.

#7

Ranger wrote:

[quote] Pretty soon the rod bearings aren’t getting much oil because the system pressure is down to 30psi and 25psi of that is squeezing out out of the large gaps in the worn main bearings.
[/quote]

D@mn I am confused. We’re not quite sure the accusump has solved the pickup problem, so we are moving on to higher flow rate (in spite of the fact that flow rate and pressure - as they relate to maintaining healthy bearings - appear to be a function of one another)?

We have 1400+/- registered members on the site. Let’s assume half are actively tracking an E30 and 3/4 of those have junkyard motors and will slap another one in for a few hundred bucks rather than buy a high flow pump and/or accusump. Let’s further assume that of those 175, they break down like this:

  • 100 - happy with a crank scraper
  • 50 - happy with a crank scraper and accusump
  • 20 - rebuild every year anyway

That leaves Ranger and four others. Hurry up and raise your hands before this thread gets out of control. :laugh: :woohoo:

Steve D.

#8

Spend money on the junkyard engine and dyno time to see what really makes the engine work.

RP

#9

Here’s how I got to this idea…

I’ve been back studying oil recently. And a lot of that is getting posted on my website if anyone’s interested. The last 2 events I used Valvoline Premium Blue 10W40 diesel oil. It’s dirt cheap and has all the right stuff. The problem is that at 34psi at redline my resulting OP was lower then I thought it would be.

I’ve also come across a 2005 BMW WebTIS tech document recommending oils. The document is a little confusing, but it clearly emphasises xW40 more often then xW50. Now don’t get your panties in a wad…I’m not saying that the 20W50 guidance that is in the owner’s manual is wrong, I’m just saying that the fact that this new document doesn’t exactly agree with the owner’s manual is interesting. It’ll be on the website by the end of the day.

So anyways, there I was using an oil that ought to be thick enough, yet my OP was a bit low, even with my big oil cooler.

OP works just like electrical voltage, resistance and current. The pump provides pressure, not flow. Flow is a byproduct of the pressure and the resistance that the flow’s path provides. Both a small pump and a big pump might have the same 60psi operating pressure. But the big pump could maintain 60psi at a much higher flow rate.

The resistance in the oil flow’s patch is largely a product of the main and rod bearing gaps. The pump pressure forces the oil into the bearing, the hydrostatic pressure of the small enclosed space and the rotation of the surfaces create the lubrication “wedge” and the only place the oil has to go is to be squeezed out of the sides of the bearings.

Worn bearings have big gaps so the oil gets squeezed out easily. Thin oil gets squeezed out more easily then thick oil, but thin oil also flows better and flow is really important. So new bearings like thinner oil more then older bearings do, everything else being equal. But it would be more correct to say that it’s really the oil pump that cares about the oil visc. A low flow rate oil pump just can’t maintain decent pressure because of the flow rate that results from thin oil splashing out the big gaps between worn bearings.

Quick sidetrack: Cams and rocker surfaces are actually under far more stress then bearings, and most modern oils don’t protect them nearly as well as the older oils did.

Back to OP and bearing gap. Since my OP was a bit on the low side, that meant that oil was being squeezed out of my bearings at a rate fast enough that the pump was not able to maintain 60psi. A higher capacity oil pump would have been able to maintain 60psi. And that’s the key.

So…

  1. I’m not saying this is some crisis.
  2. 10W40 is not unreasonably thin oil for the M20B25.
  3. Even with xW50, our oil pump does not always maintain 60psi when we’re working the motor hard. That alone should make folks go “hmmm” about the flow rate that our pump is capable of.
  4. If someone puts a scraper into an old motor, putting in a new oil pump at the same time adds only 15min. If an additional $50 buys an oil pump that is more capable of sustaining pressure with the reduced flow restriction that comes from worn bearings, then it’s worth considering
  5. I’ve yet to find this high capacity oil pump, BTW. So the laugh may be on me. I’ve got a couple good leads still tho.
#10

Is the solution a higher capacity pump, or proper (better?) bearing gap?

BTW…I have 50+ psi at redline on my 22 year old motor with 20W50. Drops to 20ish psi in big sweepers.

#11

Ranger I wouldn’t be completely convinced that the OP and issue still isn’t somewhat related to OP.

The spur gear design on our pumps has limitation especially at high RPMs.

Most performance cars use a design like this:

http://en.wikipedia.org/wiki/Gerotor

#12

OriginalSterm wrote:

[quote]Is the solution a higher capacity pump, or proper (better?) bearing gap?
[/quote]

I’m really not saying that anything is “a solution”. I’m saying that worn bearings quickly overwhelm the flow capacity of the OEM oil pump. So maybe a higher capacity oil pump could keep worn bearings alive for another season.

No one should run out and swap out their oil pump in the hopes of some fix. But imagine the guy that is a guy is already planning on putting in a scraper. And he’s thinking about the 45psi at redline he’s getting, and wondering what that might mean for the number of months left in his bearings. That guy might think about how a higher capacity oil pump might get his OP back up to 60psi and get another season out of their bearings.

#13

IndyJim wrote:

[quote]Ranger I wouldn’t be completely convinced that the OP and issue still isn’t somewhat related to OP.

The spur gear design on our pumps has limitation especially at high RPMs.

Most performance cars use a design like this:

http://en.wikipedia.org/wiki/Gerotor[/quote]

This shit’s complicated. It would be interesting to see performance data on our pumps under different conditions.

I note that the folks that create 7000 rpm M20’s seem to (my perception only, I don’t know this for a fact) retain their stock oil pump, although it’s often “blueprinted”, whatever that means in this context.

Does our oil pump have efficiency problems at high rpm? I don’t know. The more I read the more I feel like I don’t know anything.

#14

People use the stock pump for a couple of reasons…first, it is the only thing available that any of us know of. Second, it is perfectly adequate under all conditions if you keep oil over the pickup. That said, I think oil control is the issue, not volume.

As a side note, most of the motors I disassemble that show brass in the bearings are doing more so in the mains than the rods. Look at how the rods are lubricated…through the crank directly from the mains. In addition, in these motors the cam and followers show no excessive wear so I would surmise there is plenty of excess flow from the pump. If you want to increase oil pressure across the board, look at the pressure relief valve. CB

#15

cwbaader wrote:

[quote]People use the stock pump for a couple of reasons…first, it is the only thing available that any of us know of. Second, it is perfectly adequate under all conditions if you keep oil over the pickup. That said, I think oil control is the issue, not volume.

As a side note, most of the motors I disassemble that show brass in the bearings are doing more so in the mains than the rods. Look at how the rods are lubricated…through the crank directly from the mains. In addition, in these motors the cam and followers show no excessive wear so I would surmise there is plenty of excess flow from the pump. If you want to increase oil pressure across the board, look at the pressure relief valve. CB[/quote]

Re. oil control. Understood, but I’m not talking about the oil pickup running dry.

Re. main bearings going bad first. That’s good to know. I was thinking that rod bearings tended to go first, but I had only 2 engines to draw conclusions from. What are your thoughts on what caused the main bearings to go first?

Re. cam and followers. I hear you, but I think that the lube issues on the top end are very different then the lube issues down below. Therefore it’s hard to draw conclusions from one and apply it to the other.

Chuck, You have vastly more experience in this stuff then I do so I’m very interested in picking your brain on these issues. On the other hand I have to write here in such a way that some kid next year with no background will be able to make heads of tails of the discussion.

My perception is that the lubrication of cam and followers isn’t sensitive to OP and flow much. Mostly oil just needs to be dribbled around a bit. Lubrication of the top end is sensitive to the pressure in the contact region between cam and follower, and sensitive to the qualities of the lube oil that prevent one from damaging the other, i.e. ZDDP, Moly and other wizardry.

The amount of pressure at the cam/follower contact region is apparently 2 orders of magnatude higher then at the rod and main bearings. The amount of pressure at the rod bearing is ~2X that at the main bearing.

In contrast to the top end, the bottom end requires the maintenance of that oil wedge, which is to say “hydrodynamic lubrication” instead of the “boundary lubrication” required by the top end. And if sometimes the pump can’t sustain 60psi because it can’t support the flow rate demanded by the resistance of the system, then I have to wonder how it’s doing at maintain the oil wedge in the bearings.

#16

What I’ve heard with spur gear pumps is they cavitate at high RPM.

Here is another link to get you started. This is a big deal in drag racing with wet sump - stock-ish class cars.

http://www.titanspeed.com/content/pump/pump_techtalk01.html

#17

One would assume that oil pressure loss through the bearings would limit flow to the cam. My observation is that this is not so. The way I found this is that I ran the oil pump with a electric drill (long shaft) while cranking over the motor…the volume of oil around the cam and rockers is quite large. In addition, the spray rail pulses oil from holes in the cam bearings and that pulsation is at a very high pressure.

Another consideration…the oil pressure relief valve. If the pump were marginal on flow, we would not need the valve, which directs excess flow back to the pan. CB

#18

cwbaader wrote:

[quote]One would assume that oil pressure loss through the bearings would limit flow to the cam. My observation is that this is not so. The way I found this is that I ran the oil pump with a electric drill (long shaft) while cranking over the motor…the volume of oil around the cam and rockers is quite large. In addition, the spray rail pulses oil from holes in the cam bearings and that pulsation is at a very high pressure.

Another consideration…the oil pressure relief valve. If the pump were marginal on flow, we would not need the valve, which directs excess flow back to the pan. CB[/quote]

Re. spray rail. My understanding agrees that lots of oil goes up top. My perception is the the oil route to the top end is preferential because there’s no flow restriction until the diameter of the spray rail just won’t accept more oil. That reasonable?

As I’m sure you know some outfits narrow the dia of the spray rail hole in order to reduce the volume of oil up there at high rpm. Interesting, but not the same as the oil pump being able to handle a flow rate that maintains 60psi at the bearings with hot xW40.

Re. Relief valve. That too may be different. The pump could have limited ability to handle an adequate flow of hot xW40 puring out of the bearings, yet still need a check valve for cold oil situations where the low oil flow rate allows the pump to easily maintain 60psi (or whatever).

Let me point out that I’m not saying this stuff is occuring, mostly I’m just off in conjecture land.

Subject change: Most of the updating on the oil info part of my website is done. I’ve added a lot of info. You want terrific oil at <$4/qt? Go read.

Another subject change. I got a hold of a guy in Europe that says that the M20B25 turbo community out there are all running M21 (diesel) oil pumps. It’s a bolt on part for the M20 and higher volume. I’m working on getting more info.
http://www.germanimportedparts.com/OEM-Parts/1985-BMW-524td-(E28)-M21-Engine-OilPump&BlockParts-OilPump.html

#19

in my experience with old motors that smoked I could just drain all the oil and problem solved no more smoking B)

I commend your work Scott keep it up

#20

Ranger wrote:

[quote]
Another subject change. I got a hold of a guy in Europe that says that the M20B25 turbo community out there are all running M21 (diesel) oil pumps. It’s a bolt on part for the M20 and higher volume. I’m working on getting more info.
http://www.germanimportedparts.com/OEM-Parts/1985-BMW-524td-(E28)-M21-Engine-OilPump&BlockParts-OilPump.html[/quote]

It would be interesting to know the differences between the M21 and M20 pumps especially since their basic design is the same. Hopefully you can get that from the turbo guys Ranger.