Oil Pump Mods

[Dale FZ1]

Has anyone tried modifying their operating oil pressure by changing or shimming the springs in their stock pumps when putting together their engine?

I've seen the comments about stock 26DETT pumps vs the N1.

Checking over a stock 25DE vs 26DETT pump I noticed that the 26 has a main spring ~ 6mm longer than the one used in 25. Otherwise they appear to be the same spec, and the inner helper springs are identical.

The heavier spring should give a higher operating pressure but I don't know if it's worth bothering. Bearing clearances are stock spec so there's nothing to gain there.

Interested to see if anyone has modified their stock pump like this rather than using N1 pumps etc. And if so, what resulted?

[Cubes]

Mine has a washer under the spring from an RB30E pump. :S

Hasn't broke anything within 100,000km's and definitely runs a tad more pressure than the norm.

From memory over 4k it was around 90psi where it holds until its 7.3k cut.

[psi]

90psi oil pressure? wow, thats high.

On the old speedway engine RB30e, we used to shave the shim to reduce the oil pressure slightly. This made the pump happier (they sometimes cracked) and reduced pumping losses. never killed an engine from a lack of oil pressure or supply like this.

but if you want high oil pressure, go for it.

[bubba]

Is that a bad thing?

My N1 pump runs similar pressures, ~40psi @ 2k, ~60psi @ 3k, ~80psi @ 4k, over that it sits at 100psi (which is what I believe the relief spring to be rated to).

[r33_racer]

excessive oil pressure can be negative.

Rule is 10psi per 1000rpm.

[bubba]

Would you care to elaborate on "negative"?

[r33_racer]

high pressure normally equates to increased friction, increase in oil temp/bearing temp, places greater load on oil pump/gears, drains horsepower.

Good oil flow is more important then insane pressure. Good oil temps are also important...inside the motor good flow delivers cooler oil.

Good bearing choice and good oil is more important then having stuidly high oil pressure.

Good, Good and Good!

Edited November 25, 2008 by r33_racer

[bubba]

Interesting points, I thank you for elaborating

Why do all these aftermarket pumps run such high pressures?

[psi]

Yep, I agree with the above statement.

Why do they run such high pressure stanard? hmm.. dunno?

If the releif spring is set at 100psi, perhaps they are thinking you are going to be pulling 10 000rpm?

Or want you to break other parts so you are then tempted to buy more parts from them.. lol

10PSI per 1000rpm is a good ball park from what we have done..

We actually ended up with less oil pressure than the rule of thumb.

Bear in mind, that was non-turbo, and only did hard revs.(no stop start stuff like a street car)

However, the engine was running insane comp ratio, so the big ends were certainly getting their fair share of hard work.

[Cubes]

With the std crank oil pump drive and 90psi oil pressure over 4k it hasn't broke yet.

The motors done quote a few km's so hopefully it holds out until these 3.4ltr strokers are done.

Still on std rods etc so I can't really stretch the rpm out much further if I were to shove a larger turbo on it.

Time for another build.

[Dale FZ1]

I've looked at the desired operating oil pressure as having to fit with multiple parameters set by things including bearing clearances/quality, top end restrictor sizes, operating rev range, power loading on the crank, drain-back capabilities, and the capacity of the pump itself. In many ways it's like sizing up a turbo - you're balancing pressure against the total actual flow requirements. Even the oil viscosity comes into the equation when you think about it. The flow has to be efficient, and geared to the engine's needs (and hence the reason for the original question).

Mine is not going to be an "extreme" engine - far from it. It fits the bill as a straightforward 30/25 build, with some attention to detail using mainly stock type parts. That means revs limited to 7000 and power around 280-290rwkW; but it will be used often in club events. It's not a show pony build but something to be used for a purpose so it has to survive.

At first glance Cubes seems to be running higher than "desirable" pressure, but it hasn't resulted in any failures for him . Still it is worth knowing the oil pump spec he has when trying to decide optimal sizing for the oil feed restrictors to the head.

On consideration I have decided that the slightly heavier spring will be used, and I will monitor the results from this. I will post pics of the comparative spring sizes since it seems Cubes is the only engine builder to have tried this mod and be prepared to discuss. I'm happy to share any results as perhaps most other people swap in stock pumps without any other changes. I'm working on the idea that a mildly upgraded engine requires some mild improvements to the oiling system which can include operating delivery rate. Using stock pump gears, this would be achieved through bumping up the operating pressure within sensible limits. I think Michael's rule of thumb looks good, and thanks for the advice

If I'm not happy then I have the ability to revert it to stock.

Any other comments from those who've actually played around with this stuff is welcome - cheers.

[r33_racer]

Since the japs dont engineer every motor that one of the n1 or brand name pumps are going on they probably just run stupid high pressures to allow for all possibilities....high pressure is good for being on the 'safe side' eg if your tolerances are not spot on, or you have tight tolerances and your power level starts creeping up and cylinder pressures are almost forcing your big ends onto the crank then the higher pressure can stop this from happening.

Assuming everything is spot on then the higher pressure is only going to exaggerate the 'too much oil in head issue'. When we used an N1 pump in our firce race motor we didnt change the relief spring to a std one and we paid the price with overflowing catch cans....we had done all the oil control mods too.

Dale im sure your all over this one mate. You know what your doing

[Cubes]

Not only too much oil in the head issue but also early onset of valve float.

Both of which I've always struggled with until I dropped in better springs and oil restrictors.

If I were to do it again I wouldn't play with oil pressure. The RB25DET & Std GTR pump appears to be 'just' right.

r33_racer, What oil pressures do you see?

[r33_racer]

Yeh joel you're right the std pumps are pretty right.

hot temps we aim for the 10 per 1000 rule with about +5/+10 ontop which can sometimes disappear depending if the temps go out of ideal operating range...hence the extra.

limit is 7500rpm so around 80psi-85psi. idle around 35psi. As stated these are hot running temps. Cold they are considerably higher.

Besides the oil in head problem, alot of people forget about oil bypassing turbo seals and blowing smoke from the excessive pressure.

[Dale FZ1]

Here's the comparison of spring sets. The small difference between the two mains is evident, and it is about one full coil. There is noticeable extra preload required when installing, but I don't believe it will give a ridiculous boost to oil pressure. The effect is probably similar to adding a couple of washers/shims into the standard stack as Joel has done.

[psi]

The oil pump is only one part in a whole oil system. You also have to look at galleries, restrictors, coolers, oil temps, extra oil supply (turbo's, squirters), sump design and volume, oil return lines, engine condition, revs, oil viscosity, bearing clearnances.. bla bla bla. Its a whole system.

An N1 pump in a stock motor doing stock tasks will probably have issues. Same as a stock RB30e doing 8000+ rpm in a fully prepped race engine will have issues. horses for courses!

In my case, I'm building my 25/30 with the stock 25 pump at stock oil pressures. The engine consumes no more oil than the stock 25 does, and it will actually see LESS revs. So I am of the thinking that buying a larger oil pump will not help me do what I am asking of the engine.

The other thing to consider is that every part connected to the engine sucks horsepower. More oil pressure means it draws more horsepower to make that higher oil pressure. Water pumps use a little bit as do alternators. Some drag racers ditch these things to get every last bit from a maximium output eninge..

That said, the very last thing you want to do is run out of oil pressure! if it goes Ka-Booom, say good by to lots of $$$$$!

Edited December 2, 2008 by psi

[**RB2530**]

Guys,

All of the engine bearings utilise what is called hydrodynamic lubrication...(Google it)

Basically the oil enters the journal into the clearnance region between the bearing and the journal. The motion of the bearing with repect to the journal moves the oil around the clearance region into a wedge as it approaches the axis of the load on the bearing. As this happens pressure in the oil increases because the wedge is getting narrower. This pressure prevents metal to metal contact.

Now the pressure developed in the oil within the bearing is many many many times greater than the oil supply pressure to the bearing. Hundreds of times higher I think depending on many variables. It is the motion of the journal that 'pumps' the oil around it..As the rpm increases, this action requires a higher oil flow.

So as long as there is decent oil supply to the bearing it will be happy (unless the clearance is to small or too big). Even 1-2 psi supply at the bearing is enough...as long as the flow into the bearing = the flow out...

The trick is getting sufficient oil flow to ALL bearings. There are metres and metres of fine oil galleries and all of these cause pressure drop. So the pump outlet pressure may be 50psi but by the time it has gotten to the bearing it is 30 psi...All bearings will be slightly different depending on where they are ..But Nissan I am sure have designed the oil gallery schematic properly with heaps of redundacy incorporated as well...They would cater for things like wear of the pump as well, oil visosity differences and bearing wear (this changes oil flow through bearing)

So IMO very higher oil pressures do not achieve much or add extra insurance. As long as the overall oil flow demand of the engine is met by the existing oil pump.

Negatives of really high oil pressure would be higher loading on your oil pump AND adding more heat to your oil. This is because you are doing more work on the oil to increase its pressure so it would get hotter (this is by definition -not opinion)...

You also run the risk of blowing out oil seals as well...

The main thing is to run good oil and change it often. Good oil doesn't sludge up as much. Oil sludge is the enemy because it can block galleries etc. which is very bad..der!!