Viscosity Choice based on Oil temp

[ZeeOSix]

Originally Posted By: Shannow

Now, back to YOU poviding information that engine bearings (especially the big end, which don't even GET pressure for a full revolution) are overfed oil for temperature control.

Overfeeding to control temperatures isn't the design point anywhere (except in secret agent land as it appears)...


Doesn't really matter if the big end bearings don't get full flow for a full revolution (another deflection topic from you), because they are still getting more flow then they would if not pressure fed. Like I said before, that graph shows a relationship between the big end bearing oil flow rate and the supply pressure. If the pressure wasn't the cause of the increased oil flow that chart wouldn't exist.

Your turn to show me an SAE paper or similar that proves that temperature rise isn't a design criteria and that pressure feeding the bearing is never a method to control temperature rise and prevent oil film over temperature - that it could all be done with simple splash or gravity feeding of the bearing. Make sure the bearing application is a relative small physical size used in a very high RPM and high load/HP engine.

 

[ZeeOSix]

Originally Posted By: userfriendly
Zee; I get what you are saying.
Back in the day, guys racing domestic NA V8s would put as much oil pressure into the engines as they could.
Thick oils like 20w50 were also necessary to keep those engines running when they were pushed hard towing, in a boat, or hot lapping at a drag race.

The oil pans, like station wagons with 454 BBCs held 4 quarts. A 5.3L Ecotec hold 8L.
I remember guys with 351 Cleveland engines saying that if they did not shim the pump spring to 100 psi, #1 main would not last a week.


You get it. The thicker oils do cause a bit more heat generation from the shearing action in the bearings, but the overall thinning of the viscosity due to the heat should still be better than a little less heat generation effect on a thinner oil to start with. Also bearing clearances were probably a bit looser on those older engines which helped keep the oil film temperature rise down. So with more oil flow, more bearing clearance and more sump capacity the engines were able to survive while being ran to their max HP levels for a long time.

Originally Posted By: userfriendly
My question; Is the force feeding approach to engine lubrication applicable in a modern engineered power plant?

It seems to me that thick oil and high pressure is an obsolete band-aid approach to engine lubrication.

Is designing an engine to require 100 psi of pressure or thick oil, a good or best practice?


I think there is a minimum level of pressure feeding required for every engine on the road dependent on the exact engine design and performance envelope. As discussed in the other threads, it seems engine designers these days for most normal road cars are trying to get every milli-MPG more of fuel mileage out of new cars. Hence the variable flow PD oil pumps. But they are still pressure feeding bearings to flow more than they naturally would with ATM pressure supplied oil. The same reason they are going with thinner and thinner oils - it's all about fuel economy while every reducing the headroom of safety factor on the engine's reliability. Is that a good or best practice ... guess it is for the people who are responsible for meeting CAFE fuel economy targets mandated by the Feds. Is it good or best practice for a race car ... I'd say way more so.

It still seems that many new high performance sports cars (talking 400 HP or more) are still using pretty high volume PD oil pumps (not variable flow), but some are using oils as thin as 5W-20 which might be fine depending on the lubrication properties of the oil formulation and the expected use of the car. I know some manufacturers will recommend a higher oil viscosity if the car is going to be used for racing events, which goes to show that they are a bit worried about the thinner oil losing film strength when pushed real hard. Oil temps during a long road course event can get near 300 deg F if inadequate oil cooling equipment is not on the car.

 

[Shannow]

Originally Posted By: ZeeOSix
Make sure the bearing application is a relative small physical size used in a very high RPM and high load/HP engine.


I guess that I shouldn't start with 1940s oil ring fed bearings as a starting point then eh ???

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix
One of the main reason race engines typically use a pretty high volume oil pump - much higher than you'd find on grandma's mini van.


Ummmmm...they open up the bearing clearances "much higher than you'd find on grandma's mini van"...changing the bearing characteristic, and requiring a higher feed rate of oil.

For the same relief valve setting, a higher volume pump doesn't "cool" the bearings more.


You missed the point again and more grasping. If you were into high performance cars and aftermarket parts you'd know that HV oil pumps actually put out more volume per revolution, which means there is more oil volume at any given RPM compared to the stock oil pump. They may also have a higher relief valve setting than a the stock oil pump. Or as userfriendly commented, some guys would just shim the pressure relief valve on the stock oil pump to ensure the flow didn't drop off at redline RPM ... but that might not even have been enough to prevent bearing failures.

 

[Shannow]

Originally Posted By: ZeeOSix
You missed the point again and more grasping. If you were into high performance cars and aftermarket parts you'd know that HV oil pumps actually put out more volume per revolution, which means there is more oil volume at any given RPM compared to the stock oil pump. They may also have a higher relief valve setting than a the stock oil pump. Or as userfriendly commented, some guys would just shim the pressure relief valve on the stock oil pump to ensure the flow didn't drop off at redline RPM ... but that might not even have been enough to prevent bearing failures.


http://www.enginebuildermag.com/2008/10/oil-pumps/

Quote:
In a stock motor that doesn’t rev beyond 5,500 rpm, that’s not a concern. But in a performance engine that’s capable of being revved to 8,500 rpm, 9,000 rpm or even higher, a drop in oil volume and pressure could be disastrous.

When a performance engine throws a connecting rod, the underlying cause of the failure often turns out to be a lubrication problem. If the oil pump can’t maintain enough oil flow to the rod bearings, the oil film between the bearings and crank will go away causing the bearing to seize, spin and break the rod. A blackened or blued crankshaft journal is usually proof that the bearing spun and caused the rod failure.

The old school rule of engine building says that most engines need about 10 psi of oil pressure for every 1,000 rpm. That’s still good advice for the average Saturday night racer. But many ProStock drag racers and NASCAR racers are now running significantly less pressure (up to 40 percent less) to reduce the horsepower loss needed to drive the oil pump – which is okay provided bearing clearances are tight and you have enough oil volume to keep everything adequately lubricated.

 

[Shannow]

http://www.enginebuildermag.com/2015/06/choosing-the-right-oil-pump/

Quote:
Most engines don’t really require a lot of oil pressure at idle. Ten to 15 PSI or even less in some cases is adequate to keep the bearings, cam and valvetrain lubricated. A gauge reading of 30 PSI at idle looks good to many people, and some want to see even higher numbers. But most engines don’t really need that much pressure at idle or low RPM. It’s a waste of pumping effort and horsepower.

Many NASCAR teams run as little as 5 PSI for every 1,000 RPM, or even less. Of course, NASCAR engines don’t spend much time idling and mostly run flat out at high RPM. Consequently, the pump’s output volume and pressure can be minimized to deliver just enough oil to keep the engine lubed without wasting excessive power to drive the pump.

 

[ZeeOSix]

^^^ Yeah, so ... those ProStock drag racers and NASCAR race engines are also designed right on the ragged edge to basically barely last through the race event, and rebuilt before the next event. You ever watch those races and see how many blow up during the race. The same design standards are not used for public transportation. Weed whacking again.

 

[Shannow]

Originally Posted By: ZeeOSix
^^^ Yeah, so ... those ProStock drag racers and NASCAR race engines are also designed right on the ragged edge to basically barely last through the race event. You ever watch those races and see how many blow up during the race. The same design standards are not used for public transportation. Weed whacking again.


OK, so we get back to YOUR starting point and you aren't happy...again.

 

[UltrafanUK]

Kind of difficult to answer if you don't list the exact engine type.

Where is South OZ and what is the average temp during winter ??

If you are a fan of thin oils then don't forget that most OEM approved oils have higher levels of anti wear additives than normal cheaper oils. If you are not going to use the OEM spec oil and want to use an 0w20 in winter I would think about beefing the anti wear side of things up with half a can of Liqui Moly Ceratec every OCI. That additive contains both Moly and a hexagonal form of Boron Nitride. The BN forms a Ceramic layer that fills in voids and pitting whilst the extra Moly is a friction modifier. Alas BN is not a cheap additive which is why it is not included in normal oils. In fact some don't even use normal Boron or Moly add's to save money.

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix
^^^ Yeah, so ... those ProStock drag racers and NASCAR race engines are also designed right on the ragged edge to basically barely last through the race event. You ever watch those races and see how many blow up during the race. The same design standards are not used for public transportation. Weed whacking again.


OK, so we get back to YOUR starting point and you aren't happy...again.


I'm not unhappy ... and I agree with you that you can 'over feed' a bearing but it's not really causing much negative effect except maybe loosing 0.005 HP driving the pump. And there is a benifit to keeping the oil film temperature rise down by using oil pressure to put more flow through the bearing than it would "naturally" flow without supply pressure (ATM supply). It's discussed in design handbooks covering pressure fed bearings, and clearly can be used as a method of keeping the oil film healthy, especially on bearings where you might not be able to control temperature rise by changing other design parameters.

You just seem to want to shoot down every little thing said even though you probably see the logic and agree for the most part (or do you? - not real sure since you cling to the non-belief in pressure fed bearing benefits). It's starting to look like you're in trolling mode just for the sake of arguing.

 

[Shannow]

Originally Posted By: ZeeOSix
You just seem to want to shoot down every little thing said even though you probably see the logic and agree for the most part (or do you? - not real sure since you cling to the non-belief in pressure fed bearing benefits). It's starting to look like you're in trolling mode just for the sake of arguing.


LOL, I read it before your edit...please go back to your very first post in the thread before declaring troll.

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix
You just seem to want to shoot down every little thing said even though you probably see the logic and agree for the most part (or do you? - not real sure since you cling to the non-belief in pressure fed bearing benefits). It's starting to look like you're in trolling mode just for the sake of arguing.


LOL, I read it before your edit...please go back to your very first post in the thread before declaring troll.


I didn't change the trolling comment. Sorry you got all excited there, but you are a bit trolling (coming up with non-sense comments and requests to get off path/deflect) as time goes on in these discussions.

And my first comment in this thread was picking up where we left off since you still were clinging to the "The oil pump is only supplying oil to make up for the bearing's inherent side leakage ... it's not "flowing" oil through the bearings" comment, which is the baseline that got all of these discussions going to start with. Bottom line is that a PD oil pump certainly is increasing the flow of oil through the bearings ... more flow than they would naturally flow if not pressurized. And you would seem to agree with that based on your 1st comment in this post - HERE

 

[OVERKILL]

Originally Posted By: ZeeOSix
If you were into high performance cars and aftermarket parts you'd know that HV oil pumps actually put out more volume per revolution, which means there is more oil volume at any given RPM compared to the stock oil pump. They may also have a higher relief valve setting than a the stock oil pump. Or as userfriendly commented, some guys would just shim the pressure relief valve on the stock oil pump to ensure the flow didn't drop off at redline RPM ... but that might not even have been enough to prevent bearing failures.


With the SBF and SBC stuff that I have a little bit of experience (a lot more on the SBF side) the Melling pumps were available in a few different configurations:

1. Stock. OEM pressure and volume
2. HV. OEM pressure, higher volume
3. HP. OEM volume, higher pressure
4. HV/HP. Higher than OEM pressure and volume.

It was VERY (and probably still is) common for guys to fit what were otherwise stock bottom ended engines with HV oil pumps. The artifact of this was higher observed pressure on the gauge. However, with the stock relief setting, once on the relief, you were still forcing the same amount of oil through the engine, this would just happen at a lower RPM.

An example with an SBF:

You have an H/C/I 302 with the stock rev limiter (6,250RPM). With the stock oil pump and 0w-40 in the pan you observe 32psi at idle and are on the relief (65psi) by 4,000RPM. You fit this engine with a high volume oil pump and your idle oil pressure jumps up to 38psi. You are on the relief by 3,000RPM. At idle and below 3,000RPM you are pushing more oil through the engine. At 3,000RPM you are now dumping oil out the relief. At 4,000RPM the stock volume pump is now also dumping oil out the relief. Both are limited by their relief valve. At this point the volume through the engine observed through both pumps is the same. The volume through the relief on the HV pump is higher, arguably heating the oil more and providing no discernible benefit.

On the other hand, if you have an engine that you've built the bottom-end for and loosened it up a fair bit from stock, you may NEED the HV oil pump to provide adequate volume due to all the excess leakage. Even with the HV pump, hot idle oil pressure may be surprisingly low. If this engine is going to rev quite high, you may need the HV/HP pump to get adequate volume to the bearings that are furthest away from the pump at elevated RPM.

We had a rather funny one, it was a 355 SBC belonging to my buddy's dad. It was built with stock rod and main clearances but fitted with an HV (not HV/HP) pump. Realistic RPM range maxed out around 6,500RPM. Because the engine was so tight, with 15w40 in it it would go WELL past the relief pressure when cold. Relief was IIRC, around 55PSI, but you'd observe a solid 80 on the gauge when it was cold out. The relief on the pump could not flow the volume and the engine wouldn't take it, so the result was increased pressure, forcing more oil through both the relief and the engine until the oil was heated sufficiently. Hot oil pressure was around 35psi and it was onto the relief by about 2,500 or so IIRC. It was seriously over oil-pumped and probably would have been fine with a stock volume, high pressure pump.

And this brings us to where I think might be a point of disconnect between the two positions being made here:

It isn't the pressure providing oil to the first bearing in the series that is the issue here, it is the pressure feeding the LAST bearing that becomes the concern. There is pressure drop across the entire system and so observed gauge pressure at the feed end (where is is generally monitored) is not the same as observed pressure at the far end. An old SBC trick was to install a pressure gauge at both ends of the system so that you could gauge drop across that system and subsequently size your pump relief (and volume if necessary) to what the far end was observing to ensure it wasn't starving at high RPM. Higher RPM operation required more pressure IIRC, due to the operation of the crankshaft acting like a centrifuge, a characteristic that was of course exasperated by higher RPM. It took more pressure to get adequate oil to the far end bearings.

A little tangential but another thing that factors in here is firing event sequence and the subsequent layout of the loading profile for the crankshaft. The SBC and lopo SBF both had a propensity to experience early rod bearing wear on certain cylinders IIIRC and both engines shared the same cylinder (not numerical) firing order. The "HO" or 351W firing order was adopted to deal with this on higher performance version of the 302 and GM eventually adopted the same cylinder firing order, using it on the LSx engines. There was also supposedly a small power increase benefit as well (hence the "switch fire" camshafts that were available).

This SBC lube system diagram I believe might be helpful:

 

[ZeeOSix]

Good post OVERKILL. Yes, I agree that with a HV oil pump you also need a higher pressure relief setting to get any benefit at higher RPM, and as mentioned HV pumps are normally setup that way to start with.

One thing that the SBC oiling system diagram shows is that the system is normally designed to incorporate main galleries in the block to evenly distribute the oil volume to minimize any pressure drop to areas of the engine farthest away from the oil pump. If the distribution system design is flawed by bad main gallery design, then yes there could be a lack of oil supply to certain components thereby causing damage/failure.

 

[userfriendly]

Instead of raising the oil pressure, would going up in viscosity (HTHS) be a better route to save engine bearings?

 

[ZeeOSix]

Originally Posted By: userfriendly
Instead of raising the oil pressure, would going up in viscosity (HTHS) be a better route to save engine bearings?


It's all about maintaining a safe film thickness in the bearing to prevent metal-to-metal contact. Many factors affect the film thickness, viscosity being on of those factors. So yes, running a thicker oil certainly can be one solution as long as the oil isn't too thick - which it can be depending on the physical size (including clearance) and the operational envelope of a specific bearing.

 

[ZeeOSix]

Here's one for Shannow ... the info should look familiar. Note that they use the oil supply pressure in their bearing oil flow model, and that their model correlated almost perfectly with their empirical test measurements to validate the accuracy of the model.

http://www.sid.ir/en/vewssid/j_pdf/119320101802.pdf

Page Marked 13
"In AVL-EXCITE software, bearing oil flow rate due to shaft rotation, displacement and oil feed pressure for all main and pin bearings have been calculated precisely."

Page Marked 15
"For a specified engine, all of the parameters like cylinder pressure, geometry and masses are constant except oil supply pressure, engine speed, oil viscosity and bearing clearance. So, we assumed that the oil flow rate (one of the AVL-EXCITE output results) is a function of the mentioned variables (equation 2) and it is calculated for a wide range of operating points of these parameters."

 

[Shannow]

Yep, I recognise it as I posted it in another thread (and why you didn't address it there is beyond me bar bridges and billy goats)...Note that nowhere does it state that excess supply pressure over that needed to simply supply the volumes required for bearing make-up to control bearing temperatures, which is you premise all along.

As it states, it uses DP to CALCULATE the flow...I provided YOU with the equations (from Orlov) in the other thread where you were fixated on the stationary shaft and electric pre-lube pump situation as being representative of lubrication at all shaft speeds.

Shouldn't there be a 10psi per 1,000RPM or something if that was the case ?

It's where you came in after all.

As to your (well my) link, I thought that you might particularly appreciate the comments on relief valves....

Quote:
Accord-ing to our experience, the minimum value of 12-15% of oil pump flow rate should be passed through relief valve at maximum oil temperature and rated speed.


edit...

 

[ZeeOSix]

Originally Posted By: Shannow
Yep, I recognise it as I posted it in another thread (and why you didn't address it there is beyond me bar bridges and billy goats)...Note that nowhere does it state that excess supply pressure over that needed to simply supply the volumes required for bearing make-up to control bearing temperatures, which is you premise all along.


It was best to just continue the discussion in this thread since it's already well along.

I've never claimed or made it my premise that all bearings need to be pressure fed. I have said that pressure fed bearings will flow more oil then they would "naturally" due to the flow caused by their rotation with oil supplied at ATM pressure. And I have said that pressure fed bearings will have less oil film temperature rise, and that flow rate could be used as one method to help control bearing temperature depending on the application - never said it's absolutely needed. If you think I've claimed anything else beside that, then please go back in all the past discussions and find those comments.

But it's been your premise all along (even in the other two older threads, and again in this thread), and what has lead to all these discussions and side discussions, is that the oil pump does nothing but "make-up" for the bearing's inherent side leakage. At one point when you dug up Orlov that showed a comprehensive flow equation including the supply oil pressure parameter, it seemed you were more on-board with the fact that pressure fed bearings flow more than un-pressurized fed bearings. But then you flip flopped back earlier in this thread to your initial misconception that the pump only "makes up" side leakage draw from the gallery.

Originally Posted By: Shannow
The oil pump is only supplying oil to make up for the bearing's inherent side leakage, which is influenced by viscosity, RPM, speed, diameter, length, load, and diametrical clearance...it's not "flowing" oil through the bearings.


It's been shown in more than one source, and again in the paper you found on the engine oiling system modeling that the oil supply pressure is a parameter (along with all the others shown in their "Equation 2") that determines the bearing's oil flow volume. In the paper, they tested an engine to gather empirical data to compare to the flow models and it correlated very well - a pretty valid model. So if the journal bearings in their test engine would only naturally "draw/suck" what they needed from the galleries to make up for inherent side leakage, then their model wouldn't correlate at all with the engine components (main and pin/big end journal bearings included) flow rates vs RPM shown in Fig 15 and the over-all engine oil flow rate vs RPM shown in Fig 15.

Originally Posted By: Shannow
As it states, it uses DP to CALCULATE the flow...I provided YOU with the equations (from Orlov) in the other thread where you were fixated on the stationary shaft and electric pre-lube pump situation as being representative of lubrication at all shaft speeds.


I never claimed the electric pre-lube pump situation shown in the YouTube video I linked in the other thread represented lubrication at all shaft speeds, but was rather shown to kibosh the idea that the bearings only flow oil due to their rotation - if that was the case then you wouldn't see oil flowing out of all those bearings under pressure when the engine wasn't running. I showed that video to show that oil pressure makes additional oil flow through the bearing clearances. You add flow from the oil supply pressure on top of the flow caused by the bearing's rotation and you have what Orlov and the modeling discussed above represents for total bearing oil flow.

As mentioned above, it you believe Orlov, then you should not believe your own statement that "the pump doesn't cause flow through the bearings". Your post about Orlov ---> HERE

Originally Posted By: Shannow
Shouldn't there be a 10psi per 1,000RPM or something if that was the case ?

It's where you came in after all.


The "10 PSI per 1000 RPM" has always been a general rule of thumb for GM V8s. It follows pretty good on my Z06. Not too sure it applies to every engine on the road - but every engine with a PD oil pump shows an increase in oil pressure with an increase in engine RPM.

But if you look at Fig 7 in the modeling paper, the main gallery oil pressure at 800 RPM is 225 kPa and the oil pressure at 5500 RPM is 500 kPa. That works out to an average of 8.7 PSI per 1000 RPM ... so really not too far off.

 

[ZeeOSix]

Edit time ran out ... should have been:

... then their model wouldn't correlate at all with the engine components (main and pin/big end journal bearings included) flow rates vs RPM shown in Fig 15 and the over-all engine oil flow rate vs RPM shown in Fig 8.