37 replies to this topic

[cedarsf1]

I've always understood that a safe max oil temperature is 260 degrees F (127 C). However, recently someone with an engineering background told me that even temperatures above 300 degrees F (149 C) are safe. Does anyone have a definitive answer to this?

[Greg Locock]

It depends on the oil. Diff oil gets a pounding, but i was still able to find one with a flash temperature of 149 deg C, which while the diff is not a great environement to start a fire, does at least indicate a lot of volatility there. 

 

Others had a flash temp of 180.

 

whetehr this is a good way of looking at oil durability I do not know.

 

Some possible effects of high temperature operation are:

 

1) inadequate viscosity

2) thermal breakdown

3)oxidation

 

....

 

Incidentally some grades of oil are tested at 150 deg C in the lab, and some diffs run at 150 deg C in the real world

[gruntguru]

I've always understood that a safe max oil temperature is 260 degrees F (127 C). However, recently someone with an engineering background told me that even temperatures above 300 degrees F (149 C) are safe. Does anyone have a definitive answer to this?

OIl life must always be traded off against temperature. Synthetic base stocks usually heve better high temperature stability, but the quality and quantity of oxidation inhibitors in the additive package has an equally large effect. Short story is, for a given application, you can run the oil hotter provided you are prepared to pay for better oil. (The extra expense is usually more than offset by longer oil and machinery life).

[rdyn]

Heat treated components (gears, bearings, ...) will lose temper quickly, if oil temperature is too high (e.g. >150°C)

Edited by rdyn, 16 January 2015 - 18:08.

[cedarsf1]

If I am running Mobil 1 in a modern car (Corvette Z06 to be exact) what would be a good safe max oil temp?

[gruntguru]

125*C continuous and 150*C intermittent would be quite safe.

[Lee Nicolle]

While I am no oil chemist synthetic oils are normally better. Take more heat and conversely produce less heat.

For 20 plus years I have used synthetics. In my Sports Sedan engine [dry sumped 550 hp 350 Chev] when it was rebuilt with about 1.8 thou oil clearance [yes you can use less with synthetic] I actually had to put a softer spring in the pressure relief as it had too much oil pressure. This on a fresh rebuild when  first started with synthetic. Oil temp was consistently down over the 25-50 mineral race oil I had used before. The engine at 2500 race km when pulled down had bearings that were suitable to go again. Unfortunatly the crank was cracked. Oil does not solve harmonics! Previously at half that km the bearings were decidedly marked and had lost some 'spring' too.

Just before I stopped racing that car I went to synthetic in the gearbox. Super T10. It changed nicer and did not come out stinking either. With the premium mineral gearbox oil I had been using before I changed it every meeting and it always came out burnt. Though with those service intervals the gears and synchros seemed to live ok. The synthetic though will live a lot longer. The 9" diff at that time had no real alternatives, I used vegetable based lim slip and changed that too every event. And it too stunk! Others I know now with synthetic are changing it about once a year and having no troubles. And 9" with their very low and very large pinion usually fry oil!

 

With the classic speedway car I changed the synthetic once a season. Far better [and economical]  than every couple of meetings. With the Austin diff synthetic has stopped the gear wear and appreciably reduced the temp too.

Others with Quick changes are having the same success and temp reduction.

The cars I am using now, a 351C Falcon and an early Torana are both better. The Clevo, a very poorly oiled engine is living ok and the oil temp too is ok. Though more than the others with its large bearings. I will say that the synthetic is keeping the gearbox [single rail] together. I am sure one will break eventually as they are good for about 300 hp and I have 440 but so far so good.

The BW diff too is the same.

The old Torana while being driven with some care has no oiling problems. The Muncie changes so nice compared with mineral oil and the [banjo] diff stays cool. And when the oil is changed again. not burnt!

 

So yes I am a convert. I have seen 150 C oil temp [very hot day] on the Ford and changed the oil before the next event but it seems no other problems. High RPM pressure stayed the same though low rpm it is down to about 20 psi, as are the Holdens too. Though mineral oil would be about 5lb!!

 

To me oil temps ideally should be about 120C [too cold too can be a drama] Mineral I found was usually about 140 150 and synthetic normally is around the 120. And synthetic will take far more heat.

 

I use synthetic too in the collectable Ford Galaxie, change it once a year [about 2-3000 miles] It does seem not to absorb water. As many will know short running in cold weather often ends up with milky oil and water does not lubricate at all well!  The water burns off with a decent run,, just dont drive it very hard!

 

Reputedly synthetic is not compatible with methanol. I know people who seem to disprove that as the oil changes are twice a season and the engines live.

 

Also never believe the rubbish spoken about synthetic and roller cams. If you are having a problem fix the valve geometry! This fallacy came from some Stupid Car teams. I believe they are now using less radical cams!

 

I am sure there is a downside too, I just have not found it. Most hi performance cars use synthetic from the factory. Many manufacturers use synthetic in the transmissions of their hi performance models, but mineral in base models. It does make diffs live when towing or carrying heavy loads. 

 

I have used Mobil 1, Shell and these days Penrite synthetics. They all seem to be similar, the prices however are not! Mobil1 in particular has got very expensive. great product, not the price.

[gruntguru]

Reputedly synthetic is not compatible with methanol. I know people who seem to disprove that as the oil changes are twice a season and the engines live.

 

Also never believe the rubbish spoken about synthetic and roller cams. If you are having a problem fix the valve geometry! This fallacy came from some Stupid Car teams. I believe they are now using less radical cams!

 

Some synthetics are not compatible with Methanol, some are, depends on the base oil.

 

Generally agree on the roller cams but again, all synthetics are not equal. I was involved with a super car team who changed over from the sponsor's excellent mineral oil to the sponsor's synthetic race oil and destroyed the lifters in two engines. Went back to mineral - no problem. Later converted to a different synthetic without a worry.

 

I can personally vouch for Royal Purple racing oils and their compatibility with methanol (methanol floats on the oil and can be drained off after each meeting) and with roller cams.

[bigleagueslider]

I agree with rdyn's comment about hardened rolling element bearings and gears losing temper when the lube oil temp exceeds 350degF or so. This temp limit means the flash temp in the oil fluid film and not the bulk oil temperature.

 

The advantage of synthetic oil is that it has a more consistent viscosity with changes in temperature.

[Lee Nicolle]

Some synthetics are not compatible with Methanol, some are, depends on the base oil.

 

Generally agree on the roller cams but again, all synthetics are not equal. I was involved with a super car team who changed over from the sponsor's excellent mineral oil to the sponsor's synthetic race oil and destroyed the lifters in two engines. Went back to mineral - no problem. Later converted to a different synthetic without a worry.

 

I can personally vouch for Royal Purple racing oils and their compatibility with methanol (methanol floats on the oil and can be drained off after each meeting) and with roller cams.

The roller cam saga continues. Some good mineral oils seem good with roller cams. But the EP on synthetics [should be] higher so less likely to damage the cam.

I too have heard stories of Supercar teams in the past blaming oil,, though the cam supplier blamed the valve spring bind! When that was fixed problem was solved!

I have seen some very bad valve trains from some very respected engine builders. Why? It does defy belief or just lack of looking hard at things. If an engine is breaking valve train components look harder.  too soft a spring will eat cams, as will too hard. Though I have found one major suppliers cams all need 20lb seat pressure extra than recomended. No failures, just 500 more useable RPM. Recomended pressures may be ok with all Ti compenents. Which are seldom used by the budget racer.  The wrong spring too will kill cams. Dampers in springs resolve the harmonics that break cams.

These days there is some VERY radical cams being used. And racers have to go through the hassle of using soft springs to run in the cam, then changing all the springs. Though cams are breaking, even with the recomended springs fairly regularly. Machining? Bad billets? This more flat tappett than roller. 

[MatsNorway]

How does the spring damper look? rubber inserts?

[gruntguru]

Usually either friction between inner and outer springs (LH and RH helix) or a flat strip wound helically to provide some interference between inner and/or outer springs. 

 

http://lmgtfy.com/?q...e spring damper

[Lee Nicolle]

A lot of  valve springs have the flat wound damper springs. Single with damper, often used on OEM springs and double with damper between the coil springs. Usually on high rpm race cams. Usually in my experience they only make about 15-20lb seat pressure. But the whole spring dynamic changes, especially at high RPM. And when one breaks the engine feels lazy at high RPM.

The design is a true black art, I am sure there is some science there somewhere. But use the recomended springs, or very similar maybe 10% stiffer. Never use too stiff a spring, you will wipe cam lobes, conversly too light a spring [or one that has gone soft] often will do the same. as will a broken damper too. Or a dropped valve too is very likely. It is all harmonics.

[bigleagueslider]

Referring back the OP, while it would not likely pose a problem for the lube oil itself to be exposed to 260degF temps, it would surely present a problem for engine components like main/rod journal bearings. You should remember that lube oil flow is used to cool journal bearings. And if they are designed to be cooled properely with a given mass flow of oil having an inlet temp of around 180degF, but instead are fed the same mass flow of oil having an inlet temp 80degF higher, then the bearing materials would likely fail due to overheating.

[gruntguru]

Referring back the OP, while it would not likely pose a problem for the lube oil itself to be exposed to 260degF temps, it would surely present a problem for engine components like main/rod journal bearings. You should remember that lube oil flow is used to cool journal bearings. And if they are designed to be cooled properely with a given mass flow of oil having an inlet temp of around 180degF, but instead are fed the same mass flow of oil having an inlet temp 80degF higher, then the bearing materials would likely fail due to overheating.

How much hotter than the oil do you think the bearings will get? The bearing materials will be OK well beyond 300*C.

[Lee Nicolle]

Referring back the OP, while it would not likely pose a problem for the lube oil itself to be exposed to 260degF temps, it would surely present a problem for engine components like main/rod journal bearings. You should remember that lube oil flow is used to cool journal bearings. And if they are designed to be cooled properely with a given mass flow of oil having an inlet temp of around 180degF, but instead are fed the same mass flow of oil having an inlet temp 80degF higher, then the bearing materials would likely fail due to overheating.

Reutedly the hotter the oil gets [any type] the more the oil aerates. It sure gets thinner so that is probably why. That is an important function of an oil cooler, to deaerate the oil as well as cool it. A win win. Just make sure the cooler, hoses and fittings do not restrict the hell out of the oil. Most of the commercial hardware I have seen is as restrictive as blazes. 

On my Ford lump I spent several hours trying to make it all work and actually FLOW oil. And have done similar on every engine I have ever played with. the manufacturers often do some weird things too. Probably adequate, just, for a road engine. Lousy for an high performance work.

[kikiturbo2]

Reutedly the hotter the oil gets [any type] the more the oil aerates. It sure gets thinner so that is probably why. That is an important function of an oil cooler, to deaerate the oil as well as cool it. A win win. Just make sure the cooler, hoses and fittings do not restrict the hell out of the oil. Most of the commercial hardware I have seen is as restrictive as blazes. 

On my Ford lump I spent several hours trying to make it all work and actually FLOW oil. And have done similar on every engine I have ever played with. the manufacturers often do some weird things too. Probably adequate, just, for a road engine. Lousy for an high performance work.

 

Having been messing around the oiling system on my evo engine I find interesting disrepances between the theoretical pump flow and the actual hardware used... The pump can flow a litre per second at 6000 rpm, but I somehow do not see it flowing trough the stock oil cooler... even the 10AN I am using now is a bit iffy..

[gruntguru]

Have you checked the pressure drop across the cooler?

[kikiturbo2]

no, but will do later.

Actually, I am trying to fabricate some nicely packaged system of scavenging the oil from the left side of the engine (transversly mounted I4) in right hand turns. Since the oil pick up is on the right there are oiling problems in long right handers.

Dry sumps apart, the conventional wisdom is baffled sump, which I do not find adequate as at 1l per min oil flow  there is about 4 sec of oil in the sump and if most of the oil flows back to the left side of the engine then we get real oiling problems.

 

My simple solution is to have an additional oil pickup on the left and pump the oil via an external electric oil pump.... but this is where I am at a problem by not having a large enough electric oil pump.... currently available ones are at 1/5th the main pump flow...

Second solution is a completely new sump with new two stage internal oil pump.... but that presents a separate packaging problem.

 

 

Going back to original topic... Not all synthetics are the same. MY favourite example is this... two identical 60K mile engines.. being run on two different synthetic oils.. one a mass market premium and another a bit more special race oil.

 

http://img.photobuck...0917_112045.jpg

 

Edited by kikiturbo2, 23 January 2015 - 22:41.

[GreenMachine]

no, but will do later.
Actually, I am trying to fabricate some nicely packaged system of scavenging the oil from the left side of the engine (transversly mounted I4) in right hand turns. Since the oil pick up is on the right there are oiling problems in long right handers.
Dry sumps apart, the conventional wisdom is baffled sump, which I do not find adequate as at 1l per min oil flow  there is about 4 sec of oil in the sump and if most of the oil flows back to the left side of the engine then we get real oiling problems.
 
My simple solution is to have an additional oil pickup on the left and pump the oil via an external electric oil pump.... but this is where I am at a problem by not having a large enough electric oil pump.... currently available ones are at 1/5th the main pump flow...
Second solution is a completely new sump with new two stage internal oil pump.... but that presents a separate packaging problem.

Sorry, OT I know, but an oil accumulator would help, perhaps solve, this problem. I run an Accusump in the boot, no pressure drops since it was plumbed in (this with a baffled sump too).

[gruntguru]

Swinging (about a vertical axis) pickups can work in some situations.

Is the electric pump you mentioned required to deliver at gallery pressure? Perhaps a low pressure (high volume) solution that pumps oil at low pressure from the left side to a "horseshoe shaped" baffled zone around the current pickup.

 

BTW not all "synthetics" are actually synthetics. Not since some lunatic US court decided highly processed mineral (e.g. hydrocracked) base could be described as synthetic.

[Lee Nicolle]

no, but will do later.

Actually, I am trying to fabricate some nicely packaged system of scavenging the oil from the left side of the engine (transversly mounted I4) in right hand turns. Since the oil pick up is on the right there are oiling problems in long right handers.

Dry sumps apart, the conventional wisdom is baffled sump, which I do not find adequate as at 1l per min oil flow  there is about 4 sec of oil in the sump and if most of the oil flows back to the left side of the engine then we get real oiling problems.

 

My simple solution is to have an additional oil pickup on the left and pump the oil via an external electric oil pump.... but this is where I am at a problem by not having a large enough electric oil pump.... currently available ones are at 1/5th the main pump flow...

Second solution is a completely new sump with new two stage internal oil pump.... but that presents a separate packaging problem.

 

 

Going back to original topic... Not all synthetics are the same. MY favourite example is this... two identical 60K mile engines.. being run on two different synthetic oils.. one a mass market premium and another a bit more special race oil.

 

http://img.photobuck...0917_112045.jpg

 

A properly baffled sump with the correct pickup to suit should be ok. Using all the electric stuff is an accident waiting too happen. 

For proper performance a proper dry sump set up is easier and in the long run cheaper.

Theoretical pump capacity is not always so either.

To improve flow use as few bends as possible. streamline/ blend block oilways and filter mounts. So many seem not to even line up. 

To get the oil back to the pan make it go to the back or front of the engine. Simple blending and radiusing on the returns usually helps a LOT. Manufacturers simply cast or bore a hole radiusing all of these increases returns considerably. Keeping the returning oil off of the crank is a premium. Less aeration and more power too. 

On some engines a breather from the pan to the rocker cover,, or if brave the catch can will help the oil return a good deal faster. most inline engines benefit from this. For a road engine the PCV system is there for a reason. But it puts oil into the intake at high RPM. So a decent size breather or two to the catch can helps a lot. OHC engines will need good baffling or the rocker cover pressure will feed straight into the catch can.

IF you are getting more than a few mil of oil in the catch can either your breathers are not working or your engine is junk. or both!

A well breathed engine seldom leaks. A poorly breathed one pressurises the oil out everywhere.

 

My pic may not be terribly pretty,, but VERY functional. You can see the hose to breathe the pan, breathers to the catch can and the oil system. Replace filter with an adapter, remote filter and cooler and back into the engine.

If possible I use a external pick up [below distributor] and plug the original. A 3/4 pickup moves a lot more oil easier , easier to put pick up in the desired location [back centre of the pan] and from the outside you can fully baffle the well of the pan. 

My speedway pan has the kick out on the R/R corner with the pickup there. The cooler also deaerates the oil.

All of the adapters, filter mount etc have all been radiused and smoothed to decrease resistance. Reputedly every 90 degree bend loses 10 lb of oil pressure. you will note my very generous radiuses. The cooler unfortunatly has 90 deg elbows. though that is the way is was made,, it has been in use for  35 years. It was free,, ex RX3! Adequate but far from ideal.

 

And yes the car is for sale!

Edited by Lee Nicolle, 24 January 2015 - 03:59.

[Catalina Park]

An Accusump is probably the easiest way to fix a pick-up problem with a transverse sump.

They are a great tool, you can even set it up to have oil pressure before you turn the motor.

[gruntguru]

Reputedly every 90 degree bend loses 10 lb of oil pressure. 

 

Reputedly perhaps, but I wouldn't bother repeating it - especially here. You just lost 40 lb in your oil cooler alone.

[kikiturbo2]

Swinging (about a vertical axis) pickups can work in some situations.

Is the electric pump you mentioned required to deliver at gallery pressure? Perhaps a low pressure (high volume) solution that pumps oil at low pressure from the left side to a "horseshoe shaped" baffled zone around the current pickup.

 

BTW not all "synthetics" are actually synthetics. Not since some lunatic US court decided highly processed mineral (e.g. hydrocracked) base could be described as synthetic.

 

swingign axis pickup is a no-go as it is a transverse sump with a space in the middle for the exhaust..

 

The pump has to work with no pressure.. just transferring oil from the left side of the sump to the right, and that only in right hand corners.. i.e. not all the time..

 

 

Yes, accusump is an option.. Actually I prefer the solution of using a completely new 2 stage pump.. this could even be a commercial product as it would also solve the inherent weakness of the OE pump at 8+ K RPM

[kikiturbo2]

A well breathed engine seldom leaks. A poorly breathed one pressurises the oil out everywhere.

 

 

yes.. I am building a proper breather can and adding a 12AN breather hole on the block... OE engine has only breathers on the cam cover.

[Lee Nicolle]

Reputedly perhaps, but I wouldn't bother repeating it - especially here. You just lost 40 lb in your oil cooler alone.

ALL oil systems have bends. Mine are not constant tight bends but large radius ones.  That includes inside the engine also. A lot less drop. 

I see so many set ups where everything has 90 deg bends everywhere. how the hell they ever have oil pressure defeats me. Less bends = less power the pump consumes too. so the engine has more power. 

 

Oh and if I have lost 40 lb. Many others have lost twice that and more. That engine has far less oiling  hassles than most. And has done quite a lot of work over nearly 20 years in two different cars. And still has the same oil pressure as when first built.

[bigleagueslider]

How much hotter than the oil do you think the bearings will get? The bearing materials will be OK well beyond 300*C.

The overlay materials used on journal bearing surfaces are not satisfactory for sustained operation at 300degC. In fact, the back temperatures for a steel bearing insert mounted in an aluminum main bore should be maintained below 300degF.

 

The problem you face is the heat transfer process from the bearing surface to the lube oil flowing through the journal gap. If you need to maintain the bearing surface temps below 300degF and the incoming lube oil flow is 290degF, the mass flow rate of lube oil required to cool the bearing with a deltaT of just 10degF becomes extremely large. But if the incoming lube oil flow has a temp of 180degF it will take far less mass flow to keep the bearing temps well below 300degF.

[Rasputin]

A  rule of thumb for mineral oils used to be that oxidation-life above 60 C is halved every 10 C, why it depends where you began I guess.

 

Viscosity-wise however, the relation to temperature, without VI-index additives that is, is rather dramatic;

 

This is an empirical model of the Dynamic viscosity (Ns/m^2) for a VG 46 Mineral Oil; 0.000875* (10^(10^(-00482*T+0.41541))-0.8).

 

Just my two cents to the discussion.

Edited by Rasputin, 25 January 2015 - 09:01.

[Lee Nicolle]

The overlay materials used on journal bearing surfaces are not satisfactory for sustained operation at 300degC. In fact, the back temperatures for a steel bearing insert mounted in an aluminum main bore should be maintained below 300degF.

 

The problem you face is the heat transfer process from the bearing surface to the lube oil flowing through the journal gap. If you need to maintain the bearing surface temps below 300degF and the incoming lube oil flow is 290degF, the mass flow rate of lube oil required to cool the bearing with a deltaT of just 10degF becomes extremely large. But if the incoming lube oil flow has a temp of 180degF it will take far less mass flow to keep the bearing temps well below 300degF.

High oil temps will 'flake' the bearing material. And the backers lose their 'spring' too. Worse case you can spin a bearing. Usually the cam bearings seem affected first and the oil presssure goes away.

Been there and done that in the distant past. Replaced the rod and main bearings, seemed ok in the workshop. 5 laps at the track = 25lb oil pressure again. The engine aquired an oil cooler after replacing the cam bearings. That engine is still alive in a road car 30 years later!

The carbs, oil cooler, fittings are on the engine I pictured. 

[Lee Nicolle]

swingign axis pickup is a no-go as it is a transverse sump with a space in the middle for the exhaust..

 

The pump has to work with no pressure.. just transferring oil from the left side of the sump to the right, and that only in right hand corners.. i.e. not all the time..

 

 

Yes, accusump is an option.. Actually I prefer the solution of using a completely new 2 stage pump.. this could even be a commercial product as it would also solve the inherent weakness of the OE pump at 8+ K RPM

Dry sump it. It costs a deal of money, but pays for itself in the long run. 3 stage is the go [ one pickup each end ane one pressure] unless the engine  has an external oil pump with adequate volume that can be tapped. Quite a few factory oil pumps  do not have adequate volume for high horsepower and/ or rpm. Conversely some are a waste of time and load up the drives for no reason.

[kikiturbo2]

yeah... dry sump is a no brainer, but it has 3 disadvantages...

 

Currently available kits are 1. expensive, 2. not compatible with AC 3. drive belt is vournelable to dirt.

 

Actually I am thinking about engineering a commercial  semi dry sump or a full dry sump kit that would feature internal oil pumps, and in semi dry sump form, use the stock sump and only a single scavenge stage to move oil from the left side of the block to the main part of the sump.

 

As for the factory pump... volume wise it is ok.. the only problem is that it was not made for 8+K rpm which is what these engines see  these days..

Edited by kikiturbo2, 26 January 2015 - 11:18.

[Lee Nicolle]

yeah... dry sump is a no brainer, but it has 3 disadvantages...

 

Currently available kits are 1. expensive, 2. not compatible with AC 3. drive belt is vournelable to dirt.

 

Actually I am thinking about engineering a commercial  semi dry sump or a full dry sump kit that would feature internal oil pumps, and in semi dry sump form, use the stock sump and only a single scavenge stage to move oil from the left side of the block to the main part of the sump.

 

As for the factory pump... volume wise it is ok.. the only problem is that it was not made for 8+K rpm which is what these engines see  these days..

Gilmer belts on dry sump pumps do have a limited life. But if mounted out of direct dirt seem to live ok. I have seen plenty on speedway cars inc Sprintcars and have never seen one fail yet. Stones can be worse though.

IF the pump wont supply enough at 8 grand it is not big enough.  Though when you are feeding the engine oil without air it may well be. A/C and high performance really do not live together. One or the other. You will need TWO scavenges to feed one pressure pump. That is very well proven.

Not enough room for internal scavenge pumps and HOW would you drive it?  Or plum it? Hi volume presure pumps driven mechanically chew up the drives. Yet alone a couple of chattering scavenge pumps too.

Their is probable a market for a commercial simple external system. The pumps are available from several sources. So fabricating a pan, pump braket and drive. And tank and cooler set ups too ofcourse. Probably a market too for a simple remote mount filter and cooler set up. That will help deaerate the oil for hard street and mild performance use. That and deeper more efficient wet pans and pick ups.

[kikiturbo2]

actually the stock oil pump is overdriven so I guess it starts cavitating at high rpm. One of the solutions now is to underdrive it a bit with a custom pulley.

 

If I stay with a wet sump I can:

 

1. add a single scavenge pump for the left side ofthe engine and leave the stock pump as is. That would solve the oil pressure drop problem in right hand bends.

2. Add a 2 stage pump, pressure + scavenge, throw out the stock oil pump, that will solve 1. and provide a better main oil pump that will live at high RPM. pump could be driven from the crank sprocket that normally drives the balancer shaft, which is these days thrown out from most engines of this type (evo 4g63 / 4g64).

 

solution 2 requres a new sump and front engine plate to be made.... but is AC compatible and no external tanks. The pump would live at the bottom of the sump. I have checked a comperrcially available 2 stage pump for clearence.

Actually, there are lots of people running high power evos on R rated rubber on trackdays... and they want AC too..

 

Solution 3 is to fit a super slim georotor oil pump of my own design, 2 or 3 stage, inside the space where the front balance shaft used to be... this is tricky but super elegant.. can be made in wet or dry sump version and will run off the cambelt as does the oe pump.

 

Normally on this engine all dry sump systems are driven from the end of the crank which is not too much of a problem if you cover it well.

Edited by kikiturbo2, 27 January 2015 - 12:01.

[bigleagueslider]

High oil temps will 'flake' the bearing material. And the backers lose their 'spring' too. Worse case you can spin a bearing. Usually the cam bearings seem affected first and the oil presssure goes away.

Been there and done that in the distant past. Replaced the rod and main bearings, seemed ok in the workshop. 5 laps at the track = 25lb oil pressure again. The engine aquired an oil cooler after replacing the cam bearings. That engine is still alive in a road car 30 years later!

The carbs, oil cooler, fittings are on the engine I pictured. 

Inlet oil temps that are higher than what the bearings are designed for don't cause the overlay materials to "flake". What happens is the steel shell surface eventually becomes hot enough to degrade its compressive strength to the point that it experiences fatigue failure, and pieces of the steel shell surface spall out. The overlay materials themselves (copper-lead, nickel, and tin-lead) are thin and soft enough to resist spalling.

[kikiturbo2]

I guess that it why some constructors do not use bearing shells at all..

Edited by kikiturbo2, 28 January 2015 - 09:55.

[gruntguru]

The overlay materials used on journal bearing surfaces are not satisfactory for sustained operation at 300degC. In fact, the back temperatures for a steel bearing insert mounted in an aluminum main bore should be maintained below 300degF.

 

The problem you face is the heat transfer process from the bearing surface to the lube oil flowing through the journal gap. If you need to maintain the bearing surface temps below 300degF and the incoming lube oil flow is 290degF, the mass flow rate of lube oil required to cool the bearing with a deltaT of just 10degF becomes extremely large. But if the incoming lube oil flow has a temp of 180degF it will take far less mass flow to keep the bearing temps well below 300degF.

 

King Bearings http://kingbearings....g_Materials.pdf

 

Edited by gruntguru, 29 January 2015 - 01:44.

[bigleagueslider]

gruntguru- Thanks for the King Bearings link. The data shown was interesting, but also came with lots of qualifications like this one accompanying the chart you posted above: "Note: All our data regarding the load capacity of different materials was obtained in our Test Rig under similar test conditions. It is incorrect to compare load carrying capacity of a material measured in different Test Rigs.There is no standard method of bearing fatigue test. Bearing manufacturers use different equipment and different test conditions, which produce different results for the same material. Therefore only the results obtained under the same conditions and in the same test machine may be compared."

 

I also have some questions about the values shown in that chart. For example, the max sustained operating temp of steel backed tri-metal bearings is limited mostly by the elevated temperature fatigue capability of the steel backing material. Assuming the "XP" and "GP" bearings shown both use the same steel backing material, there should be little difference in their max sustained operating temperature capability. As for the effect of the intermediate layer and overlay materials on max operating temperature capability, both designs use a bonded copper alloy intermediate layer. The purpose of this bonded copper alloy intermediate layer is to improve conductive heat transfer from the bearing surface to the steel shell, and also to provide an interface with mechanical properties that are compatible with both the backing and overlays. The real difference between the "XP" and "GP' bearings is the overlay material. The "XP" uses a nickel flash with a plated babbit (lead-tin?) surface layer, while the "GP" uses some form of polymer overlay coating. I don't see how the polymer overlay would provide the huge improvement shown in load pressure or max operating temp capability. However, polymer surface overlays are now commonly used by many production auto engine bearings. The main benefit of the polymer overlay is reduced scuffing/wear during periods of operation with minimal lubrication, such as during start-up.

 

The main design parameters for auto engine journal bearings are POFP (peak oil film pressure) and POFT (peak oil film temperature or flash temperature). The design of a journal bearing is largely an excercise in fluid mechanics and heat transfer, and making sure the bearing structure has adequate fatigue capability for the application.