^^^ I agree. CyFi - the effect your bearings have on oil pressure are a lot more than you think...especially on a motor with that many miles. The 0W-40 is very appropriate for your engine.
Oil Flow vs Pressure
- Thread starter CyFi6
- Start date
IJ - Viscosity is 24.0 cst at 100 deg C; 168 cst at 40 deg C
Edge 10W-60 is an API SM/CF (most current) and meets ACEA A3, B3, B4.
http://www.castroledge.com.au/downloads/EDGE_Sport_10W-60_466129_2008_08.pdf
Edge 10W-60 is an API SM/CF (most current) and meets ACEA A3, B3, B4.
http://www.castroledge.com.au/downloads/EDGE_Sport_10W-60_466129_2008_08.pdf
Well it looks like I need to revive an old thread 
. I had a few other questions regarding oil pressure vs flow.
Question 1:
I hear this tossed around so much on this forum "The 7M has a low pressure high volume oil system"... I just cant wrap my mind around what this means. The bearing clearances are not any bigger than any other typical engine which runs higher oil pressures- therefore the increased flow cannot be through the bearing clearances. The only other increase in flow compared to a different engine (that I can think of) would be the factory oil cooler (not even present on most non turbo's). Granted, the 7M does have more bearings in total compared to other engines, but each bearing will not flow more oil than that of a different motor, considering the clearances are about the same if not smaller in the 7M. Now considering the clearances are all pretty consistent with other engines, where does this "high flow" label for the 7M come from? From all I can gather, considering the restriction is constant between the 7M and other engines, and the pressure is lower than that of other engines, the flow through each bearing clearance would be less in a 7M than that of a similar engine....now I know there must be something flawed with how I am looking at this, what I need is someone to tell me where because I cant seem to figure it out!
Assuming restriction stays the same (small block chebby vs 7m, if anything 7M has tighter clearances), pressure/flow will increase and decrease proportionately, so how is it that the 7M restriction is the same/similar, the pressure is lower, but SOMEHOW flow is increased.
Question 2:
Am I right in saying that the bearings are the greatest point of restriction in the 7M oil system? Assuming this is the case, why would Toyota choose (on a high performance engine) to lower the pump volume and pressure? Assume with the stock oil clearances and 0w30 oil that maximum pressure on the bearings before erosion and other things affect the durability of the bearing, was about 70PSI. With clearances constant, and pressure at 70PSI, flow would be at its maximum. Any reduction in pressure at this point would directly correlate to a reduction in flow through the bearing clearance. In an ideal system, wouldn't running pressure be 70PSI at all times?
Because the engine speed varies, of course constant pump volume is not possible without some type of control. Why not create a pump that will allow for 70PSI (max flow) at idle, and as engine/pump speed increases, relieve any excess volume through the relief? This way, 70 PSI (and maximum flow) can be achieved regardless of RPM. Would this not have a positive impact on engine life and lubrication?
There are only three reasons I could think to NOT do this. One would be cost- maybe manufacturing this higher volume pump would be more expensive. Two would be gas mileage- maybe the extra load on the engine at all times would decrease gas mileage. Three would be space- maybe there is not enough room in the engine to fit a higher volume pump?
Anyone care to enlighten me here?
. I had a few other questions regarding oil pressure vs flow.Question 1:
I hear this tossed around so much on this forum "The 7M has a low pressure high volume oil system"... I just cant wrap my mind around what this means. The bearing clearances are not any bigger than any other typical engine which runs higher oil pressures- therefore the increased flow cannot be through the bearing clearances. The only other increase in flow compared to a different engine (that I can think of) would be the factory oil cooler (not even present on most non turbo's). Granted, the 7M does have more bearings in total compared to other engines, but each bearing will not flow more oil than that of a different motor, considering the clearances are about the same if not smaller in the 7M. Now considering the clearances are all pretty consistent with other engines, where does this "high flow" label for the 7M come from? From all I can gather, considering the restriction is constant between the 7M and other engines, and the pressure is lower than that of other engines, the flow through each bearing clearance would be less in a 7M than that of a similar engine....now I know there must be something flawed with how I am looking at this, what I need is someone to tell me where because I cant seem to figure it out!
Assuming restriction stays the same (small block chebby vs 7m, if anything 7M has tighter clearances), pressure/flow will increase and decrease proportionately, so how is it that the 7M restriction is the same/similar, the pressure is lower, but SOMEHOW flow is increased.
Question 2:
Am I right in saying that the bearings are the greatest point of restriction in the 7M oil system? Assuming this is the case, why would Toyota choose (on a high performance engine) to lower the pump volume and pressure? Assume with the stock oil clearances and 0w30 oil that maximum pressure on the bearings before erosion and other things affect the durability of the bearing, was about 70PSI. With clearances constant, and pressure at 70PSI, flow would be at its maximum. Any reduction in pressure at this point would directly correlate to a reduction in flow through the bearing clearance. In an ideal system, wouldn't running pressure be 70PSI at all times?
Because the engine speed varies, of course constant pump volume is not possible without some type of control. Why not create a pump that will allow for 70PSI (max flow) at idle, and as engine/pump speed increases, relieve any excess volume through the relief? This way, 70 PSI (and maximum flow) can be achieved regardless of RPM. Would this not have a positive impact on engine life and lubrication?
There are only three reasons I could think to NOT do this. One would be cost- maybe manufacturing this higher volume pump would be more expensive. Two would be gas mileage- maybe the extra load on the engine at all times would decrease gas mileage. Three would be space- maybe there is not enough room in the engine to fit a higher volume pump?
Anyone care to enlighten me here?
drjoez took apart the two oil pumps and the GTE pump is bigger and moves more oil. But the GTE has squirters and a cooler, so that is a controlled leak.It has more volume, but less pressure. I don't like the statement either, and don't use it.
Question 2..
Efficiency. Think of an automatic transmission. At a given load low pressure would make it slip, high pressure would waste energy because of the unnecessary output of the pump(more load).
The correct pressure will maximize efficiency ( not waste energy) by not letting it slip or overclamping the disks, making it just right.
I have a question also.
A pump is supplying oil to bearing X to match the rate it bleeds it off (0psi, right at where pressure would begin.)
1. Is this the flow is needed and any pressure is a safety margin?(from loss of flow. Like accusump or something)
2. Does pressure hold the surfaces up from eachother.
3. Is flow what is required to keep a film at all times.
Efficiency. Think of an automatic transmission. At a given load low pressure would make it slip, high pressure would waste energy because of the unnecessary output of the pump(more load).
The correct pressure will maximize efficiency ( not waste energy) by not letting it slip or overclamping the disks, making it just right.
I have a question also.
A pump is supplying oil to bearing X to match the rate it bleeds it off (0psi, right at where pressure would begin.)
1. Is this the flow is needed and any pressure is a safety margin?(from loss of flow. Like accusump or something)
2. Does pressure hold the surfaces up from eachother.
3. Is flow what is required to keep a film at all times.
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For 1. I think it's cultural habit that people heard about for years... for eg.. Longetivity is pronounced as lon-jevity but we all pronounce it was lon-gevity so in a nutshell everyone is pronouncing it wrong but we've been doing it for so long.. it doesn't really matter. So yeah I agree with the state it's really mis-leading for people thinking it's for all the "7m blocks" so i'm guessing from nick M the "high flow" statement was referenced for the GTE block/oil squirters . Or within that M family of engines. that's IMO
For Mecevans
1: From my understanding, i'd repeat it's efficiency. If the bearing bleeds Xm/l of oil per min then it would be efficent to put the equal amount to supply for the next bleeding cycle as it lubricates. Supply too less then the bearing would starve. As for pressure, the faster the crank rotates the faster the bleeding period becomes, so more pressure to keep controled in relation to higher rpm. That's how I percieve it. I maybe wrong at many parts and missed other circumstances like bearing clearances, viscosity and etc, this is coming for a young dude so I'm still a novice here. Accusump is mainly used on track cars because all the turning in high speeds exposes air to the oil pump pickup as oil sloushes around the pan which is why they have an Accusump to compensate that loss of flow. but still good to have never the less.
2: It the Lubrication keeps the metal surfaces from contacting. As long as oil is present there's lubrication which why it's easy to slip on a small puddle of oil because it lubcriated your foot from the surface.
3: Spot on. Flow = lubrication (got that from the write up)
For Mecevans
1: From my understanding, i'd repeat it's efficiency. If the bearing bleeds Xm/l of oil per min then it would be efficent to put the equal amount to supply for the next bleeding cycle as it lubricates. Supply too less then the bearing would starve. As for pressure, the faster the crank rotates the faster the bleeding period becomes, so more pressure to keep controled in relation to higher rpm. That's how I percieve it. I maybe wrong at many parts and missed other circumstances like bearing clearances, viscosity and etc, this is coming for a young dude so I'm still a novice here. Accusump is mainly used on track cars because all the turning in high speeds exposes air to the oil pump pickup as oil sloushes around the pan which is why they have an Accusump to compensate that loss of flow. but still good to have never the less.
2: It the Lubrication keeps the metal surfaces from contacting. As long as oil is present there's lubrication which why it's easy to slip on a small puddle of oil because it lubcriated your foot from the surface.
3: Spot on. Flow = lubrication (got that from the write up)
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Another point to consider is that one of the primary functions of oil, other than lubrication, is cooling. Anyone who has spent any time on a road course can tell you, that even though your coolant temps are in the 212-220 deg F range, your oil will spike well over 325 deg F at the cooler easily, sometimes much higher if you're hot lapping on a broiling day. Flow provides the ability to move that heat to the oil cooler. More flow = oil closer to it's designed operating temperature and closer to it's designed viscosity. Remember that the hotter the oil gets, the thinner it is. Overheated oil will not maintain proper viscosity, oil that has restricted flow has a harder time moving heat to the cooler. Pressure is a measurement of resistance to flow.
I found out that alot of people over tighten there drive belts causeing the crank snout to be pulled and desort the oil wedge at the frist main bareing some times causeing it to fail
Not sure what that's got to do with anything lol, but every 7M I have taken apart was showing copper on the upper half of the front main bearing right at that spot.
I am going to respond to some of the questions above. Oil pumps in automotive applications are sized for hot idle requirements. These gear pumps are oversize once you get into the higher rpm range. There is significant recirculation (relif valve flow) on most pumps if the inlet is not a significant restriction. Chevrolet recognized this and implemented a variable displacement oil pump on the Cruse engine.
To completly beat this horse to death here is my attemp to explain journal bearings. a journal bearing has to develop a oil film, this is the wedge as discussed above. in order to develop this wedge inlet pressure is not necessary, only flow. You need only enough inlet pressure to overcome the pressure drop into the bearing. journal bearings are MASSIVE restrictions. think of your bearing clearance and think of the size of your oil feed hole. That cylinder is the flow area of that bearing. Now this is where it gets complicated.
For internal combustion engines there are many other considerations. The connecting rod drillings due to the inertia losses from the spinning crank shaft "loose" flow. This means you need to supply the rod drillings with significant "over pressure" just to end up with 1-2 psi at the inlet to the connecting rod bearing. Any pressure beyond the minimum supply pressure for film thickness is only for cooling. this is very important to understand. when you have 40 psi in the riffle about 2-3 psi of that is developing the film the rest is dissipating heat. traditionally higher speeds help develop the oil film. If you are interested in this phenomena look up the stribeck curve. high speeds also generate heat, lowering the viscosity so adequate flow needs to be provided to prevent film break up. This is a very complicated subject and I have done significant work in my field with journal bearing design, failures, and simulation.
One thing to think about is that the bearing do work to support the load. Where does this work go? It goes into heat which ends up dissipating structurally or into the oil. I did a bearing analysis recently for a bearing system at work and found that only 3% of the heat generated from the bearing was to support the load. The rest was losses due to "shearing" the oil. This was a very very inefficient bearing system that was grossly over sized. That brings me to my last point. The number 1 mistake people make when dealing with journal bearing systems is making them to big. This is one of the few things mechanically that don't improve with size.
To completly beat this horse to death here is my attemp to explain journal bearings. a journal bearing has to develop a oil film, this is the wedge as discussed above. in order to develop this wedge inlet pressure is not necessary, only flow. You need only enough inlet pressure to overcome the pressure drop into the bearing. journal bearings are MASSIVE restrictions. think of your bearing clearance and think of the size of your oil feed hole. That cylinder is the flow area of that bearing. Now this is where it gets complicated.
For internal combustion engines there are many other considerations. The connecting rod drillings due to the inertia losses from the spinning crank shaft "loose" flow. This means you need to supply the rod drillings with significant "over pressure" just to end up with 1-2 psi at the inlet to the connecting rod bearing. Any pressure beyond the minimum supply pressure for film thickness is only for cooling. this is very important to understand. when you have 40 psi in the riffle about 2-3 psi of that is developing the film the rest is dissipating heat. traditionally higher speeds help develop the oil film. If you are interested in this phenomena look up the stribeck curve. high speeds also generate heat, lowering the viscosity so adequate flow needs to be provided to prevent film break up. This is a very complicated subject and I have done significant work in my field with journal bearing design, failures, and simulation.
One thing to think about is that the bearing do work to support the load. Where does this work go? It goes into heat which ends up dissipating structurally or into the oil. I did a bearing analysis recently for a bearing system at work and found that only 3% of the heat generated from the bearing was to support the load. The rest was losses due to "shearing" the oil. This was a very very inefficient bearing system that was grossly over sized. That brings me to my last point. The number 1 mistake people make when dealing with journal bearing systems is making them to big. This is one of the few things mechanically that don't improve with size.