OMP Oil Metering pump output and modification
#126
I have also detected an oil level increase in the sump, although my circumstances are different from those mentioned in the Post:
I have a 192 with manual change and except the Sohn, without modifications. I make an exclusive use of street, agile driving but not sport; with routes of 25 km and some long trips (about 10,000 km per year).
Currently it has 90000 km and with 85000 km I had done a compression test, which I think is quite correct
Front
Psi - kpa - kgf/cm2
116.94 - 806.28 - 8.22
120.63 - 831.70 - 8.48
113.65 - 783.59 - 7.99
Rear
Psi - kpa - kgf/cm2
113.79 - 784.54 - 8.00
113.39 - 781.80 - 7.97
117.32 - 808.87 - 8.25
I use oil Petronas Syntium 3000 AV 5W40 and for the Sohn I use either Castrol Power 1 Racing 2T or Motul 710 2T
I mix ethanol to gasoline (until I reach E10) and to compensate for the greater dryness of ethanol I do some premix, but very little (800:1)
I have increased somewhat the map of the OMP, circulated since then about 5000 km; but until recently I had not noticed the increase in the level of the sink.
According to what you have commented throughout the post, my profile does not fit those causes of "sump creep" and for that reason I am left wondering if I will have problems with the Cut-off seal or with the Oil seal.
What is your opinion? Can there be another circumstance that causes this level increase?
I have a 192 with manual change and except the Sohn, without modifications. I make an exclusive use of street, agile driving but not sport; with routes of 25 km and some long trips (about 10,000 km per year).
Currently it has 90000 km and with 85000 km I had done a compression test, which I think is quite correct
Front
Psi - kpa - kgf/cm2
116.94 - 806.28 - 8.22
120.63 - 831.70 - 8.48
113.65 - 783.59 - 7.99
Rear
Psi - kpa - kgf/cm2
113.79 - 784.54 - 8.00
113.39 - 781.80 - 7.97
117.32 - 808.87 - 8.25
I use oil Petronas Syntium 3000 AV 5W40 and for the Sohn I use either Castrol Power 1 Racing 2T or Motul 710 2T
I mix ethanol to gasoline (until I reach E10) and to compensate for the greater dryness of ethanol I do some premix, but very little (800:1)
I have increased somewhat the map of the OMP, circulated since then about 5000 km; but until recently I had not noticed the increase in the level of the sink.
According to what you have commented throughout the post, my profile does not fit those causes of "sump creep" and for that reason I am left wondering if I will have problems with the Cut-off seal or with the Oil seal.
What is your opinion? Can there be another circumstance that causes this level increase?
Last edited by manuRx8; 05-17-2019 at 02:12 PM.
#127
77 cylinders, 4 rotors...
Brett runs alcohol, so most of the 2 stroke oils that are compatible with alcohol are castor based.
#128
77 cylinders, 4 rotors...
Manu,
How much are you seeing the level increase and over how many km?
Increasing OMP rate and having a Sohn will still cause the sump to begin to fill in my opinion, my point was that it seems to fill much less since I have run less premix and more injection. I have not taken detailed experiments, but over a couple of oil change intervals now, the level does not rise nearly as fast, but the same ratio of oil is entering the engine, just the source of the majority of it has changed.
If those compression numbers are normalized, it would seem that you are unlikely to have any concern of faulty seals causing the oil rise.It seems like you have a good engine.
Again this seems to be controversial, but I believe oil rise in the sump it to be a by product of the standard function of this engine when premixing, and to a lesser extent, using a Sohn and increasing OMP rates.
I'll say this too: This happens in healthy piston engines as well. (!) Premix at a 200:1 ratio in your Honda, Ford, Opel or whatever, and watch what happens over a standard oil interval. Static and dynamic compression will increase, idle vacuum will increase, idle will be more uniform, the engine may feel more responsive, unless the computer is pulling timing due to the lower octane (knocking) from the oil burning. And, finally, your sump oil level will increase if your car does not use oil, or it will go down less than you are used to over the same period. The oil will migrate into the sump. It will burn some, and blow some by.
In a piston engine, the primary contributor to premix oil going into the sump will be blow-by, but the fuel injector position and timing can also exacerbate the problem in a piston engine as well, like I believe it does in the Renesis.
Again, this is my opinion. Comments welcome.
How much are you seeing the level increase and over how many km?
Increasing OMP rate and having a Sohn will still cause the sump to begin to fill in my opinion, my point was that it seems to fill much less since I have run less premix and more injection. I have not taken detailed experiments, but over a couple of oil change intervals now, the level does not rise nearly as fast, but the same ratio of oil is entering the engine, just the source of the majority of it has changed.
If those compression numbers are normalized, it would seem that you are unlikely to have any concern of faulty seals causing the oil rise.It seems like you have a good engine.
Again this seems to be controversial, but I believe oil rise in the sump it to be a by product of the standard function of this engine when premixing, and to a lesser extent, using a Sohn and increasing OMP rates.
I'll say this too: This happens in healthy piston engines as well. (!) Premix at a 200:1 ratio in your Honda, Ford, Opel or whatever, and watch what happens over a standard oil interval. Static and dynamic compression will increase, idle vacuum will increase, idle will be more uniform, the engine may feel more responsive, unless the computer is pulling timing due to the lower octane (knocking) from the oil burning. And, finally, your sump oil level will increase if your car does not use oil, or it will go down less than you are used to over the same period. The oil will migrate into the sump. It will burn some, and blow some by.
In a piston engine, the primary contributor to premix oil going into the sump will be blow-by, but the fuel injector position and timing can also exacerbate the problem in a piston engine as well, like I believe it does in the Renesis.
Again, this is my opinion. Comments welcome.
#129
77 cylinders, 4 rotors...
Manu,
How much are you seeing the level increase and over how many km?
Increasing OMP rate and having a Sohn will still cause the sump to begin to fill in my opinion, my point was that it seems to fill much less since I have run less premix and more injection. I have not taken detailed experiments, but over a couple of oil change intervals now, the level does not rise nearly as fast, but the same ratio of oil is entering the engine, just the source of the majority of it has changed.
If those compression numbers are normalized, it would seem that you are unlikely to have any concern of faulty seals causing the oil rise.It seems like you have a good engine.
Again this seems to be controversial, but I believe oil rise in the sump it to be a by product of the standard function of this engine when premixing, and to a lesser extent, using a Sohn and increasing OMP rates.
I'll say this too: This happens in healthy piston engines as well. (!) Premix at a 200:1 ratio in your Honda, Ford, Opel or whatever, and watch what happens over a standard oil interval. Static and dynamic compression will increase, idle vacuum will increase, idle will be more uniform, the engine may feel more responsive, unless the computer is pulling timing due to the lower octane (knocking) from the oil burning. And, finally, your sump oil level will increase if your car does not use oil, or it will go down less than you are used to over the same period. The oil will migrate into the sump. It will burn some, and blow some by.
In a piston engine, the primary contributor to premix oil going into the sump will be blow-by, but the fuel injector position and timing can also exacerbate the problem in a piston engine as well, like I believe it does in the Renesis.
Again, this is my opinion. Comments welcome.
How much are you seeing the level increase and over how many km?
Increasing OMP rate and having a Sohn will still cause the sump to begin to fill in my opinion, my point was that it seems to fill much less since I have run less premix and more injection. I have not taken detailed experiments, but over a couple of oil change intervals now, the level does not rise nearly as fast, but the same ratio of oil is entering the engine, just the source of the majority of it has changed.
If those compression numbers are normalized, it would seem that you are unlikely to have any concern of faulty seals causing the oil rise.It seems like you have a good engine.
Again this seems to be controversial, but I believe oil rise in the sump it to be a by product of the standard function of this engine when premixing, and to a lesser extent, using a Sohn and increasing OMP rates.
I'll say this too: This happens in healthy piston engines as well. (!) Premix at a 200:1 ratio in your Honda, Ford, Opel or whatever, and watch what happens over a standard oil interval. Static and dynamic compression will increase, idle vacuum will increase, idle will be more uniform, the engine may feel more responsive, unless the computer is pulling timing due to the lower octane (knocking) from the oil burning. And, finally, your sump oil level will increase if your car does not use oil, or it will go down less than you are used to over the same period. The oil will migrate into the sump. It will burn some, and blow some by.
In a piston engine, the primary contributor to premix oil going into the sump will be blow-by, but the fuel injector position and timing can also exacerbate the problem in a piston engine as well, like I believe it does in the Renesis.
Again, this is my opinion. Comments welcome.
#130
I think the best compromise might be to do what I'm doing currently and run 120:1 for all situations except track or dyno , at which point I should up the useage to 100:1. If there was a way I could inject a high ratio premix after a certain rpm/load ................ and run that in conjunction with the omp ...........that might be the ideal!
#131
Manu,
How much are you seeing the level increase and over how many km?
Increasing OMP rate and having a Sohn will still cause the sump to begin to fill in my opinion, my point was that it seems to fill much less since I have run less premix and more injection. I have not taken detailed experiments, but over a couple of oil change intervals now, the level does not rise nearly as fast, but the same ratio of oil is entering the engine, just the source of the majority of it has changed.
If those compression numbers are normalized, it would seem that you are unlikely to have any concern of faulty seals causing the oil rise.It seems like you have a good engine.
Again this seems to be controversial, but I believe oil rise in the sump it to be a by product of the standard function of this engine when premixing, and to a lesser extent, using a Sohn and increasing OMP rates.
I'll say this too: This happens in healthy piston engines as well. (!) Premix at a 200:1 ratio in your Honda, Ford, Opel or whatever, and watch what happens over a standard oil interval. Static and dynamic compression will increase, idle vacuum will increase, idle will be more uniform, the engine may feel more responsive, unless the computer is pulling timing due to the lower octane (knocking) from the oil burning. And, finally, your sump oil level will increase if your car does not use oil, or it will go down less than you are used to over the same period. The oil will migrate into the sump. It will burn some, and blow some by.
In a piston engine, the primary contributor to premix oil going into the sump will be blow-by, but the fuel injector position and timing can also exacerbate the problem in a piston engine as well, like I believe it does in the Renesis.
Again, this is my opinion. Comments welcome.
How much are you seeing the level increase and over how many km?
Increasing OMP rate and having a Sohn will still cause the sump to begin to fill in my opinion, my point was that it seems to fill much less since I have run less premix and more injection. I have not taken detailed experiments, but over a couple of oil change intervals now, the level does not rise nearly as fast, but the same ratio of oil is entering the engine, just the source of the majority of it has changed.
If those compression numbers are normalized, it would seem that you are unlikely to have any concern of faulty seals causing the oil rise.It seems like you have a good engine.
Again this seems to be controversial, but I believe oil rise in the sump it to be a by product of the standard function of this engine when premixing, and to a lesser extent, using a Sohn and increasing OMP rates.
I'll say this too: This happens in healthy piston engines as well. (!) Premix at a 200:1 ratio in your Honda, Ford, Opel or whatever, and watch what happens over a standard oil interval. Static and dynamic compression will increase, idle vacuum will increase, idle will be more uniform, the engine may feel more responsive, unless the computer is pulling timing due to the lower octane (knocking) from the oil burning. And, finally, your sump oil level will increase if your car does not use oil, or it will go down less than you are used to over the same period. The oil will migrate into the sump. It will burn some, and blow some by.
In a piston engine, the primary contributor to premix oil going into the sump will be blow-by, but the fuel injector position and timing can also exacerbate the problem in a piston engine as well, like I believe it does in the Renesis.
Again, this is my opinion. Comments welcome.
In a motor without Sohn and not premix, the OMP takes oil from the sump and injects it: a part returns to the sump, but another part are burned, which does not give rise to the level.
When premixing, the unburned part of that oil will increase the oil in the sump, so either the level will lower more slowly or it could increase (if the premix level is high).
Something similar will happen if we use a Sohn, but in that case even more accentuated since we will not be taking oil from the sump so, unless the engine is loose and consumes a lot of oil, the level will always increase.
In my case, I have Sohn, I just do premix and I have increased the oil injection map somewhat and I think that explains the increase.
I do not have exact figures, but in the last oil change (I do it every 10000 km) I took about 6 ls and to fill the same level as before I had to contribute 5 ls, so the extra liter I guess comes from Sohn.
All this leads me to think: given that, either via premix or via Sohn, we are contributing 2-stroke oil to the sink, in which we will have a 4-stroke oil and since the 4T engine oil needs and incorporates some additives that the 2T does not have, I wonder if this contribution could degrade and / or prejudice the characteristics of the engine oil?
#132
All this leads me to think: given that, either via premix or via Sohn, we are contributing 2-stroke oil to the sink, in which we will have a 4-stroke oil and since the 4T engine oil needs and incorporates some additives that the 2T does not have, I wonder if this contribution could degrade and / or prejudice the characteristics of the engine oil?
The following users liked this post:
kevink0000 (05-18-2019)
#133
I'd be more concerned about fuel making it's way in than two stroke oil. That said, if your oil level is rising, has anyone confirmed that it is just oil and not fuel as well? A lot of FD guys got to the point of needing to change oil at 1k miles due to fuel diluting the oil.
I know this thread is regarding OMP injection, so I have to wonder, has anyone verified that increasing OMP injection alone without premix causes the oil level to rise? I see a lot of conjecture. I'd be able to test this but I don't put many miles on my vehicle... I'm currently using a slightly modified version of Brettus' NA table with a Sohn and about 256:1 premix.
I know this thread is regarding OMP injection, so I have to wonder, has anyone verified that increasing OMP injection alone without premix causes the oil level to rise? I see a lot of conjecture. I'd be able to test this but I don't put many miles on my vehicle... I'm currently using a slightly modified version of Brettus' NA table with a Sohn and about 256:1 premix.
#134
77 cylinders, 4 rotors...
Manu,
Yes you are right. If the OMP pulls from the sump there is an apparent net loss of oil over time, some gets pushed back into the sump through blowby, some gets burned.
If the oil for the OMP comes from a tank, some of that oil fills the sump, some is burned.
With premix, I personally have noticed that the sump level seems to rise faster than with OMP delivery of oil. If you premix heavily, it can rise pretty fast. Again, I don't have any facts or figures on that, just my observations, in my one sample engine.
I feel that if the oil seals, side seals, and cutoff seals were weak and leaking abnormally, the sump oil would not rise, or rise as quickly, because some would get pulled into the combustion chamber under vacuum on the intake stroke, or other evidence, like sump pressurization would show.
If you are premixing, and/or running a Sohn, and your oil level is rising, I think that indicates normal operation. Combustion pressure is sufficient to push past any combustion seal type on any IC engine, its the extent that matters.
This leads me to wonder what Mazda thought about marketing strategy for an engine that would need to have two separate oil reservoirs, and the consumer would have to keep checking to see that one is filled, and make sure the other doesn't get overfilled due to operation. Imagine a salesman having to explain THAT on a test drive! Or the ensuing Consumer Reports road test!
I guess future rotaries will probably always have sump oil injected.
Yes you are right. If the OMP pulls from the sump there is an apparent net loss of oil over time, some gets pushed back into the sump through blowby, some gets burned.
If the oil for the OMP comes from a tank, some of that oil fills the sump, some is burned.
With premix, I personally have noticed that the sump level seems to rise faster than with OMP delivery of oil. If you premix heavily, it can rise pretty fast. Again, I don't have any facts or figures on that, just my observations, in my one sample engine.
I feel that if the oil seals, side seals, and cutoff seals were weak and leaking abnormally, the sump oil would not rise, or rise as quickly, because some would get pulled into the combustion chamber under vacuum on the intake stroke, or other evidence, like sump pressurization would show.
If you are premixing, and/or running a Sohn, and your oil level is rising, I think that indicates normal operation. Combustion pressure is sufficient to push past any combustion seal type on any IC engine, its the extent that matters.
This leads me to wonder what Mazda thought about marketing strategy for an engine that would need to have two separate oil reservoirs, and the consumer would have to keep checking to see that one is filled, and make sure the other doesn't get overfilled due to operation. Imagine a salesman having to explain THAT on a test drive! Or the ensuing Consumer Reports road test!
I guess future rotaries will probably always have sump oil injected.
#135
77 cylinders, 4 rotors...
Kimura,
I wish I had a definitive answer to this. I drive about 2000-3000 miles a month, and I have observed what I have previously stated.
If oil is getting into the oil, fuel is also, but since the flash point of gasoline is about -40 degrees F. and 2 stroke oil is about +350 F, it burns before it can make it into the sump. The FD guys are running such high fueling rate and such rich mixture, some unburnt fuel is bound to get to the sump, like it does with piston engine cars running high boost. The fuel has a chance to evap out of the oil if the car is run long enough and the oil gets warm enough, but the 2 stroke will mix with the sump oil.
There are a lot of modern cars that can run long oil change intervals, but I don't think this is one of them. For many reasons there seems to be a consensus that it is better to use a short OCI, regardless of modifications to the oil injection system.
I wish I had a definitive answer to this. I drive about 2000-3000 miles a month, and I have observed what I have previously stated.
If oil is getting into the oil, fuel is also, but since the flash point of gasoline is about -40 degrees F. and 2 stroke oil is about +350 F, it burns before it can make it into the sump. The FD guys are running such high fueling rate and such rich mixture, some unburnt fuel is bound to get to the sump, like it does with piston engine cars running high boost. The fuel has a chance to evap out of the oil if the car is run long enough and the oil gets warm enough, but the 2 stroke will mix with the sump oil.
There are a lot of modern cars that can run long oil change intervals, but I don't think this is one of them. For many reasons there seems to be a consensus that it is better to use a short OCI, regardless of modifications to the oil injection system.
#137
77 cylinders, 4 rotors...
Brett,
Hard to say actually. I can't recall for sure, but I don't think I ran this engine at all in my normal day-to-day with an unmolested OMP. That was a day one modification for me. Based on what others report, its a pretty big amount going thru the OMP system. A quart every 400-500 miles, and more than that if I am running it harder. My normal driving is a pretty much 50-50 mix of city and highway. Yes, I still premix at that level also. Like you, I don't fully trust the OMP system to give full coverage.
Hard to say actually. I can't recall for sure, but I don't think I ran this engine at all in my normal day-to-day with an unmolested OMP. That was a day one modification for me. Based on what others report, its a pretty big amount going thru the OMP system. A quart every 400-500 miles, and more than that if I am running it harder. My normal driving is a pretty much 50-50 mix of city and highway. Yes, I still premix at that level also. Like you, I don't fully trust the OMP system to give full coverage.
#138
The race series I'm involved with has about half the field running OMP and half running premix at 100:1 . Should have a good idea over the next year or so which is better !
Last edited by Brettus; 05-18-2019 at 07:22 PM.
#140
When I installed the Sohn I spent a lot of time searching the forums, to determine which was the best oil for the sump, now that it was not going to be burned. In the end I prefer a synthetic, somewhat better and in 5W40 viscosity, since having these higher HTHS viscosity will protect the gears of the stationary from the shear effect.
During the search I read several times about the increase in level in the sink, but never delve into the subject thinking that only happened in engines with problems.
Now that I know what is the reason for that oil passage to the sink and that is also inevitable, I think that maybe I have to go back to find another oil, maybe with another viscosity, maybe return to the mineral, with a view to minimize the effect of contamination with 2T oil.
If it were not for the problem of char, I would have considered feeding the Sohn with the same 4T oil that I use in the sump: it would be like not having the Sohn but always injecting clean oil.
The most obvious solution is to change the oil more often, I agree, but in that case:
Does it make sense to use a synthetic oil or even a quality oil considering that it will lose its properties very quickly by the contribution of 2T?
Would it be better to switch to a denser oil (eg a 20W50) to compensate for this loss of properties?
During the search I read several times about the increase in level in the sink, but never delve into the subject thinking that only happened in engines with problems.
Now that I know what is the reason for that oil passage to the sink and that is also inevitable, I think that maybe I have to go back to find another oil, maybe with another viscosity, maybe return to the mineral, with a view to minimize the effect of contamination with 2T oil.
If it were not for the problem of char, I would have considered feeding the Sohn with the same 4T oil that I use in the sump: it would be like not having the Sohn but always injecting clean oil.
The most obvious solution is to change the oil more often, I agree, but in that case:
Does it make sense to use a synthetic oil or even a quality oil considering that it will lose its properties very quickly by the contribution of 2T?
Would it be better to switch to a denser oil (eg a 20W50) to compensate for this loss of properties?
#141
77 cylinders, 4 rotors...
Manu,
If you check out the oil analysis thread on this site, you can glean a good overview, and do what you think is right for your car.
I have chosen to run a cheap, thick, oil (high HTHS) for myself, and change it relatively often, since it suits my climate, driving style, and sensibilities.
Burning crankcase oil in rotor chambers will always be dirtier than a good 2t oil. Many of the good 2t oils are designed for high film strength, and are designed to "cling" to moving parts better, and are designed to work well in a much harsher environment than what a street rotary will see. And they burn clean, with low or no smoke.
I personally will always split the lubrication duties for my rotary engines between 2 different oils.
If you check out the oil analysis thread on this site, you can glean a good overview, and do what you think is right for your car.
I have chosen to run a cheap, thick, oil (high HTHS) for myself, and change it relatively often, since it suits my climate, driving style, and sensibilities.
Burning crankcase oil in rotor chambers will always be dirtier than a good 2t oil. Many of the good 2t oils are designed for high film strength, and are designed to "cling" to moving parts better, and are designed to work well in a much harsher environment than what a street rotary will see. And they burn clean, with low or no smoke.
I personally will always split the lubrication duties for my rotary engines between 2 different oils.
#142
Registered
Do you have an idea how much oil went through your Sohn in comparison to your one liter gain?
#143
Registered
iTrader: (1)
FWIW I've been running with a Sohn and synth in the engine on annual 6-7000km changes for 7 years and never saw an increase in pan oil level or unexpected changes in the UOA. So this whole thing about gaining oil seems very strange. It should not happen, if you think about the path oil would have to take to exit the chamber and end up in the pan. It would have to go through oil control rings against the pressure gradient.
#144
Do you have an idea how much oil went through your Sohn in comparison to your one liter gain?
Last edited by manuRx8; 05-20-2019 at 01:53 PM.
#145
FWIW I've been running with a Sohn and synth in the engine on annual 6-7000km changes for 7 years and never saw an increase in pan oil level or unexpected changes in the UOA. So this whole thing about gaining oil seems very strange. It should not happen, if you think about the path oil would have to take to exit the chamber and end up in the pan. It would have to go through oil control rings against the pressure gradient.
Jackpot. Got all of the papers plus a few others (I e-mailed the author directly and he responded pretty fast). They are in a Google Drive folder which contains the following.
- Oil Transport Cycle Model for Rotary Engine Oil Seals 2014-01-1664
- Modeling of the Rotary Engine Apex Seal Lubrication 2015-01-2035
- Visualization of the rotary engine oil transport mechanisms 2014-01-1665
- Predicting Gas Leakage in the Rotary Engine—Part I: Apex and Corner Seals 2016/6/1
- Predicting Gas Leakage in the Rotary Engine—Part II: Side Seals and Summary 2016/6/1
#146
77 cylinders, 4 rotors...
The oil seals and cutoff seals are "one way" if you look at them. The lip is designed to keep oil in.
#147
Registered
FWIW I've been running with a Sohn and synth in the engine on annual 6-7000km changes for 7 years and never saw an increase in pan oil level or unexpected changes in the UOA. So this whole thing about gaining oil seems very strange. It should not happen, if you think about the path oil would have to take to exit the chamber and end up in the pan. It would have to go through oil control rings against the pressure gradient.
#148
Registered
iTrader: (1)
I lost track of how many liters of Sohn oil that is per engine oil change. probably 10 ish?
It should be the same as any other RX8 though, the Sohn is still a metered system.
The pressure after the compressions seals but before the oil ring should be lower than oil main pressure, yes. On a regular RX8 that is; once you start boosting and opening up tolerances to match, all bets are off. But I haven't read the stuff linked above yet, it's obviously much better researched than my sample of one.
It should be the same as any other RX8 though, the Sohn is still a metered system.
The pressure after the compressions seals but before the oil ring should be lower than oil main pressure, yes. On a regular RX8 that is; once you start boosting and opening up tolerances to match, all bets are off. But I haven't read the stuff linked above yet, it's obviously much better researched than my sample of one.
#149
77 cylinders, 4 rotors...
Loki,
I am trying to remember, do you have an "built"engine? Or is it just stock Mazda?
I am trying to remember, do you have an "built"engine? Or is it just stock Mazda?