Oil cooling brainstorm
09-26-2006, 11:22 AM
#1
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Oil cooling brainstorm
OK people, let's work out how something would or would not work. After seeing the Courage cooling system update, it mentions that they are now using an oil/water cooling system for the oil as opposed to the standard oil/air systems that we all know. This has got me thinking of an idea for the RX-8 and I'm not sure how sound it is so I'd like some feedback, criticism, or an other ideas or reasons why it may or may not work this way.
When we think of oil cooling, we tend to think of it as independent of the coolant system. They are both different fluids, they flow through different parts of the engine, they each have different pumps, they each have their own thermostat, and they use different coolers. Having each system work perfectly is very important as they both reject a lot of heat from the engine. On the stock oil cooler setups on the car, we use air as a medium to cool the oil. The more airflow we have, the cooler the oil. Ultimately we should have our oil temperatures and coolant temperatures roughly the same as each other or at least very close. What if we are thinking about oil cooling all wrong? What if instead of cooling it down as much as we can, we should really be just trying to equalize it's temperature with the coolant?
Here's the idea. It may already be in use in race cars or it may not. I'm just brainstorming here and trying to work out the issues in my head. (The issues in my head will never work themselves out!) Part of me just doesn't see how this is possible but then another part of me thinks it's so weird it might actually work. What if we used an oil cooler or 2 that was cooled down not by air but by the engine coolant? I know it sounds like a terrible idea as the coolant is always hot. What if we made it efficient enough that they would just try to equalize in temperature? Isn't that what a heat exchanger is trying to do anyways? We want them to exchange heat with each other to try to reach a common ground. This would of course raise the coolant temperature but that's where a good radiator comes in. If this could be made to work, we wouldn't need an oil thermostat anymore as coolant and oil temperatures would be tied together. The engine parts should all heat up at the same rate.
I'm partially convinced that it MIGHT work but another part of me says no. The 1st generation RX-7's in '80-'81 used oil coolers in this fashion and they were a problem on that car but the cooler was pretty small. The nice thing is that you don't need to have these coolers placed in an airstream at all so they can be tucked away. The other part of me that says it might work is basing this assumption on the fact that the Courage now has an oil/water system. I'm just not sure if they are using a separate radiator for that system or not. It doesn't make much sense to me to add complexity to a race car but you never know.
Anyways that's my brainstorm for the day. Please provide any ideas, feedback, etc. I'd like to hear ways that people think it could be made to work as well as reasons why it wouldn't. Even if it wouldn't work, at the very least it is interesting.
When we think of oil cooling, we tend to think of it as independent of the coolant system. They are both different fluids, they flow through different parts of the engine, they each have different pumps, they each have their own thermostat, and they use different coolers. Having each system work perfectly is very important as they both reject a lot of heat from the engine. On the stock oil cooler setups on the car, we use air as a medium to cool the oil. The more airflow we have, the cooler the oil. Ultimately we should have our oil temperatures and coolant temperatures roughly the same as each other or at least very close. What if we are thinking about oil cooling all wrong? What if instead of cooling it down as much as we can, we should really be just trying to equalize it's temperature with the coolant?
Here's the idea. It may already be in use in race cars or it may not. I'm just brainstorming here and trying to work out the issues in my head. (The issues in my head will never work themselves out!) Part of me just doesn't see how this is possible but then another part of me thinks it's so weird it might actually work. What if we used an oil cooler or 2 that was cooled down not by air but by the engine coolant? I know it sounds like a terrible idea as the coolant is always hot. What if we made it efficient enough that they would just try to equalize in temperature? Isn't that what a heat exchanger is trying to do anyways? We want them to exchange heat with each other to try to reach a common ground. This would of course raise the coolant temperature but that's where a good radiator comes in. If this could be made to work, we wouldn't need an oil thermostat anymore as coolant and oil temperatures would be tied together. The engine parts should all heat up at the same rate.
I'm partially convinced that it MIGHT work but another part of me says no. The 1st generation RX-7's in '80-'81 used oil coolers in this fashion and they were a problem on that car but the cooler was pretty small. The nice thing is that you don't need to have these coolers placed in an airstream at all so they can be tucked away. The other part of me that says it might work is basing this assumption on the fact that the Courage now has an oil/water system. I'm just not sure if they are using a separate radiator for that system or not. It doesn't make much sense to me to add complexity to a race car but you never know.
Anyways that's my brainstorm for the day. Please provide any ideas, feedback, etc. I'd like to hear ways that people think it could be made to work as well as reasons why it wouldn't. Even if it wouldn't work, at the very least it is interesting.
09-26-2006, 12:08 PM
#3
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Actually I need to go research that one to be sure. Logic would say that it must if there are actually oil/water coolers out there on race cars.
I do know that the heat rejection ability of water is 4 times greater than that of air meaning that you need much cooler air than water to get the same effect.
More research is needed.
I do know that the heat rejection ability of water is 4 times greater than that of air meaning that you need much cooler air than water to get the same effect.
More research is needed.
Last edited by rotarygod; 09-26-2006 at 12:18 PM.
09-26-2006, 12:18 PM
#4
interesting --yes.
Summit racing sells such a cooler. I am sure it has it's uses already.
in monitoring my temps my coolant and oil temps roughly are the same. defining same is approx 10-20 degrees F differance. This exists in all the enviroments I have thus been in this vehicle.
Say on the track--coolant temp 210F, oil temp 230F. On the street coolant temp 185-190--oil temp 190-195-and on rare occasions 200F. on warm up i notice the variation is about the same.
Roughly this is my car features that I think may influence this
1- coolant mix is currently at 60/40
2- agency underdrive pulley(15-20% underdrive)
3- NO protective screens installed(i took them off)
4- running royal purple 5W/30
5- run premix at 1/2oz/gal
This differance is not dependant on ambient temps. I have observed the same in 70degrees and at 100degrees
So to continue to brainstorm this thought--does the 20degree differance make a differance? Do others have a more wide variation than I? I am pretty sure FI does.
I still like the idea of the electric water pump. One day------
olddragger
Summit racing sells such a cooler. I am sure it has it's uses already.
in monitoring my temps my coolant and oil temps roughly are the same. defining same is approx 10-20 degrees F differance. This exists in all the enviroments I have thus been in this vehicle.
Say on the track--coolant temp 210F, oil temp 230F. On the street coolant temp 185-190--oil temp 190-195-and on rare occasions 200F. on warm up i notice the variation is about the same.
Roughly this is my car features that I think may influence this
1- coolant mix is currently at 60/40
2- agency underdrive pulley(15-20% underdrive)
3- NO protective screens installed(i took them off)
4- running royal purple 5W/30
5- run premix at 1/2oz/gal
This differance is not dependant on ambient temps. I have observed the same in 70degrees and at 100degrees
So to continue to brainstorm this thought--does the 20degree differance make a differance? Do others have a more wide variation than I? I am pretty sure FI does.
I still like the idea of the electric water pump. One day------
olddragger
09-26-2006, 12:45 PM
#5
Rotary lover
RG
You are right, Here by us in SA I saw one of my friends who race a 3 rotor 20B peripheral port and who battled to get the oil temps down.
Eventually they went to a heat exchanger type "cooler" I remember its about 15" long and looks fairly round, it lies horisontally.
They then used a bigger radiator with good cooling and the problem was solved.
The oil tend to get much hotter than the water temps, so it makes sense.
Philip
You are right, Here by us in SA I saw one of my friends who race a 3 rotor 20B peripheral port and who battled to get the oil temps down.
Eventually they went to a heat exchanger type "cooler" I remember its about 15" long and looks fairly round, it lies horisontally.
They then used a bigger radiator with good cooling and the problem was solved.
The oil tend to get much hotter than the water temps, so it makes sense.
Philip
09-26-2006, 02:13 PM
#7
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The problem is this; no process is 100% efficient. With a direct air cooling for the oil, you're looking at a one process heat rejction. With coolant cooling for the oil, you're looking at two processes (oil to water, water to air). Therefore, your overall system temperature (the heat energy present in both the coolant and the oil) will always be higher with coolant cooled oil than with air cooled oil. However, it might still be advantageous to use this method if your oil temperatures are cooking, but you have a reserve in coolant heat capacity.
09-26-2006, 03:37 PM
#8
well i'm quite the bug enthusiast and oil/air colling is it there. best thing I've seen is a huge oil cooler a HUGE sump and radiator type fans. you regulate the oil temp via a thermostat and a bypass. even with water jackets and radiators you can't beat that.
09-26-2006, 03:54 PM
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We are thinking on the same page. I was also trying to think of ways to keep the oils temperature down.
See my thread from yesterday https://www.rx8club.com/series-i-tech-garage-22/fan-oil-cooler-99647/
This is another idea I had, but probably wouldn't work for us. Basically, combine the oil and coolant systems and use only oil. This would mean we would have three oil coolers. One Big one (The old radiator) with a fan, and then the two current oil coolers would remain intact. So basically, oil in our car would server two purposes, 1, lubricate the engine as always and,2, cool the engine. Of course oil changes would become more difficult, but that is a different issue.
Here is my non-scientific logic for why this might work. Air is bad for cooling the engine because it is not very dense. Since it isn't dense, it can't carry heat from the engine. So we use water. Water is more dense then air so it provides greater cooling ability. And oil is more dense then water.
[Edit]
Damn it... My ideas are never original
http://www.suzukicycles.org/GSX-R-se...X-R750_a.shtml
See my thread from yesterday https://www.rx8club.com/series-i-tech-garage-22/fan-oil-cooler-99647/
This is another idea I had, but probably wouldn't work for us. Basically, combine the oil and coolant systems and use only oil. This would mean we would have three oil coolers. One Big one (The old radiator) with a fan, and then the two current oil coolers would remain intact. So basically, oil in our car would server two purposes, 1, lubricate the engine as always and,2, cool the engine. Of course oil changes would become more difficult, but that is a different issue.
Here is my non-scientific logic for why this might work. Air is bad for cooling the engine because it is not very dense. Since it isn't dense, it can't carry heat from the engine. So we use water. Water is more dense then air so it provides greater cooling ability. And oil is more dense then water.
[Edit]
Damn it... My ideas are never original
http://www.suzukicycles.org/GSX-R-se...X-R750_a.shtml
Suzuki went counter to the conventional design by developing SACS (Suzuki advanced cooling system) whereby the cylinder head and the pistons are oil cooled via the engine oil injection, achieving cooling efficiency as good as water-cooling without its weight increase. The computer designed engine package was 10% lighter than the water-cooled versions.
Last edited by lethologica; 09-26-2006 at 04:05 PM.
09-26-2006, 04:13 PM
#10
Rally Car Racer
^^ a waterless oil cooling system..
Now there's an interesting idea which would also allow you to incorporate an additional feature - dry sump (since the majority of the oil would/could be stored in the radiators.)
Just a thought.
Now there's an interesting idea which would also allow you to incorporate an additional feature - dry sump (since the majority of the oil would/could be stored in the radiators.)
Just a thought.
Last edited by The Mighty Red; 09-26-2006 at 04:18 PM.
09-26-2006, 04:30 PM
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i am in no way a cooling expert but i do like the idea of having 100% cooling system based on oil. It would make oil changes more difficult and if we have the same amount of coolant in oil form we are looking at 2 gallons of oil for coolant! on top of the 8 something quarts of oil?
Another thing to think about would be after a few tanks of gas say you need to add 2 quarters of oil to the system? As the engine slowly eats oil wouldnt the cooling capasity of the system be negatively effected?
Another thing to think about would be after a few tanks of gas say you need to add 2 quarters of oil to the system? As the engine slowly eats oil wouldnt the cooling capasity of the system be negatively effected?
09-26-2006, 05:44 PM
#13
Rotary Wanker
Automatic transmission fluid cooled at the radiator so this idea is a variation of that. Just install an AT radiator and route the engine oil through it before it goes into the regular air-oil cooler (assuming you can get enough flow rate through the AT radiator).
09-26-2006, 06:09 PM
#14
Bummed, but bring on OU!
I like the idea. Relocating the battery to the trunk would free a space for an oil/water intercooler. You could then replace the (in my case) single oil cooler with an air/water radiator. In theory this should keep the oil much cooler than stock, since water can absorb so much more heat. Water to air heat exchange would be more efficient than oil to air I would think. The battery in the trunk would offset the added weight up front. The added benefit would be: a hole in the air/water radiator won't drain the oil from the car, and a level sensor could be attached to the water/oil intercooler to indicate any water leaks. A high flow rate electric pump would be needed for good cooling.
A choice would need to be made, or the physics would dictate (research would tell) between a pressurized or unpressurized system. High flow rates would likely prevent any boiling in the system under most circumstances. A pressurized system adds complexity in an overflow tank and more space used. I think you could pull it off unpressurized (other than the d/p from the pump).
As for efficiency, in this case, the original system would be scrapped for an improved 2 step system. You're not really adding a step, more removing a step and adding 2. Water is much better at removing heat from the oil than air ever could be. The oil to water to air exchange cannot be less efficient than the oil to air exchange currently is. Oil to water alone would be more ideal, but this isn't a boat . As long as you could keep the water temps under around (SWAG) 150F I think you'd see much cooler oil temps. Radiator size and flow rates would need some tweaking. Winter could be an issue, and you might need a "coolant" change twice a year to keep it from freezing in the cold weather.
Good discussion topic regardless.
A choice would need to be made, or the physics would dictate (research would tell) between a pressurized or unpressurized system. High flow rates would likely prevent any boiling in the system under most circumstances. A pressurized system adds complexity in an overflow tank and more space used. I think you could pull it off unpressurized (other than the d/p from the pump).
As for efficiency, in this case, the original system would be scrapped for an improved 2 step system. You're not really adding a step, more removing a step and adding 2. Water is much better at removing heat from the oil than air ever could be. The oil to water to air exchange cannot be less efficient than the oil to air exchange currently is. Oil to water alone would be more ideal, but this isn't a boat
. As long as you could keep the water temps under around (SWAG) 150F I think you'd see much cooler oil temps. Radiator size and flow rates would need some tweaking. Winter could be an issue, and you might need a "coolant" change twice a year to keep it from freezing in the cold weather.Good discussion topic regardless.
09-26-2006, 06:27 PM
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i think you could realistically put a plate type heat exchanger before the inlet of the radiator and use the stock water pump to push the coolant through the water side of the exchanger and the plumb the oil side in a similar fashion to how the oil coolers (which we will chuck) are plumbed up now. If sized properly you should get ~90% heat transfer efficiency so your oil temps would approach your coolant temps or around 200 deg which is really right where you want them. In the winter, the car should warm up much quicker as a positive side effect since the thermostat will bypass the coolant system and now the oil cooling system.
Downsides are you need 2x the radiator capacity (maybe utilizing the area where your oil coolers use to be) and if the exchanger ever fails your going to have oil in you water (or reverse depending on which is higher pressure at any given moment)
Downsides are you need 2x the radiator capacity (maybe utilizing the area where your oil coolers use to be) and if the exchanger ever fails your going to have oil in you water (or reverse depending on which is higher pressure at any given moment)
09-26-2006, 06:44 PM
#16
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Originally Posted by therm8
I like the idea. Relocating the battery to the trunk would free a space for an oil/water intercooler. You could then replace the (in my case) single oil cooler with an air/water radiator. In theory this should keep the oil much cooler than stock, since water can absorb so much more heat. Water to air heat exchange would be more efficient than oil to air I would think. The battery in the trunk would offset the added weight up front. The added benefit would be: a hole in the air/water radiator won't drain the oil from the car, and a level sensor could be attached to the water/oil intercooler to indicate any water leaks. A high flow rate electric pump would be needed for good cooling.
09-26-2006, 06:50 PM
#17
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Originally Posted by r0tor
i think you could realistically put a plate type heat exchanger before the inlet of the radiator and use the stock water pump to push the coolant through the water side of the exchanger and the plumb the oil side in a similar fashion to how the oil coolers (which we will chuck) are plumbed up now. If sized properly you should get ~90% heat transfer efficiency so your oil temps would approach your coolant temps or around 200 deg which is really right where you want them. In the winter, the car should warm up much quicker as a positive side effect since the thermostat will bypass the coolant system and now the oil cooling system.
Downsides are you need 2x the radiator capacity (maybe utilizing the area where your oil coolers use to be) and if the exchanger ever fails your going to have oil in you water (or reverse depending on which is higher pressure at any given moment)
Downsides are you need 2x the radiator capacity (maybe utilizing the area where your oil coolers use to be) and if the exchanger ever fails your going to have oil in you water (or reverse depending on which is higher pressure at any given moment)
09-26-2006, 07:04 PM
#18
Why not use a seperate "coolant" system for the oil cooler....more complex I know....but the delta across the cooler should be greater without all the engine heat to interfere...as well it could be made smaller....Kinda like the new computer coolers...You could find a much better transfer medium if it was a sealed system as well...
09-26-2006, 07:05 PM
#19
Bummed, but bring on OU!
Originally Posted by rotarygod
It appears that you are adding an extra step and I'm not sure if it is necessary. You want to have the oil get it's cooling from water and the water you want to use to cool the oil system is in it's own sealed system independent of the car's cooling system and is cooled by it's own radiator? That's a bit extreme and I'm not sure if that would work too well.
I guess I'm looking at it from a maximum cooling effect. Which is probably overkill for a vehicle engine. Cooling to optimum oil temp would be easier. I could add a couple more steps to include a boiler, steam turbine, and condensor if you really want unnecessary
.Using the Coolant system to cool the oil seems like it would work, but I would worry about a failure in the heat exchanger like mentioned before.
Perhaps you could supplement the coolant system with extra radiators where the oil coolers were, but a hole in one of them would be rather catastrophic (moreso than in an oil cooler at least).
I come from a world of independent and most of the time redundant systems. It's hard to think any other way.
09-26-2006, 07:34 PM
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Don't forget the added weight of the extra coolant needed.
Almost all race cars especially purpose built ones seem to favor seperate systems. I prefer a seperate large oil cooler placed in front of the radiator that is ducted (adjustable) properly.
Almost all race cars especially purpose built ones seem to favor seperate systems. I prefer a seperate large oil cooler placed in front of the radiator that is ducted (adjustable) properly.
09-27-2006, 06:35 AM
#21
one thing to also consider is flow. would you want bigger pipes/low pressure flow or medium pipes with higher pressure flow? would you want variable flow rate vs constant flow rate with thermostatic control? this is applicable to the coolant and the oil.
It would be nice for the system to respond to load and/or rpm also.
More flow at a lower rpm(idling/stop and go, pullin the travel trailer etc) would be a great advantage in this engine with such a large flame front.
Such a system could also relocate the hard to reach oil filter and a larger filter with it's own limited cooling function could be used.(this is an area in regard to cooling that i wish to see more off).
definately use a better pump than we have now.
As far as volume is concerned, i think what we have now is adequete. The area needing improvement the worse is airflow.
The present high angle of the raditor,the a/c condensor impending air flow, the crowded back of the raditor and the fans not activating until temps are already borderline high(thank you emmisions) all add up.
So flow rate of the coolant/oil has to be taken in considerantion with the air flow rate also. (Monitor what happens to oil/water temps when you coast for about 1/4 mile at idle!)
I know people are probably tired of me mentioning electric water pumps, but I really think that -properly done--would help us rotory owners out in regard to better heat control and give us a little more power(15-20hp).
olddragger
It would be nice for the system to respond to load and/or rpm also.
More flow at a lower rpm(idling/stop and go, pullin the travel trailer
etc) would be a great advantage in this engine with such a large flame front.Such a system could also relocate the hard to reach oil filter and a larger filter with it's own limited cooling function could be used.(this is an area in regard to cooling that i wish to see more off).
definately use a better pump than we have now.
As far as volume is concerned, i think what we have now is adequete. The area needing improvement the worse is airflow.
The present high angle of the raditor,the a/c condensor impending air flow, the crowded back of the raditor and the fans not activating until temps are already borderline high(thank you emmisions) all add up.
So flow rate of the coolant/oil has to be taken in considerantion with the air flow rate also. (Monitor what happens to oil/water temps when you coast for about 1/4 mile at idle!)
I know people are probably tired of me mentioning electric water pumps, but I really think that -properly done--would help us rotory owners out in regard to better heat control and give us a little more power(15-20hp).
olddragger
09-27-2006, 06:58 AM
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There is a company that makes water/oil coolers. They are cylinderical and come in 3 sizes. I just saw the site the other day, and thought about posting it, but thought you all would think im just being paranoid about the rotary's heat......
Guess not. It was like molec or something, started with an m, but now I cant find the site.
Guess not. It was like molec or something, started with an m, but now I cant find the site.
09-27-2006, 09:27 AM
#24
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One interesting aspect of the coolant/oil heat exchanger is that when you're sitting in traffic, oil temps wouldn't rise as much (might've saved a few of those AT's engines out in Phoenix and LV, eh?).
One thing I was thinking that could be done pretty easily is a system to "weep" water over the existing oil coolers. You could control the weep rate based on oil temp - or even the oil cooler temp itself, i.e. only use the water when it's really needed. With this method you might even be able to get away with using a relatively small water reservoir - say the windshield washer tank?
Seems like this would be pretty easy to mock up and try, just to see if it's feasible...
One thing I was thinking that could be done pretty easily is a system to "weep" water over the existing oil coolers. You could control the weep rate based on oil temp - or even the oil cooler temp itself, i.e. only use the water when it's really needed. With this method you might even be able to get away with using a relatively small water reservoir - say the windshield washer tank?
Seems like this would be pretty easy to mock up and try, just to see if it's feasible...
09-27-2006, 09:49 AM
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Well, first of all do we really need this? I'm just really against the idea of adding more pumps and more complexity to the system if it doesn't really need it.
http://www.opcon.se/index.asp?sPage=1&langID=2&cID=15
Laminova, link above, has some interesting stuff about this. Though, they are very expensive. To get Laminova cores for cooling boost, the cost is around $2,400.
http://www.opcon.se/index.asp?sPage=1&langID=2&cID=15
Laminova, link above, has some interesting stuff about this. Though, they are very expensive. To get Laminova cores for cooling boost, the cost is around $2,400.