This came form another post for a slightly different question; it raises many intresting mechanical & engineering questions about duc engines; cooling, heat generated vs hp vs engine size ...
Why and what size Duc engines can effectively be air cooled; oil cooled and water / antifreeze cooled?. (question slightly revised to clarify se2809 at 8:30 pm pacific time)
Further; is this limit is due to overheating of the cyl rings? At what temp is air cooled not enough? I imagine its that traffic jam stop and go low speed in an Rome heatwave that there thinking about ... has anyone ever had an engine seize due to overheating???
So
What size engines have been engineered by Ducati for air ,oil & water/antifreeze applications? Why use water as opposed to oil?
by my recollection ....
air cooled; yrs? - 400; 600 620
Oil cooled; Yrs? - 750 ? to 02; 800 ; 900; 1k 1.1k - 2 valvers (and what about the oil cooled cyl jacket Nate mentioned; intresting)
water antifreeze cooled Yrs? Its related to the 4 cyl valves right?- 749? 848? 849? 916? 999? 1k etc
s4rs and race bikes ... and they also have an oil cooler right?
(added) SO ... as heman points out below ....more valves = more power = more heat = more cooling requirement (seems simple enough; but I know theres gotta be more technical details to it than that)
I'll reiterate from the other thread...
To the best of my knowledge the early 900s were the only air/oil cooled engines. It actually used an oil jacket around the cylinders to assist in cooling the cylinders.
An oil cooler does not mean the engine is oil cooled. It simply means the oil is cooled.
Quote from: ducpainter on September 28, 2009, 12:10:10 PM
I'll reiterate from the other thread...
To the best of my knowledge the early 900s were the only air/oil cooled engines. It actually used an oil jacket around the cylinders to assist in cooling the cylinders.
An oil cooler does not mean the engine is oil cooled. It simply means the oil is cooled.
+ 1 and because the oil is cooled by air they are still called air cool.
Maybe Stu can give us some more light into this..! [cheeky]
If I understand the original question correctly, the reason for the progression from air to oil to water relates more to the state of tune than the engine size or number of valves. I don't know what the biggest engine that can be air cooled is, but it is bigger than most motorcycle engines. Older VWs were air cooled, the larger Porsches were air/oil cooled and now they are water cooled. Suzuki GSXRs went from oil to water cooling when the heat output of their engines exceeded the oil cooling's capability. Suzuki's engines had to make more and more power to keep up with the competition and they just needed more cooling to run reliably at the level of tune.
More power = more heat.
999cc 2v = less power less heat, than a 999cc 4v
4v burns more air and fuel per a cycle than a 2v hence more power more heat.
Quote from: Bill in OKC on September 28, 2009, 01:45:52 PM
If I understand the original question correctly, the reason for the progression from air to oil to water relates more to the state of tune than the engine size or number of valves. I don't know what the biggest engine that can be air cooled is, but it is bigger than most motorcycle engines. Older VWs were air cooled, the larger Porsches were air/oil cooled and now they are water cooled. Suzuki GSXRs went from oil to water cooling when the heat output of their engines exceeded the oil cooling's capability. Suzuki's engines had to make more and more power to keep up with the competition and they just needed more cooling to run reliably at the level of tune.
biggest i am aware of...
(http://www.newspapercutting.com/images/b26fo_4.jpg)
Quote from: vw151 on September 28, 2009, 12:34:37 PM
so. After reading through all this. Water cooled vs. Air cooled in the traditional sense would be antifreeze/water vs. Just Oil. I get that. I am thinking an oil cooler is not necessarily what makes a bike oil cooled. Is it jackets and channels in the motor to allow the oil to cool the engine that make it oil cooled. These sound like places the oil is doing something other than lubricating.
A straight up explanation would be great.
On a side note. up until 1996 the Porsche 911 was air cooled. Least that is what people said, I believe in actuality it was oil cooled as it took 9 quarts of oil and had an oil cooler up front where you would find a radiator on normal cars.
I assume my s2r1000 is oil cooled.
from other thread ... ;D
If your asking why they use water over oil for cooling. I think the answer is in heat absorbtion.
Water's specific heat capcity is 4.16 kJ/kg K. That is it takes 4160 joules of energy to heat 1 kg of water 1 kelven.
4160 joules of energy.
I looked it up, and most oils are around 2kj/kgK.
Well, this engine is pretty big, Pratt & Whitney 4360:
(http://upload.wikimedia.org/wikipedia/commons/7/74/1955_Pratt_&_Whitney_R-4360-CB2_Wasp_Major_HAM.JPG)
(http://www.bikeland.org/bridges/images/DSCF45911.JPG)
Big advantages to water over oil for cooling; thermal conductivity is good and specific heat is good.
In simple terms, it can pull heat out of the engine quickly, and can store a lot of heat per pound.
So it can be a smaller and lighter cooling system if you use water instead of oil.
Advantage of oil cooling, you don't have an extra 'system', and you can put oil where you can't put water.
For example, many Duc engines spray oil on the bottom of the piston.
Perhaps another variable in the equation is the location of the engine? I can imagine that air cooling is a bit difficult if it's fully enclosed in bodywork, even if the displacement or the state of tune is relatively low? Interesting topic though!
[popcorn]
In an ultimate sense, true cooling of the engine itself is achieved through convection and radiation.
Convection carries heat away by transferring it to the air. Most of the heat lost through air is actually the air coming from the exhaust; most of the rest is shed via the air which moves through the fins found on radiators and engines themselves.
Heat is also lost in the form of radiation, primarily infrared but also long-wavelength visible light in extremely hot components such as an exhaust header at WOT near redline.
Some of the geeks may be thinking "what about conduction?" But conduction, for the most part, does not take heat from the engine except where the engine touches other components such as the frame which carry the heat away. What conduction does do is move heat to another area, such as an engine cooling fin or coolant which will be circulated through a radiator, where the heat will actually be shed through convection and radiation.
Ultimately, all motorcycle engines are "air-cooled" but reasonable people understand that the term "air-cooled" specifically refers to engines which shed heat without the assistance of a dedicated liquid circuit. Is there a limit to engine size due to air-cooling? Not at all.
What water cooling allows is much more precise control over the temperature of the engine through the use of the thermostat (a valve which determines the engine's minimum running temperature) and a cooling fan (which determines the engine's maximum running temperature). You can't very well just shut off the supply of oil, now can you? This precise control results in one less variable and thus makes it easier to design an engine with far tighter tolerances; it also allows you to keep an engine at a temperature which is superior for power and emissions.
On an air-cooled engine, the best you can do is use a fan on an oil cooler to provide a maximum operating temp, but there's no real control to prevent the temperature from dropping too far.
ooow; yes, yes, yes ... [popcorn]
yyyyyooooouuu guyyyyyyyyyys .... are good! ......... told ya theres more to it! I knew it. [thumbsup]
keep it comming; ita a multifacited question ...
Also, water cooling allows you to maintain a very specific operating temperature. The operating temperature of air cooled engines vary widely because you can only put so much control over the air flow around the engine and the ambient temperature. A thermostat in a radiator can open and close to keep the temperature right where you want it. The significant advantage here is that since the engine has a limited operating temperature range you can make then tolerances on everything in the engine tighter. This means more efficiency, more power. Air cooled engines have to be looser for the larger temperature ranges they operate in.
Airplane engines are great candidates for air cooling. There's always plenty of cool air around and then tend to run at set speeds rather than throttling up and down like land vehicles. It also removes the water cooling system, just another system that could fail. They are no doubt among the largest and most powerful air cooled engines.
For more traditional land based vehicles, the twin turbo Porsches that ran at Le Mans through the late 60s and early 70s (I think) were staggeringly powerful.
Scott
Quote from: scott_araujo on October 02, 2009, 08:09:46 PM
Airplane engines are great candidates for air cooling. There's always plenty of cool air around and then tend to run at set speeds rather than throttling up and down like land vehicles. It also removes the water cooling system, just another system that could fail. They are no doubt among the largest and most powerful air cooled engines.
You also save some weight, a good thing when airborne ;D
Quote from: Keld on October 03, 2009, 03:48:02 AM
You also save some weight, a good thing when airborne ;D
Also a good thing on a bike ;D
Quote from: Scissors on September 29, 2009, 09:54:53 AM
Ultimately, all motorcycle engines are "air-cooled" but reasonable people understand that the term "air-cooled" specifically refers to engines which shed heat without the assistance of a dedicated liquid circuit. Is there a limit to engine size due to air-cooling? Not at all.
OK, first, well put. I think I had a good understanding of this to begin with but wanted to hear a more precise explanation. This part of your response really hits the nail on the head. There is no reason for anyone to bring up the point that all engines are "air cooled" technically that is true but not the question at hand.
Anyway. From what I've read here is what I have gathered in simple terms
1. Air Cooled - Just an engine, doing it's thing with oil as a lubrication but not channeled anywhere specific for cooling. An oil cooler could be used to cool the oil. So, the oil cools the motor but isn't specifically routed through the motor to do so and otherwise like all engines the heat leaves the engine via the metal contacting the outside air.
2. Air/Oil cooled - Just like air cooled except the oil also runs through channels much like a water cooled engine to more evenly cool the motor. So, more oil is likely required since it will be running through channels and also doing it's normal lubrication job.
side note- air cooling and air oil cooling will allow larger variances in temperature so the way the engine is designed will have to allow for this higher variance through lower tolerances and ultimately lower power in order to keep temps in check. (less fuel/air can be burned and less RPM can be achieved as both of these things make more heat)
3. Water cooling - separate fluid and channels dedicated to cooling the engine, a water pump moves the fluid through the engine and a dedicated radiator cools the fluid. A thermostat regulates the temp of the coolant with the use of a fan on the radiator in many cases and the engine ultimately stays at a more even temperature and is also able to dissipate a larger amount of heat allowing for more power to be made with out overheating the engine via higher RPMs and larger air/fuel burned.
This is the lableling I've usually seen too but I think there is another option, call it 2 1/2.
Oil cooled with the oil being forced through channels similar to those used in water cooling. It sounds like this is what the 900 does from what has been metioned here. This is a step up from option 2 you mentioned where the oil being used as lubrcant is simply pushed through an external cooler, there are additional passages the oil is pumped through exclusively to remove heat from the engine. Someone correct me if I'm wrong.
Scott
Quote from: scott_araujo on October 05, 2009, 09:34:26 AM
This is the lableling I've usually seen too but I think there is another option, call it 2 1/2.
Oil cooled with the oil being forced through channels similar to those used in water cooling. It sounds like this is what the 900 does from what has been metioned here. This is a step up from option 2 you mentioned where the oil being used as lubrcant is simply pushed through an external cooler, there are additional passages the oil is pumped through exclusively to remove heat from the engine. Someone correct me if I'm wrong.
Scott
That is what I was meaning to say for option 2. Oil cooler doesn't change the definition at all by what I'm reading here. The difference between air cooled and oil cooled simply seems to be the pushing oil through cooling channels or other things specificly made for cooling.
I was trying to get away from the "semantics" and precise definition and get further into the technical why and how it works; there has been some intresting explanation as to how and why; and perhaps part of the explanation is in the definition ... but the actual definition isn't as important as the other technical details ... some noted below.
- oil being circulated as a coolant jacket around the 900 cylinder (is that the only engine that does that?) and
water cooling with a thermostat will hold the temp at a better constant, holding a constant and more precise engine temp to design around ....
that water absorbs heat at twice the rate of oil ... (who knew?)
This has some real engine design considerations. I have some understanding of how engines work and are cooled but have learnt some further details ...
... the internet can be the collective brain ... (lol. can it?)
Air-cooled 1200 hp diesel that runs in desert land: http://www.army-technology.com/projects/merkava/ (http://www.army-technology.com/projects/merkava/)
This problem is far too complicated to fully describe in this forum, but I'll throw a couple of more wrenches into the works.
As far as I know, all bevel driven Ducatis, both desmo and spring head, were air-cooled animals. When the Pantah was introduced, they, too, were air-cooled. The first liquid cooled Ducati I remember was the 851 in the late 80s. All four valvers since (888, 916, 748, 996, 998, 749, 999, 848, 1098, 1198) have been liquid cooled. All Pantah derivatives (400, 500, 600, 650, 696, 750, 800, 900, 1000, 1100) with the exception of the hybrid ST3 engine have been air cooled. The ST3 engine was liquid cooled.
Air cooled engines have a problem disposing of heat near the centers of their cylinder heads, as all heat generated must be transferred toward the cooling surfaces via conduction. This can lead to detonation problems and there is a practical bore limit given a valve/spark plug/compression/rpm ceiling/cylinder arrangement in four stroke gasoline engines. Lower operational speeds give longer time intervals to dispose of heat. Valves are cooling devices (heat sinks), but can also be hot spots for detonation. Compression directly affects the predisposition of an engine to detonate.
Diesels are another matter entirely, as diesel is a VERY high octane fuel by comparison.
The assertion that more valves = more air/fuel is a bit simplistic. When it comes down to it, an engine is an air pump. A 900cc air cooled engine moves as much air per stroke as a 900cc liquid cooled one, yet a liquid cooled engine will typically make more power than an air cooled one. The difference can be attributed to a few primary design differences.
First, a liquid cooled engine, since it is more resistant to detonation, can be designed with a higher compression ratio, yielding greater volumetric efficiency at a given speed.
Second, since they can move heat away from the cylinder and cylinder head more quickly, liquid cooled engines can operate at higher speeds, yielding more horsepower (as horsepower is a simple mathematical formula relating torque to rotational speed). These higher operational speed mean the liquid cooled engine pumps more air/fuel (the same per rev, but more revs!).
Finally, since Ducati liquid cooled engines use three or four valves per cylinder,which flow more air/fuel over a given time interval than two valves, the cam profiles can be optimized to allow better cylinder filling and exhausting in a shorter portion of the piston's stroke. This also yields greater efficiency and more power.
The emissions advantages of liquid cooling have already been mentioned, so I won't venture there.
It's been a little more than 20 years since engineering school, so forgive me if I don't remember all the math to support my assertions, but this is kinda how I remember engine design. Remember that the best internal combustion engines run around 25% efficiency, and you'll see why even a small increase in efficiency is worth pursuing.
Dude!
Posted by: Cloner
Quote from: Cloner on October 06, 2009, 03:27:45 PM
This problem is far too complicated to fully describe in this forum, but I'll throw a couple of more wrenches into the works.
As far as I know, all bevel driven Ducatis, both desmo and spring head, were air-cooled animals. When the Pantah was introduced, they, too, were air-cooled. The first liquid cooled Ducati I remember was the 851 in the late 80s. All four valvers since (888, 916, 748, 996, 998, 749, 999, 848, 1098, 1198) have been liquid cooled. All Pantah derivatives (400, 500, 600, 650, 696, 750, 800, 900, 1000, 1100) with the exception of the hybrid ST3 engine have been air cooled. The ST3 engine was liquid cooled.
Air cooled engines have a problem disposing of heat near the centers of their cylinder heads, as all heat generated must be transferred toward the cooling surfaces via conduction. This can lead to detonation problems and there is a practical bore limit given a valve/spark plug/compression/rpm ceiling/cylinder arrangement in four stroke gasoline engines. Lower operational speeds give longer time intervals to dispose of heat. Valves are cooling devices (heat sinks), but can also be hot spots for detonation. Compression directly affects the predisposition of an engine to detonate.
Diesels are another matter entirely, as diesel is a VERY high octane fuel by comparison.
The assertion that more valves = more air/fuel is a bit simplistic. When it comes down to it, an engine is an air pump. A 900cc air cooled engine moves as much air per stroke as a 900cc liquid cooled one, yet a liquid cooled engine will typically make more power than an air cooled one. The difference can be attributed to a few primary design differences.
First, a liquid cooled engine, since it is more resistant to detonation, can be designed with a higher compression ratio, yielding greater volumetric efficiency at a given speed.
Second, since they can move heat away from the cylinder and cylinder head more quickly, liquid cooled engines can operate at higher speeds, yielding more horsepower (as horsepower is a simple mathematical formula relating torque to rotational speed). These higher operational speed mean the liquid cooled engine pumps more air/fuel (the same per rev, but more revs!).
Finally, since Ducati liquid cooled engines use three or four valves per cylinder,which flow more air/fuel over a given time interval than two valves, the cam profiles can be optimized to allow better cylinder filling and exhausting in a shorter portion of the piston's stroke. This also yields greater efficiency and more power.
The emissions advantages of liquid cooling have already been mentioned, so I won't venture there.
It's been a little more than 20 years since engineering school, so forgive me if I don't remember all the math to support my assertions, but this is kinda how I remember engine design. Remember that the best internal combustion engines run around 25% efficiency, and you'll see why even a small increase in efficiency is worth pursuing.
standing [clap]
.... wow .... right on ... and that was the more technical design info I was searching for; thanks!
Ummmm ... It'll trake a few days to absorbe and ask an intelligent qestion back .... wow right on! Dont have an engineering background; but! i do have a design and some mechanical know how ...
[moto]