Aftermarket oil cooler question

[2-Skinny]

From an engineering stand point, it is likely that the Ducati engineers considered operation of the engine in a variety of environments (limited of course, after all, we live on planet Earth...) and designed the cooling area of the heads accordingly.  In other words, there is an upper limit and lower limit to the temperatures which the engine can reliably operate.  I doubt we will exceed those here, and if we do, we may have other things to worry about than our motorcycle engines ...

EXCEPT one thing...

Although the bike will run in those ranges, the lack of an oil cooler stock is likely a financial decision- not an engineering one.  The question here, I think, is will having an oil cooler lower overall temps and thus increase the longevity of the engine/ reliability of bike.

The answer is YES.  Whether or not the cost of your install is "worth it" is up to how old your bike is now and/or how long you intend to keep and ride it.

Figuring Ducati makes 30k or so Monsters a year and the cost to them to add an oil cooler is ~$100- they would almost certainly opt to produce the engine "on the line" so to speak in terms of temperature than add the cooler...as it would save them $3,000,000 a year...

Just a thought...

[bikepilot]

Also you have to consider over-cooling which is as bad, if not worse, than running too hot.  If you ride in cold weather consider whether the little monster motor will make enough heat to stay reasonably warm on the cold days with the cooler installed.  If not, then you get into the situation of blocking off the cooler, installing an oil t-stat etc.

fwiw, my wife's 620 seems to do pretty well without a cooler - even on the hotter days it has stayed <260F and its usually around 200-230 which is pretty near ideal. 

[elgallo73]

Bikepilot brings up an excellent point, I found some posts regarding this when considering a cooler for my bike.  Here is an example:

http://www.hdforums.com/forum/touring-models/449680-oil-running-too-cool-140-degrees-wtf.html

And this is with a THERMOSTAT AND COOLER, granted, it is specific to Harley Davidson, but gives you some idea of the challenges associated with air cooled engines.

An excellent point made from the previous URL:

There's really no way to run an aircooled engine within tight oil temperature ranges, even with an oil cooler. I suggest relaxing and riding more . . . H-D oil is intended to run over a wide operating range and so's the engine.

Although cost was possibly somewhat of a factor with the 695/695 in the decision to NOT implement an oil cooler, I find it highly unlikely it was that SIGNIFICANT of a factor...  Furthermore, a company has to consider class action suits, brand reliability, etc.  I don't have much information on the inner working of the Ducati leadership, but I find it hard to believe that Ducati would risk their brand to save what is honestly a small amount of money (may not seem small to the casual reader here, but $3,000,000 is not as much as one might think it is, and definitely not worth ruining a company name for).  Ducati is well aware of how information disseminates on these boards and in general, I highly doubt the company would risk having a reputation for overheating motorcycles...

Adding or removing any component, while driven by cost, is an engineering task.  The addition of an oil cooler also lends to COMPLEXITY, hence COST and RELIABILITY.  There is always a trade off involved.  I'd love to see what software the engineers use to model the engines, particularly in the area of thermodynamics...

One more note with Ducati, the brand has been around for some time, thus, I am inclined to believe that long term thinking can be ascribed to the company.  If I recall correctly, I recently read an article where American management was brought in an advisory capacity with the company (someone please correct me here if I am wrong), thus, their intent is brand reputation.  I'll trust their engineers on this one, although if I am riding in Rub' al Khali, maybe an oil cooler would be a welcome addition on my bike (although my Honda did fine, so maybe not)...

I cannot speak for the 695, but the 696 is not an overly stressed engine, having a relatively average compression ratio and power output.  Although advertised at 79.5hp @ 9,000 rpm (somewhere thereabouts), in practice, my bike RARELY comes close to 9,000 rpm (I'm not much of "hot dogger" with my bike).

Additionally, note the following: automotive/motorcycle engines typically spend 20% of their time near top rated output and 80% of their time "cruising", in other words using very little of what the engine is capable of producing, thus not producing as much heat...

My bike seems to fall into the same category as the 620 owned by Bikepilot's wife.  Since this board comprises a diverse array of Ducati owners in disparate locations, it would be interesting to see a poll regarding this...

What I found interesting in the information provided by the 695 owner is that the bike had an oil temp of nearly 300 degrees fahrenheit in 83 degree ambient air temperature with low stress riding.  In his situation, seems to me even a cooler would not likely solve his problem...

[duc_fan]

(Background: I am an aerospace systems engineer specializing in propulsion systems)

Monster 620 is less HP/L, so I would expect it to run cooler.

The more power you make, the more heat it's going to generate.  This is a result of those immutable laws of thermodynamics (darn them!).  Otto cycle automotive-type engines are typically around 35% thermodynamic efficiency... so every 3.5 HP you make at the crank results in ~6.5 HP (= 4850 W = 16500 BTU/hr) of waste heat that has to go somewhere.  Now compare the power difference between a 620 and a 695... 63 vs 73 HP... 10 HP mechanical difference... assuming 35% efficiency, we're talking about 18.8 HP (= 14000 W = 47835 BTU/hr) of additional waste energy...  that's a lotta extra heat!

The gages on everything before the 696 get their values from bulk oil temp, so a reading of 300*F is what's in the sump... that's not a healthy temperature.  Low to mid 200's are healthy bulk oil temps.  300 should be the reading on a hot day after working the motor hard.  I don't know where the "oil temp" reading is taken on the newer bikes.

If you're getting readings of 300 degrees with mild riding and the sensor has been replaced, it's time for an oil cooler.  The 695 should have come with one anyway, just because of the power density.  Cobble together the parts yourself if you need to save a buck or two, but get thineself an oil cooler.  Also, the extra oil capacity you're adding to the engine also helps, because you have more oil for the heat to distribute through.  This is one of the reasons bigger oil sumps are typically used on race engines.

Ducati, as most mfr's would have, made a bean-counter decision to leave the oil cooler off the 695... that wasn't a sound engineering decision.  Very few if any auto or moto companies actually let the engineers do everything they say is needed for something to work properly and safely for a long time.  Hell, even NASA ignores their engineers when management sees fit, and they've lost two shuttles because of it.  Anyway, the very slight additional complexity of an oil cooler is going to be more than offset by the increase in reliability and longevity.  Ducati's bean counters probably looked at the sales figures, then looked at how many miles MOST of their bikes see, how long most owners keep them, and determined that the drop in longevity would not be a significant problem.  As a somewhat extreme example, Ford decided it was cheaper to pay off a few wrongful death lawsuits than fix the suspension on the Explorer.  Do not overestimate the morality of the beancounter, nor underestimate the power of money.

As an aside... comparing cyl head temps on a Lycoming to a Corvair or a Ducati is like comparing apples and oranges.  We have no data on what materials are used, what the tolerances are on wear surfaces, etc.  Aircraft engines are built completely differently from car or bike engines, because they're designed to run at 100% power for takeoff and climbout, then cruise at anywhere from 60%-80% power for hours on end.  Street motorcycles and cars use 100% power for less than a minute at a time, and cruise at much less than 50% power.  Race vehicles use 100% power for a longer period of time, but race car or motorcycle engines don't go 2000+ hours between inspections and overhaul like aircraft engines do.  And in my engineering judgement, the Corvair is not the best example of acceptable anything.  Neat cars, but they weren't common enough nor reliable enough to be used as a solid example of allowable temps, tolerances, or materials.

[2-Skinny]

Although cost was possibly somewhat of a factor with the 695/695 in the decision to NOT implement an oil cooler, I find it highly unlikely it was that SIGNIFICANT of a factor...  Furthermore, a company has to consider class action suits, brand reliability, etc.  I don't have much information on the inner working of the Ducati leadership, but I find it hard to believe that Ducati would risk their brand to save what is honestly a small amount of money (may not seem small to the casual reader here, but $3,000,000 is not as much as one might think it is, and definitely not worth ruining a company name for).  Ducati is well aware of how information disseminates on these boards and in general, I highly doubt the company would risk having a reputation for overheating motorcycles......etc...

I disagree and as duc_fan said, it isn't always an engineering decision. 

The difference we are talking about is between oil cooler/ no oil cooler and centers around longevity and long term reliablity of the motorcycles in question.  These bikes WILL last,  but the oil cooler is difference between 5 years on the road and 10 years, or premature bearing/valve seal failure (after thousands of miles)- neither of these things is going to damage reputation or leave Ducati vulnerable to litigation. (And some may argue, but when I think "Ducati", I think of alot of things- the first of which isn't usually reliable...)

$3,000,000 IS alot of money, even for Ducati.   For a relatively small company who is only doing ~40k units a year, thats HUGE.  Think of all the areas you don't typically associate with costs savings that they have shed dollars (regulators/rectifiers, clutch components, bearings,etc)...  I remember reading about how bikes from the 70s and early 80s typically last "forever"- it was with regards to how companies rate the "uses" of individual components like switches in hundreds of thousands of uses.  In the mid eighties, companies realized that they could shave lots of money by incorporating components rated in the tens of thousands of uses... as an example.

[bikepilot]

Just curious, does hp/liter matter for a given % power production provided that actual power produced by both is equal to or less than the maximum power of the less powerful motor?  For example, lets say you ride a 695 and 620 down the freeway at 80mph, same rider etc.  The power required from both motors is the same, the fact that the 695 could make more peak power, I would think, doesn't result in any extra heat being produced as compared to the 620 untill its asked to make more hp/cc than the 620 is capable of. 

Also, IIRC about the same time they went from 620 to 695 they went from rear wheel to crank hp.  Diff might not be as big as we think, but I could also be totally off on that.

Anyway, max heat production at peak power might have less to do with the issue than heat production for a given level of fairly low power output.  Maybe the 695 with its short stroke, arguably higher state of tune and leaner mixture makes more heat for a given fairly low power output than a 620.

FWIW light aircraft engines are able to run fairly high CHTs in part because the rate of change in temp is very slow.  You don't chop the throttle on an airplane in normal use and most of the time you are not supposed to at all.  I know that our glider tow plane pilots were instructed to level off and gradually reduce power rather than cutting power and getting back down ASAP because doing so cracked the heads in short order (I would know, me and another guy changed one on a Saturday night).

[elgallo73]

For example, lets say you ride a 695 and 620 down the freeway at 80mph, same rider etc.  The power required from both motors is the same, the fact that the 695 could make more peak power, I would think, doesn't result in any extra heat being produced as compared to the 620 untill its asked to make more hp/cc than the 620 is capable of.  

EXACTLY!  A "real world" example that factors a dynamic system rather than a static comparison of maximum horsepower for each motor...  I am NOT an aerospace engineer specializing in propulsion systems, but I have worked around enough gas turbines and reciprocating engines to have some idea of what I am talking about, this is actually fairly simple stuff.

I also argue the 620 would have to work "harder" than the 695 to maintain the same velocity and thus would produce MORE heat at the same speed (in the form of engine friction as a consequence of a higher RPM, thus higher oil temperature).

If you check www.gearingcommander.com, you will note a nearly 600 rpm increase for the 620 to maintain a given speed over the 695 with stock gearing...

[2-Skinny]

EXACTLY!  A "real world" example that factors a dynamic system rather than a static comparison of maximum horsepower for each motor...  I am NOT an aerospace engineer specializing in propulsion systems, but I have worked around enough gas turbines and reciprocating engines to have some idea of what I am talking about, this is actually fairly simple stuff.

I also argue the 620 would have to work "harder" than the 695 to maintain the same velocity and thus would produce MORE heat at the same speed (in the form of engine friction as a consequence of a higher RPM, thus higher oil temperature).

If you check www.gearingcommander.com, you will note a nearly 600 rpm increase for the 620 to maintain a given speed over the 695 with stock gearing...

I'm not sure if you both are suggesting that a 620 motor would more likely need an oil cooler over a 695... 

[elgallo73]

More or less that is exactly what we are arguing, but interestingly enough, from various postings, to include the one made by Bikepilot regarding the fact that the 620 owned by his wife runs relatively cool (without a cooler), we would expect the 620 to run hotter given the same amount of work compared to the 695.

I am a newcomer to Ducati ownership, but it would seem the 695 was a sort of "test bed" for a higher output motor.  The issues may have been ironed out and thus we have the 696, for example, which in my opinion runs relatively well, even in hot temperatures, without an oil cooler (at least mine does, and during a heat wave in Texas, no less...)

The argument made by Bikepilot is simply that although an engine may be CAPABLE of producing a given amount of horsepower, it may NEVER see that amount.  For example, factory specs state that my 696 should put out around 79 hp@9000 rpm, in "real world" conditions, my bike has never seen this.  I'm sure some folks around here might push their bikes to the limit, but for an hour?  Having spent time in 26 countries, I have seen VERY FEW where you could get away with running a bike at 125 miles per hour, for an hour!  (nor 8,000 rpm in any other gear for an hour)  This makes some of the arguments regarding BTU dissipation moot, as those who ride their bikes in this manner may only do so for a VERY SHORT period of time.

When we consider the operation of our bikes, off the track, anyways, we have to take "slices" or "snapshots" of the machine during various stages of a trip.  This will involve stops, slow speed operation (around town or city streets), high speed operation (freeway), etc.  Once we SUM these slices we get an AVERAGE of what our bikes see during a given period of operation.

I believe Bikepilot may have hit it on the head with:

Anyway, max heat production at peak power might have less to do with the issue than heat production for a given level of fairly low power output.  Maybe the 695 with its short stroke, arguably higher state of tune and leaner mixture makes more heat for a given fairly low power output than a 620.

We have drawn this discussion way out, D3vi@nt, I hope any of this helps, but likely only has further confused you...

[elgallo73]

One more note, and this ties in engine size to other areas of study.  There is likely some marketing "ideal" with regards to horsepower for a motorcycle engine.  In other words, the limiting factor for engine power and consequently speed being the infrastructure (read: roads) and the human body.  Get too small an engine, and it has to work too hard to keep up with other traffic.  Too large an engine, and you have your "speed racer" who did not realize that a liter bike can kill you very fast...

When I was much younger (and not that long ago, but long enough for most folks on these boards), 500cc was considered a "big bike".  I started riding when the switch from air cooling to water cooling was in it's infancy and the power output now is incredible compared to those years.  My 696 is the largest bike I have owned and this is considered A STARTER BIKE!

Go overseas and observe that many cars have displacements smaller than this (or did for the period I was there)!

[2-Skinny]

One more note, and this ties in engine size to other areas of study.  There is likely some marketing "ideal" with regards to horsepower for a motorcycle engine.  In other words, the limiting factor for engine power and consequently speed being the infrastructure (read: roads) and the human body.  Get too small an engine, and it has to work too hard to keep up with other traffic.  Too large an engine, and you have your "speed racer" who did not realize that a liter bike can kill you very fast...

When I was much younger (and not that long ago, but long enough for most folks on these boards), 500cc was considered a "big bike".  I started riding when the switch from air cooling to water cooling was in it's infancy and the power output now is incredible compared to those years.  My 696 is the largest bike I have owned and this is considered A STARTER BIKE!

Go overseas and observe that many cars have displacements smaller than this (or did for the period I was there)!

...And since this thread has now been hijacked...

I think this was more an issue related to value added taxes associated with larger displacement vehicles (in countries such as Japan) as they are a "luxury" as opposed to a relationship to efficiency.  The US had a similar import tax in the 80s related to displacement.


Also, regarding your post before this-

  The irony regarding an oil cooler (or even radiator for that matter) is that when a bike is more likely to be working harder is at acceleration/ initial cruising or racing through the twisties and going through the gears- this though is the time that the bike receives the most convection cooling across the engine. 

  Conversly, while at idle (the most likely time for the engine to heat up- stoplight, etc.) is when there is the least amount of convective cooling and also lower oil pressure means that there isn't really much oil if any moving through the cooler anyways...

[elgallo73]

I assume "hijacking" implies moving the thread in a different direction than originally intended and for that I apologize, once my mind starts moving it is sometimes difficult to "rein it back in"...  Enjoyed the discussion, learned a few things...

[2-Skinny]

Enjoyed the discussion, learned a few things...

Agreed. 

[elgallo73]

Conversly, while at idle (the most likely time for the engine to heat up- stoplight, etc.) is when there is the least amount of convective cooling and also lower oil pressure means that there isn't really much oil if any moving through the cooler anyways...

I had not even thought about that...

[ChrisH]

This is an interesting discussion. All I can contribute is that an oil cooler  is on my must buy in 2011 list. My 696 gets upwards of 6-7 bars during the summer depending on how long and what type riding i have done. I don't really like to see such high temps. This 100* heat is a killer.