I just got finished riding back to work over my lunch break, and there was very heavy traffic due to an accident. I was in stop and go traffic for ~45 minutes, and luckily my bike did not encounter any problems during this time, but it got me thinking about problems this could cause in theory. So, I have a few questions I'd like to pose to the more knowledgeable members around here:
1. Since these bikes are air-cooled, would being in stop and go traffic for an extended period eventually cause an overheat? If so, how long would it normally take for this to be an issue?
1a. Since the air temperature outside is almost always going to be cooler than the engine, there is always some amount of cooling going on. Slightly more so for F models with the oil cooler, like my bike. Is this amount of temperature differential enough to keep the bike from overheating? If the bike is stopped entirely, it would eventually heat up the air surrounding the engine to a temperature at which it would no longer be effectively cooling, wouldn't it (assuming there is little/no wind)? With that in mind how much effect would wind or moving the bike side to side have? I guess wind effect would probably entirely depend on how strong the wind is, but the question remains.
2. How long can the battery be sustained by the charging system at low RPMs? I know from first-hand experience that the charging system alone is not enough to keep the battery from draining at least a little bit during idle. So, how long would you have to be in stop and go traffic for it to really start to cause an issue?
1. I may be pulling this out of my ass but I think on hotter days there is some risk of overheating, I know that mid summer in stop go my engine will read a good 20-30Deg Celcius higher than at highway speeds (according to my vapor gauge which reads off a crush washer sensor deal on the spark plug, hard to say how accurate it is.
1a. any air heated by the engine will rise and cooler air will replace it so you'll never have a situation where it isnt cooling but the engine is always producing heat as well. With that in mind you'll essentially reach an equilibrium point where the engine temp is constant because as the temperature difference increases, engine gets hotter, the rate of cooling will increase.
This is a basic physics principle where the rate of cooling, lets call it r, is determined by r = C(DeltaT) where C is some number representing the effective cooling rate between your material, in this case your engine and the air, and DeltaT is the difference between the material temp.
Whether or not that equilibrium point is below the overheating point for the engine will be dependant on how hot it is outside, because of that DeltaT term, and how efficiently the engine sheds heat.
2. Curious about this myself
Quote from: lefty1615 on January 25, 2017, 11:17:50 AM
1. I may be pulling this out of my ass but I think on hotter days there is some risk of overheating, I know that mid summer in stop go my engine will read a good 20-30Deg Celcius higher than at highway speeds (according to my vapor gauge which reads off a crush washer sensor deal on the spark plug, hard to say how accurate it is.
1a. any air heated by the engine will rise and cooler air will replace it so you'll never have a situation where it isnt cooling but the engine is always producing heat as well. With that in mind you'll essentially reach an equilibrium point where the engine temp is constant because as the temperature difference increases, engine gets hotter, the rate of cooling will increase.
This is a basic physics principle where the rate of cooling, lets call it r, is determined by r = C(DeltaT) where C is some number representing the effective cooling rate between your material, in this case your engine and the air, and DeltaT is the difference between the material temp.
Whether or not that equilibrium point is below the overheating point for the engine will be dependant on how hot it is outside, because of that DeltaT term, and how efficiently the engine sheds heat.
2. Curious about this myself
First of all, great post! Secondly, I guess what I really mean to ask then is: how long would it take to reach the point at which R=0 (if i understand your equation correctly), given no other factors (wind, moving the bike, etc.)? I guess that would depend on the outside temperature... Maybe someone else on here has at least a good rule of thumb in lieu of actual numbers lol.
Also: What engine temperature is considered "overheating"? And is the engine temperature at R=0 greater than that temperature?
People have overheated the GS and even seized up. Now was it low on oil was it in stop and go was it due to some earlier problems - no idea.
Cool.
Buddha.
I'm willing to bet your legs would be getting pretty damn hot as well if it was getting to the point of overheating enough to be damaged.
If you are starting to get uncomfortable, it's a good bet so is the bike.
You probably have increased risk with a faired GS opposed to a naked one, since there's no "static" airflow, but unless you are in 100°F heat I don't think the risk is that great.
Regarding the battery it doesn't take much to boost the charging system in terms of RPM.
Unless you are just letting the bike be pulled along at idle the small revs you'd give the bike every time you go should compensate for the drain when you stop.
I'd assume, at least...
I commuted by GS every day for almost a whole year, from stop and go to smooth, from rain and cold to the dead heat of summer.
Never drained a battery and never overheated.
QuoteFirst of all, great post! Secondly, I guess what I really mean to ask then is: how long would it take to reach the point at which R=0 (if i understand your equation correctly), given no other factors (wind, moving the bike, etc.)? I guess that would depend on the outside temperature...
Thanks! I was actually sitting through a (quite slow) heat transfer lecture so I got inspired to get a bit technical.
To answer the following up question, no R never equals zero, keep in mind that the outside temperature is constant so DeltaT is always positive for an engine and, we can assume, always greater than zero when the engine running. Similarly C is always a positive number so multiplying the two we will never get zero or less than zero.
So what's happening is that the combustion process produces heat which dissapates into the engine block, call this R1. Then the heat transfers from the engine block into the surrounding air in the cooling process, call this R2. So what happens at equilibrium is R1 = R2 and the overall temperature of the engine block will remain steady.
As to the overarching issue of overheating the bike personally I lean to the assumption that if your bike is properly maintained and your not in some crazy desert heat it won't overheat. I imagine Buddha's point of low oil or some such is likely the culprit. I would like to think the engineers at Suzuki at least considered the possibility that you might have to idle.
That being said if I know I'm at an extremely long light, like 2 minutes, I generally will just shut the bike off to save gas. If your in level ground and traffic is mad slow you can probably keep up just shuffling anyways right?
Quote from: Watcher on January 25, 2017, 01:28:03 PM
...
You probably have increased risk with a faired GS opposed to a naked one, since there's no "static" airflow, but unless you are in 100°F heat I don't think the risk is that great.
...
I wonder if the oil cooler was added to the F model specifically because of the decrease in airflow due to the fairings.
Quote from: lefty1615 on January 25, 2017, 01:47:50 PM
Thanks! I was actually sitting through a (quite slow) heat transfer lecture so I got inspired to get a bit technical.
To answer the following up question, no R never equals zero, keep in mind that the outside temperature is constant so DeltaT is always positive for an engine and, we can assume, always greater than zero when the engine running. Similarly C is always a positive number so multiplying the two we will never get zero or less than zero.
So what's happening is that the combustion process produces heat which dissapates into the engine block, call this R1. Then the heat transfers from the engine block into the surrounding air in the cooling process, call this R2. So what happens at equilibrium is R1 = R2 and the overall temperature of the engine block will remain steady.
As to the overarching issue of overheating the bike personally I lean to the assumption that if your bike is properly maintained and your not in some crazy desert heat it won't overheat. I imagine Buddha's point of low oil or some such is likely the culprit. I would like to think the engineers at Suzuki at least considered the possibility that you might have to idle.
That being said if I know I'm at an extremely long light, like 2 minutes, I generally will just shut the bike off to save gas. If your in level ground and traffic is mad slow you can probably keep up just shuffling anyways right?
Ahh okay, I get what you're saying. So then, would the amount of time it takes for the bike (at idle) to reach the point where R
1=R
2 be affected by the outside air temperature? I feel like it would have to... If its 20 degrees out, it would have to take much longer for the bike to reach that point than if it were 100 degrees out, right?
As for the actual issue of overheating, you and Watcher are probably right that the risk is minimal. And I just checked my oil today and the level is right where it should be, and the oil was put in there semi-recently, so theoretically I shouldn't have a problem with cooling under normal conditions. Like I said, I didn't actually have any overheating or battery problems, I just started to wonder about these things while I was in traffic.
Synthetic oil will still be oil at temps that dyno juice would fail at, couldn't hurt if your worried about stop and go? :dunno_black:
QuoteAhh okay, I get what you're saying. So then, would the amount of time it takes for the bike (at idle) to reach the point where R1=R2 be affected by the outside air temperature? I feel like it would have to... If its 20 degrees out, it would have to take much longer for the bike to reach that point than if it were 100 degrees out, right?
Exactly, and the temp at which R1 = R2 will be higher. So if your bike just overheats at say 35deg celcius it likely won't ever overheat at 20deg celcius.
Quote from: Suzuki Stevo on January 25, 2017, 02:25:41 PM
Synthetic oil will still be oil at temps that dyno juice would fail at, couldn't hurt if your worried about stop and go? :dunno_black:
I'd be curious to know of synthetic oil has better heat transfer properties or vice versa, I'm sure it could have a pretty big impact on the situation
Quote from: lefty1615 on January 25, 2017, 04:06:25 PM
I'd be curious to know of synthetic oil has better heat transfer properties or vice versa, I'm sure it could have a pretty big impact on the situation
For heat transfer I am
assuming it would be worse, because it retains it's viscosity (stays thick)
Granted we are talking about an air cooled engine...but in the water cooled world, straight Ethylene Glycol or even a 50/50 mix transfers heat far WORSE than just straight water.
Heat transfer in a stop & go situation would not be my concern, my oil retaining enough viscosity to keep metal to metal contact from happening would though :icon_idea:
Quote from: Suzuki Stevo on January 25, 2017, 08:49:00 PM
Quote from: lefty1615 on January 25, 2017, 04:06:25 PM
I'd be curious to know of synthetic oil has better heat transfer properties or vice versa, I'm sure it could have a pretty big impact on the situation
For heat transfer I am assuming it would be worse, because it retains it's viscosity (stays thick)
I think it would be BETTER. Synthetic molecules are less likely to break down under high heat so it retains optimal fluidity.
Quote from: Watcher on January 25, 2017, 09:18:45 PM
I think it would be BETTER. Synthetic molecules are less likely to break down under high heat so it retains optimal fluidity.
Yes it retains it's
fluidity when cold...it also retains it's viscosity (stays thick) when hot.
Quote from: Suzuki Stevo on January 25, 2017, 08:49:00 PM
...
Granted we are talking about an air cooled engine...but in the water cooled world, straight Ethylene Glycol or even a 50/50 mix transfers heat far WORSE than just straight water.
...
Isn't that because ethylene glycol is added not to aid in cooling, but to prevent freezing? Correct me if I'm wrong here.
Quote from: qcbaker on January 26, 2017, 11:17:49 AM
Isn't that because ethylene glycol is added not to aid in cooling, but to prevent freezing? Correct me if I'm wrong here.
Correct, but if you want to overheat anything water cooled use pure antifreeze, straight water (viscosity 0.890 cP) transfers heat in a cooling system better than (thicker) pure antifreeze. So on that premise in an air cooled engine if you used 90W gear oil instead of say 30W motor oil, the thicker more viscous gear oil would not transfer heat as good as the thinner less viscous motor oil. Yes I'm pulling all of this straight out of my ass but do you see the connection with heat transfer? Because that's what we where talking about.
Quote from: Suzuki Stevo on January 26, 2017, 12:13:36 PM... air cooled engine if you used 90W gear oil instead of say 30W motor oil, the thicker more viscous gear oil would not transfer heat as good as the thinner less viscous motor oil.
Then why is it common practice to use a thicker oil in higher heat applications?
Even the chart in the GS500 manual reflects this, it shows temp ranges based on viscosities and the trend is thicker for higher temperature.
My Buell calls for 20W50 full synthetic, manual specification, and it's an air-cooled monster of a bike. If thicker oil wasn't as good at heat transfer I'd think they wouldn't be recommending me one of the thickest viscosities of motor oil available.
I'm kind of spit-balling too, though. I'm far from an expert in this stuff.
But I can see how since a thinner oil can circulate easier it is going to travel through the oil coolers and such faster. At the same time it may not be able to pick up as much heat to bring to the cooler.
But that's less to do with the actual heat transfer rate and more to do with the circulation rate.
A thicker oil may have more capacity to absorb heat and once it's in the cooler it may be able to expel just as well as a thinner oil, especially considering if it's exposed to the cooler longer due to a slower overall flow rate.
Honestly in practice the difference might be marginal.
Like, imagine one small high velocity fan vs one large low velocity fan. The low velocity fan may move just as much CFM as the small one, and can regulate a larger area, while the smaller one may handle a local area better but over time cannot maintain the temperature of the whole area.
So they have the same transfer rates, but which one handles heat better?
Relating to my computer, if I didn't have large fans circulating the air in the case the small fans on the chipsets would eventually succumb to a higher overall internal temperature. They can pull heat away quickly but they can't expell it so efficiently.
At the same time if I took out the small fans on the chipsets the large fans in the case wouldn't be able to effectively keep certain chips cool enough... So you run both, small fans on the chip and large fans on the case.
You can't run two weights of oil in an engine to handle separate jobs, so you compromise. Thin enough oil to move quickly through the system, while thick enough to handle the heat.
Quote from: Suzuki Stevo on January 26, 2017, 12:13:36 PM
Correct, but if you want to overheat anything water cooled use pure antifreeze, straight water (viscosity 0.890 cP) transfers heat in a cooling system better than (thicker) pure antifreeze. So on that premise in an air cooled engine if you used 90W gear oil instead of say 30W motor oil, the thicker more viscous gear oil would not transfer heat as good as the thinner less viscous motor oil. Yes I'm pulling all of this straight out of my ass but do you see the connection with heat transfer? Because that's what we where talking about.
I get what you're saying, but I'm not sure the viscosity of a liquid is directly linked to its heat transfer ability. Antifreeze just happens to be more viscous than water, I'm not sure that particular property of it has any real impact on its ability to transfer heat. As Watcher pointed out, it is common practice to use heavier grade oils in higher-heat applications.
I believe the property of any given material directly related to its efficiency as a cooling liquid would be specific heat capacity. If I'm wrong, lefty can probably correct me. He seems to know quite a bit about physics lol.
Yeah...that was my angle :thumb:
QuoteI get what you're saying, but I'm not sure the viscosity of a liquid is directly linked to its heat transfer ability. Antifreeze just happens to be more viscous than water, I'm not sure that particular property of it has any real impact on its ability to transfer heat. As Watcher pointed out, it is common practice to use heavier grade oils in higher-heat applications.
I believe the property of any given material directly related to its efficiency as a cooling liquid would be specific heat capacity. If I'm wrong, lefty can probably correct me. He seems to know quite a bit about physics lol.
Quick Disclosure, I had to look around a little before I wrote anything, too many terms floating around when you deal with academics haha.
Your basically on the ball here. Specific heat capacity isn't generally used to do these kinds of calculations as it is related to mass but they are related and I believe, one can be found or at least closely estimated with the other.
Quote from: Watcher on January 26, 2017, 01:06:41 PM
Quote from: Suzuki Stevo on January 26, 2017, 12:13:36 PM... air cooled engine if you used 90W gear oil instead of say 30W motor oil, the thicker more viscous gear oil would not transfer heat as good as the thinner less viscous motor oil.
Then why is it common practice to use a thicker oil in higher heat applications?
Even the chart in the GS500 manual reflects this, it shows temp ranges based on viscosities and the trend is thicker for higher temperature.
Oil's job is not cooling, it's lubrication. At lower temperatures it flows less easily making it harder on the oil pump and also less likely for it to find its way into small spaces where it needs to be in order to lubricate properly... mostly at cold startup. Once the engine is hot, the higher viscosity oil is better as long as it is thin enough when it is a film to fit between things that must be lubricated, like the rings-cylinder, cam journals, rod bearing, etc.
And BTW 90W gear oil is the equivalent of 40W SAE motor oil. Gear oil viscosity is on a different scale than motor oil.
Now, regarding how well water cools engines vs. ethylene glycol, it's mostly about the thermal resistance, or the reciprocal function thermal conductivity. Here's a handy chart:
http://www.engineeringtoolbox.com/thermal-conductivity-liquids-d_1260.html
Notice water is over 2x as conductive as ethylene glycol. There are other factors as well, such as how much surface area of the engine's cooling surfaces is in contact with the coolant. This is where the viscosity of water gives it a slight additional edge, since it flows into smaller spaces more rapidly than anti-freeze but this is a marginal difference. If you really want to improve cooling then you can add a surfactant such as Redline Water Wetter to distilled water in the coolant that will break the surface tension of the water and allow it to "coat" the cooling surfaces better... water's surface tension will ordinarily cause it to sort of "float" on top of irregular surfaces, for example it won't just flow all the way into micro grooves in a machined surface etc., but WW will allow it to flow more readily and increase surface area by some margin so you get better heat transfer into the coolant and also better heat transfer from the coolant to the radiator. It's all on the margins but if you have an engine that either has a high penalty for overheating (like my Miata's engine) or that has a marginal cooling system (water-cooled VWs) then every bit matters.
BTW, ethylene glycol not only lowers the freezing temperature of engine coolant compared to straight water but it also increases the boiling temperature, so it's a catch-22. Once the water boils in a H2O engine, it will no longer cool successfully and you are going to overheat in no time. Straight water may cool better in ordinary use, but it is more likely to boil, which is bad. Water Wetter increases the boiling point very slightly. There are also other chemical concerns with different formulations of anti-freeze (OAT, HOAT, P-HOAT, etc.) wherein some are more or less compatible with certain cooling system hard parts and some are not compatible with others so you can't mix and match. There's a bit of an art to water-cooled engine cooling... drive a high-revving sports car in rush hour traffic in Austin TX for a couple of decades and you'll be forced to figure it out like I was.
It's all irrelevant for an air-cooled engine. The king of air cooling is surface area of the heat sink, in this case the entire surface of the engine that is exposed to the air, including the crankcase and covers and sprocket and chain and everything else, to an extent, that is mechanically coupled to the engine. A lot of the friction in the engine is in the piston-to-cylinder interface, and the heat from combustion is present directly in the cylinder, which is why it makes the most sense to form the cylinder into a giant heat sink, making it out of aluminum with fins cast into it so you maximize surface area sufficient to cool the engine in most cases. It's the heat transfer between the cylinder fins and the air around it that cools the engine, and aluminum-to-air has a better thermal conductivity than steel (or iron) to air, which is why most air cooled motorcycle cylinders are made of aluminum alloy. There's a huge tradeoff in durability, emissions, fuel economy, oil consumption, etc., but it's worth it for the cooling improvement.
The difference in temperature between the air and the cylinder fins basically defines the rate at which you can cool the engine, so sitting in traffic in hot weather is bad since the air directly in contact with the cylinder fins becomes hot quickly and is not displaced by new cool(er) air as quickly as it is when you are moving. If you really want to avoid overheating in stop and start traffic it's simple. Reduce the cause of heat to begin with by using the best engine oil you can to reduce friction, keep the level high enough so you don't starve the piston rings for oil, don't let the idle mixture be lean since lean running is higher combustion temperature, and keep the idle speed low as possible. Don't "blip" the throttle while sitting like all the kids like to do with their 4-cylinder water-cooled motorcycles.
A small fan of some kind wouldn't hurt even for an air-cooled engine. VW and Porsche used a big crankshaft-driven fan to ensure air is always moving if the engine is running. But it'd look funny on a GS500.
Quote from: mr72 on January 27, 2017, 06:07:01 AM
Oil's job is not cooling, it's lubrication. At lower temperatures it flows less easily making it harder on the oil pump and also less likely for it to find its way into small spaces where it needs to be in order to lubricate properly... mostly at cold startup. Once the engine is hot, the higher viscosity oil is better as long as it is thin enough when it is a film to fit between things that must be lubricated, like the rings-cylinder, cam journals, rod bearing, etc.
And BTW 90W gear oil is the equivalent of 40W SAE motor oil. Gear oil viscosity is on a different scale than motor oil.
While that is true, oil in air cooled motorcycles (especially ones with oil coolers, like the GS500F) does play a part in removing heat from the engine as it circulates.
Quote
Now, regarding how well water cools engines vs. ethylene glycol, it's mostly about the thermal resistance, or the reciprocal function thermal conductivity. Here's a handy chart:
http://www.engineeringtoolbox.com/thermal-conductivity-liquids-d_1260.html
Notice water is over 2x as conductive as ethylene glycol. There are other factors as well, such as how much surface area of the engine's cooling surfaces is in contact with the coolant. This is where the viscosity of water gives it a slight additional edge, since it flows into smaller spaces more rapidly than anti-freeze but this is a marginal difference. If you really want to improve cooling then you can add a surfactant such as Redline Water Wetter to distilled water in the coolant that will break the surface tension of the water and allow it to "coat" the cooling surfaces better... water's surface tension will ordinarily cause it to sort of "float" on top of irregular surfaces, for example it won't just flow all the way into micro grooves in a machined surface etc., but WW will allow it to flow more readily and increase surface area by some margin so you get better heat transfer into the coolant and also better heat transfer from the coolant to the radiator. It's all on the margins but if you have an engine that either has a high penalty for overheating (like my Miata's engine) or that has a marginal cooling system (water-cooled VWs) then every bit matters.
BTW, ethylene glycol not only lowers the freezing temperature of engine coolant compared to straight water but it also increases the boiling temperature, so it's a catch-22. Once the water boils in a H2O engine, it will no longer cool successfully and you are going to overheat in no time. Straight water may cool better in ordinary use, but it is more likely to boil, which is bad. Water Wetter increases the boiling point very slightly. There are also other chemical concerns with different formulations of anti-freeze (OAT, HOAT, P-HOAT, etc.) wherein some are more or less compatible with certain cooling system hard parts and some are not compatible with others so you can't mix and match. There's a bit of an art to water-cooled engine cooling... drive a high-revving sports car in rush hour traffic in Austin TX for a couple of decades and you'll be forced to figure it out like I was.
It's all irrelevant for an air-cooled engine. The king of air cooling is surface area of the heat sink, in this case the entire surface of the engine that is exposed to the air, including the crankcase and covers and sprocket and chain and everything else, to an extent, that is mechanically coupled to the engine. A lot of the friction in the engine is in the piston-to-cylinder interface, and the heat from combustion is present directly in the cylinder, which is why it makes the most sense to form the cylinder into a giant heat sink, making it out of aluminum with fins cast into it so you maximize surface area sufficient to cool the engine in most cases. It's the heat transfer between the cylinder fins and the air around it that cools the engine, and aluminum-to-air has a better thermal conductivity than steel (or iron) to air, which is why most air cooled motorcycle cylinders are made of aluminum alloy. There's a huge tradeoff in durability, emissions, fuel economy, oil consumption, etc., but it's worth it for the cooling improvement.
The difference in temperature between the air and the cylinder fins basically defines the rate at which you can cool the engine, so sitting in traffic in hot weather is bad since the air directly in contact with the cylinder fins becomes hot quickly and is not displaced by new cool(er) air as quickly as it is when you are moving. If you really want to avoid overheating in stop and start traffic it's simple. Reduce the cause of heat to begin with by using the best engine oil you can to reduce friction, keep the level high enough so you don't starve the piston rings for oil, don't let the idle mixture be lean since lean running is higher combustion temperature, and keep the idle speed low as possible. Don't "blip" the throttle while sitting like all the kids like to do with their 4-cylinder water-cooled motorcycles.
A small fan of some kind wouldn't hurt even for an air-cooled engine. VW and Porsche used a big crankshaft-driven fan to ensure air is always moving if the engine is running. But it'd look funny on a GS500.
Now THIS is podracing... Great info!
As said above...good oil at the right level and don't blip the throttle, as a rider that's really all you can do in stop and go traffic to keep the heat down.
My opinion of the importance of oil viscosity to the cooling of air cooled engines copied from old post of mine:
Use 10w-40 or 15w-40 unless you have a high oil consumption problem and really need the 20w-50. I put 15W-50 Mobil 1 synthetic in my 97 GS for about 45k miles after breaking it in on 10W-40 dino for 5k miles and when oil consumption increased I switched to the cheaper 15W-40 Rotella T for the next 30k miles. I used the 15W-40 Rotella T in my 02 GS for all it's 100k miles. Engine wear due to miles seems to have progressed about the same on both bikes regardless of oil type.
My 97 GS progressed from regular to mid grade to premium gasoline to prevent gas knock in hot weather as the miles and carbon built up same as the 4 Hondas I used 20W-50 in summers did previous to the GSs.
When I switched from the 15W-50 to the 15W-40 in the 97 I went back to regular gas year round without gas knock and have used regular gas all my 100k miles on the 02 also w/o knock.
The GSs run cooler on a xxW-40 oil than on a xxW-50 oil and your doing it no favor using the heavier oil in hot weather unless oil consumption is real bad. Besides lubricating the engine the oil also provides cooling by carrying heat away from the head to the sump. This cooling flow is reduced with the heavier oils.
@mr72 :cheers:
In the case of an oil cooler you can say oil plays a larger role in temperature management. But I agree that the actual fins provide a larger role in maintaining operating temp.
Food for thought, my Buell is air cooled but has several devices to aid it.
Oil cooler. It's actually pointed indirect to air flow but with a scoop, presumably to avoid damage from rocks and such.
Either side has a scoop that directs air at the rear cylinder.
Under the seat and pointing straight at the rear cylinder head is an electric fan.
(http://imagizer.imageshack.us/v2/800x600q90/922/lznSWf.jpg) (https://imageshack.com/i/pmlznSWfj)
(http://imagizer.imageshack.us/v2/800x600q90/924/MOAPyW.jpg) (https://imageshack.com/i/poMOAPyWj)
(http://imagizer.imageshack.us/v2/800x600q90/924/8BTpy9.jpg) (https://imageshack.com/i/po8BTpy9j)
The rear cylinder needs all the help it can get, since it's half stuffed between a frame.
No kidding about the electric fan on the rear cylinder in a V like that.
I would think you could whip up a fan in some of the area taken up by the factory air box if you switched a GS to pods or lunchbox, possibly a fan and a duct to get the air where you want it. I don't think it's necessary but it wouldn't hurt especially if it were controlled by a temperature switch like in a car, so it would only come on for example when you are stopped in traffic and the temp rises a certain amount. I'd think switching it based on oil temperature would be a good idea, or just use some kind of thermal sensor affixed to the cylinder somehow.
Quote from: mr72 on January 27, 2017, 01:03:49 PM
... it wouldn't hurt especially if it were controlled by a temperature switch like in a car, so it would only come on for example when you are stopped in traffic and the temp rises a certain amount. I'd think switching it based on oil temperature would be a good idea, or just use some kind of thermal sensor affixed to the cylinder somehow.
That's more or less how this one works.
It's noisy since it's a relatively high velocity fan, so I can hear when it switches on. Usually comes on in traffic and may actually turn off at a steady 50mph or so, depending on air temp. I can't hear it at those speeds and engine RPMs but sometimes after a stretch I'll come to a stop and I won't hear it.
It also stays on for a minute or two after the ignition is switched off.
Sort of a double edged sword, though. It's designed to draw air away from the cylinder and ends up dumping it under the seat.
In the winter it means you don't completely freeze your nuts off. In the summer... Well, you can imagine.
Quote from: Watcher on January 27, 2017, 01:28:19 PM
That's more or less how this one works.
It's noisy since it's a relatively high velocity fan, so I can hear when it switches on. Usually comes on in traffic and may actually turn off at a steady 50mph or so, depending on air temp. I can't hear it at those speeds and engine RPMs but sometimes after a stretch I'll come to a stop and I won't hear it.
It also stays on for a minute or two after the ignition is switched off.
Sort of a double edged sword, though. It's designed to draw air away from the cylinder and ends up dumping it under the seat.
In the winter it means you don't completely freeze your nuts off. In the summer... Well, you can imagine.
You're in AZ currently, right? I'd imagine having your bike dump a lot of heat onto your legs all the time in the desert heat could get pretty swampy pretty quickly. Is it a big problem for you?
It's so dry here that you tend to avoid the "swamp" you would assume it causes.
That being said, the rear header wrapped around the right side causes more of a problem than the fan under the seat.
Even with that little heat shield it cooks the inside of your leg if you're at relatively low speeds. I would have to push my knee out to catch some wind every now and then.
And the fan under the seat honestly isn't so bad. Especially with the Corbin seat. It has a further back seating area so you aren't so close to the spot in the subframe where it dumps out (right at your crotch). It's also a much more rigid (thicker) basepan and a denser packing which would lead me to assume it takes longer for the heat to actually make it all the way through to my delicate region.
Also, you can see the spot in the subframe where the hot air exits. It's by the rear brake fluid reservoir on the right side, and it's next to where my straps are hanging on the left. So it's not like the air just stagnates under the seat, it does flow out.
I suppose I could always add some heat resistant material under the seat if it gets too uncomfortable. I got the Corbin towards the beginning of autumn so I didn't have much time in the 100s to really give it a good test.
Quote from: qcbaker on January 25, 2017, 10:59:16 AM
If the bike is stopped entirely, it would eventually heat up the air surrounding the engine to a temperature at which it would no longer be effectively cooling, wouldn't it (assuming there is little/no wind)? With that in mind how much effect would wind or moving the bike side to side have? I guess wind effect would probably entirely depend on how strong the wind is, but the question remains.
Don't forget about convection. Even though your bike is stationary the air around the cylinder head is not - hot air rises!
Quote from: Watcher on January 27, 2017, 01:28:19 PM
That's more or less how this one works.
It's noisy since it's a relatively high velocity fan, so I can hear when it switches on. Usually comes on in traffic and may actually turn off at a steady 50mph or so, depending on air temp. I can't hear it at those speeds and engine RPMs but sometimes after a stretch I'll come to a stop and I won't hear it.
It also stays on for a minute or two after the ignition is switched off.
Sort of a double edged sword, though. It's designed to draw air away from the cylinder and ends up dumping it under the seat.
In the winter it means you don't completely freeze your nuts off. In the summer... Well, you can imagine.
I assume it would not be too hard to buy a small fan designed for this (off a small car) at the wrecker, and install it either with a manual switch, or a temperature controlled one. I think one could even place it in front of the cylinders, it would not matter much at speed, but would be helpful once stopped when it's hot-hot-hot.
Quote from: Atesz792 on January 31, 2017, 09:18:43 AM
I assume it would not be too hard to buy a small fan designed for this (off a small car) at the wrecker, and install it either with a manual switch, or a temperature controlled one. I think one could even place it in front of the cylinders, it would not matter much at speed, but would be helpful once stopped when it's hot-hot-hot.
You can buy universal cooling fans for cars inexpensively, but most are going to be too big to fit in any of the spaces in a GS.
Plus, there is the problem is air pressure. Normally to make the fan work you would have to have essentially a shroud of some sort over the cylinders so that the fan will force air to be drawn across the fins rather than just picking up ambient air. This is not trivial to do, and would likely affect cooling to the degree that it would be necessary to run the fan all the time, and use a pretty big fan. The only reasonable place to put it is where the air intake is on the GS in place of the airbox, but then you have to find a way to get air in from somewhere besides the low-pressure zone created by the fan. There's just not much room to work with there. The engine was never really designed for this. If you make a "pusher" fan without any (or much) shrouding then you waste a lot of energy running the fan since the air is not being directed only over the fins so it would be terribly inefficient. And noisy, and bulky, and you are still stuck with the problem of where to put it.
I think on a GS500F there might be a really creative way to get forced air onto the head without first pulling it over the headers, but you'd have to fab up something quite ugly and bulk to put a "pusher" fan at the front of the bike pushing air over the head towards the rear. A duct and an air intake shroud up to the sides of the head tube/fork interface. Or just get a little bit of help from a small but powerful computer power-supply style fan mounted where the oil cooler mounts in front of the head and hope for the best. You might get a small amount of improvement... better than nothing I suppose. It would not be too weatherproof.
Anyway, in theory anything could be done but I doubt it's worth it. Of course I haven't ridden a GS500 in the TX summer yet, so maybe I'll be convinced it's a worthwhile effort by the end of August.
There's also the fact that an open air fan, mounted up front, will turn from the air pressure from simply moving.
Fans that work backwards are generators, and this isn't particularly good for the fan or anything else connected to it.
Fans behind radiators are fine because there's not enough air pressure diffused through the radiator to turn the fan.
It's fine on my Buell because where it's tucked away there's almost no air flow without running the fan.
There's a reason you don't see them just hanging out up front suspended from the frame.
Yeah you'd ideally have it on a clutch so the blades could turn without turning the motor. Also you'd ideally have it draw air from a directed source so it isn't in the wind, but any air pressure difference will make it turn.
So nevermind, I can't imagine a good way to put a fan on a GS500. And the truth is, being simple and air-cooled is a big part of the charm.
In fact if I buy another bike, it'll most likely be a fully air-cooled twin like a Ducati Scrambler for this very reason. Fewer things is fewer things to go wrong.