| Author | Message | ||
     Hybridmomentspass |
AKbuell - if that were true then ALL the bikes would be switching to watercooled heads, this is not so, only a few bikes on their touring line. Leaves a lot of models left without them. Im sure it helps with emissions, but its not a forced thing or ALL the bikes would have them. | ||
| Hootowl |
"as air cooled engines warm up more slowly" Exactly the opposite is true. | ||
| Azxb9r |
Exactly the opposite is true. It takes an air cooled engine much longer to come up to full operating temp than it does a water cooled engine. Air cooled engines also cool more quickly when shut off, which means additional warm up cycles for short trips. Controlling engine operating temp is much easier with water cooled engines. | ||
| Hootowl |
"Controlling engine operating temp is much easier with water cooled engines." That is true, but not germane to the question of whether an air cooled engine comes up to temp quicker. FULL operating temperature isn't necessary to achieve combustion efficiency. An air cooled motor, without all that water to heat up, comes up to the temperature necessary to support efficient combustion quicker than a water cooled engine. | ||
| Sifo |
An air cooled motor, without all that water to heat up, comes up to the temperature necessary to support efficient combustion quicker than a water cooled engine. You don't have to heat the water up. The thermostat controls the cooling to accomplish that. An air cooled motor typically has 100% cooling going on right at start up. If it's cool outside it will never get up to full temp. Even if it's hot out, it will warm up slower than a thermostatically controlled engine that can shut off the cooling until it's up to temp. | ||
| Azxb9r |
Sifo  | ||
| Hootowl |
"You don't have to heat the water up. " Think about what you just said. The only water you don't have to heat up is what's in the radiator. The water in the block and in the head is still there, and requires a significant amount of heat input to warm up. Water can absorb a great deal of heat. And since the passage between the block and the bottom of the radiator is wide open all the time, you're losing heat to that water as well. | ||
| Sifo |
"You don't have to heat the water up. " Think about what you just said. The only water you don't have to heat up is what's in the radiator. The water in the block and in the head is still there, and requires a significant amount of heat input to warm up. Water can absorb a great deal of heat. And since the passage between the block and the bottom of the radiator is wide open all the time, you're losing heat to that water as well. But it's a small percentage of the total needed to control the heat. With the air cooled engine you are dealing with 100% of the total mass necessary to control the heat. | ||
| Akbuell |
The discussion is taking an interesting direction. Hybrid- You are correct. The point I was trying to make: "Could the purpose of this platform be to get the core customer ready for the introduction of the 2025(ish) Heritage Ultra powered by a water cooled, overhead cam, 60deg V-twin?" | ||
| Hootowl |
On a cool day, I can drive my car all the way to work without it ever getting up to 190 degrees, the temperature at which the thermostat opens. Work isn't far, I admit, but even on a cold day, that's not the case with my bikes. They warm up very quickly. Air is not as great a conductor of heat as water. The fins must achieve a far greater temperature delta with the surrounding air to dump heat as effectively as a water cooled hunk of metal does at a much lower delta. So until the engine is 280 degrees, it isn't dumping a whole lot of heat very quickly, whereas the water cooled engine is dumping heat into the water immediately. Why do you think our air cooled engines operate around 280 degrees? That's where equilibrium is reached between the heat being generated and the heat being dissipated to the air. A 100 degree day and a 50 degree day is only a 50 degree difference to the 280 degree engine. That's not much. You may be cold, but your motor is fine. | ||
| Sifo |
AKbuell - if that were true then ALL the bikes would be switching to watercooled heads, this is not so, only a few bikes on their touring line. Leaves a lot of models left without them. Im sure it helps with emissions, but its not a forced thing or ALL the bikes would have them. It's a transition that is only partly because of emissions. Any engineering project is a matter of compromising many things to reach acceptable aspects of numerous factors. Power and economy also factor in as well as longevity of the parts. All of these aspects are helped by better heat control. With HD another BIG factor has always been to look traditional. That's been the big hangup on going liquid cooled. Now they've managed to hide radiators in the lower part of the fairing on the touring models and kept most of the engine looking like a traditional HD. They can't simply do the same thing on a model that lacks the fairing though. It is the first step in HD attempting to get a customer base to accept liquid cooling though. I know you could say that the V-Rod was really the first step, but it pretty much failed with their customer base. Then we have the next step with the 500/750cc models that are new and simply have a radiator hanging on the front of the frame. This is going to be a harder sell with their traditional customers. Hopefully those customers will realize that liquid cooling isn't a bad thing. It's got lot's of benefits. I do agree with HD on one thing though. I don't like the look of a radiator simply hung on the front of the frame. Never have, not even on my '76 Water Buffalo. That bike would hold it's temp needle right in the center of the gauge though, regardless of weather or driving conditions and managed the heat pretty darned well for the rider. | ||
| Cityxslicker |
internationally, it will be a boon. more so if they make concessions for the dirty roads that are unimproved and festooned with pot-holes | ||
| Sifo |
On a cool day, I can drive my car all the way to work without it ever getting up to 190 degrees, the temperature at which the thermostat opens. Work isn't far, I admit, but even on a cold day, that's not the case with my bikes. They warm up very quickly. Air is not as great a conductor of heat as water. The fins must achieve a far greater temperature delta with the surrounding air to dump heat as effectively as a water cooled hunk of metal does at a much lower delta. So until the engine is 280 degrees, it isn't dumping a whole lot of heat very quickly, whereas the water cooled engine is dumping heat into the water immediately. Why do you think our air cooled engines operate around 280 degrees? That's where equilibrium is reached between the heat being generated and the heat being dissipated to the air. A 100 degree day and a 50 degree day is only a 50 degree difference to the 280 degree engine. That's not much. You may be cold, but your motor is fine. Comparing one engine to another is tricky. My 2003 van will open the thermostat in less than a mile. It's predecessor from 1994 took much longer to warm up. Auto manufacturers have done a lot to warm engines up more quickly, for EPA reasons mentioned by others earlier. The bus I drive OTOH takes about 5 miles of driving before the thermostat opens. Different engines. They work differently. I'm not sure how you are gauging how fast you're air cooled bike warms up. The bottom line though is that the "cooling system" starts working as hard as it can as soon as it's above ambient temperature. OK, that's not entirely true with an XB, they do have a cooling fan that kicks on when they are hot, but that's more to deal with the compromise of packing an air cooled engine inside of a frame that limits air flow. You are correct that air doesn't conduct heat as well though. That's why they add so much area with the cooling fins, to compensate for that fact. They start the cooling process just as soon as they get above ambient temperature. Typical air cooling is a mess for an engine. You need enough cooling for when it's running hard, and there's just no way to shut it off with the exception of certain installations I know of with thermostatically controlled dampers to block air flow, but that really is beyond the scope of what we are talking about. | ||
| Hootowl |
"They start the cooling process just as soon as they get above ambient temperature" The heat being lost to the air when the temperature differential is low is insignificant. The vast majority of the heat being generated is staying within the engine under that condition. | ||
| Sifo |
No doubt true. The point though, is that there's no control for it. A thermostatically controlled engine OTOH can warm up quickly then when needed suddenly start cooling. Look at it this way. Compare a typical liquid cooled engine to the same thing, only designed without the thermostat. Without the thermostat it will be cooling sooner than you want it to, so it will take longer to warm up. That's exactly why they add the thermostat. Same temperature delta issues you mentioned still apply with liquid cooling BTW. A typical air cooled engine operates just like the liquid cooled engine lacking a thermostat. | ||
| Sifo |
Here's the new HD trike! *  * Tassels optional | ||
| Hootowl |
'Without the thermostat it will be cooling sooner than you want it to" Yes it would, because it has the full effect of the water cooling system working to kept it at the temperature of the water. But you are comparing that to an air cooled motor, which is no where near as efficient at cooling itself when there is not a high temperature delta between itself and the surrounding air. The water cooled motor has to heat up all that water (and then dump the heat to the air), the air cooled one does not. I think you're confusing control with rate of increase. The water cooled system absolutely gives greater control over the operating temperature. But all things being equal (as equal as they can be when comparing two different engines) the air cooled one will warm up faster. | ||
| Sifo |
The water cooled motor has to heat up all that water (and then dump the heat to the air), the air cooled one does not. Well here's your stumbling block. It doesn't have to heat all that water up until the engine is up to normal operating temp, thanks to the thermostat. It doesn't even start to heat it. While the transfer of heat is not as good with an air cooled engine, that is accounted for by greatly increasing the cooling capacity with the use of cooling fins, and there is just no way to turn that off. The full cooling capacity goes into effect as soon as you generate heat. I think you're confusing control with rate of increase. No. I'm recognizing that control allows you to have a faster rate of increase. | ||
| Natexlh1000 |
One other thing air cooled engines have to deal with is the range of temperatures the thing will be expected to run at. They have to run slightly looser tolerances so they won't bind up or worse. A water cooled engine can be held to a nice narrow comfort zone. New cars run very thin oil due to the crazy tight tolerances they can get away with. | ||
| Hootowl |
"Well here's your stumbling block. It doesn't have to heat all that water up until the engine is up to normal operating temp, thanks to the thermostat. It doesn't even start to heat it." Here's your stumbling block: It does have to heat it. There is water in the block and in the heads, probably just as much as is in the radiator. The cylinders are jacketed in water. "I'm recognizing that control allows you to have a faster rate of increase." How is that? Turning on the flow of coolant once it is up to temp doesn't negate the fact that there is coolant already in the engine that has to be heated. | ||
| Coxster |
I noticed the ultra-deluxe-whatever bagger has water cooled heads this year. A limited model means limited recalls I guess | ||
| Sifo |
How is that? Turning on the flow of coolant once it is up to temp doesn't negate the fact that there is coolant already in the engine that has to be heated. Keep in mind that you are just heating thermal mass. Sure that takes energy, but all those cooling fins on the air cooled engine also have a lot of thermal mass. The big difference between the two is that the water in the water jacked is stagnant and not really able to efficiently pass that thermal energy anywhere. The cooling fins on the other hand are both heating thermal mass and passing that energy off to the ambient air during the warm up phase. It's kind of like filling two buckets with water. Both have a hole in the bottom, but one has a valve that can control the hole. If you close the hole while filling it, it will fill faster. Same principle, just with BTUs. | ||
| Hootowl |
The bucket analogy doesn't hold water. (rim shot  ) You are assuming that the buckets are equal in volume, and are draining at the same rate. They aren't. The water cooled engine has more thermal mass than the air cooled engine, and the ability to shed heat to air that is not substantially cooler than the fin is paltry in comparison to the ability of the water in the block and heads to absorb heat. | ||
| Sifo |
Well that's the problem with comparing apples and oranges. Assumptions have to be made. Real world experience has shown me that a lot of engineering has gone into newer engines to get them to warm up faster. What was true 20 years ago is long forgotten history. What I do know is that my Triumph will show full temp at a point where I can still put a bare hand on the cooling fins of my XB with no problem. It's been a fun chat. Go for a last word if you like. There's plenty of back and forth for all to chew on for a while.  | ||
| Hootowl |
OK Water has more than 4 times the specific heat capacity of aluminum. That means it take 4 times as much heat to heat up water than it does aluminum. Chew on that  | ||
| Midknyte |
* Tassels optional blasphemer! | ||
| Hootowl |
I'm betting the Buell has a longer stroke than the Triumph, so it is more thermally efficient. More of the heat energy released during combustion is converted to movement, and not lost to heat. Another factor to consider when comparing apples and oranges. | ||
| Sifo |
Mmmmm... Chewy! Keep in mind that aluminum is much denser than water when doing your heat capacity calculations.  | ||
| Hootowl |
It isn't 4 times denser though. The water cooled engine still has more thermal mass. | ||
| Ourdee |
WooHoo. Side note: To get the water cooled engines up to temp faster, the water jackets are made thinner with smaller passages between the cylinders and into the heads. Emission regulating can ruin a lot of things. |
