| Author | Message | ||
     Blake |
Tom, I don't know what to say. >>> liquid cooled version has some control over that though and limits heating in the radiator until more critical areas are up to temperature. That is inaccurate. All the coolant is constantly circulating and must be heated by the engine. Until the coolant is heated to a high enough temperature, the engine cannot reach normal operating temperature. That coolant has much greater heat capacity than the fins of an equivalent air cooled engine, and is also in thermal contact with the significant cold thermal mass of the heat exchanger, the connecting plumbing, and the water pump and thermostat, all having significant thermal mass. In simple terms, a liquid-cooled engine requires significantly more heat to warm the engine and its entire cooling system to normal operating temperature compared to a comparable air-cooled engine. You're point does have validity for the case where the air temperature is near to being so cold that the air-cooled engine cannot reach normal operating temperature. Maybe that is the scenario you're envisioning. It's not one I have to deal with often here in Texas.  Tootal, That's a valid point. | ||
| Hootowl |
I noted the thermal efficiency of long stroke engines earlier in this thread. | ||
| Sifo |
Blake, I have no idea what to say either. If you can't see that restricting the coolant flow to the radiator will get you faster warm ups, well I just don't know where to go with it. What I can add, is that like they say on Mythbusters, we have a result. I hooked up the PC to the bike and started a log file, fired up the bike and rode down to the corner gas station where my Triumph get five bars showing on the gauge. Weather BTW is about 45 degrees, just a couple degrees cooler than the other day on the Triumph. I turned around and rode home again. Here's the results. The start of the log file has the AIT (air inlet temp) at 12 and the ET (engine temp) at 11, or about 52 and 54 Fahrenheit. The bike stays in the garage, so it's slightly warmer than outside. At my turn around point the ET was up 88, or 190 Fahrenheit. When I got home, the ET had gotten up to 130, or 266 Fahrenheit. That still isn't quite up to full temp. The cold start enrichment shuts off at 180, or 356 Fahrenheit. So bottom line is that the XB seems to take about twice the driving as my Triumph to reach normal temps, probably a bit more. Now toss in the fact that the Buell is measuring the actual head temp vs. the Triumph measuring the coolant temp at the head, so there will be some delay as the head heats the coolant, I think it's safe to say that the Triumph certainly seems to heat the combustion chamber faster. Far from a perfect test, but the results aren't even close. Y'all can feel free to post up any tests you can come up with. | ||
| Hootowl |
Tom, "If you can't see that restricting the coolant flow to the radiator will get you faster warm ups, well I just don't know where to go with it." That's not what he said, and that's not what I said. "about twice the driving as my Triumph to reach normal temps" Not in dispute. What is in dispute is that the air cooled motor will warm faster than the water cooled motor. "Normal temps" was never part of the equation. The temperature at which you get a clean burn is the relevant point of warming, since we're talking about the perceived inferiority of air cooled engines when it comes to emissions. Of course the water cooled motor will reach 180 before the air cooled one will reach 280, but again, not relevant. | ||
| Sifo |
"Normal temps" was never part of the equation. The temperature at which you get a clean burn is the relevant point of warming, since we're talking about the perceived inferiority of air cooled engines when it comes to emissions. Well correct me if I'm wrong here, but isn't that about normal operating temperature? I mean, isn't that largely why the try to control the heat at that temperature? That certainly isn't going on while the ECM is adding fuel as part of the cold start enrichment tables, is it? Of course the water cooled motor will reach 180 before the air cooled one will reach 280, but again, not relevant. Well, yes and no. It's not relevant in the fact that you are not measuring exactly the same thing. It is relevant in that both are a proxy measurement of the heat of the combustion chamber. The reading from the XB is probably the better of the two for what we are looking at, and that's why you see much higher temps. The reading from the Triumph is farther removed from the combustion chamber and will show a somewhat delayed and lower reading. Here's the thing, this favors the XB in this apples to oranges comparison, yet the Triumph seems to be getting up to temperature quicker. A lot quicker. | ||
| Blake |
>>> I have no idea what to say either. If you can't see that restricting the coolant flow to the radiator will get you faster warm ups, well I just don't know where to go with it. Straw man. Not what I've stated. Air cooled engines generally heat more quickly than comparable liquid cooled engines. Why? Because they must heat a LOT more thermal mass. | ||
| Sifo |
Air cooled engines generally heat more quickly than comparable liquid cooled engines. Why? Because they must heat a LOT more thermal mass. Of course, that isn't what I'm seeing in the real world. Why? Because the air cooled engine has a cooling system that is trying to dump heat as you are warming up the engine. The liquid cooled engine has a thermostatic control that prevents that and makes it so you don't have to heat the entire thermal mass of the cooling system right away. Real world observation favors what I'm saying. | ||
| Tootal |
I noted the thermal efficiency of long stroke engines earlier in this thread. Sorry Hootowl, I was speed reading the previous pages and missed it. Good to see I wasn't alone...I hate being alone.  | ||
| Hootowl |
"Because the air cooled engine has a cooling system that is trying to dump heat as you are warming up the engine." It may be trying, but it is failing. 100% of its heat shedding capacity isn't available when its cold. In fact, it will never reach 100% of its heat shedding capacity. It will never get that hot without ceasing to function. See my previous posts about the ability of an air cooled engine to transfer heat to air when it is not significantly hotter than said air. | ||
| Sifo |
100% of its heat shedding capacity isn't available when its cold. In fact, it will never reach 100% of its heat shedding capacity. It will never get that hot without ceasing to function. And the liquid cooled variant won't pass heat to the coolant when cold either. Same thing applies. On the other end, the liquid cooled variant will boil, allowing the engine to get even hotter. I don't think that means anything to this conversation though. I'll still go with my real world data where I drove the XB twice as far and it was still running with the cold start enrichment. | ||
| Hootowl |
"And the liquid cooled variant won't pass heat to the coolant when cold either" Yes, it absolutely will. The engine readily gives up heat to the water, even with small temperature deltas. Water is a great conductor of heat. Air is not. Ask yourself why trapping little pockets of air in insulation is such an effective barrier to the movement of heat energy. Why doesn't insulation work if it gets wet? | ||
| Hootowl |
If you're in 60 degree air, you're probably pretty comfortable. If you're in a 60 degree pool, you're freezing your balls off. The same applies to an engine. Water conducts heat well, air conducts heat poorly. | ||
| Sifo |
Both work on the exact same formula...  where Q = heat flow rate or heat transfer rate, J/s = W h = heat transfer coefficient, W/(m2•K) A = heat transfer surface area, m2 ΔT = difference in temperature between the solid surface and surrounding fluid area, K Both need a temperature delta. Again, the difference in the ability to transfer heat (h) is accounted for by the engineering department by providing far more surface area (A). When the surface area has been engineered correctly, the heat flow rate (Q) will be dependent on the temp delta for both systems equally. http://en.wikipedia.org/wiki/Heat_transfer_coefficient | ||
| Sifo |
If you're in 60 degree air, you're probably pretty comfortable. If you're in a 60 degree pool, you're freezing your balls off. The same applies to an engine. Water conducts heat well, air conducts heat poorly. And again, there is no surface area correction engineered in for that example. | ||
| Hootowl |
Surface area has nothing to do with the heat conductivity of air. That factor would be a constant in the equation. Surface area would be the variable. | ||
| Hootowl |
"h = heat transfer coefficient, W/(m2•K)" This is a constant, and depends on what material you are using to conduct the heat. Air has a very low coefficient. Not all of the heat is given up directly to the air either. It is radiated as infrared energy. There again, it doesn't do much at low temperatures, only when it's smokin' hot. | ||
| Sifo |
"h = heat transfer coefficient, W/(m2•K)" This is a constant, and depends on what material you are using to conduct the heat. Air has a very low coefficient. And that is why an air cooled engine has big cooling fins, to provide enough area to provide sufficient cooling by the air. A water cooled engine transfers heat more readily to the cooling water, but has much less surface area to do that with. The heat flow rate (Q) will be about the same for both engines though. Both are equally dependent on the temperature delta. The difference is that as soon as you have a temperature delta, the air cooled engine will be dumping the heat to the atmosphere at it's full capacity, given the temp delta. The liquid cooled engine won't start dumping heat to the atmosphere until the thermostat opens up to let hot coolant into the radiator. That is why the liquid cooled engine warms up quicker, simply because the cooling system doesn't fight against the warm up process like an air cooled engine does. | ||
| Mr_grumpy |
Ok, I'm now going to throw another factor in the mix, shrouding & forced air. Think VW, Porsche, Deutz, Lombardini. Here again there's thermostatic control for fast warmup. Many aircooled motors got phased out due to being unable to meet noise pollution limits. | ||
| Sifo |
Ok, I'm now going to throw another factor in the mix, shrouding & forced air. Think VW, Porsche, Deutz, Lombardini. I've touched on the earlier, without mentioning any examples. Add many aircraft too. I even mentioned that the XB falls somewhat into that category, being shrouded by the frame, with a powerful cooling fan for when hot. It still warms up much slower than my Triumph. | ||
| Midknyte |
Cap is an entry level super hero? http://ultimatemotorcycling.com/harley-street-750- breakout-captain-america-winter-soldier/ | ||
| Elsinore74 |
Captain America on an entry level bike? Had to borrow it from one of his groupies, I hope. What's Red Skull chasing him on, a G650GS Beemer? I'm OK with product placement; it pays the bills and all. Someone's brand of pizza here, someone's brand of beer there, but is there no sense of decency? What next, Wolverine endorsing Viagra? | ||
| Hybridmomentspass |
I realize we are all moto enthusiasts, but the common movie goer wont know if its an 'entry level' bike or not who cares man, its a movie | ||
| Jayvee |
"entry level bike" Because of the displacement? Like a XR750? Nobody seems to mind water cooling in their car, why mind when its a motorcycle? I don't think I would even have one, but only out of stubbornness. I also won't buy a 1911 with a trigger safety lock, external extractor, or a rail. Not rational. | ||
| Elsinore74 |
My mini-rant was simply a weak attempt at humor. No offense to any G650GS owners out there, either, BTW. Lisa Thomas has ridden one around the world at least once. Good bikes, and maybe as much as anyone really needs. The H-D Street models aren't "entry-level" by displacement, but by market placement, sort of like a 1200 Sportster, 900cc metric cruiser, or 600cc supersport are to some. I've put as many miles on a 250cc street bike in the last year as I have on the larger bikes in the garage. "Entry level" is a more accurate label for the rider than the bike. I hope some iteration of the 750 Street engines find their way to dirt track racing. I count myself among the many fans of the XR750, but just like the KR750, its best days are long in the past. | ||
| Blake |
Tom, Please study the physics of thermal mass and heat capacity. As stated before, you have no idea how much fuel your Triumph is burning during your "test" ride. Without knowing that information, there is virtually nothing to be gleaned concerning enginge warmup efficiency from the purely anecdotal evidence. Erik Buell has explained that the Buell air-cooled engines could pass EPA requirements absent any catalytic converter specifically because they warm up much more quickly than liquid cooled engines. In some extreme scenarios, that may not hold, but it absolutely does hold for the EPA cold start emissions test. Put two pots on a gas stovetop. Put a cup of room temp water in one (liquid cooled) and blow a fan on the other (air cooled). Light the burners. Now begin adding more water to the liquid cooled at a slow rate, two cups per minute. Continue for five minutes then turn off the burners and fan. Which pot has the warmer bottom? Heat capacity and thermal mass (m) each favor the air-cooled engine. It's not at all clear that initial cooling rate is more favorable to one or the other. Whic | ||
| Sifo |
As stated before, you have no idea how much fuel your Triumph is burning during your "test" ride. Without knowing that information, there is virtually nothing to be gleaned concerning enginge warmup efficiency from the purely anecdotal evidence. True, it's purely anecdotal evidence. Of course it goes directly against the claim made by Erik Buell. That is one half of the equation. Is the Triumph typical of what Erik is comparing his air cooled engine to? I really don't know. I don't really think there's anything unusual about the Triumph in it's cooling system though. How much fuel is being burned in it? Based on how it runs, it's pretty damn spot on. I really wish my Buell was delivered running that well. Erik Buell has explained that the Buell air-cooled engines could pass EPA requirements absent any catalytic converter specifically because they warm up much more quickly than liquid cooled engines. I would have been more impressed if he built an engine that didn't need to be re-tuned to run correctly, with or without the cat. Put two pots on a gas stovetop. Put a cup of room temp water in one (liquid cooled) and blow a fan on the other (air cooled). Light the burners. Now begin adding more water to the liquid cooled at a slow rate, two cups per minute. Continue for five minutes then turn off the burners and fan. Which pot has the warmer bottom? Boy, where to begin with that one. First, your air cooled pot needs huge cooling fins on the top side, large enough to prevent the temp from going above the designed temperature, what ever that is in this experiment. That adds a lot of mass BTW. Then on the air cooled one, you have no need to pour in water until you are getting up to the designed temperature. And then, only at a rate necessary to keep it at the designed temperature. It's not at all clear that initial cooling rate is more favorable to one or the other. I know you keep going back to the initial cooling. That's virtually nonexistent in both designed. As you get near the designed temperature though, one design will be cooling at 100% of it's capacity, while the other will still have it's thermostat closed. That's where the water cooled engine has it's big advantage on this issue. No doubt my comparison of using my Triumph is less than perfect. Still, it's not like I tried this with a large number of bikes and cherry picked data to confirm my position. It's simply what is available, and from what I can see is representative of typical. Just as important, the results aren't even close. Even riding twice the distance, the Buell still wasn't up to normal operating temperature. | ||
| Hootowl |
"while the other will still have it's thermostat closed." You are forgetting, though it has been said numerous times, that the closed thermostat isn't relevant. Some water bypasses the thermostat when it is closed, which means that, while the effectiveness of the radiator is reduced due to reduced flow, the water itself is still being heated by the engine, and must be included it its thermal mass. | ||
| Sifo |
the water itself is still being heated by the engine, and must be included it its thermal mass. A very limited amount. Enough to make calculations difficult, but in practical terms the radiator is cool to the touch until the thermostat opens up. | ||
| Midknyte |
as to the title of this thread, this is not a Sportster replacement http://rideapart.com/2013/11/2014-harley-davidson- street-500-review/ | ||
| Ezblast |
Why same power area, easier to ride, cheaper - a lead into "real" Harley's - sounds like the descriptor used for the Sportster - if it quacks like a duck.... EZ |
