| Author | Message | ||
     Adamd |
I use to be in building computers but haven't touched them in a while. I do remember that some fans could pack a whallop.. They're small but do you think one of two could make a difference mount somewhere in behind the rear cylinder? | ||
| L_je |
No. The waste heat from a CPU is < 30 Watts. The waste heat from the engine is > 30000 Watts. 6 months out of the year, nobody cares about thermal management. Welcome to the other 6 months! | ||
| Reepicheep |
Well, probably more like 30 watts versus 600 watts, but your point still stands... Maybe if you put 6 of those smaller fans and ran all of them... and don't use the heat sinks, just move air over the head (which is already a heatsink). Wonder if that would be quieter then the big factory XB fan? The bigger problem I see is running those fans on a motorcycle immersed in rain, dead bugs, tar, etc. Those fans already have a short enough life span in your computer, can't imagine them running after a few hours in the rain on the interstate. | ||
| Hughlysses |
Court intimated a while back that Buell engineers were working on better/quieter cooling fans for the XB's, evidently because of complaints from Uly riders. I'd imagine the main problem is that having a relatively small diameter fan impeller requires it to be spun at high RPM to move the required quantity of air, and high fan speed leads to high noise. Maybe they'll figure out a location to fit a larger, slower-turning fan which would help things. I'll bet you could mount one horizontally under the rear subframe (which would allow a diameter of 12" or so) and use a molded plastic duct to move air from the rear cylinder head. This would have the additional advantage of discharging the hot air down and away from the rider. I wouldn't be a bit surprised to see a change in this area on the 08's. Of course, if you were really industrious, you could figure out how to do this on your own. Using a larger, quieter cooling fan from a Japanese water-cooled bike would be a good place to start. | ||
| Thunderbox |
I think the Uly engine puts out a little more heat than the average 3000w heater. Quite a bit more. I am sure you could find a quieter fan that moves that much air but you have to remember the Uly fan blows air out by the rear wheel. That means the fan is subjected to all the heat that it moves. Air flow is over the head over the fan and out. It gets 300 degrees under there and not many fans will take that type of torture. Good luck in your search. On the other hand computer fans blow air over the CPU and have nice cool air flowing over them and are not subject to much heat at all. Maybe they should have put the fan in the left air scoop and it would not get too hot there. But if you really look at the problem the fan noise is nothing compared to some of the exhausts that people are installing and somehow thats a good thing. Fan noise bad, exhaust noise good?????? | ||
| Reepicheep |
It's what, 640 watts in a horsepower? So in terms of power going to the rear wheel, an XB is probably putting out somewhere around 60,000 watts. But that's not heat, that's power that didn't get turned to heat. And thats only at max RPM. So lets take 1/3 of that (which is probably the average of the power an XB puts out on a normal ride). That takes us down to 20,000 watts. But thats across the whole engine, split that in half for the rear cylinder. So we are down to 10,000 watts. But that's power output, not heat generated. So lets assume an internal combustion engine is only 50% efficient (half it's power becomes kinetic energy, half is lost to heat). So that brings us down to 5000 watts of heat to dissipate. But we have an oil cooler, and that oil is carrying heat away from the heads. Say that's 20% effective, and we are down to 4000 watts or so. So you are right, it's a lot more then 600 watts... probably 2000 to 5000. I didn't calculate it the first time, I used a way of swagging I have used since college. Picture a 100 watt light bulb... everyone probably has a fairly intuitive feel for the kind of heat that puts out. That is a marginal efficiency system (it is supposed to put out light, but it really puts out lots of heat and some light). So when "picturing" heat, picture light bulbs. A 100 watt bulb gets freaking hot, as does it's enclosure. So picture how hot it would get to cram 7 of these bulbs in an area the size of the rear cylinder of an XB. That's a ton of heat in a little space... and would correspond to 700 watts of waste heat. And thats just one horsepower. A horsepower is doing a LOT of actual work. But I digress. 3000 watts of waste heat would be the same as 30 100 watt bulbs. Thats a lot of heat when you pack it in a little space. Another good "picture it" tool is a 15 watt soldering iron. It makes you appreciate that 15 watts of heat, when concentrated, is a non trivial chunk of heat. 3000 watts of waste heat would correspond to 200 15watt soldering irons in a small area. How much fan would you need to keep those cool? Also, heat dissipation can be thought about like a Voltage / Current / Resistor problem. The bigger the Voltage (the bigger the temperature difference between the hot thing and the cold thing) the more current (heat) will flow from the hot thing to the cold thing across a given resistance (thermal insulation barriers). Lowering the resistance (better thermal bonding between the hot thing and the cold thing) will flow more heat away, or increasing the voltage (quickly replacing your now hot air with new fresh cold air) will also increase how fast heat flows away. Flat black will transfer heat away much more efficiently then shiny metal surfaces. Fun topics to think about... | ||
| Treadmarks |
With all the math aside, I have installed two 60mm extruder cooling fans on the back of my jagg oil cooler on my HD softail. My oil temps went down from 250-260 to 200-210. I used an automotive (Hayden) solid state fan controller for a thermostat and set it to come on at 200 and go off at 190. This setup cycles in traffic just like the Uly does with the RSS. They are much quieter than the Uly fan and did a great job at shakin the heat from the rear cylinder that I used to feel in traffic. Those were in place for over a year and had about 5000 miles on them, rain or shine without any failure. While installing the rotrex supercharger I opted to switch to a pair of tornado PC fans because they moved much more air than the fans I had before. I have almost 4000 miles on the tornado setup and had zero failures with them as well. All in all I think oil cooling is a good supplement to temp management, but there still needs to be some air flowing around the rear cylinder to help keep the frame rails (fuel) cooler. | ||
| Snowscum |
Treadmarks: Pictures! | ||
| Hughlysses |
Treadmarks, Glitch was considering a similar setup for his XB9S to help it deal with Atlanta traffic, but I don't know if he ever got around to implementing it. Yes, pics please! | ||
| Treadmarks |
Ohh man. You guys are gonna make me install these on the Uly too! I actually bought two extra fans and planned to put them on the Uly oil cooler, but the RSS seemed to cool things off enough that I felt it was not needed, yet. The upside to putting them on the uly, is that there is already a relay for the main cooling fan that supplies enough power to support a couple of PC fans. This would eliminate the need for a separate thermostat. On the Softail, I used a horizontal low mount cooler so I could hide everything (cooler, 2 fans and thermostat) inside an aftermarket lower faring, as not to spoil the clean lines of the bike.  If you look closely at the opening on the lower faring, you can see the tornado fans mounted to the cooler.  I will bet an ice cold beer,  that if/when we mount a fan to the oil cooler that fan run times will decrease drastically. On the other hand, if the fan run times in traffic is reduced (even though the engine temps are reduced as well), the possibility of heat penetrating the frame rail(fuel) will increase due to lack of air flow. Hot fuel baaad. What do you guys think? | ||
| L_je |
Cruising at 60mph in 5th gear, I'm thinking that an XB12X is putting about 17 hp to the rear wheel. 17 hp is maybe 20 hp at the crank. An Otto cycle is only about 25% efficient at converting combustion energy into power. So, this means that the combustion process is generating about 60 hp between the two cylinders = 20hp(@crank)+40hp(waste heat). Of this 40hp of total waste heat: -some is blown out the exhaust -some convects through the fins/etc -and the remainder is stored in the metal of the engine casings My first SWAG of 30kW of waste heat isn't as far-out as it first appears. Hot Hot Hot. In short: If the bike is ~25% efficient, that means that means the waste heat is roughly 2-3 times your rear-wheel-horsepower. If your rwhp can smoke a tire, just image how easily 2-3 times that amount can smoke YOU. Oh wait, we're all on XBs here, so we don't have to imagine anything, because we live it! Ha! Embrace the heat! Just be careful with what you choose to snuggle up to! | ||
| Swampy |
Treadmarks, Nice "Death Charger" you have there! | ||
| Thunderbox |
Hey Treadmarks, can you get a different thermostat? 200-210 is not hot enought to boil any condensation out of the oil so the water that is made when the engine is running stays in the oil. Your oil temps should be 220-230 optimum. This will ensure all the condensate is removed from your oil. Just a thought. Does it take longer to warm the engine up to temp also? | ||
| Electraglider_1997 |
Thunderbox, I wrote this once before elsewhere on BWeb and it is only my theory but here it is again. Some of the oil gets very hot for short periods of time while it gets sprayed on the underside of the pistons and cylinder walls and other places as well. And just because Treadmark's thermostat turns on at 200-210 doesn't mean that the oil cools to that temp in the time it is in the oil cooler. I've got a temp probe built into the dipstick (homemade) in the swingarm oil tank (ULY) and I've never seen that thermometer register over 220 and rarely that. BUT I'm pretty certain that the oil in the rear cylinder is hotter than that. I've never had condensation goop built upon my thermometer/dipstick. Usually the thermometer reads 180 to 200. Oh yeah, and I realize Treadmark is talking about his Harley and not the ULY but my posit still applies. | ||
| Treadmarks |
Swampy, Thanks man. I think about Death every time I ride that bike. Thunderbox, You can set the solid state thermostat at whatever you like. The temps I was reading were at the oil tank, where I have a thermodipstick thingie. It evaps the water just fine, as I drain it from a remote catch hose regularly. The sensor probe for the fan controller is attached to the oil cooler, and the oil cooler adapter has it's own thermostat so it only sends oil to the cooler when it reaches operating temp. I don't know if the Uly has a thermostat on the oil cooler or not. After giving this some thought, I am considering not using a thermostat to control the fan on the Uly oil cooler. Since the draw for a couple of tornado fans is so low they would not need a relay. I may decide to just use a traffic switch with a bright LED indicator light. This will keep everything functioning as normal, but when you get stuck in traffic just flip the switch and the oil cooler fans will run until turned off. |
