fotoguzzi Posted February 27, 2009 Share Posted February 27, 2009 John A, are you following this thread? Do you want to try Ratchets experiment on my Lemans? Link to comment Share on other sites More sharing options...
emry Posted February 27, 2009 Share Posted February 27, 2009 Just another two cents here. I have read about who spec'ed what and why and when. They (engineers, particually at small companies) spec from what is available. They get a catalog and look in it and point their finger and say that will work, order up!!! It is in all aspects a COOLANT TEMP SENSOR. Not an oil temp sensor or head temp sensor. Thanks for pointing this out Dan and summerizing. So they bodged it to work and took a imperfect reading sensor and mapped the bike accordingly. Great two problems. Hats of to Ratch for creating a cheap PowerCommander. But since we are all so zealous about this why don't we spec out our own sensor?? Our engines are simple and the FI system is just as simple. The conditions (locations, temps, humidity, etc..) that our bikes can run into make for many situations that our bikes don't run well in. So the map is to lean, compress your pressure reg to add more preload to the spring and bump up the fuel presure. Well great it is fine at 3/4+ throttle you say, but what about idle. Advance your TPS. Oh no not more timing!! Slot your timing reluctor and retard it. Oh ackk. This is like work. LOL!!!! Link to comment Share on other sites More sharing options...
Guzzi2Go Posted February 27, 2009 Share Posted February 27, 2009 Volume II - Influence of a heatsink on temperature sensor - General Audiences As promised, here is a short discourse on the effects of applying a heatsink to the temperature sensor. Observe the following two tables: First table shows how temperature measured varies depending on the heatsink efficiency (size) at constant power delivery. For the sake of the argumentation, assumed power input to the sensor is fixed to 10W. Convection (air flow) is disregarded, although it would contribute quite a lot (provide for even better sensor cooling) in a realistic situation. Another assumption is ideal thermal contact of the sensor (no air gap). So consider this to be a best case scenario. Heatsink values are in the range of 10°K/W (let us assume that this is the sensor's nut) and 0.1°K/W (a really big'un). A garden variety heatsink like the one shown in one of the previous posts would have a value of ~5°K/W. First column (10K/W - no heatsink). Sensor is heating up quite nicely, and the readings would show the heat source's temperature. In an ideal case, sensor dissipates excessive heat through the object whose temperature it is measuring, namely, the cylinder head. In less than ideal case, some of the heat escapes through the sensor's nut. Last column (big'un). Sensor temperature barely differs from the ambient temperature. One could practically stick the sensor in the air and save himself a trouble of drilling cylinder heads, constructing holders, "thermo pasting" them, etc. Second table shows how temperature measured varies with power input and heatsink size at constant ambient temperature. This would be your 1-hour run through Mojave desert in summer, 7:00 AM. The purpose of this table is to verify the "10W input power" assumption. Observe "ridiculous" values (1025°C, 525°C) in the "100W row". One can conclude that either 100W is most likely to high value for input power, or that thermal resistance of the sensor's nut is significantly lower than 10K/W. However, looking at the nut and a proper heatsink, this is most likely not the case. Draw your own conclusions here. Conclusion Adding heatsink to the sensor is a bad idea. The bigger the heatsink, the closer one gets to measuring air temperature instead of motor temperature. Since your bike already has an air temp sensor it makes no sense to add another one. If you still chose to add a heatsink to the sensor, YMMV. A lot. I am running out of space on this bumper sticker. Will post some info on the influence of the air gap on the measured temperature on another one. Link to comment Share on other sites More sharing options...
Greg Field Posted February 28, 2009 Share Posted February 28, 2009 I never cease to be amazed here. Link to comment Share on other sites More sharing options...
Guzzi2Go Posted February 28, 2009 Share Posted February 28, 2009 ...Looking at the spec'd sensor's values. It is ranged to be most sensitive in the 90C to 110C area. ... How do you come to that conclusion? Could you define "most sensitive" for us (or for me if I am the only one who does not understand) please? Link to comment Share on other sites More sharing options...
Guest ratchethack Posted February 28, 2009 Share Posted February 28, 2009 Hats of to Ratch for creating a cheap PowerCommander. My PC III wasn't all that cheap when I installed it 6 years ago. If it could override wonky inputs from the temp sensor "on the fly" as needed, I'd've had nothing to do whilst sitting out the cold and rain. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted February 28, 2009 Share Posted February 28, 2009 I never cease to be amazed here. Nor I. How're those square wheels workin' out, Greg? Y'know, there are times when there's no alternative to working with a flawed thing, when it can be smoothed out very satisfactorily by means of "unusual measures" that might by casual observation (and to those closed to learning beyond their own understanding), would seem counter-intuitive. http://video.search.yahoo.com/video/play?p...id=000164727961 Link to comment Share on other sites More sharing options...
gstallons Posted February 28, 2009 Share Posted February 28, 2009 Psssst! Don't tell ANYONE.... I've found the hot tip is to get away from the square tires that Neanderthal Greg uses and go to the Fred Flintstone granite tires. The do not do much for unsprung weight,balancing or traction but they are guaranteed to last 3,000,000 yrs. Link to comment Share on other sites More sharing options...
Dan M Posted February 28, 2009 Share Posted February 28, 2009 How do you come to that conclusion? Could you define "most sensitive" for us (or for me if I am the only one who does not understand) please? Look at where the numbers tighten up: -40 100950 -30 53100 -20 29120 -10 16600 0 9750 10 5970 20 3750 25 3000 30 2420 40 1600 50 1080 60 750 70 525 80 380 90 275 100 205 110 155 125 100 In the range of 90C to 110C the variation is only 120 ohms. Pretty easy to pin point a temp. By comparison, 0C to 20C it is 6000ohms. Far greater margin for error. Make sense? Link to comment Share on other sites More sharing options...
GuzziMoto Posted February 28, 2009 Share Posted February 28, 2009 No, that's backwards. The larger the difference in resistence between two temps, the greater the precision in the reading. The less difference in resistence between two temps the harder it is to tell the diference. Picture a tach. What would allow to read the tach more accurately, more or less space between the numbers? Link to comment Share on other sites More sharing options...
Dan M Posted February 28, 2009 Share Posted February 28, 2009 No, that's backwards. The larger the difference in resistence between two temps, the greater the precision in the reading.The less difference in resistence between two temps the harder it is to tell the diference. Picture a tach. What would allow to read the tach more accurately, more or less space between the numbers? Sorry but you have it wrong. If you've ever measured one, the readings are steady and repeatable in the tight range and vary substantially when you get into the range out side of calibration. Edit: A sensor is more accurate if 10 degrees is represented by only 50 ohms rather than 500. Remember, the ECU is reading voltage after the sensor. Small ohm changes mean small voltage changes or accuracy. What you are suggesting is the engineers are having these sensors be in their most accurate range at -40C rather than in normal operating operating temperatures. Why? Link to comment Share on other sites More sharing options...
big J Posted March 1, 2009 Share Posted March 1, 2009 Only on the V11 forum............................20 pages on a temp sensor. Link to comment Share on other sites More sharing options...
Dan M Posted March 1, 2009 Share Posted March 1, 2009 Only on the V11 forum............................20 pages on a temp sensor. Of course, it's winter. As least it is not 20 pages on drilling holes in rubber cush-drive pucks. Link to comment Share on other sites More sharing options...
Guzzi2Go Posted March 1, 2009 Share Posted March 1, 2009 In the range of 90C to 110C the variation is only 120 ohms. Pretty easy to pin point a temp.By comparison, 0C to 20C it is 6000ohms. Far greater margin for error. Make sense? Thanks for the answer Dan. It is certainly not my intention to start a flame war on this, but I must state I disagree. The reason is the following: The sensor has a resistance span of some 100k over temp range of some 160°C (-40/125°C). Let us say this is being measured using a 10-bit ADC by measuring a voltage drop over the sensor. At 0-100k, 1 bit resolution would account for ~100ohm. The way I see it (correct me if I am wrong please) is that past 80°C the ADC would be unable to distinguish between 80° and 90°, 90° and 100°, 100° and 125°, etc. The resistance change would simply be to small to affect the readings even if the influence of noise (voltage fluctuations, radio emissions/sparking, etc.) is disregarded. As for the question why would engineers use it in that range, I can state (mere speculation here, so everyone is free to go at it at will) that it was never intended to be used as a fine regulator but more like a on/off switch. Example, once the resistance drops bellow 100 ohm-> off, once it raises over 300 ohm -> on. Does that make sense? Link to comment Share on other sites More sharing options...
gstallons Posted March 1, 2009 Share Posted March 1, 2009 You would have expected a linear reading from a (I've forgotten the proper name for resistors that vary with temp.)temp sensor? Link to comment Share on other sites More sharing options...
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