Guest ratchethack Posted March 16, 2009 Posted March 16, 2009 Act II scene 1 The Bass-baritone, Don-Davido Lainguini gets off his ass, goes to the garage, removes the sensor and brass adapter, takes out the cold solder that he had coiled under the probe tip, like a spring, wraps slightly more teflon tape around threads of sensor and reinstalls, sans solder. He then goes for a 70+ mile ride, and not notices not one single POP! But please note, the weather was cool today, but should be warming to near 80 later this week....stay tuned, for reports of falling MPG but quite likely a happier ride. Still there is plenty of room to lean up the cold zones in the map using Tuneboy. Hm. I suggest that wrapping teflon tape around the threads of the sensor would be unlikely to make any difference wotsoever. Ever notice how sliced-up teflon tape comes out after being used this way? It's sliced-up when seated, also, allowing substantial direct metal-to-metal contact. In the spaces NOT sliced-up, it's wedged so thin when seated that it can't possibly provide much heat insulation in the best of conditions, even if the sensor is not fully seated. It will provide a good pressure seal on threaded joints, though. So the air pressure in there probably goes pretty high when it's up to operating temp. BTW -- In my own case, after some 300+ miles on the plastic holder with thermo-compound, heat sink and variable resistor installed, the spark plugs are reading a nice even tan now, with noticeably less of the former soot shadow on the exhaust valve side than they had ever read previously. It continues to run flawlessly, with none of the previous lean symptoms at idle and off-idle throttle positions when fully warmed up and sitting at a very long stoplight. Would like to see if I can get 45 MPG on the current tank of fuel, and expect I'll get pretty close, not having done any sustained heavy-throttle mountain climbs that gave ~43 MPG previously. Will advise (Part XII).
dlaing Posted March 16, 2009 Posted March 16, 2009 So the air pressure in there probably goes pretty high when it's up to operating temp. Thanks, I did not think of that, so following that, the increased pressure will result in more heat transmitting to the probe. Not completely un-wanted in the absence of thermal goo, as long as it doesn't grenade Maybe we need a bleed path to ensure consistent pressure loss.
Guest ratchethack Posted March 16, 2009 Posted March 16, 2009 . . .I did not think of that, so following that, the increased pressure will result in more heat transmitting to the probe. Not really. There's negligible mass, therefore negligible potential heat content in a volume of air in a space that small no matter how high the pressure. Relative to the heat quantity (in BTU's) passing into the sensor probe and sensor body from the head, any internal air pressure wouldn't make any difference a-tall. Boyle's Law: http://www.iun.edu/~cpanhd/C101webnotes/gases/boyleslaw.html Hey Dave Have you considered J-B Welding the remains of your shattered OE plastic sensor holder back together or using the brass part that threads into the head with the "probe interface" on the inside as a base to fab up a new holder out of phenolic or some other heat-impervious insulator material? That'd have been my first inclination in your case. But o' course, that's just me. . .
badmotogoozer Posted March 16, 2009 Posted March 16, 2009 Has anyone actually bench tested the characteristics of the sensor itself? It would be interesting to see if it is the tip of the sensor that determines the resistance or if temp of the body has any effect on resistance. All this plug and play is fine and dandy but so far there really hasn't been any hard knowledge gleaned, mostly still speculation on the results of pseudo-scientific trial and error. I have no interest in taking any of my bike apart now that she's happy and ready for the spring. If someone has the sensor out, a little testing with a water bath, ohm meter, thermometer and a fan should give some hard results as to what kind of effect the holders may have. I suspect temp at the tip is the important part, and that the sensor body temp has little effect on the resistance. Any takers on proving/disproving the hypothesis?
Guzzi2Go Posted March 16, 2009 Posted March 16, 2009 ...I suspect temp at the tip is the important part, and that the sensor body temp has little effect on the resistance. Any takers on proving/disproving the hypothesis? Well, look at this article: http://www.tetech.com/docs/thermoelectric_...ermocouples.pdf True, it is about thermocouples, not NTCs, but you'll get the gist... The following (important) statements are in there: The temperature measured by the controller is the temperature of the SENSOR and not necessarily the temperature of the TE device! So, the key to good control is to make the temperature of the sensor equal (as much as possible) to that of the TE device or object you are cooling. How do you do this? 1. Sensor placement: The time lag time between when the TE device changes temperature and when you measure that change with the sensor needs to be minimized. This usually means placing the sensor as close to the thermoelectric module as possible. (That means as deep in the C-head as it goes) 2. Proper Thermal attachment: Make certain that the temperature sensor has the best possible thermal connection to the object you wish to measure. (That means thermo-goo or similar. No air-gap!) 3. Removal of external influences: External influences such as Infra Red (IR) radiation and heat conducted by the sensor wires to the measurement point need to be minimized. (That means no fat, metal nuts, brass holders, fins, heatsinks, etc. A thermal cul-de-sac is better then a thermal highway.) I think especially this last statement provides answer to your question. Placement of the NTC inside the sensor apparatus is irrelevant, since you cannot influence it. That is why it is important to take care of #2 and #3.
badmotogoozer Posted March 16, 2009 Posted March 16, 2009 NTC's? NTC, PTC is not refering to a type of RTD but rather wether you have an increasing resistance or a decreasing Res wrt to increase in temp. Has anyone determined what type of RTD the sensor is? Thermocouple? Thermistor? I have little experience with auto sensors but am very familiar with medical temperature monitoring and its associated transducers. NTC - negative temp. coefficient PTC - pos temp coefficient RTD - resistance-temperature detector or device My question is - In THIS sensor how much difference in R do we see in the different configurations discussed so far? How much actual deviation do we see with the various holders, gaps, etc.? Does the temp of the housing, or its ability to shed heat even matter? Without a detailed manufacturers spec sheet, the only way to determine this is by bench testing. Testing on the bike leaves far too much uncertain to be of any real conclusive value. In my eyes anyway. Ratch's done a great job of figuring out what works with HIS bike, in IT'S configuration, under the conditions found in HIS part of the world. Someone in Sweden, with a different bike, at a different part of the year could very well hang himself following in Ratch's footsteps...
Guzzi2Go Posted March 16, 2009 Posted March 16, 2009 NTC's? NTC, PTC is not refering to a type of RTD but rather wether you have an increasing resistance or a decreasing Res wrt to increase in temp. Has anyone determined what type of RTD the sensor is? Thermocouple? Thermistor? It is a NTC thermistor. We've been through that all over the last 30 pages. Ratch's done a great job of figuring out what works with HIS bike, in IT'S configuration, under the conditions found in HIS part of the world. Someone in Sweden, with a different bike, at a different part of the year could very well hang himself following in Ratch's footsteps... Well, how about an attempt (over 30+pages) to go for a consistent result, regardless of the bike, its configuration, conditions, time of the year and part of the world? I'd say it would be hard target to reach by linking everything to something as variable as weather. Why going that road? And I doubt very much that ratchet has in this particular case figured out what works on HIS bike. Or on any other bike for that matter.
dlaing Posted March 17, 2009 Posted March 17, 2009 Not really. There's negligible mass, therefore negligible potential heat content in a volulme of air in a space that small no matter how high the pressure. Relative to the heat (in BTU's) passing into the sensor probe and sensor body from the head, any internal air pressure wouldn't make any difference a-tall. Boyle's Law: http://www.iun.edu/~cpanhd/C101webnotes/gases/boyleslaw.html Hey Dave Have you considered J-B Welding the remains of your shattered OE plastic sensor holder back together or using the brass part that threads into the head with the "probe interface" on the inside as a base to fab up a new holder out of phenolic or some other heat-impervious insulator material? That'd have been my first inclination in your case. But o' course, that's just me. . . Why are you limiting to Boyle's law? In any case, yah, even if you obey the ideal gas law, the theoretically significant rise in temperature is instantaneous, so the real rise in temperature would be largely lost as it dissipates over time. One cc of air with a 40% increase in pressure might have a theoretically corresponding 40% increase in temperature (I am sure some will argue the theory, and I could be wrong, but I won't argue, because it is not relevant), but the heat retention of one cc of air in a brass enclosure over a 15 minute warm up would be almost completely unmeasurable.(an thus the irrelevance) What MIGHT be a factor is the increase in thermal conductance of the air, such that the gap at high temperatures could behave conductively as if gapped 40% tighter, which is opposite of what I would like. Still the difference in air conductivity is not gonna make much difference, nothing like the difference of adding a conductive paste. I had to hammer the adapter with an impact driver to get it out. JB Weld bodge master, that ain't me Maybe I should slice the brass fitting in thirds, throw out a third and JB Weld it back together?, Nah, that ain't me either Or maybe I'll search the garage for the damaged pieces, as they might not be as bad as I remember???
dlaing Posted March 17, 2009 Posted March 17, 2009 My question is - In THIS sensor how much difference in R do we see in the different configurations discussed so far? How much actual deviation do we see with the various holders, gaps, etc.? Does the temp of the housing, or its ability to shed heat even matter? Without a detailed manufacturers spec sheet, the only way to determine this is by bench testing. Testing on the bike leaves far too much uncertain to be of any real conclusive value. In my eyes anyway. The various gaps won't make nearly as much difference as contact versus no contact. I am pretty sure the housing temperature, shed ability, and transmission ability all matters. I think testing on the bike is more ideal than on a bench. A lot could be told from a volt meter that can't be told in 30 pages of instructions.
Greg Field Posted March 17, 2009 Posted March 17, 2009 And here I thought you boys were starting to run out of steam. Yes, by all means find out which particular gas works best inside the sensor holder on your particular machine. That'll get us to 40 pages for sure . . .
helicopterjim R.I.P. Posted March 17, 2009 Posted March 17, 2009 I'd try methane first. Who's going to hold the lighter?
Guest ratchethack Posted March 17, 2009 Posted March 17, 2009 I think testing on the bike is more ideal than on a bench. A lot could be told from a volt meter that can't be told in 30 pages of instructions. The operation of the sensor is highly INTERDEPENDENT upon real-world engine dynamics and mode of operation, heat flow through the head, air flow over the head, and heat flow through the sensor holder/sensor body (regardless of plastic or finned brass holder, and/or heat sink) -- none of which is possible to simulate on a bench. The TIME FACTOR relative to heat flow is critically important here, as noted previously in my comments on THERMAL INERTIA and the relatively large MASS of the sensor body. Taking the sensor/holder out of its multiple INTERDEPENDENCES on the Guzzi (including the engine config and specific map used) removes the ability to both measure and understand how it actually works as installed. (Again) -- What would you hope to learn from taking voltage readings? The temp/resistance table is a "given", as posted many times. You can calculate voltage readings at temp intervals from the resistance table without measuring, as I think somebody already did. Now (again) -- I asked this before of someone who was apparently "overjoyed" to get the data and got no answer: What would you intend to do with this data, and for what possible purpose? Unless the sensor is faulty, any attempt to accurately extrapolate how it functions on the road from measuring it on a test bench would yield useless information, including measurements of the output with a volt meter. As noted in post #415, page 28: . . .the more ideal [and accurate] laboratory setup [would be] with a brake dyno in a wind tunnel, and a brace of diagnostic gear connected via a long tangle of cabling and wires -- should you happen to have such a collection of gear handy. The only alternative to the above? Why, test it on the road under all possible configurations of holders, air gaps and thermo-compound and compare and contrast the real-world results -- as I've done.
jrt Posted March 17, 2009 Posted March 17, 2009 I'd try methane first. C'mon, man, think big! Charge the space with tritium and see if it initializes fusion.
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