mike wilson Posted March 31, 2009 Share Posted March 31, 2009 Consider that head temp very seldom reaches a steady state of equilibrium in an air cooled motor. That is, on the road, under varying conditions of speed, throttle, engine RPM, load, ambient temperatures, etc., lacking a cooling jacket to effectively stabilize engine temps, the operating temps of air cooled cylinder heads vary considerably over relatively short timelines (fractions of a minute), and are constantly either heating up or cooling down. It is this temp variance that the ECU attempts to monitor to effectively control pulsewidth signals to the FI. Now consider what happens when conditions on the road change, as when one slows down, descends a long grade, closes the throttles, hauls up to a stop after hard riding, or any combination thereof. In all of these cases, heat production at the source from combustion drops off sharply, and the heads suddenly cool (continue to dump heat) due to air convection via the cooling fins. Now the temp of the heat-soaked sensor body is suddenly higher than the heads, due to the thermal inertia of the sensor body. Lacking any other avenue of escape, the relatively higher heat of the sensor body now flows back into the cooler head and out through the cooling fins. This doesn't happen instantly. It takes time for heat to flow in either direction through the relatively constricted path available to it at the sensor probe. This delay is what I have been referring to as the inherent LAG TIME in temp change response of the OE sensor, and a source of significant inherent ERROR of the OE plastic sensor/holder. This understanding is supported by my weeks of testing and experimenting on the road, and particularly obvious when observing the relief of over-lean heat soak lean burn symptoms when adding a heat sink to the sensor body. It is actually worse than you suggest, I think. The head temperature will not be the same at all points on the head, most of the time. Under accelleration, the area around the exhaust port will heat up more rapidly (from hot gases) than the area around the intake, which is being cooled by incoming gases, in turn cooled by evaporating fuel. Much of the heat around the exhaust port will be conducted along the nearby fins, due to the steep heat gradient there as airstream takes away the heat nearer the tips. I suspect there will be a noticable heat gradient from front to back and there may be even more of a lag in sensor readings with respect to average head temperature at any given moment. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted March 31, 2009 Share Posted March 31, 2009 I suspect there will be a noticable heat gradient from front to back and there may be even more of a lag in sensor readings with respect to average head temperature at any given moment. Certainly and without much question. The location of the mounting boss for the head sensor with its bias toward the intake side of the head was not likely an accident. I suggest that many tradeoffs were consolidated, and nothing resembling perfection is to be found hereabouts, hence such additional tradeoffs as "slop" in the spec of the OE sensor/holder with its ~.015" air gap, and the previously spec'd "slop" of ~.25" air gap of the brass holder of the Sport-i. Link to comment Share on other sites More sharing options...
Dan M Posted March 31, 2009 Share Posted March 31, 2009 Sooo...you're saying that we humans, like our V11's, are run by electricity.... And some people say that my negativity keeps me grounded.... Emperical evidence now leads me to believe all those years I was paying for a particular herbal substance and thought I was getting "tuned in", I was really just leaking electricity ?!?!? NOW I know why they are refered (reefer'd?) to as "Wasted Years"...and I totally dig yer whole "mysteries" thing, that's very heavy Man, but I was WAY MORE than a casual user...Sorry Ladies and Gentlemen, don't let me stop you in your pursuit for that elusive page 40! P.S. Hey big J, I think you are leaking electricity, Dude There are parallels SH. In my foggy recollection of the '70s, stoners like Lucas components strived to keep the smoke in albeit not usually successfully. Link to comment Share on other sites More sharing options...
Greg Field Posted March 31, 2009 Share Posted March 31, 2009 One more page . . . and thence on to the destined 90 pages. Link to comment Share on other sites More sharing options...
Quotamason Posted March 31, 2009 Share Posted March 31, 2009 Managed to get many more hours of experimenting and testing on the road this weekend, more about which later. Here's my understanding of the answer to that Q, based on many weeks of testing the OE sensor and a solid grasp of the fundamentals of thermodynamics -- both of which seem to be extremely rare commodities hereabouts. . . Consider that head temp very seldom reaches a steady state of equilibrium in an air cooled motor. That is, on the road, under varying conditions of speed, throttle, engine RPM, load, ambient temperatures, etc., lacking a cooling jacket to effectively stabilize engine temps, the operating temps of air cooled cylinder heads vary considerably over relatively short timelines (fractions of a minute), and are constantly either heating up or cooling down. It is this temp variance that the ECU attempts to monitor to effectively control pulsewidth signals to the FI. Consider then the OE plastic head temp sensor/holder, with the weight of its ~1.4 oz. sensor body and probe (nearly 100% brass), that weight being a direct indicator of its 1. mass, 2. heat capacity, and 3. thermal inertia when exposed to a heat source higher than ambient. As the motor heats up in operation, the heat of combustion is conducted into the sensor body from the head through the probe end of the sensor (more directly in the case of thermo-paste or less directly through an air space). In either case, heat will flow into the "heat reservoir" of the sensor body from the head until the sensor body is the same temp as the head, and temp equilibrium is attained. In the same way that the heads are always either heating up or cooling down, the temp of the sensor body is also always either heating up or cooling down. The cylinder heads, being at the heat source, must always lead the temp changes at the sensor body by heat flow through the temp probe, and the sensor body temp must always follow temp changes of the heads. The OE temp sensor body/holder lacks both a heat source and an avenue for cooling. The head provides both heating and cooling for the temp sensor body/holder through the only avenue of heat flow between them, a relatively constricted pathway for heat flow -- the sensor probe, where the thermistor is located, and where the temp is actually read. Now consider what happens when conditions on the road change, as when one slows down, descends a long grade, closes the throttles, hauls up to a stop after hard riding, or any combination thereof. In all of these cases, heat production at the source from combustion drops off sharply, and the heads suddenly cool (continue to dump heat) due to air convection via the cooling fins. Now the temp of the heat-soaked sensor body is suddenly higher than the heads, due to the thermal inertia of the sensor body. Lacking any other avenue of escape, the relatively higher heat of the sensor body now flows back into the cooler head and out through the cooling fins. This doesn't happen instantly. It takes time for heat to flow in either direction through the relatively constricted path available to it at the sensor probe. This delay is what I have been referring to as the inherent LAG TIME in temp change response of the OE sensor, and a source of significant inherent ERROR of the OE plastic sensor/holder. This understanding is supported by my weeks of testing and experimenting on the road, and particularly obvious when observing the relief of over-lean heat soak lean burn symptoms when adding a heat sink to the sensor body. I replaced the plastic piece with the brass one and now the bike sputters and runs like crap. When I disconect the plug for the sensor, it runs fine. I have replaced the temp sensor and it still runs bad, sputters and coughs. What is going on here? Help Link to comment Share on other sites More sharing options...
savagehenry Posted March 31, 2009 Share Posted March 31, 2009 I really have nothing to add of any value, like the rest of my additions to this mind numbingly long and drawn out thread about sensors, theory and egos as much as the pursuit of perfection under constantly changing conditions, from all parts and climates around the world, ridden in all types of weathers and conditions, added to by published and generally acknowledged as quite smart guys to schlubs like me, with bikes in all states of tune from "race ready" (for "fat" bikes anyway ) to "it runs, I'll deal with the bothersome issues when it doesn't". It's just that this post MAY be the one to push this on to the 40th page....Oh God....PLEASE....And now I will hit the "ADD REPLY" box, and hold my breath, and here goes nuthin'.... Link to comment Share on other sites More sharing options...
savagehenry Posted March 31, 2009 Share Posted March 31, 2009 I really have nothing to add of any value, like the rest of my additions to this mind numbingly long and drawn out thread about sensors, theory and egos as much as the pursuit of perfection under constantly changing conditions, from all parts and climates around the world, ridden in all types of weathers and conditions, added to by published and generally acknowledged as quite smart guys to schlubs like me, with bikes in all states of tune from "race ready" (for "fat" bikes anyway ) to "it runs, I'll deal with the bothersome issues when it doesn't". It's just that this post MAY be the one to push this on to the 40th page....Oh God....PLEASE....And now I will hit the "ADD REPLY" box, and hold my breath, and here goes nuthin'.... And one more try, fingers crossed.... Link to comment Share on other sites More sharing options...
savagehenry Posted March 31, 2009 Share Posted March 31, 2009 And one more try, fingers crossed.... SHIT!!!! Link to comment Share on other sites More sharing options...
GuzziMoto Posted March 31, 2009 Share Posted March 31, 2009 I replaced the plastic piece with the brass one and now the bike sputters and runs like crap. When I disconect the plug for the sensor, it runs fine. I have replaced the temp sensor and it still runs bad, sputters and coughs. What is going on here? Help Why did you replace the plastic holder with the brass one? Some bikes have fuel mileage issues (low fuel mileage) and they benefit from adding some sort of heat transfer goo between the sensor and the copper tip of the holder. This gives a more accurate temp reading to the ECU. If your bikes runs perfect the the ETS reading a little low and you add heat transfer goo or replace the plastic holder with a brass holder the more accurate temp reading may make the bike run lean. You can then adjust your map accordingly or put the platic holder back on. Alternately, you could add a variable resistor as RH did and give yourself manual control over the temp reading. If it does not run better with the plastic holder back on then you have other issues. Link to comment Share on other sites More sharing options...
Dan M Posted March 31, 2009 Share Posted March 31, 2009 I replaced the plastic piece with the brass one and now the bike sputters and runs like crap. When I disconect the plug for the sensor, it runs fine. I have replaced the temp sensor and it still runs bad, sputters and coughs. What is going on here? Help Hey QM, To spare you from reading 40 pages of stuff here. It has been determined that if your bike has the tendency to run lean, making better temp contact with the head as brass does and as adding paste to the cavity does, the computer senses higher temp and the bike will run even leaner. Disconnecting your sensor causes the computer to think it is very cold so it is adding fuel covering your problem. The trouble is it is too much fuel and your mileage will be bad and you will likely foul spark plugs. Do you still have the plastic holder? If it runs good with it, why change? Hope this helps. edit - only 6 more posts to hit the magic 40 Link to comment Share on other sites More sharing options...
savagehenry Posted March 31, 2009 Share Posted March 31, 2009 Results do not lie! Not only will we roll right on to page 40+, but there have been OVER 18,000 views on this thread to date. We owe it to the curious onlookers to continue on, no matter what the cost!!! We now return you to your regularly scheduled program... Link to comment Share on other sites More sharing options...
helicopterjim R.I.P. Posted April 1, 2009 Share Posted April 1, 2009 One more page . . . and thence on to the destined 90 pages. I think they are ready to give up ...they'll never make it! Link to comment Share on other sites More sharing options...
Greg Field Posted April 1, 2009 Share Posted April 1, 2009 Do not give up, I beg you. Convince us all we need a manual choke on our EFI bikes . . . Link to comment Share on other sites More sharing options...
dlaing Posted April 1, 2009 Share Posted April 1, 2009 I replaced the plastic piece with the brass one and now the bike sputters and runs like crap. When I disconect the plug for the sensor, it runs fine. I have replaced the temp sensor and it still runs bad, sputters and coughs. What is going on here? Help According to Greg Field, you neglected to fill with conductive goo and wrap it in duct tape. But apparently I am the only one who disagrees with his method. For me, adding conductive made it run much worse. I used a coil of solder as a conductive. Removing it made it run much better. In the interest of "science", give his method a try. My replacement plastic adapter has been on order for years, so I am considering ratchets patentable cooling fin design! Link to comment Share on other sites More sharing options...
Greg Field Posted April 1, 2009 Share Posted April 1, 2009 David: Guzzi has sensor holders in stock. Link to comment Share on other sites More sharing options...
Recommended Posts