| Author | Message | ||
     Uly_man |
The IAT will measure the air temp in the box and this will be more that the outside temp as it will pick up some heat from the engine via the base plate. Now this is normal/right and not a problem as long as the air temp, in the box, is correct. What can happen though is that the IAT sensor can pick up heat through the wires/sensor pins and give a false reading. This will not kill the engine but it may not let it run as well as it should. While doing some other stuff, to find problems, I once again found that the IAT was giving high numbers IE 50C and the out side temp was 25C. The pins on the IAT was 35C. I then insulated the wires/plug right up into the base plate and re-tested. It now shows about 10C plus over the outside air temp. The log also shows that the temp changes via increased engine temp and cools once the fan comes on. At that time the max engine temp, standing idle, was 200C with a outside temp of 25C and a IAT reading of about 35C. Once the fan came on it cooled the air and engine and the air temp dropped to about 30C. This I proved correct with a second sensor in the air box. This one was a Pro unit and within a tested 2C band IE The meter said 28C and TunerPro said 30C. | ||
| Thumper1203 |
Wow, good stuff Uly_man.. sooo, would accurate(lower temp) IAT data to the ecm effectively lean fueling? or the opposite? your thoughts? | ||
| Froggy |
IAT is at the bottom of the totem pole of sensors. You could have the sensor say the air is like 9000 degrees and the bike would still run fine. While having the IAT sensor be spot on would be ideal, it is not necessary. The O2, TPS, ETS are the main 3 to worry about. | ||
| Thumper1203 |
@ Froggy.. ahh, gotcha.. thx Found this.. IAT Sensor If present, the Intake Air Temp (IAT) sensor (aka: MAT – Manifold Air Temp) is used by the ECM to tell it the temperature of the air coming into the engine. The ECM uses this input to aid in the calculation of fuel and spark delivery. The IAT sensor is a simple thermistor which means its resistance changes based on its temperature. The ECM supplies the IAT sensor with a ground and a reference signal. The IAT sensor pulls down (towards ground) the reference signal based on temperature and the ECM looks at this to calculate temperature. High resistance equates to less reference voltage pull down which the computer interprets as low temperature while low resistance equates to more reference voltage pull down which the computer interprets as high temperature. The actual amount of impact this sensor has on engine operation is relatively minor, depending on programming. Most stock programming I have looked at doesn’t adjust fuel or timing much at all based on IAT sensor readings. Most TBI-type fuel injection systems do not use an IAT sensor. http://www.gmtuners.com/tech/MAF_MAP_IAT.htm And this.. This experiment is for the IAT sensor mod in which the signal from the IAT sensor is bypassed with a fixed value resistor. The value of the resistor is chosen such that the ECU reads a temperature hotter than the IAT sensor is reporting. The theory: Fuel mix is determined by a very large number of factors and is directly controlled by the length of time the fuel injectors stay open. Each factor is supplied to the ECU through all the engine's sensors. The ECU then takes each value to a lookup table which will return a constant multiplier for a given input. For example, if a lean condition is detected from the oxygen sensor, the multiplier will be greater than 1, resulting in a richer mix next cycle. The same thing goes for the intake air temperature. If the sensor is reading a hot temperature (hotter than normal) then the lookup table for the IAT sensor will report a multiplier less than 1. By tricking the ECU into thinking it's always reading a very hot temperature from the intake, the ECU can be forced to reduce the length of the pulse controlling the fuel injector by manipulating one of the many factors controlling fuel mix. I used the same resistors SVOBoy showed. The two 220 Ohm resistors measured 107.8 Ohms in parallel. This should produce a reading of approximately 240 to 250 degrees F. The coolant temp gauge read the same temp as before the mod. It does not appear that the leaning effects of this mod has enough effect to overheat the engine. http://www.gassavers.org/f6/iat-sensor-mod-experim ent-149.html So, it looks like keeping the IAT cooler has a small measure of benefit, albeit very small.. shucks, I was hoping Uly_man could be on to something substantially "Uly-beneficial" here,  | ||
| Uly_man |
It is not, as said, a substantial problem. I was just looking to re-check that the IAT did in fact change as it should because my old one did not. My old one would read the temp going UP, it got to 55 C, but it would NOT GO DOWN while riding. That was with the outside air at 20 C so the box air should have been about 30 C. The bike run but not as well as it did before. On the highway it was ok (ish) but the low speed stuff was a pain and not like it was before. I changed out the IAT, the one I am using now, and it was fine again. And still is for that matter. I use air temp sensors in my work all the time and I know that they can go bad. It is just my opinion but I think because the IAT sits on top of the engine it can get "cooked" by the heat and damage it. It does get VERY hot under that air box plate even on the 10 bike so what it would be like on a 06 bike is something else. Cool air is denser than warm air and the ECM uses, on this bike, the IAT to tell it (via the air temp) how dense it is. The ECM will then, with all the other input sensors, "crunch the numbers" to make the engine run as it was designed to do. Bad numbers IN will give BAD results. |
