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Old 10-14-2008, 08:34 AM   #1 (permalink)
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start to play with IAT sensor on Mercedes E250D-Turbo 98'

Hello, found this forum is something interesting for me
Ok, i got car mercedes e250turbo diesel, non-direct diesel injection, car has ECU, but mostly its regulated by vacuum, since last christmas, as i bought it it was so terrible slow, especialy at low rpm, and nobody could tell why, i change a lot of things, turn off EGR valve, etc.. i got slightly better perfomance at high rpm, but still my economy was bad, intown driving pensioneer style, i got 11l/100km outside town i have over 7l @100km/h /100km. And what was surprising me that this turbo diesel has no black smoke totaly. This engine has no MAF sensor.

But my old friend told that guys at the car service found one car has some modification - instead of the intake air temp sensor the plug had wires and resistor atached to it for better perfomance and mpg. Then i got an idea to check and test it on my car. In autodata i found that my IAT sensor has resistance 5960-6030ohm @ 20C temp. I measured with multimeter in the roomtemp, and it was correct, i blew it with hair fan, resistance is droping down. So what i did, i took resistor witch had 10 000ohm and put in the plug, leaving the iat sensor in the intake alone. I think that 10kOhm resistor will make ecu think that air temp is lower than orginal IAT is telling and will make diesel/air mixture more ritch. Then i made a test drive, and car became totaly diferent, huge torque at low rpm, still no smoke, but car is perfoming much better, since now is less than a week, so i cannot tell the mpg, but i thing it will be a bit better. But the question is for me now, as i did it only for test purpose: how can i find out what is the "right diesel/air mixture" for this engine, or when its the right ? Other thing,i found that IAT sensor is oily, this means oil was comming thrue the intercooler up to the intake air temp sensor.
Could this oil make iat sensor measure incorect temperature ?
other question how much oil could be in the intercooler ? :
i will need to take it down and clean with jet fuel.
So what i'm interested how can i calculate or improove my mpg via IAT sensor adding some resistance, or POT with regualting ? how much change in resistance in IAT sensor are while driving since cold engine till hot ? i cannot measure it while driving...

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