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Discussion Starter #1
Hi All,

I am curious as to what others are reading at operating / running temps at the engine oil temp sensor as far as resistance goes?

Its pretty easy to take a small strand of wire, put it down into both of the harness side plug holes and plug it back on to the EOT sensor, then hook a multimeter up to that and go for a ride.


Trying to get an idea of what the EOT reads for a stock or close to stock setup that away i have a baseline.

It would be even MORE awesome, if you also had an engine oil temp guage, that away we can get data plots for temp vs resistance and figure out the curve of resistance the EOT sensor has.... Compile that info, make a graph, n boom, now we have a poor mans EOT chart.
 

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Do a search, you may have to go way back and search random tuning threads but I believe this has been done.. I remember someone plotting it at one point.
 

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The service manual also includes 2 different resistance/temp values. take a couple readings and you can figure out the beta value
for the resistor.

(and ofc i lost my entire post cause my inet is crap)

TL;DR: easy but only accurate in a small range eFunda: Theory of Thermistors
harder, but more accurate: fit a steinhard equation to it. 4 points, solve for 4 coefficients, done.

And once you do that, fit it up in a wheatstone bridge and hook it up to the pcv so we can have oil temps.
 

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Discussion Starter #6
Also did some digging

here the temps/resistance i measured on mine

20°C - 2.6
30°C - 1.85
35°C - 1.5
40°C - 1.3
45°C - 1.1
50°C - 0.92
55°C - 0.78
60°C - 0.68
65°C - 0.59
70°C - 0.51
75°C - 0.45
80°C - 0.40
85°C - 0.34
90°C - 0.30
95°C - 0.26
100°C- 0.22

as you can see, completly within specs
Using these values and my good ole trusty Ti83, we get an exponential function graph that "best fits" this data with a function of y=4344.013066*.9703536569^x


Extrapolating it out we get.

220*f/104.44*c = 187ohms
230*f/110*c = 158ohms
240*f/115.5*c = 134ohms
250*f/121*c = 113ohms
260*f/126.7*c = 98ohms


Granted this is some guestimation, but id say its pretty darn close.
 

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Discussion Starter #7
FYI, that function above seems to be pretty accurate.

I have not done testing with higher temps. But at 81.1*f that my digitial probe thermometer was reading when i dipped it down into the oil after the bike sat all night and day, the EOT sensor was saying 1980ohms. If you convert 81.1 to c you get 27.27*C ... pop that into the function and you get 1911 ohms. Thats within 3.5%!


I shall get more readings at higher temps as well.
 
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