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About the reading going from 190 to 188 and back to 190..
Imagine, the temperature is 189.1 (it likely gets rounded to 190) then it reads 188.9 - it rounds to 188.
No mystery or anything "odd" to me. Just remember back to the day when gauges were "analog" and you could NEVER have known the actual temp just that the gauge was between 180 and 200....
This isn't like your bank balance where the numbers had BETTER not change...
Over a 24 hour cold soak, EOT, ECT, IAT, TFT should all equal ambient. Probably include the wiper fluid as well... LOL.
In practice though, ambient isn't constant.. Once the sun come out in the AM, ambient begins to rise and so do the fluids/air around the sensors all at different rates. +/- 2 degrees (or 2.8) wouldn't bother me, if your ECT to EOT was 14 vs. 16* I'd not feel better (or worse) having 1 over the other.
When you realize even the speedometer is off by 3-5 MPH at highway speeds it becomes necessary to take stuff with a grain of salt.
The main reason I am asking is with the 15 delta rule 2.8 degrees could mean a lot. If you are reading a 15 delta when it is actually a 12 delta an oil cooler could be replaced prematurely. Look at it this way too, if an owner has a 2 degree delta and it reads 5 delta he is not aware he has 6.0L bragging rights.
I use fWT to read the coolant temp. It reads in increments of 1. Sometimes my ECT will be 196 and fWT will be 197 or 195. And rarely if ever have my coolant/oil temps been the same after a 12+ hour cold soak. They are always close, but not the same.
In practice though, ambient isn't constant.. Once the sun come out in the AM, ambient begins to rise and so do the fluids/air around the sensors all at different rates. +/- 2 degrees (or 2.8) wouldn't bother me, if your ECT to EOT was 14 vs. 16* I'd not feel better (or worse) having 1 over the other.
When you realize even the speedometer is off by 3-5 MPH at highway speeds it becomes necessary to take stuff with a grain of salt.
We could place the rig in a climate controller garage for 72 hours and test. That is what NASA would do! LOL
Just joking. These sensors are not the most accurate reliable things in the world when manufactured, not considering how the thousands and thousands of heat/cool cycles effect their accuracy, so even of the sensors were closer in readings there is still the possibility they are off.
For example, what is the one reading 2.8 higher is actually closer to the real temp and the lower reading is inaccurate? What if they were both off and the readings were closer.
In this case, close is close enough for me. I am more worried about bad fuel, hpo leaks and ficm voltage.
We could place the rig in a climate controller garage for 72 hours and test. That is what NASA would do! LOL
that's funny...
I read this thread yesterday so out of curiosity I checked mine this morning. I'm also at 2.2 degrees off oil being higher. My sensors are less than a year old.
Keep in mind the SG2 (or whatever ODB2 device you use) also does math that "rounds" and has a formula to convert the PID value into a reading to display..
The ECT sensor might report it's 100.9* F
The EOT sensor might report it's 101.1* F
The SG2 (or equiv) does math and rounds to even temps.. resulting in
100* for ECT
102* for EOT
even though the sensors are reporting within 0.2* of each other..
I just checked my Scangauge and the EOT reads 3.6 degrees higher than the FWT. TFT and IA2 temps are all within 1 degree of the FWT. Could be why I have always had a higher delta, usually around 9 or 10 degrees running solo. Sometimes I have seen it go to 15 when running solo but never more.
On another note, I set the EOT at 2 positions at the same time, and they don't always read the same. They vary by .1 or .2.
This was done a 14 hour cold soak. I checked last night after a 3 day cold soak and the EOT was 2.8 degrees higher than the FWT.
Last edited by Tennesseepowerstroke; Jul 26, 2015 at 10:17 AM.
Reason: Added cold soak times.