IAT Transfer curve LS3 to LS1

[DSteck]

There's no other way to read voltage across the thermistor. Without the pull up resistor, voltage across the thermistor would always be the reference voltage.

[RonSSnova]

Do you have a schematic for these PCM's? It would be interesting to see how the circuitry for the temp sensors is configured.

[RonSSnova]

I am good buds with CTD.
I verified the 5v with no sensor plugged in. Replaced the sensor with a 5k pot, and adjusted for 2.5v. Measured the pot at 2500 ohms.

I could hook up hpt and get a resistance/temp reading I suppose.

[Jabbott]

That works too. Pushing the numbers around between 2450 and 2550 changes where it fits better. 2450 seemed to have a better overall R^2.

The actual pull up is 2490 though. We measured it on the ECU.

[RonSSnova]

Ha! I better send my ohm meter off to the natl. bureau of standards for calibration! :-)

[DSteck]

The actual pull up is 2490 though. We measured it on the ECU.

Good to know.

[LSxpwrdZ]

Good info to know, still appears the back calculation I did was pretty close...

[MikeOD]

If anyone is curious...here's what I got...a little different than what was posted above, but no much. The 0 and 100% values are just the min/max allowed in the table since I actually calculated -48.8 and 345.9 for those.

Gen 4 IAT on Gen 3.jpg

[ctd]

MikeOD how did you arrive @ your values? Nice

[MikeOD]

Converted the gen 4 axis to % based on the 2490 ohm pull up resistor that Jabbot said he's physically measured in the PCM.

After that I graphed the Gen 4 temperatures (from my LS3 Camaro calibration) versus % in Excel and put a trend line through it. Best fit I could find in Excel was a 6th order polynomial. After that I had Excel output the equation to the most resolution it could.

Once I had that equation, I popped the Gen 4 % numbers back into it to see how close I was with the calculation (mostly within 3%, one cell was just under 5%), then I used the Gen 3 axis numbers with the same equation to get the results I posted.

I'll put the Excel sheet up when I'm at my PC. I'm on my phone now.

[ctd]

I'll put the Excel sheet up when I'm at my PC. I'm on my phone now.

I would like to give this a try this weekend & I will post up results.

Tx's

[MikeOD]

I would to give this a try this weekend & I will post up results.

Tx's

Sorry!!! I forgot to post this last weekend. I'm not saying it's the best way to do it...it's just the way that I knew how to attempt to do it.

[ctd]

Tx's!

[ctd]

LS3-LS1 IAT transfer corrected -4% from calculated.jpg

Results, I let this settle for a couple of hours. The heater will skew quickly, .96% of the table. Same as before I had the scanner logging prior to plugging the MAF in.

[MikeOD]

That's with the table/spreadsheet I posted? Nice.

[ctd]

Yes it was, I multiplied your original by .96% & that is the result. A 3.8% error to the ECT & External temp sensors

[MikeOD]

You multiplied the whole table by 0.96? Post up what you're running for values.

[ctd]

Labels 0.00 6.25 12.50 18.75 25.00 31.25 37.50 43.75 50.00 56.25 62.50 68.75 75.00 81.25 87.50 93.75 100.00
Inlet Air Temp 272.61 216.57 160.32 133.04 116.94 103.51 89.45 75.31 62.09 50.98 41.77 33.12 22.58 7.88 -11.59 -33.11 -38.38

[MikeOD]

Google Sheets is able to fit a better trendline than Excel, but I'm still trying to figure out how to get the equation back from it with enough resolution to make it useful. The r^2 value in sheets is basically 1, but it's not sharing enough coefficient data, so calculating back goes bananas.

[DSteck]

You won't find an equation that really fits. It's better to visually line up the break points.