Sensor data, just pulled from the car:

It's a 3 wire sensor: 5V, ground, signal. So the ECU is measuring voltage. Internally, the mechanism is resistance, but that is translated to voltage for convenience.

Thanks for explaining it. I was puzzled a little. Pretty clever measuring it in the car.

Don

Glad I'm rehabilitating my reputation after the cardboard in the intercooler fiasco. :)

Here are the pressure vs voltage characteristics for various A/C pressure sensors. The one you asked for is MT1247.

https://www.omega-usa.com/client/ima...ns%20Flyer.pdf

Thanks! My lab data was close enough, but I appreciate the engineering data.

I'll use the official data, rather than my experimental stuff.

Finally.

I bought a salvage yard E67 off a V6 Malibu, sent it to a fellow in Austin TX who flashed a 2013 ZR1 OS on it, picked up a special copy of HP Tuners (2.25.xxx, still in beta), and copied my tune from the crate motor tune, and wrote the calibration out.

Voila, PWM fans.

Finally.

Geez, what a bunch of walls to knock down!

Net: The GMPP crate motor E67 OS does not and can not support PWM fans or AC pressure sensors. You have to use a late model passenger car E67 or E38 and OS, and deal with all the extra equipment implied in that. I've got a bunch of work left to deleted all the DTCs that don't apply, plus puzzle out all the differences in the tuning tables.

Glad you got it fixed.

The question I have is this, Mikels reworked the E67 for the Lous Change car, and I thought that was a GMPP harness and ECM for the LS9, so what did he do that you didn't?

Thanks Donny.

Lou's car is an LSA, maybe that matters, but yeah, I've been wondering the same thing myself.

Yesterday, I transferred the tune from the old GMPP file to the new ZR1 OS tune file. I moved every single table, one by one, and did a complete audit of all the DTC codes and their behaviors. The end result was unexpected, in a good way.

I finally fired up the car, monitoring all the usual parameters, including fan desired/fan %/AC pressure.

With an identical tune (as near as I can tell) the car runs better. The idle is smoother, throttle response is better, TPS % at idle is better (27% to 19%), fuel trims are markedly improved, and O2 voltages are smoother.

There's no doubt the car runs better with the ZR1 OS than with the GMPP OS, with an identical tune. Oh, and the fans function perfectly. AC and ECT desired both work exactly as documented.

Anyway, after 4 weeks' delay, the project is back on track. I'll never use a GMPP crate controller or OS again. From now on, I'll make my own harness, and get my own controller.