500psi Line Sensor

[shaodome]

I'm having trouble getting getting the line pressure to read in Tuner Studio. I picked up the aem 500psi sensor for it. The details are here:

http://aemelectronics.com/files/instruc ... Sensor.pdf

When I turn on the line pressure sensor gauge in tuner studio it reads ZERO. Any suggestions? I figured at least initially it would be at least "reading" something from the sensor....albeit, not the correct value. I'm going to double check the input with a DMM in a few minutes here.

[Bernard Fife]

shaodome,

Did you actually build the input circuit (other users didn't do this and forgot about it when they went to implement a pressure sensor)? Have you measured the sensor's voltage at the sensor itself and at the 25x2 header? What code are you running? Could you post your MSQ?

Lance.

[shaodome]

OK, played it it some more tonight....

I didn't have the line pressure setting to "USE TWO POINT CALCS". Instead it was on USE TABLE. Once I changed that I started to see some life in the line pressure gauge. I'm using a 500psi sensor that reads on the curve found here:

http://www.internetwork.org.uk/aem/Pres ... 30-xxx.pdf

0.5v = 0psi

4.5v = 500psi.

at 50-70% dc on the line pressure solenoid, I only saw 18psi, which I don't think can be correct or the car would just slip in every gear, no?

Perhaps I should choose two closer points to get a better slope?

[shaodome]

Just thought about something....If I change it to the use two point calcs, I'm seeing ADC?

Code: Select all

an ADC count of zero is zero psi,
an ADC count of 1024/2 = 512 is 250 psi.

(note the 250psi at a adc of 512, which I think is what it should be on the 500psi sensor)

250/512 = 0.488 * ADC, which would be even worse if that was showing ADC. IE 18ADC = about 9psi.

Is there more clarification of what "use table" means????

[Bernard Fife]

shaodome,

"Use Pressure Table" means get the line pressure values from the 1024 element line pressure table (which has the advantage that it can be non-linear). See: http://www.msgpio.com/manuals/mshift/V41tune.html#gi

Lance.

[shaodome]

OK, that line pressure table is specific to that digikey sensor, which is basically hard coded. Gotcha.

I'm still confused though as to why it didn't work when I put in the 2 point calc?

[Bernard Fife]

shaodome,

Attached is some test code (and corresponding INI) that will narrow down the issue. If you could try this with the 2-point pressure calcs and post a short datalog and the MSQ of the settings in place while the datalog was made, it would help enormously.

Monitor_4144d.abs.s19

Test code.

(73.18 KiB) Downloaded 674 times

GPIO_MShift_4144.ini

(220.09 KiB) Downloaded 685 times

Also, if you are able to measure the sensor's output at both the sensor and the 25x2 header, that would be helpful. I don't know anything about your sensor, but the reference sensor provides a 0.5 to 4.5 V signal. If yours needs a pull-up circuit to provide a signal, you may have to add that to the standard circuit build.

Lance.

[shaodome]

I did measure the sensor and it is putting out voltage around 1v at idle and closer to 2v with some revs up.

I'll try this for you tonight Thanks for the prompt reply on this lance as always!!!!!

[shaodome]

I verified the sensor works. I just ran some alligator clips from the senor output wire to Analog 3 input on the MS3pro and set it up in generic sensors. It works as expected. So that's checked off the list.

I flashed the attached code and logged it for you. There are two logs. One that was just with the laptop connected to the GPIO and the other was logged through the MS3pro. You can find the Line Pressure gauge in the log to compare.

As the sensor is putting out a legitmate 0-5v range, I could imagine a pullup is NOT required.

[Bernard Fife]

As the sensor is putting out a legitimate 0-5v range, I could imagine a pullup is NOT required.

Shaodome,

Yes, that's correct, you don't need the pull-up if the sensor puts out a voltage signal.

From your log, it appears that the code is functioning as intended. However looking at the log the pressure appears to be responding to something, but I wonder if it is possible that there is an error in the INI that makes the pressure come out as 1/10th the actual value (so your actual pressures would generally be around 145 to 220 psi). I will look into this.

Lance.