Sharing oem sensors

[warp21]

Can the Microsquirt module share oem temperature sensors with the factory ecu? It looks like I'd have to lift R7 and R10.

[Matt Cramer]

Depends on how exactly the factory ECU behaves. I take it you've seen this link:

http://www.megamanual.com/v22manual/sharesen.htm

[warp21]

Yes I have. I've done it with the MSII PCB 3.0 and it worked fine. I didn't know if there was a way other than removing the resistors.

[warp21]

I have one more question. Would it be possible to share the factory map sensor signal assuming that I could get accurate kpa vs voltage values?

[Matt Cramer]

Yes I have. I've done it with the MSII PCB 3.0 and it worked fine. I didn't know if there was a way other than removing the resistors.

You could possibly do something with an op amp and a voltage follower circuit as well.

I have one more question. Would it be possible to share the factory map sensor signal assuming that I could get accurate kpa vs voltage values?

As long as it's voltage based and not frequency based, yes.

[warp21]

Does this look like correct? If so do I calibrate the sensors just as if the factory ecu was not there?

[Matt Cramer]

That's about what I had in mind.

[warp21]

Awesome, Thanks! I really didn't want to lift a surface mount resistor.

[warp21]

I used this on a spare MS I to test the accuracy of the circuit. I have a factory ecu with two of these LM741 circuits, one tied to the coolant sensor and one to the intake sensor. The MS is calibrated to work with the oem sensors and seems accurate. If I have the MS hooked to the sensors by itself the readings look OK but once I tap into the op amp output they read really low. I'm using the 5v from the factory ecu to power the op amp. Should I be using the 5v from the MS?

[Matt Cramer]

I used this on a spare MS I to test the accuracy of the circuit. I have a factory ecu with two of these LM741 circuits, one tied to the coolant sensor and one to the intake sensor. The MS is calibrated to work with the oem sensors and seems accurate. If I have the MS hooked to the sensors by itself the readings look OK but once I tap into the op amp output they read really low. I'm using the 5v from the factory ecu to power the op amp. Should I be using the 5v from the MS?

I'd definitely use the MS 5 volt. Is the voltage different on the input and output of the op amp?