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EVO1-3 Baro Input Workaround

The baro input of the EVO1-3 ECUs may not be compatible with aftermarket sensors. These ECUs have a 3.3K ohm pull-down resistor (R27), which may (probably will) put more load on the sensor than it can drive properly. For example, a GM 3-bar sensor can only drive this input to 1.76 volts at maximum pressure. The GM 3.3-bar sensor seems to have a bit lower output impedance and will drive the baro input a little higher, but it's still unsuitable.

Short of removing R27 from the ECU (described below), the EVO1-3 baro input is suitable for use only with very low impedance sensors (even a 50-ohm output impedance will produce a little over 1% of voltage offset). Since most sensor designs have a resistor in series with its output for protection, the EVO1-3 ECU's baro sensor input is probably not suitable for use with most sensors.

NOTE: Instead of this process, you can also consider using the buffer circuit.


If you're really looking to maximize inputs, you can consider removing R27 from the topside of the ECU board. Best to use a couple small-tip soldering irons for this. Heat 'em up, apply one to each side of the resistor and slide it right off. I'm including a picture of the location of the resistor of interest below. Once you have done that, you can use either the baro or the intake air temp inputs for whatever you want.


e3baroinputworkaround.txt · Last modified: 2009/09/22 14:53 by twdorris