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e3baroinputworkaround [2009/09/22 14:53] (current)
twdorris created
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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 [[ECUInputData|buffer circuit]].
 +====== Process ======
 +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 ยท Last modified: 2009/09/22 14:53 by twdorris