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SW20 Dash wiring notes for motor swap use.
Please note: The wire colors and pin locations for these signals to the dash can be found in our SW20 chassis harness video: There are numerous examples of engine swap MR2 including k series with fully operational factory dashes.
Tachometer: The Factory SW20 ignition was distributor based and the tach was driven from the coil. When converting to a coil on plug setup like the Gen 4/5 3sgte, 2GR , or K-series, we need to modify the tach signal. We are going from a coil driven signal to an ecu driven signal. You first need to decide if you only want to correct the tach in the dash or do you want to feed a correct tach signal to front half of the car. Things like power steering , a.c. amplifier, and ABS would prefer a correct tach signal.
Tach only: Gen4 resistor mod. This is a modification to the tach circuit board to correct tach reading for an ecu driven-coil on plug signal. Watch this video to see what is involved Link to Video
Tachometer signal to front of car: This really comes down to what ECU you are using. Anything based on a stock ECU will require a tach adapter such as MSD # 8920 or Dakota Digital # SGI-100BT. Aftermarket ECU like Link, AEM, ECU Master, Etc, have the ability to modify tach signal output built in. Follow the instructions of the version you are using. I provide tach wire color/location in the chassis harness video. Link to Chassis Harness Video
Speedometer: 91-92 USDM MR2 use a mechanical speedometer drive from the s54 or e153 transmission. Swapping to a transmission without a cable drive provision will leave you without a factory speedo unless you swap to an aftermarket dash display or perform the daunting task of converting to a 93+ cluster. Many have installed the 93+ speedo into the mechanical speedo clusters and ran external wires to power them. Most k series swap customers opt for the aftermarket display if using the k series transmission.
93+ USDM MR2 use an electronic speedometer and most aftermarket ecu as well as KPro have the ability to send the proper speedometer signal to the MR2 cluster.
Coolant Temperature: The SW20 uses a dedicated 1 wire coolant temp sensor that will need to be installed on the coolant outlet side of the cylinder head. This will be the transmission side of most 4cylinder. Beck/Arnley part#201-1220. Please note the dash has a sensor ground wire that runs to the rear of the car and must be grounded for the temp sensor to work.
Oil Pressure Light: SW20 utilize a dummy light and as such will continue to function as normal if wired to a grounding pressure switch.
Alternator light: Nothing special here. Connect to the normal alternator light output on your harness. This is the typical grounding type signal.
Fuel Level Gauge: These wires do not even run through the chassis harness and as such you need to do nothing as this will function as normal.
Check Engine Light: Connect to the MIL or CEL wire of the ECU you are using.
Turns/Headlight/Dash illumination: These wires do not even run through the chassis harness and as such you need to do nothing as this will function as normal.
Unused warning lights: Depending on deletions, options level, and upgrades you might now have numerous indicator lights that mean nothing. These include things light intercooler fan, oil level, power steering, cruise control, catalytic convertor, Etc. Simplest solution is to remove the bulbs.
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