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Forum nameEngine Management Systems & Controllers
Topic subjectRunning MSnS v3 Board as FULL Standalone (No Spikes)!
Topic URLhttp://forums.2gnt.com/dcboard.php?az=show_topic&forum=54&topic_id=2549&mesg_id=2549
2549, Running MSnS v3 Board as FULL Standalone (No Spikes)!
Posted by WickedESi, Dec-31-69 05:00 PM
I'm going to be slightly brief with this because I can't wait to go drive around some more! I finally got it working *perfectly*!

Set up the board and software for the standard 420a setup:

Board Mods
- Replace R12 with a 1K (1/4 watt) resistor (DEPENDANT ON STANDALONE SETUP)
- Remove Jumper from OptoOut - Tsel
- Build VR Circuit, If not Already Done (A filtering idea that came from Corbin)
- Jumper OptoOut - VrIn
- Jumper VrOutInv - Tsel
- Adjust hysteresis pot (R52 near middle of board) all the way to 0 (turn counter-clockwise till clicks)
- Adjust crossover pot (R56 at bottom of board) all the way 0 same way as above
- Turn R56 clockwise 7 turns (more on how to tune these later on)

- Build the tach output circuit (to drive your stock indash tachometer)

External Wiring Setup
- Setup a relay to power the MegaSquirt when ign. on and cranking (make sure it's fused) using the ignition switch signal at the ECU, and also send the +12v from this relay to the ASD circuit as well (flat pin at ASD relay), and scratch the ASD relay. Your relay/wiring to the ASD circuit MUST be able to support 30 amps!!!

This wire powers the coil, injectors, and alternator generator field.

- The wires I ran to the crank sensor is a shielded pair. Availible at Lowes/Home Depot as intercom/security wire on the rails they have. I ran the crank sensor signal on one wire, 5v+ from the MS on another, then the sensor ground on the shield (I know there are even better ways to do this, but I believe this is the most practical). I used the same 5v+ that powers the opto circuit to send to one of the unused wire input/outputs on the v3 board.

- I setup my own relay for my walbro fuel pump to get power directly from the battery. The MS outputs a ground signal to this relay. I highly recommend reading the fuel pump setup in the MS manual and noting the importance of putting a inertia cut off switch on it, in case the worse happens.

- Send the tach output from the MS to your tach wire under the dash.

- IAC control includes blocking off the IAC housing or filling the IAC motor with JB weld. Adding an adjustable throttle stop. Then you can add a fast idle valve with vacuum lines the MSnS can control. I currently am just using the throttle stop, then again, it's really warm where I live.

- To COMPLETELY remove the ECU you'll need to install a voltage regulator on the field wire to the alternator. I can post a diagram (from the FSM) on how to do this if you're actually intrested in it.

- Run your power/grounds to your sensors that need it if not providing from the stock ECU.

Tuning the MS Pots
- To tune the crossover point (R56) disconnect your fuse on your ASD supply wire. Crank the car, turn the pot 1 revolution clockwise till the crank RPM dissappears, then note how many it was in that direction. Then do the same in the other direction, then put it in the middle.

- Leave the hysteresis pot at zero to 1/4 turn for the most stable signal. If you happen to get any noise crank this clockwise until it vanishes (too much and your signal will dissappear completely).

If you have questions and have already done your homework, ask.
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