bthomp Posted June 15, 2011 Share Posted June 15, 2011 So im getting ready to wire my car up and thought about going with no relay board option. I noticed some people have said that they wired up their car this way, but so many more people after that said to buy a board so nothing was really ever posted on how to. Now im asking how the people wired up their car without a relay board for anyone else that might be wondering how it was done. Im not saying that its the smartest or best way of adding MS to your car, just an option. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted June 15, 2011 Share Posted June 15, 2011 If costs of a MS relay board is a problem, you can always make up your own. Look up MS Posts by Cygnus. He did a nice self made relay board with pics. Personally I would not wire up a car without some type of relay and fuse board. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted June 16, 2011 Share Posted June 16, 2011 (edited) Look at this thread: http://forums.hybridz.org/index.php/topic/98694-glove-box-mounting-of-ms-and-fuse-box/ , That is how I wired my MS without the relay board. It takes more time and thought than going the relay board route but it makes things more "modular" in that you can add fused circuits or relays as you please where as the relay board is somewhat limiting in that regard. I liked the idea of hiding it all in the glovebox, and it has been working out great for me so far. A little off topic, but I would love to someday find a PCB company to make me a custom circuit board of my own design to replace the rather large power distribution blocks I am using. Edited June 16, 2011 by Cannonball89 Quote Link to comment Share on other sites More sharing options...
Tennesseejed Posted June 16, 2011 Share Posted June 16, 2011 I wired my car without a relay board. Didn't see the need to use one. Wasn't so much a cost issue, as a desire to keep things as simple as possible. I started by looking at the wiring diagram at http://www.megamanual.com/index.html (the V3 schamtic) and the EFI wiring diagram from the EFI Bible (http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf) The wires on the stock EFI harness are numbered so they are easy to trace between the engine bay and the pigtail at the EFI box. I located my MSII box where the stock EFI box was and then chose which factory wires to use based on thier use in the stock system, i.e, a ground wire, a battery voltage wire, a sensor wire, etc. In the end I made only one mistake and cut one corner. The corner I cut was not bothering about having my fuel pump turn off when the key is "on" and the engine is not running. On the stock system, the fuel pump relay switch is in the AFM. Since the AFM goes away with Megasquirt, so does the circuit. I could have designed something similar, but just really didn't care enough to bother. The one mistake I made was wiring the IAT sensor. The factory wire I used to connect the IAT initially received battery voltage when the key was turned on. Because the IAT sensors works by having 5VDC applied from the MS box, the added DC voltage cause the sensor reading to default to 70 degrees. When I put a DMM (voltmeter) on the sensor and discovered 15 volts, I realized what the problem was. Simple enough to grab another wire from the stock harness for a substitute. Quote Link to comment Share on other sites More sharing options...
akeboshi Posted June 19, 2011 Share Posted June 19, 2011 i also did not use a relay board. i just fiured out where i wanted to place the megasquirt box (in my case in the glove box) and ran all the individual wires to thier respective locations. i mocked it up that way took it out of the car loomed and taped it all up and reinstalled it again. i removed my dash to hide it all and installed my lc-1 gauge where the vent is on the left hand side by the driver door. i just grinded the vent thingy till my gauge fit then used rubber tape to secure it inside. very sleeper. i just used inline fuses from autozone, you know the kind that has wire on each end and you add the fuse size you want. it looks just like the harness in the diagram. if i were to do it again i would use the relay board. cheaper and eisier in the long run and you can make a harness for under the hood and a harness for inside the car and if you need to remove any sensors you dont have to cut and recrimp/solder. just my 0.2 cents marcus Quote Link to comment Share on other sites More sharing options...
misterZ Posted June 24, 2011 Share Posted June 24, 2011 (edited) ^^ that sounds like a lot of work. I opted out as well since you can wire to the stock relays... or what dexter72 said: "Look up MS Posts by Cygnus. He did a nice self made relay board with pics." I also see it as added trouble points with extra cable connections and like to keep things simple. Edited June 24, 2011 by misterZ Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted July 7, 2011 Share Posted July 7, 2011 you can see mine in my video i got the relay kits from a International Truck dealer @ $17 each. I needed a special crimper to crimp the terminals. I did my own because I needed more than 3 relays. Quote Link to comment Share on other sites More sharing options...
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