1987 Iroc TPI 350 - Turbocharged T70 turbo with Megasquirt II 3.0
Turbocharged 1987 Iroc TPI 5.7

August 3, 2009 - After wasting a lot of time and money on a 7730 ECM conversion and switching to the Code 59 bin,  I ended up going to the Megasquirt II 3.0!  Basically Code 59 worked great until I installed my Precision Turbo 65 lb injectors and then everything went wrong. After two months of troubleshooting all I ended up with was a terrible surging problem.  I also did not like having to deal with a Romulator and unstable on-the-fly updates which left me stranded in a busy intersection once!  As well, the Tuner Pro RT software had a bad habit of crashing, requiring a reboot on some occasions. The Megasquirt has been a great experience so far!  I have about $400 total in it since I bought the kit version.  That includes a nice harness that was $60.  The kit and harness came from http://www.diyautotune.com/ . They have great customer service!

The contents of the Megasquirt kit were nicely packaged and organized in tiny bags labeled by instruction step. You do need a decent soldering iron (and skills!) and some basic electronics knowledge before building one, but the instructions were quite clear and could be followed by a novice. You can also see the harness at the top right.

About half way through the build, it is beginning to look like something.  I am installing the transistors across the heat sink along the metal strip at this point.  Some components will be left in the bags, depending on various choices you will make along the way. Some components are just extras that wouldn't be used at all.

Finally the base build is completed. Total time was about ten hours to this point. Time to start on that harness.

The original OEM harness is first removed, along with the factory ECM.

I temporarily ran the new wiring as if it were installed.  I am installing the Megasquirt in the same place as the factory ECM, and left a little extra wire there to make it easier to work on the MS while still hooked up.  You can see here they give you plenty of length to the wiring. This is where we start cutting various wires to their appropriate lengths. I can't say much about this part.. it's alot of work and you need to pre-plan everything correctly, or you'll end up with a bunch of spliced wiring!  Also note the harness wires come with their function printed every several inches!  Made life much easier than just using colors.

Several days and no photos later, here is the first part of the MS harness. A friend of mine has the tools and pins to build GM weatherpack plugs, so all of my sensor wiring is unspliced!  I also made all new injector pigtails and Y'd them together just like the factory does it. The bundle of wires near the plug will connect to several things, including the factory harness under the dash, the PLX wideband O2 analog output and ground. The separate gray wires next to those are the injector +12v wires that will connect to the factory harness by the ECM.  The remaining wires with no connectors will go to the distributor, knock sensor module, IAT sensor and I don't remember what else since it was months ago now! LOL

Here is where the original harness gets merged with the MS harness.  All of the fan control, fuel pump control and ignition power wiring is now in place. You can see at the bottom right several connectors now.. not just the MS plug but the factory harness plug that provides injector power and more. Also note at the right center,  I retained the factory bypass plug for setting the distributor base advance. The white wire bundle near the top center will be going to the knock sensor when I get around to that project.

All of the injector harness and sensor was ran under the intake plenum to keep things looking clean. Before anyone asks, YES that is REAL heater hose from ORielly auto, NOT waterhose!  I've had a lot of people ask. You can see here I also have the stock passenger side exhaust manifold back on after doing some test fitting of the turbo manifold during the MS build.

Our kitchen table after finishing up the harness. Yes,  I'm still married.  The secret is to take her out to dinner every night, so she doesn't notice the mess. Also you can see the various tools and supplies I used to complete the harness. The car started right up and ran once everything was in place. The only problem I had was the fuel pump feed from the Megasquirt is opposite from the factory.  I added in a ground and swapped pins on the relay plug and it fired right up. Initial tuning to get the car drivable was under an hour and within a couple of days I had it running great. Now time to start on the turbo installation!

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