Posted on 29/09/2013 at 16:11

Kitty Injection : Electronics

The "brain" of all the setup is a Megasquirt : I went with the MS2 with a v.3 board, i.e. with standard components, as opposed to the V.3.57 which is provided fully assembled with SMD components.

For those of you who don't know about it, the Megasquirt is an Engine Control Unit (ECU) able to deal with almost everything you can imagine : engines from 1 up to 12 cylinders, naturally aspirated or supercharged, staged/semi-sequential/full-sequential injection, wasted spark or sequential ignition, Dwell, NOS, lambda, water injection, additional air valve, etc... Obviously I'll use only a slimited set of these options.
The ECU is tuned with a PC computer, via a dedicated software (details to come in the "software" section). You can make modifications live to your engine setup, without even having to shut it down!

The Megasquirt takes in different inputs from sensors on the engine :
  • Crank/TDC position sensor (VR sensor)
  • Manifold Air Pressure (MAP)
  • Throttle Position Sensor (TPS)
  • Air Intake Temperature (IAT)
  • Coolant Temperature (CLT)
  • Lambda/Air Fuel Ratio (AFR)

Depending on these data the MS manages the engine : fuel pump, injectors, ignition, idle valve... And maybe a couple more on my setup! icone smiley wink

I bought the ECU from DIYAutoTune as a DIY kit. Not that difficult if you can handle a soldering iron (well, get a proper temperature-controlled soldering station, and a good magnifying lamp), but it still took me 12 hours to complete it! To be fair, it can be done in much less time than that, but I was doing it in parallel with a freind whom I had to micro-manage (his first PCB soldering experience! Come on Franck, you gotta install your MS now!). I guess this can be done in less than 6 hours ; the kit is very well made, each and every component is labelled in its own individual plastic bag, you just have to follow the build manual.
I strongly believe it is recommended to assemble/solder your Megasquirt yourself, not only for financial reasons, but it helps a lot to understand how everything works together!

I've made a couple of modification to the standard design (everything is very well documented for that purpose) of my Megasquirt : I've flashed the firmware to MSExtra (more options), I've added a transistor to control the idle valve (additional air, the original 1600i on the Mexico beetles had one), and I've wired two outputs for the wasted spark ignition coil.
I've installed the two transistors controlling the ignition coil in a dedicated box (Spark Box), bolted below the MS. It makes their cooling a bit better, limits the interferences, and prevents overpopulation inside the MS box (it's already pretty crowded in there!). Well, that's just my opinion...
In the very same spark box I install the three diodes that allow me to extract a proper signal for my tachometer (Tach Output).
The whole thing is then installed in the car, below the back seat, on the driver's side, on a set of silent-blocs.
OK, electronics, check... Now, let's connect it to the engine, right? icone smiley wink
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