Megasquirt Update, with PICS Options

[yarin]

I Was about to dig up my old thread from two months ago... but I felt some of these pics deserve there own thread.

I'm really moving along on my upgrade from carbs to MS. I should be able to power up the system this weekend and crank it the following weekend.

I chose a rather different approach to my install, a combination of logic, simplicity and durability. Please give me your input. For those who aren't familiar with MS go to www.megasquirt.info and www.msefi.com (forums).

I bought all of my Megasquirt parts from DIYautotune.com. Excellent vendor, i suggest doing business with them for anything.

What's left:

finish db-37 connector
connect all wires in relay box
mount intake plenum, connect DIY PVC intake
install gas tank
checked double check and triple check all fuel connections and wiring
configure MS
crank!!

Here are pics:

[jsteele22]

QUOTE (lapuwali @ Mar 29 2006, 10:50 AM)

I'm also NOT going to be using the zillion ground wires run through the DB-37 all the way out to the main connector, but will be joining them to one screw post inside the big case, which will then run to a single 14g ground wire to be run to the big case (metal, so it should provide shielding) and then to the engine case.

A zillion might be a few too many, but you definitely don't want to skimp on ground wires in the main cable. For purely DC currents, it really doesn't matter where the ground current runs, as long as it makes it where it needs to go. But for anything with high frequency AC components (including on/off pulses, like the ones to the injectors)) you need to have a ground path really close to the signal path.

Lets say the current in one of the injector lines changes abrubtly. This is going to cause an abrubt change in the magnetic field circling around that wire. Consider anonther wire right next to it : Lenz's Law tells us that an EMF is going to be induced in that nearby wire to try and negate the change in the local magnetic field. If that nearby wire is a ground wire, it's no big deal - a little current flows along it, and at either end of the wire the current spreads out into the chassis and becomes insignificant. But if the nearby wire is a signal (as are most of the other wires in that cable), then the induced EMF is going to be superimposed on that signal.

It might be that it won't matter too much, since the other signals are things that should vary slowly compared to the injector firing frequency, but I don't know if MS does any low-pass filtering on them or not. Safest approach, IMO, is to keep the ground wires.