Megasquirt Installation Continued...
The case was bought from RS Components in Penrose, Auckland, New Zealand, price was ~$25 inc GST. Stock Number 3439928. The case was a reasonable fit, just a little too long to be snug, and perhaps a little too tall. But the height may come in handy when/if I fit extra boards in. I just mounted the ECU on 9mm spacers from Jaycar, and ran long screws between the board and out the other side of the case, with a star washer and nut on the other side. I just used 4, 2 in each connector (DB9 and DB37). However, since putting the vacuum hose on, and having forgotten to drill the vacuum hole, I will probably need to take the board out again, and bolt down the MAP sensor. Pictures to come LOOM: I started with an AW11 Loom, because one was handy cheap. However it really is best starting with a RWD loom for a 4AGE, as that way you don't need to lengthen any wires. I had to lengthen a number of wires, but luckily I could find some colours that were pretty close. I hope to put up a wiring diagram of my current Megasquirt loom, as it's pretty small and not too tough. The injectors have 2 wires going to them (2 wires, tee'd into for each injector), a positive feed that is powered by a relay when the ignition is turned on, and a negative feed, which is run to the 4 injector earths on the ecu, and grounded when fuel is needed. I am using high impedence injectors (14ohm) out of a Nissan RB20DET, these are about 280cc, or about 310cc at 2.9kg fuel pressure. With high impedence injectors the wires can be slightly smaller in size, and I could run them all into just 2 main wires. Thus the loom decreased in width remarkably. THIS INFO IS INCORRECT - SEE UPDATE 10/2/04!!. Also, most of the sensors have the ground looping through the loom to various places, sometimes back to the 4AGE ECU. I just ran all grounds for the sensors to a spot on the manifold, I think there was only 3 grounds connected here. The 4AGE TPS has 4 wires; 5v, idle circuit, ground, output(varies with throttle movement). So you only need to run the 5V and the output back to the Megasquirt. So, TPS, IAT (intake air temp), CLT (coolant), injectors and ground were the only wires on the fuel side. NB: No cold start injector is used, MS just bumps up the main injector rate to make up for cold starting. On the Exhaust side, I ran the tacho of the -ve of the coil, and an O2 sensor wire. I took the time here to run other wires and powers through the conduit I had laid out. Good idea to use conduit everwhere, rather then just taping up loom. Thanks Stu for helping with the final tidy up and mounting of the ECU in the car, as I was really starting to run out of momentum.
UPDATE -- 10/2/04
I had initially wired it up with one power, and one earth for the injectors, with the earth connected back to the 4
output pins on the MS ecu. This is as per a bluetop 4AGE computer, which I assume runs simultaneous injection (all
at once). However, I believe this caused me to fry U7, which gets a signal from main chip, inverts it to power the
transistors, that ground the injectors. In other words, if this is no good, then you've got no fuel. Or, in my case,
100% duty!. The output pins of U7 had short circuited, and thus the injectors were ground all the time.
So, when wiring up the MS, run it as per the MS wiring diagram, and run a ground from 2 pins of the ECU to 1 pair of
injectors, so you need 2 ground wires. If you've got high impedence injectors, then the current is stuff all and you
can a lot skinnier wire then that used for the standard low impedence injectors. To make it easy, use the same gauge
(wire diameter) as the plugs/injectors you are going to be using.
Now running the turbo setup, with CA18DET injectors which combined with 2.9kg fuel pressur are about 445ccs.
Injectors had to be filled so they fit in the RB20DE plug, but the side outcrops on the injector still look into the
plug.
UPDATE -- 23/3/04
I'm getting faint tacho spikes when the car is cold. The R10 resistor which takes the tacho feed from the coil
negative was getting too hot to touch too. I've increased the size of this resistor to 480Ohms, and it's a lot
cooler, and spikes have been reduced a bit. But I'm still not happy with it. I will change the dizzy->ignitor wiring
to be shielded and see if that helps. I've also got the DAVE cap to try as well.
Currently my TPS Threshold is highish at 1v/s, which I'd like to lower, but that means running a shieled TPS line
all the way back through the loom, and it's a bit of a mission at the moment. Something I recommend for someone
starting out though.
UPDATE - 3/05/04
The Dave cap and 1k Ohm of resistors for R10 fixed my tach jumps, and it's made the car much nicer to drive when
cold. Haven't been able to lower TPS threshold yet, maybe on the next motor I'll replace that wire with a shielded
one.
