20vt conversion megasquirt wiring

Right guys had so many people asking me about the wiring i thought id give you a rough idea of what to expect

firstly the megasquirt has a db37 connector which you solder the engine harness into the below diagram gives you a rough idea


so whats needed supprisingly not much of the original engine harness is needed


ill do each item as i remeber please note each engine cod may have different colour wires in the harness i wont worry you with colours just basics

1, injectors pins  32 33 34 35

bank 1 = 32 and 33
bank 2 = 33 and 34

most people only use bank 1 i have all 4 injectors on pins 32 33 you dont need to pair them in any order and they will fire at the same time

injectors have 2 wires

1 12volt switched
2 signal wire

take all 4 12v wires and connect them to an igniton 12v switched this means they only go live when the ignition is on

then you could connect all 4 injectors to either pin or spread them across all for if you want for ease

temp sender

20v temp sendors have 4 wires

1 to the ecu
2 to the temp gauge with a 47 ohm resistor
3 to head earth
4 to dash earth

iat sensor

2 wires

1 to the ecu signal
2 to the ecu earth pin

tps(throttle position sensor


7 wires but you only need 3

1 to the ecu signal pin
2 to the ecu vref pin
3 to the ecu earth

you will need a multimeter to get the correct 3 wires from the 7 depending on which tb you use

more tommorow i need bed now

I'll leave this post here if you're going to carry on.  I'll move it to over to FAQ  once you're done  8)

bringing back for an update

as you all know the weak point on a 20v is the coil on plug packs

so i need some testing with variouse coils and found a peugeot 306 pack works the best with megasquirt

the pack has a 4 pin plug


coilpack

pin 1  Spark output A
pin 2  spark output B
pin 3  12v swiched live via fuel pump relay
pin 4  earth with suppresor block this bolts to the head

this pack is ideal to run 16v plug leads with in a wasted spark action so basicaly

spark A controls plugs 1&4 B controls 2&3 thus thr name wasted spark

the coilpack must be powered via the fuel pump relay or you will burn out the coil or vb921s ignitors in the ecu .

so when the ignition is switched on the ecu sends a tach signal to the fuel pump relay for 2 seconds to prime the pump once its finished it cut all the power to the coils and ignitiors :wink:

Origninal wiring kept

on my apllication i wanted to keep it as simple as possible so i kept the following

starter loom is seperate to the original engine so leave in place
alternator loom on the starter loom just splice one wire to alternator connector

as for the warning lights i found it was easier to get vdo gauges i run

oil temp
oil pressure

so ive disabled my dash warning lights you dont have to


then its a choice as to weather you remove the old engine loom or coil it up and cable tie it under the dash somewhere

i cut mine out as i wanted a clean install with no annoying wires popping up to say hello

i am in the process of making a loom that is a easy fit for the mk1 application with a minimun of 8 wires to connect

keep you all posted