matrussell122

iTrader: (1)

Been searching around tonight with the intent of building a small harness for the injectors and coils. Found the USCAR connectors for the injectors but where is some info on the ls coil wiring? That led me down the rabbit hole why not just do a whole engine harness with a bulkhead connector for both motors for easy swaps. Can anyone point me to a pinout or wire diagram for just the engine and point me in the direction of the proper plugs. The current motor is a 1.6 (boring 230hp) the motor the harness will be for is a 95 block with 02 VVT head. Probably wont run the IAC and going to run a mustang throttle body if that matters.

Wiring makes my brain hurt

Akina_Downhill

iTrader: (1)

What's important is the car's MY assuming you have kept stock harness.
Is it a 1990 na?
For the injectors, are you running Sequential?(i hope you are)
You'll need a constant 12V for them (white/red wire) and 2/4 wires from MS3 injector outputs.
For the coils, the wires you want are :
Brown/Yellow-1/4 Trigger
Brown- 2/3 Trigger
Blue- +12V
Black- GND
Yellow Blue+Black/white- Tach
You can find these plugged to your ignitor.
LS2 Coils Pin out:
A - Coil Primary Ground
B - Ignition low noise ground from ECU (ground)
C - Ignition digital signal from ECU (+5V)
D - +12V Supply to Coil Primary

So you could ground B to black wire, ground A to cylinder head, C to Brown/yellow+Brown for 1/4, 2/3 respectively and D to blue wire.
Or you could ground all the pins to cylinder head.
You will also want to connect the tach signal to your ECU appropriate pin.
1990 Wiring:

curly

iTrader: (25)

Correction, injectors should be yellow and yellow/black.

You'll want to run two extra wires, most recently I wired a Hydra to FM's adapter harness, which requires cutting the yellow/black wire going to inj 4 and the yellow wire going to inj 3 and connecting them to the final 2 injector outputs on the hydra. I forget if MS requires different cylinders.

Remember MS, Hydra, and most every stock ecu only controls the GROUND side of a circuit. Therefore, things like IAC, VVT, injectors, coils, VICS solenoids, etc, all need to be constantly powered. Generally by the white/red wire that runs everywhere in a Miata engine bay and is controlled by the main relay.

Some sensors, like the TPS, MAP sensors, oil pressure, and others have a ground and 5v reference pin, then the senor itself outputs to a 3rd pin, changing from 0V to 5V according to where, in the TPS at least, it is positioned. So be careful, these circuits shouldn't get the white/red 12v wire.

Other sensors, namely the CKP and CMP (CranK Position and CaM Position) have three pins as well, but are 12v sensors. So the white/red 12v wire again, ground, and then they output a signal any time they sense the trigger wheel on the cam or crank passes by.

The last type of sensor I can think of is temperature, such as air, coolant, and oil. These are either grounded through their body and have one pin, or have 2 pins, including a ground. The 2nd pin or single pin will give a resistance according to what temperature it's at. Most ECUs require this resistance to be "translated" into a 0-5v signal. They do this with a pull-up resistor to 5 volts. So you apply 5 volts through a resistor to that resistance signal wire, pulling it up to 0-5v, changing as the resistance changes.

I think that pretty much covers everything, with this basic info you can wire the entire engine pretty easily.

TL;DR-just apply power and ground to everything.

Akina_Downhill

iTrader: (1)

Injectors are indeed yellow and yellow black as seen on the diagram, and the acc +12v is white/red.
I didn't mention injector wire color codes though, i'm not following what is being corrected.
Very nice simple explanation of the various wiring concepts/sensors and how they operate

matrussell122

iTrader: (1)

The dilemma is that currently im running a stock 1.6 harness and going to a 1.8 vvt setup and would like to have a separate harness on the engine for both motors to do quick swaps if necessary. Then on the car side of things run a single bulkhead connector on the firewall.

And thanks for the replies thats exactly what i was looking for. Does anyone know where i can get engine connectors

Akina_Downhill

iTrader: (1)

Well, I don't see why you would want to go back to 1.6L ever again, but if you want it so badly, you could make 2 harnesses using a buckle connector.
Swapping in vvt motor with ms3 is a breeze(wiring-wise), you just have to make simple modifications(wiring up coils, cam and crank sensor, vvt, injector sequential wiring,vtps wiring if you didn't have already)

hi_im_sean

iTrader: (3)

paging albert

@afm

curly

iTrader: (25)

Sorry, missed the part where you were talking about ignition not injection.

Most of the critical pigtails can be bought from TSE:

Miata Wiring Pigtails

I really don't understand why you'd be swapping engines frequently enough to justifiy a new harness. I'd probably be cheaper to buy a sub 100k VVT motor as back up. They go for like ~$800, and a few of those circular mil-spec connectors, pins, and crimping tools will run you about $500, which doesn't include any time put into assembling it all.

matrussell122

iTrader: (1)

Awesome thank you for the link. As much as im on their site ive never seen the pigtails. And in all actuality the 1.6 will probably never go back in. i guess its just me wanting to have a super clean engine harness and engine bay instead of the factory harness that looks jumbles together.

As far as tools and other connecters i have a bunch of deutsch connectors and tools already

afm

iTrader: (3)

Here's a spreadsheet of connector part numbers -- look under the row for "LS coils," which has the part numbers for the appropriate 4F, index-keyed GT-150 3.5mm centerline plug and terminals for LS coils.

Note that there are multiple flavors of USCAR injector connectors. This spreadsheet lists parts for a Delphi variant, which uses GT-150 3.5mm centerline (not to be confused with regular GT-150) terminals. You may have a Ford variant, which would use different terminals.

The terminal / wire seal selections are based on the type of wire I used (18ga M22759/16 or /32). If you use 18ga TXL wire, it will use the same yellow GT-150 3.5mm centerline seals and the same terminals for the coils.

https://docs.google.com/spreadsheets...n8X4-7/pubhtmll