chucker

iTrader: (4)

Car 1994, stock. I’m installing MS slowly and (hopefully) methodically by way of the schematics here and Brain’s hugely helpful MS how-to.

The original goal was to go standalone since I have no A/C. In place are the miata ignition mods, the fan mod and the IAC transistor.

The following is a list of circuits that are wired to the stock ecu and would not be accounted for (or operated by) a standalone MS, as far as I can see in the available documentation.

Things I don’t care about:
EGR vent solenoid
EGR vac. solenoid
EGR function sensor
charcoal can purge
rear defrost relay
* vehicle speed sensor (what’s this? a/t only?)
steering pressure sensor

The well documented items:
a/c relay
condenser fan relay (a/c)
refrigerant pressure switch (a/c)

* The items which seem important to me but I’m not clear about (the reason for my post):
heater control unit (what’s this do?)
pressure regulator control solenoid (fuel pressure drop at idle?)
malfunction indicator (cel?)
TNS relay (wtf is this?)
3 (of 6) wires at the data link connector not accounted for
main fuse block (+12 to ecu) 1C violet wire (the only indicated hot lead in the MS docs seems to be the ecu-controlled +12 wht/red)


I’m starting to think parallel is the better strategy.

* Is there ANY degradation of signal accuracy when the signals (low voltage) are shared by two ecu’s? Just making sure….

* Would it be fair to assume there would be zero drawbacks to running parallel units?



* = my questions

Thanks again for everyone’s help

cjernigan

iTrader: (13)

No
Yes

You can do either on your 94 without issue.

Joe Perez

iTrader: (8)

Of the items you're uncertain about:

* Heater control unit is an input to the ECU (active-low) that tells the ECU that the cabin fan is switched to one of the three higher speeds.

* PRC solenoid... No clue, apart from a note that it's on or near the front of the engine.

* Malfunction indicator is indeed the CEL. It's an active-low output.

* TNS Relay is the relay that turns on the parking lights, side marker lights, and taillights. No idea why the ECU cares about this, but it's an active-high signal.

* The violet wire at 1C comes from the starter. It tells the ECU that the starter is cranking. MS doesn't need this- it infers it from RPM.

* No idea about your datalink wires. They're not important.

It's probably be easier to discuss the wires you do need to run to the MS for a standalone installation, rather than the ones you don't.

You need:
1- Power (switched only)
2- Ground. Lots of 'em. Big ones. Wired straight to the head.
3- CKP and CMP from CAS.
4- Intake and Coolant temperature
5- TPS (both signal and Vref)
6- Wideband O2
7- Fan relay
8- Fuel pump relay
9- Idle solenoid
10- Spark x2
11- Injector x2

Things you should also provision for while you're in there:
1- EBC output
2- Knock input
3- WI driver (relay and PWM) if you plan to use it

That's about it.

chucker

iTrader: (4)

Awesome Joe. Thanks.

I'm covered on the "needed" items... and the "uncertain" items have now been cleared.

Much appreciated.

elesjuan

iTrader: (11)

Do full standalone, with no A/C on a 94 theres NO reason to do a parallel install.

I'm running full standalone on my 95.5 so not everything will be identical, but I've got a spreadsheet that I'd be more than happy to share with you about my wiring on the car.

http://spreadsheets.google.com/pub?k...A0Z3FkV_q0Wjbg

Keep in mind that it won't be 100% identical, but you should get 99% with that sheet. I'm sure you know what the 1A, 1B, etc correspond to but just in case..


From Scott's DIY Thread.

Lastly, if you'd like to make yourself a PnP harness I have a spare 60 pin connector that I might be willing to give up. Good luck!