I meant the 4 wires that required on the backside not all the extra mods that are optional. But yeah, a whole new MS specially designed for the miata sounds alot like a MSPNP with a proto area...

AND
I go to Rose. (stop reading here if you don't care) Which none of you have heard of, but it's actually a top ranked engineering school. For those younger forums members (if there are any), it's the best school you can go to if you are really serious about being good at what you do (much better than PurDON'T). www.rose-hulman.edu

This sounds like a very interesting concept especially if you include the A/C circuit

It seems like the hot side of the fuel pump is switched by some relay somewhere which is triggered by the ignition. The ground side is switched by the AFM. It seems to me that an easier solution than tapping the FP wire under the dash and having the MS switch it would be to just jump the fuel pump on the diagnostic connector, so its always on when the ignition is hot.

Is there a reason I shouldn't do this?? (I can't think of any)

http://www.boostedmiata.com/technical/fuel_control.jpg

http://www.boostedmiata.com/technical/FuelPump.gif


Diy was able to do something to get it working....im too stupid to understand what it is.

I figured out how to do the fuel pump from from the ECU connector!!! (for NA's)

DIY removes the ST SIGN fuse from under the hood which isolates the circuit opening relay from the starter. There are two coils in that relay one of which has a connection to the ECU. The one that normally turns on the fuel pump doesn't, but we can just use the other one. Then everything will be happy.

Can you explain that for me...

i see two inputs on the lower coil: one from the starter and one from the ecu (1c) both positive. Then the positive to the other coil from the ecu (1B) and AFM the ground.

The MS grounds the signal right? So you remove the fuse to prevent battery from seeing the MS circuit...then what, the bottom coil has two grounds then, and the second coil has a positive and missing a ground from the AFM....dont' see how that will trigger the solenoid.

I am very interested this, as I plan on going MS DIY myself soon (within a year), however have just started my journey, still have a lot of reading to do. I also have a 1996 so my car could be a good candidate for an OBDII board.

BTW, you asked if anybody in here is an EE. Well, I am, but I am sure I am not the only one.

You don't ground the other side of the bottom coil, you give it 12V from the ECU. The current will travel from the ecu (through a resistor), through the coil and out to ground. This should turn on the fuel pump.

I think the OBDII plan has been nixed due to to legal issues, plus I don't really care about it since I have a 91. It probably wouldn't be that hard to implement. Its just a special serial protocol. Chips exist that convert RS-232 to OBDII and vice versa. There is a lot of information available if you are interested, just google it.

Hey Brain,
Looking at the first pic you posted, it appears the ecu needs to pull the STA circuit high (pull up circuit in the MS) via the 'V' labelled trace with teh 11 in the circle.
You would then need to remove the STA fuse so it doesn't blow if the MS grounds the connection (for example if you are flashing the ECU).

Cheers
Nuno

Well, here we are, the pictures. Yes, I am a little embarrassed about how messy everything is on the backside.

http://img120.imageshack.us/img120/3...ontsidevp5.jpg

http://img120.imageshack.us/img120/7720/backsidepf5.jpg

That is why I'm so fired up about building a new mainboard...


Well, the mods that you see on my board are:

1- The "usual" twin spark outputs, with 100 ohm pullup instead of 1k.
2- Abe's dual comparator circuit for CKP and CMP input.
3- PWM idle
4- Relay driver for fan
5- Baro MAP
6- Knock input
7- Table switching input
8- PWM driver for EBC
9- Relay driver and PWM driver for WI

Of these, #1 thru #4 are absolutely necessary for operation, and I consider #5 thru #7 to be almost essential as well, in terms of making the MS equivalent to a "real" ECU. #8 could be considered "optional", and #9 is really the only one that I'd consider superfluous.

Observant observers will note that there is one dead wire on the board- it's got a pullup resistor on one end, and the other is cut an goes nowhere. This was part of the old trigger input, and I forgot to remove it completely.


Safety.

Now, I admit that when I was using an EMU and I removed my AFM, I jumpered the fuel pump on. The point of having it controlled by the ECU is that if you get in a crash, assuming the engine stalls then the fuel pump will shut off. You don't want to be in a severe front end collision that ruptures the fuel system and have the fuel pump happily continue to empty the entire contents of the tank out into the engine compartment.

On a 1.6 you have two options. You can tap the wire that goes from the AFM to the COR and provide it a closure to ground. This allows you to use the "stock" MS fuel pump driver circuit. Or, you could invert the circuit (making it a +12 active-high output) and connect it to pin 1C of the ECU, which is technically supposed to be the Start Signal input. This is how DIy does it, and as yertnamreg1218 points out, it's why you have to pull the ST SIGN fuse.

The one that goes to the ECU 1c is, in stock form, an input to the ECU, not an output from it. It tells the ECU that the starter is running.

No, it pulls it up to +12. The other coil in the relay goes totally unused.

yertnamreg1218, I've hijacked your thread, and I apologize for that. I'll take this back over to my 4.0 thread.

duh, wtf I'm stupid.

I like the hijacks they add flavor and culture to the thread. Not to mention I like talking all this stuff out before I go designing something. I'd prefer it to work the first time.

Joe I take back my earlier comments about wiring the MS, you win...(damn that is alot of wires)

I don't think I've heard about the comparator circuit for the CMP and CKP. Could someone enlighten me.

More and more I think you are right about a total redesign...

I just finished up the 90-93 schematic for the board. Its not everything you guys asked for, but it will make the install a whole lot easier than a DIY and approx $200 cheaper than a PNP. I still have to layout the board, but that shouldn't take to long because I only added a few components from the first layout I did. I'll get this board prototyped probably by the end of the week and I'll let you know how it works out.

The layout is done and the I've handed off the gerber files. The guys at school will probably do the board at night so they don't have to listen to the mill, so assuming they start it tonight (and do a side a night). I should get the board back in my hands thursday or friday. Assuming I get the connectors in by then I should be running on the prototype by this weekend.

Here are the final specs on the 90-93 board:

approx 3"x5"
Fuel Pump fix
AC fix
Fans mod
EBC

No proto area, but all signals are brought out the MS connector and the important ones are brought out of the ECU connector to breakout points.

Here is a picture of the layout:
http://img178.imageshack.us/img178/2...taboardet0.jpg

Got a schematic for that we could see? My eyes hurt from trying to follow all the traces in that proof.

umm already been done...

http://tuner-deals.com/index.php?mai...b1ce704d15223c

Closeout price is nice

Edit: but the connector looks different in the purchase website. The right connector was pictured on msextra
http://www.msextra.com/viewtopic.php?t=27404

Edit (again) found it witht he miata connector
http://tuner-deals.com/index.php?mai...b1ce704d15223c

I have a schematic, and would be happy to post it. However, my computer shit all over itself last night. It tries to boot, bsod's for a fraction of a second then reboots. Sadly all the miata stuff I've been working on is on that computer. Our IT people at school are fixing it, and I should have it back soon. I'll post it when I get back.

Ampz,

I hadn't seen those before. Those are nice, but its still not a great solution. The board I'm building will plug in directly to the megasquirt (or using a standard DB37 cable), and the car's wiring harness. All you have to do is solder on the components and plug it in.

Hope you work on the 99-00 after you get this one working. You'd have a real chance to hit a sweet spot in an underserved market (beat DIY to the punch). Currently, 90-97 have plenty of options for relatively cheap solutions with MS and others.

Hope your computer problem is solved quickly. Minimally, I hope you can salvage the data on your hard disk!