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Old 08-31-2008, 04:51 PM   #1
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Default Final Check and Parallel Harness Construction

I had to sit my Megasquirt assembly aside for a bit while I took care of a few things. Now I am getting back to and I'm excited about being nearly done. But, I am also stuck and getting frustrated with some remaining questions.

First, this is how I completed my assembly
1. Followed Brianeack guide except that electronic boost control was not added. Per the guide, I'm using a v3.0 board with a MS-1 processor.
2. Spark output #1. Wire run from the top leg of D14 (the flat side of the LED) to IGN. A 1K resistor was run from the same leg of D14 to the innermost leg of R24 (furthest from the DB9 connector). This should put spark output #1 on pin 36 of the DB37 connector.
3. Spark output #2. Wire run from the top leg of D16 (the flat side of the LED) to IAC2B. A 1K resistor was run from the same leg of D16 to the innermost leg of R28 (furthest from the DB9 connector). This should put spark output #2 on pin 31 of the DB37 connector.
4. Tach input. Two seperate wires run from IAC1A. The first is run to +5V (in the proto area) and has a 470 ohm resistor inline. The second is run to pin 11 of the MS-I processor (via socket pin on bottom of board) and has a 470 ohm resistor inline. This should pick up the tack input on pin 25 of the DB37 connector.
5. Relay control mod with the 1K resistor terminated to JS0, the banded end of the diode terminated to the banded end of U5 (on the opposite side of the board), and the output to IAC2A. This should allow pin 29 on the DB37 connector to trigger the cooling fan. Is it okay that I read about 1 ohm between JS1 and IAC1A? IAC1A is where the tach input comes through (see note 4 above).
6. Idle control mod with TIP120 replacing Q4 and mounted in place of Q16. The required diode was installed by picking up 12 VDC from the center pin of Q9 (attached to banded end of the diode). The non-banded end is terminated to one of the holes left from removal of D8 (the hole closest to the DB37 connector). This should send the output to pin 30 on the DB37 connector.
7. Circuit filter on tach input. A .1uF capacitor installed from GND (in the proto area) to JS8.
Someone please tell me if I missed anything.

I should complete my Megasquirt assembly. I've moved on to the harness, but need some guidance. I belive I have mapped the correct Megasquirt pins to the correct pins in the Miata's multilock connectors. Could I get someone to review them (zipped Excel document attached) and then help me with these lingering questions.

Questions:
1. What is pin 26 on the DB37 connector used for? On the DiyAutotune harness, it is labeled "TPS VREF". I assume this wire is unused. Right?
2. In my harness, where on the 64-pin multilock connector should I ground the sheild for the tach signal (pin 24 on the DB37 connector)?
3. Harness grounds. The documentation from DiyAutotune on thier pre-built harness shows that pins 7, 8, and 9 on the DB37 connector are bridged and should be used as a ground. Pins 17, 18, and 19 are also bridged, but DiyAutotune specifies these as sensor grounds. I have verified that the two groups of pins are not shorted together within the harness. I have seen a post where it was suggested that all six pins be shorted together and run to a single ground. Given that I am able to connect these wire seperately, is combining all of them the best approach? If so, which wire in the Miata's 64-pin connector should they go to? I know that the Braineack guide specifies pins 4C adn 4D, but those pins are used for fuel injector grounds (I believe). Wouldn't it be better to keep the sensor grounds seperate? How about this instead: pins 7, 8, and 9 from the DB37 go to pin 4D on the multilock connector; pins 17, 18, and 19 from the DB37 connector go to pin 4A on the multilock connector (this is also the ECU ground)?
4. Braineack guide has the DB37 with a green wire on pins 34 and 35 and a blue wire on pins 32 and 33. The DiyAutotune harness has these colors reversed. Since the Megasquirt does not do sequential injection, I assume this is not worth swapping. For my purposes, the green wire (pin 32 and 33) will be injector bank #1. The blue wire (pin 34 and 35) will be injector bank #2. Any problems with that?
5. What pin on the Megasquirt's DB37 connector should I used for the clutch switch? I understand that launch control requires a variable TPS (on pin 22 of the DB37) and a connection to the clutch pedal switch (pin 1L on the Miata 64-pin connector). I have searched, but cannot see that anyone ever specified which Megasquirt pin they used.
6. When flashing firmware after the Megasquirt is installed, how can I plug in the stimulator? I don't see a way to get it in there physically. I'm looking for creative/cheap ideas. My local computer parts store does not carry DB37 extension cables.
7. Is anyone knowledgeable located near Jacksonville, FL and willing to help me if I get stuck again?

Thanks,
Chris Dobbins
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File Type: zip 1997 Miata ECU-Megasquirt Harness.zip (87.0 KB, 120 views)
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Old 08-31-2008, 10:49 PM   #2
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That is the most insanely detailed pinout I have ever seen in my entire life. And I used to design audio networking hardware for a living.

Quote:
5. (blah blah) Is it okay that I read about 1 ohm between JS1 and IAC1A? IAC1A is where the tach input comes through (see note 4 above).
This does not sound right. I1A does not connect directly to anything, it goes through resistors. So even if there was a short elsewhere, you should read 470 ohms from I1A to the short.

This is actually a helpful observation, It limits the potential number of places where the fault could be to the area of the DB37 itself, the area of the I1A pad, and the legs of the two resistors.
Quote:
Someone please tell me if I missed anything.
You'll figure out what you missed eventually.


Quote:
1. What is pin 26 on the DB37 connector used for? On the DiyAutotune harness, it is labeled "TPS VREF". I assume this wire is unused. Right?
A TPS, being a variable voltage divider, requires that 5 volts be run across it in order to produce a reading. Since you're parallel, the stock ECU will still be providing this function. Leave this pin disconnected.

Quote:
2. In my harness, where on the 64-pin multilock connector should I ground the sheild for the tach signal (pin 24 on the DB37 connector)?
It's already grounded at the DB37, right? Leave the other end of the shield floating. It's kinda silly to even use shielded wire for an open-collector sensor input. Grounding the other end to the harness will actually create noise in the CKP signal, as it will cause current to flow through the shield. That's never a good thing to have happening.

Quote:
3. Harness grounds. The documentation from DiyAutotune on thier pre-built harness shows that pins 7, 8, and 9 on the DB37 connector are bridged and should be used as a ground. Pins 17, 18, and 19 are also bridged, but DiyAutotune specifies these as sensor grounds. (...)Given that I am able to connect these wire seperately, is combining all of them the best approach?
Internally, all grounds in the MS are commoned at the DB37. Although the grounds are somewhat segmented on the rest of the board, they all come together at the connector.

If you wanna be really proper, 4C is the injector ground, 3O is a sensor ground, 4A is the shield ground for for O2 sensors, and 4D seems to be just some general-purpose ground.

Quote:
4. Braineack guide has the DB37 with a green wire on pins 34 and 35 and a blue wire on pins 32 and 33. The DiyAutotune harness has these colors reversed.
The injectors don't know what color insulation is on the wire that's driving them. The pin numbers on your spreadsheet are correct in this regard. (I must admit, I'm only looking at the very last page- the rest of it is too hard to see on my laptop's 11" screen)

Quote:
5. What pin on the Megasquirt's DB37 connector should I used for the clutch switch?
Doesn't matter, since you have to build your own circuit to handle it. Here's the writeup: http://www.msextra.com/manuals/MS_Ex...al.htm#launchC You'll build the same circuit as for map switch input, but run it to pad JS11 rather than JS9. You can choose any of the unused SPR or IAC pins to wire it to. The clutch switch is active-low.

Quote:
6. When flashing firmware after the Megasquirt is installed, how can I plug in the stimulator? I don't see a way to get it in there physically.
Once you're done bench-testing and it's installed in the car, you shouldn't need to use the stim anymore. To flash firmware, just unplug the ignition coils and turn the key on to supply power.

Quote:
7. Is anyone knowledgeable located near Jacksonville, FL and willing to help me if I get stuck again?
Well, I'm about 320 miles south of you. Bearing in mind that Hanna will be creating a tailwind for you, How fast can you push your car?
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Old 08-31-2008, 11:52 PM   #3
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Default Final Check and Parallel Harness Construction

Joe, thank you for the quick and thorough response. You helped me out with my first set of questions back in July, too. Good luck weathering the storm.

The pinout may be a little much, but I'm really trying to learn and I just couldn't get it without laying this stuff out graphically.

I've checked a little more with the 1 ohm between JS1 and IAC1A. I can't find any solder bridges or misplaced wires in any of the places you mentioned. So, I poked around a little more. JS1 connects directly to pin 37 of the MS-1 processor. I pulled the processor and I can no longer read any continuity between JS1 and IAC1A. Maybe it is supposed to be like this--I guess I'll find out when I install it and something blows up.

I appreciate the note on the 5V throttle position sensor. I had missed that when I researched.

Just when I thought I was done with modifications, I followed your link to the launch conrtol mod. If I don't have all the required parts in my spares, I'm not going to add it until later. There are wires all over the bottom of my board and I am running out of different colors for the different mods. I'd post a picture, but our digital camera is in Tokyo until December. I took some shots on my film camera and will be able to scan them in after I have them developed.

I'm making the adjustments you pointed out in my diagram. If anyone sees any other errors or ommissions, please let me know. Otherwise, I'll try to get a finalized .pdf made early next week. Honestly, this harness has been more troublesome than the Megasquirt construction for me. I'm sure I'm not the only person to get confused by it.

Thanks,
Chris Dobbins
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Old 09-01-2008, 12:02 PM   #4
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You need exactly (1) piece of wire for the launch control mod. Wire from 1L to JS11, that's it.

As far as the resistance from JS1 to IAC1A (????) I get 1192 ohms.
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Old 09-02-2008, 12:21 AM   #5
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Quote:
Originally Posted by Braineack View Post
You need exactly (1) piece of wire for the launch control mod. Wire from 1L to JS11, that's it.
You're not using a pullup?
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Old 09-02-2008, 10:11 AM   #6
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Originally Posted by Joe Perez View Post
You're not using a pullup?
It was suggested to me from everyone else who was running it prior not to bother (everyone else being Chad).
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Old 09-03-2008, 12:11 AM   #7
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Default Updated Harness Wiring Diagram, 1997 Parallel Install

I have updated my harness wiring diagram for a 1997 parallel install (see attached .pdf). The previous Excel version had the spark outputs crossed--do not use that one. If someone can tell me how to delete the attachment from my earlier post, that would be even better. I have retained the master file if anyone sees any errors or has suggestions.

Chris Dobbins
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File Type: pdf 1997 Miata ECU-Megasquirt Harness.pdf (189.5 KB, 937 views)
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Old 09-07-2008, 06:04 PM   #8
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Ok something is wrong here, either the parallel harness (for 97) scott made for me is way off, or your diagrams are turned around. Assuming Scotts harness was made correctly, then i think the 26 and 16 pin connections need to be flipped horozontally, while the 22 pin connector remains the same.
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Old 09-10-2008, 02:02 AM   #9
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Check out pic 1, it should be the same orientation as the diagram, at least from what i can gather. The connections on connector 1 are the same as in your diagram, but connector 3 and 4 they are flipped around.
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Final Check and Parallel Harness Construction-wiring-harness-001.jpg   Final Check and Parallel Harness Construction-wiring-harness-002.jpg  
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Old 09-12-2008, 07:46 AM   #10
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Default Final Check and Parallel Harness Construction

Sections of your harness do look like a mirror image of mine, so I'll need to start at the beginning and see what I missed.

Can anyone confirm that I labeled the pins correctly (i.e. 1D, 3B, 4U) on my diagram? Pages 2-4 area all showing the connector as though you were holding it with the solder pins towards yourself and the mounting tab pointing down.

Can anyone confirm that the wiring diagram, http://www.madracki.com/miata/images/wiring/97sys.pdf, labeled the ECU's pins the same way that I labeled my diagrams? Look on page 8. All of the pins are labeled with the same code as the 64-pin AMP connector uses. This is the document I used to trace the function of each pin.

If those check out, I'm not sure where I missed it. I'll take any suggestions.

I wish I had sorted all this out before I soldered my harness together...

Chris
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Old 09-13-2008, 03:31 AM   #11
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Default Akaryrye, you ruined my weekend. Thank you.

akaryrye, I appreciate your response. I see what I did. Right at the beginning, I started my file with all of the pins in mirror image. I built the rest of the file on the assumption that I had them right. Then, I built my harness based on the file. I've got a lot of work ahead of me; fixing the document, de-constructing my harness, and putting it back together again. And I wanted to install the Megasquirt this weekend...but it is better to fix this now.

Can anyone explain how to delete attachments from my earlier posts. They are completely wrong and could really mess up anyone who tries to use them.

Chris
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Old 09-13-2008, 04:41 AM   #12
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glad i could help. As far as the attatchments, you can manage your attachments in your user CP.

Word of caution, when you do hook up the 'Squirt, make sure your spark inverted option is set to "no"
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Old 09-22-2008, 11:03 PM   #13
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Default Final Check and Parallel Harness Construction

Okay, I de-constructed my harness, made a new document, and rebuilt it. I guess I built a sturdy harness last time, because taking it back apart was more difficult than it should have been. Now mine looks more like the one pictured above.
I have attached the (hopefully) final version of the construction.

I still can't figure out how to delete old attachments. I checked the User CP without success. If case I'm missing something obvious, someone point out how easy it is. Under User CP, I only see how to delete the last item. Here's a screenshot of what I see. There is no check box available by the earlier attachments.

Chris Dobbins
Attached Thumbnails
Final Check and Parallel Harness Construction-user-cp.jpg  
Attached Files
File Type: pdf 1997 Miata ECU-Megasquirt Harness.pdf (145.7 KB, 298 views)

Last edited by Cosmic_Eraser; 09-22-2008 at 11:07 PM. Reason: Screenshot posted
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Old 11-19-2008, 04:05 PM   #14
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Chris,

I you want to remove an attachement, don't go through CP. Instead, edit the post with the attachement and remove it there.
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Old 11-16-2010, 11:19 PM   #15
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Sorry for the necrothread resurrection, but my current questions would directly reference data on this thread so I think it makes sense to post it here.


I'm preparing to fabricate my parallel boomslang harness and would like some confirmation on a few items before I potentially do something stupid. I've configured my boomslang design based on a blend of Arkmage's parallel install and Cosmic_Eraser's parallel install here. Between Arkmage's wiring diagram, Cosmic_Eraser's last schematic, and the diagrams in Brain's "How to make and install your own Diy MegaSquirt" guide, I think I've got everything set up the way it should be, but I've found a few discrepancies that I'm hoping someone can clear up for me.

I've attached a layout of my DB37 pinout with the planned connections from the Megasquirt to the car, and would appreciate if someone could give it a once over to make sure I haven't missed anything. Also, I'm wondering if I should connect the ground at 4C to the grounds to 4A and 4D as well? Or should I use 4A or 4D instead of 4C? Does it matter which ground I use, or should I connect them all? Suggestions?

Relevant data about my MS1v3:
I purchased Arkmage's old MS unit and the general layout of my board looks identical to the board layout in Brain's thread except that R7 has not been removed (as I will be running redundant CLT sensors) and the Q20 and Q4 transistors are still installed on my board. I'm assuming that since Arkmage had Q20 and Q4 installed and it worked properly (and since I'm not doing the PWM IAC mod), that I can just leave these installed without worry?

I've changed the spark output circuit to Joe Perez's inverted circuit, but this shouldn't affect the wiring of my boomslang.

The only other relevant change that Arkmage made was to jumper JS11 to SPR3, which I assume is to enable launch control. After some searching/reading, I seem to be seeing conflicting information regarding whether or not I need to build the circuit (as seen here) or can simply output JS11 to the clutch switch? Can someone please clarify this?
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Old 11-19-2010, 03:22 PM   #16
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It's been so long since I've looked at this stuff I can't really offer much assistance. I think the last time I had the MS open was about 2 years ago.

I can say that the clutch switch input worked fine the way I had it run, I didn't have that internal circuit and launch control was fully functional. I'd suggest bypassing the transmission neutral switch though as it's connected in series. So if the car is in neutral you will hit the launch control regardless of clutch position.

Don't remember what Q20 and Q4 were for... fan control and idle control? I left both in there intending to someday put them to use. It didn't seem to affect anything having them there and not using them.

I had all my grounds connected directly the the chassis at the stock ECU ground location. I also ran ground wires from each sensor to the ECU chassis ground as I had a noise problem at one point.
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Old 11-19-2010, 03:37 PM   #17
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sounds/looks fine. q20 and q4 have no effect on your setup.
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Old 11-19-2010, 05:31 PM   #18
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Quote:
Originally Posted by Arkmage View Post
It's been so long since I've looked at this stuff I can't really offer much assistance. I think the last time I had the MS open was about 2 years ago.

I can say that the clutch switch input worked fine the way I had it run, I didn't have that internal circuit and launch control was fully functional. I'd suggest bypassing the transmission neutral switch though as it's connected in series. So if the car is in neutral you will hit the launch control regardless of clutch position.
Yeah, I've been sitting on it for a year now because I had just been too busy to sit down and dive into it. Thanks for the heads up on the neutral switch!

Would you recommend tying the grounds in to the ECU harness or simply bringing all of my MegaSquirt and extra sensor ground to the chassis there where the ECU is mounted to the bulkhead? Is there any significant benefit of one over the other?
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Old 03-17-2011, 01:32 AM   #19
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Edit: Nevermind, I'm an idiot. I forgot that I had already run dedicated grounds for my MegaSquirt.

Last edited by jnshk; 03-27-2011 at 03:32 AM.
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