37 pin connector and wasted spark wiring questions

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Conrad_Turbo
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37 pin connector and wasted spark wiring questions

Post by Conrad_Turbo »

I will be running the latest version of MSnSpark+Extra on my V3 MS1 board.

I do plan on doing hardware changes for:

- boost control
- water injection control
- shift lights
- launch control/flat shift
- knock sensor input
- tach output pin

The reason why I want to do all these extra features right away (before having the MS working in the car) is because I am building the wiring harness and I want to include all the appropriate wires to allow all these features to work when the time comes. Now along with the above hardware mods I am also running a wasted spark setup, so I have purchased an extra VB921. Now I am just confused on how I get all these peripherals to the actual wiring harness…

1. When I wire in the 2nd VB921, it is wire to the top of spark B (R29)? The output then goes to pin 6 of the 37 pin connector correct?
2. As for the outputs that require hardware changes…why cannot I wire that into the 37pin connector as well? I notice there are quite a few extra pins and I don’t want to have to add an extra connector to the case if I don’t need to. Do I have to cut up the case to add a 2nd connector?
3. If an extra connector is needed why are there so many wasted pins on the 37 pin connector? Such as tying up 6 pins to ground. Couldn’t they have all been internally tied together and had the remaining 5 pins open for outputs/inputs to the MS?

I found the below diagram on here while digging some info on wiring everything. Now what are the other pins on the 37pin connector used for? Can I wire my additional outputs to the unused pins? Why does it show on the MSnSpark+Extra page using a 25pin connector for the VR input? Especially when that above diagram shows it being wired to the 37pin connector on the MS board.

Any info you guys can share would be great!
masterx81
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Post by masterx81 »

From what i know, there isn't a real standard on this...
In the extra site is mentioned an additional db25...
Also i'm doing the wiring on my car, and i'm using only the db37 connector (not much space to put another connector on the same panel, but on the led/rs232 panel there is a lot of space).
If you want to use the db37 pins, take a look at the v3 schematic, nearly the whole rear row of pins is ground, you can pull out them from the circuit, and connect them with a wire to the relative circuit for the feature that you want to use (i'm doing this).
Conrad_Turbo
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Post by Conrad_Turbo »

So all the pins that are grounded on the DB37 must be grounded on the board? How is this done?

So how do I feed, say a boost control output, to the connector without having it short out to the board (where it is grounded)?
masterx81
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Post by masterx81 »

You need to desolder the db37 connector, disassemble (with a cutter) the rear panel of the connector. Pay attention that now all the internal pins of the connector probably drop...
After this, i've straightened all the pins that i need to use for the other features (like shown in image). Only pins that are not used by ms can be used for other features! There are a lot of grounding pins on the db37... You can leave only the groundings suggested by the v3 assembly guide (5 pins).
After this, i've drilled the rear panel of the connector, so that i can get out the spare pins, then close the connector with the drilled backpanel. Now you can solder a wire and put everything you want.
Conrad_Turbo
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Post by Conrad_Turbo »

AWESOME! I like your little picture too. :lol: :D

So is that diagram I posted showing the use of all the MSI (and possibly MSII) pins? Is there any other pins that are soldered to the board for another function or future function? Reason I ask is I don't want to pull all the pins out, wire everything up and find out that I disabled a current or future feature of the MS. Know what I mean?
PSIG
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Post by PSIG »

There is a limit to the load the DB37 pins can take. I use the leftover pins on my wasted spark coils as well. I figure that the coils take ~7A each but only 4uS at a time or less so... :D I would be careful deleting any grounding pins however, as the total amperage load of all the circuits must go/return through those pins.

FWIW,
David
masterx81
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Post by masterx81 »

Ok, but how much current current can handle a single pin on db37?
Conrad_Turbo
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Post by Conrad_Turbo »

I did some digging...they can handle 5Amp peak...although I am sure the whole connector can't handle all that much. I decided not to reduce the ground points, since the coil can potentially draw up to a maximum of 7.5A so that along with the injection and whatever else the ground needs to be beefier. I am going to uninstall the connector and pull up the pins that are not used on the MS (on that diagram I posted there are quite a few unused pins). That way I can still have a solid ground as well as get my ouputs out for the other features I need.
masterx81
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Post by masterx81 »

In my installation i've leaved 4 grounding pins... Like shown in v3 assembly guide. 2 more for cts/tps/etc and vr.
I'm nearly sure that them are sufficient...
I've gained 9 more pins...
Conrad_Turbo
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Post by Conrad_Turbo »

I've decided to leave the grounds the way they are since it's low side switching for the coils and if anything potentially shorted out the current max output from the vb921 is 7.5A...which is a lot. I am using all the unused pins on the DB37 connector without any issues. Now I am wondering is the wasted spark an afterthought? What I mean is that the injection side has the use of 2 pins each to distribute the current, while as each coil only has 1, does the solenoids on the injectors draw a lot more current than an ignition coil?
jsmcortina
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Post by jsmcortina »

Conrad_Turbo wrote:Now I am wondering is the wasted spark an afterthought?
Correct. The board was not designed with wasted spark in mind.

Adding a second connector (if you need more pins) really isn't that hard. I added one much like the diagram on the MS1/Extra site.

On the V3 board there are more spare pins on the DB37 and for many installs they are enough.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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Conrad_Turbo
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Post by Conrad_Turbo »

James, thanks for the reply. I am just not sure if 1 pin on the DB37 can handle the current output to the coil, can 1 pin handle the current? I am not sure how much current a coil takes as compared to injectors...but just assuming I'd think the coil would take the same if not more?
jsmcortina
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Post by jsmcortina »

I had thought that a single pin might be insufficient but to my knowledge there are plenty of cars now driving around like that without problems.

If you choose to use IAC1A etc. for spark outputs you MUST wire direct to the DB37 pin because the thin trace leading from the jumper hole to the DB37 is too narrow.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
Conrad_Turbo
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Post by Conrad_Turbo »

jsmcortina wrote:I had thought that a single pin might be insufficient but to my knowledge there are plenty of cars now driving around like that without problems.

If you choose to use IAC1A etc. for spark outputs you MUST wire direct to the DB37 pin because the thin trace leading from the jumper hole to the DB37 is too narrow.

James
So why does MSnSpark show the use of two pins for each coil output? http://megasquirt.sourceforge.net/extra/

While as the MS1 or MS2 with single coil control only show one pin (assembly guide for MS version 3 board)?

Should either one be corrected?
jsmcortina
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Post by jsmcortina »

Conrad_Turbo wrote: So why does MSnSpark show the use of two pins for each coil output? http://megasquirt.sourceforge.net/extra/
Because (as I wrote above)
jsmcortina wrote: I had thought that a single pin might be insufficient
and I drew the diagram.

Doubling up doesn't hurt, however I am actually using single pins in my install and no problems so far.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
Conrad_Turbo
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Joined: Fri May 05, 2006 6:48 am

Post by Conrad_Turbo »

Okay as long as I know a single pin can handle the current load per coil then that’s fine. So with the MSnSpark using the additional DB25 connector it shows Spark A, B, C…coil output on the connector. Shouldn’t Spark A be ignored on the DB25 connector since it’s already wired on pin 36 of the DB37 connector?
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