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-   -   MS3, MS3x, for a 2002. What to buy? (https://www.miataturbo.net/megasquirt-18/ms3-ms3x-2002-what-buy-55077/)

skidude 02-13-2011 09:39 AM

Don't worry, I absolutely will. I just have to go out and find a variable power supply. The one I thought would work only goes down to 15 volts, so it won't work.

y8s 02-13-2011 10:40 AM

you can use that. just whip up a voltage divider with a potentiometer. the circuit doesn't require a lot of power for testing. you just need to know voltage in and voltage out.

when the output turns on as you drop below 14.2V input voltage, you're golden.

skidude 02-17-2011 12:45 PM

Well, I made the voltage divider (actually just using a 24 power supply and a pot) and the circuit doesn't work and I can't for the life of me figure out why. I made it exactly like the picture posted above, and checked all the bands on all the resistors, and I get 0V across field and GND, and I get whatever supply voltage is across field and 12V. I get 0A across field and GND and somewhere between 0 an 4mA across field and 12V, with no cutoff when supply is at 14.4 (or anywhere else for that matter). Any ideas what to check? I have a simple multimeter and my eyes and a magnifying glass to use.

skidude 02-17-2011 01:30 PM

Well, I did it again. I figured out the problem 3 minutes after I got so frustrated I had given up and posted here. Then I looked at it once more and noticed something I hadn't noticed before, and now it seems to work great.

y8s 02-17-2011 01:35 PM

what's your battery setpoint voltage where the alt kicks in?

skidude 02-17-2011 01:40 PM

Seems to be between 14V and 14.5V, if you mean the supply voltage when the current (and voltage) at field drops to zero. The pot I had makes voltage variation between 10 and 24V very difficult, but after a few attempts, I never saw more than about 14.3 before the field dropped to zero.

skidude 02-17-2011 01:46 PM

I narrowed it down, it's between 14.21 and 14.42.

skidude 02-17-2011 03:02 PM

I just tried out the MAP sensor with a rubber bulb thing and it doesn't register in TS at all, which makes me wonder if it's actually a problem with the stim, or a problem with my board. Below is a picture of my board, does anybody notice anything missing or wrong? I'm guessing that whatever I did, if anything, is pretty substantial since NONE of the sensors are registering anything but they are all giving some reasonable value (MAP reads 91kPa, CLT and MAT read 115F, and TPS reads 325).


http://farm6.static.flickr.com/5172/...77b75742_b.jpg

shuiend 02-17-2011 03:08 PM


Originally Posted by skidude (Post 691183)
I just tried out the MAP sensor with a rubber bulb thing and it doesn't register in TS at all, which makes me wonder if it's actually a problem with the stim, or a problem with my board. Below is a picture of my board, does anybody notice anything missing or wrong? I'm guessing that whatever I did, if anything, is pretty substantial since NONE of the sensors are registering anything but they are all giving some reasonable value (MAP reads 91kPa, CLT and MAT read 115F, and TPS reads 325).

I think you are missing a lot of stuff. That is what franks looks like built.

http://westfieldmx5.devocht.com/star...t_circuits.jpg

skidude 02-17-2011 03:17 PM

Wow, look at that. I don't know how I managed to skip all of that! I found it and I'm installing that part now. Thanks for pointing out the obvious for me, who knows how long it would have taken me.

y8s 02-17-2011 03:22 PM

C2 thru C10 are all for basic sensors.
same with the row of resistors to their left.

http://www.msextra.com/doc/general/ms3v3schems.html

this is also helpful i knowing what goes to what:
http://www.megamanual.com/ms2/V3assemble.htm

between those two links, you should be able to determine what to include and exclude.

This may or may not be the final version of mine. I think it doesn't have the NB trigger circuitry yet:

https://lh6.googleusercontent.com/_e...M/IMAG0444.jpg

shuiend 02-17-2011 03:27 PM

Basically you followed just Frank's directions and left out some stuff from the megamanual. He does not say to go back and do the steps he does not mention in his write up.

Braineack 02-17-2011 04:16 PM

i want to play.

http://www.boostedmiata.com/gallery2...C_0006+_2_.JPG

skidude 02-17-2011 04:19 PM

Brain, you missed Q20.

y8s 02-17-2011 04:57 PM

also I can see his nipple.

skidude 02-17-2011 05:00 PM

Looks like this thread needs a NSFW label!

skidude 02-17-2011 05:03 PM


Originally Posted by Braineack (Post 680321)
There is no need to do "Joe's Spark Circuit".

When you buy the MS3 kit and MS3x, they come with the DB37 connectors you need to make a harness. Talk to y8s about the mazda ECU connector, I think he has a spare.

The Input Circuit you DO need to add is this one outlined here: http://westfieldmx5.devocht.com/index.php?section=35
see Step 50.

You will also need to do the alternator control circuit outlined above.

Also very little needs actually be populated on the mainboard, so save yourself the trouble when building it and omit the circuits that are pointless. It should also be outlined on the build thread linked above.


Don't follow any other "additional/optional circuits" or the step 65.

What about step 80? It looks like it goes with 65, which you said not to follow. It's tach output, right? Isn't that covered by 3X so I don't need it?

skidude 02-17-2011 05:15 PM

And what is the thought on cleaning the flux off the board? Is it necessary, and if so why? I never did it on my MS1, but I only had it for a couple years.

y8s 02-17-2011 05:41 PM

I wired up the LEDs as standard. One of them I use for an output, but they can magically be both.

find the purest isopropyl alcohol and an old toothbrush and clean that flux!

Braineack 02-17-2011 06:01 PM


Originally Posted by skidude (Post 691227)
Brain, you missed Q20.

missed? it was excluded for a reason.


It's tach output, right? Isn't that covered by 3X so I don't need it?
correct sire.

WestfieldMX5 02-18-2011 08:10 AM


Originally Posted by skidude (Post 691253)
And what is the thought on cleaning the flux off the board? Is it necessary, and if so why? I never did it on my MS1, but I only had it for a couple years.

You must clean off the flux. It'll suck up moisture and can kill your board in the long run.

WestfieldMX5 02-18-2011 08:14 AM


Originally Posted by shuiend (Post 691194)
Basically you followed just Frank's directions and left out some stuff from the megamanual. He does not say to go back and do the steps he does not mention in his write up.

Maybe my instructions aren't clear enough. My instructions follow the standard manual, so you do all steps. Where my instructions deviate from megamanual, I provide new instructions. So, if I don't talk about a step, it means you do that step according to the manual.
Basically, follow the manual with my instructions next to it. Replace the manual's steps with my steps :).
Mmm, this is even less clear I suppose ... :laugh:

I do a couple of things differently than most, like the LEDs for instance. I don't need them because I can't see them. If you want them, just add them. It's only a led and a resistor.


Originally Posted by Braineack (Post 688218)
Finally someone posts a diagram that makes logical sense to me.

If anyone feels like drawing out my circuits 'the proper way', I'll put them up on my site. Seems they cause some confusion, altough they make perfect sense to me http://cdn.forumediainc.com/fmi/mt/i...lies/laugh.gif.

skidude 03-05-2011 11:18 AM

I'm having trouble with the alternator thing... When the input voltage is applied directly to the alternator circuit, field voltage cuts off exactly at 14.4 volts, but when I apply (and measure) the voltage at the DB37 connector, it cuts off at about 14.2V, and the field is usually 0.1V below the input. Also, I can't seem to get any current, even though I had it yesterday. I'm getting the 12V from the left side of D3. Any suggestions?


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