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MEGAsquirt A place to collectively sort out this megasquirt gizmo

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Old 07-17-2008, 12:28 AM   #1
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Default First it worked, now it doesn't

I had the megasquirt all built but not modded for a miata at the end of last week.

When I plugged the stim in, all the gages in MT showed what they were supposed to. Since then, I've followed the DIY thread and jumpered what the pictures and diagrams told me to jumper, and put the proper resistors in, and the capacitor, and added the fan mod kit.

Now when I plug into megatune, the RPMs don't respond. When I move ***** on the stim, the appropriate gage moves on MT, but it's the only gage that moves. Except RPM, that one doesn't do anything.

I hope all that makes sense. It's easy to understand from this end because I know what it's doing before I read that.
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Old 07-17-2008, 12:32 AM   #2
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Normal.
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Old 07-17-2008, 12:34 AM   #3
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oh. Which part made the stim stop working? part of the jumpers and resistors, the capacitor, or the fan mod?

Also, any ideas on that megatune crashing all the time deal? It's really quite frustrating
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Old 07-17-2008, 12:37 AM   #4
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The resistors for the ignition triggers and the spark. Also if you have no bias resistor in r7, clt wont work either.

Megatune crashing all the time? Check your computer for memory faults by running memtest for 10 min.
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Old 07-17-2008, 12:48 AM   #5
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Skidude,

Now that you've configured your MS hardware for two trigger inputs and presumably set up the software config as well, you need to make sure that your stim is set up to provide two ignition triggers. This is only possible if you have a JimStim- the regular one won't do it.

Assuming that's true, the primary will stay as it's always been, the secondary, if you followed DIY's directions precisely, needs to be jumpered from 2nd Trigger to I1A and switches 2 and 3 set on. Make sure none of the Stim's pullups jumpers are on.
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Old 07-17-2008, 12:52 AM   #6
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Nope, no JimStim. :( I was cheap and borrowed a Stim from school for the build process. Is there any way to test the (hopefully) completed megasquirt without the JimStim before I start trying to install it in the car? Or is the tach signal working, then not working probably enough to know I did it right?
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Old 07-17-2008, 01:27 AM   #7
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You could set the MS software back to a single trigger and do a partial test, however a lot of basic stuff like two-channel wasted spark ignition won't work without either a second trigger or a missing tooth.

If you're feeling up to it, you could build a simple divide by two counter and use that to derive a second channel from the main channel.

I'm curious- what school do you go to that has a stim lying around? Is this a FSAE thing?
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Old 07-17-2008, 08:30 AM   #8
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I think I'll just take my chances and plug this thing in.

I'm a mechanical engineering student at the University of Maine. The stim is left over from when we put megasquirt on the Clean Snowmobile so it would be Flex Fuel.
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Old 07-17-2008, 09:05 AM   #9
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The RPM input for the Miata often doesn't work on most Stims besides the JimStim. There is a "Stim for Wheel" test mode, but with V2.1 and V2.2 Stims you also have to remove the pull-up resistor on the CKP input. If everything else works besides RPM, it ought to be OK on the car.
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Old 07-17-2008, 10:14 AM   #10
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RPM works half the time for me with a 200ohm 1watt resistor on R4 (IIRC) on my stim. With "stim for wheel" turned on of course.
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