MS1 v3 buildup RPM input test
 

so i was building up a megasquirt and im stuck at step 55 because i cannot get the rpm input to work on my stim. After a good deal of troubleshooting, I noticed that when i would flip the RPM switch (next to the potentiameter) I would get an rpm reading that corresponded 1:1 every time I flipped it. So I am guessing there may be a problem with my stimulator? I did the same test on my old board that I was never able to get working and it did the same exact thing.

Anyway, im going to go ahead and continue building the rest of the board, but im wondering why its doing this?

Oh and heres an old thread on the same topic: https://www.miataturbo.net/forums/sh...light=rpm+stim

btw, splitime, ever get your setup working out?

I also was never able to get rpm working on my stim. I just skipped it and kept going with my build. I just made sure d1 and d2 are jumpered and it worked fine in my car which is all that matters.

I got mine working... but I sent it for repairs and he said a few trans/resis/tors were bad... on stim/board. When I got it back... RPM worked again.

BTW: I never got anything from RPM testing... no reading at all.

When you do the miata mods you won't get any RPM reading. The miata mods disables that ability.

I think he is before getting to the miata mods. Also have you tried cahnging to stim on wheel? or an option like that.

I get RPM readings with the Miata mods as per the DIYautotune page. With the Stim as Wheel setting.

Also, remember he is at step 55 of a build, so he most likely hasn't done the miata mods yet.

Hmm maybe i'll try that.

ya i decided to keep going. Just find it a bit odd that it would show an rpm signal when i flipped that switch ... perhaps it simulates a square wave where the stim wasnt able to? Anyway ive gone ahead and nearly finished the board now but no miata mods yet. Im happy I went ahead and built it myself because everything makes so much more sense now to me and it does not seem so freaking complex anymore.

What version of the stim are you guys using? The 2.1/2.2 won't work with the 12v pullup on the ignition input by default, the 2.0 will. More on that in a minute. Regardless of which version of the stim you're using, if you've got a .msq loaded up from a Miata, or have already configured the wheel decoder settings, you'll need to enable 'stim for wheel' to get the RPM to trigger properly as this makes the simple square wave signal provided by the stimulator get interpreted by the ECU as a 4+1 wheel decoder compatible signal. MAKE SURE you turn 'stim for wheel' back off before you plug the ECU into your car or it won't run for more than a second or two and you'll wonder why... and you could hydro lock your engine if you keep trying while scratching your head.

Now... for you v2.1/2.2 stim guys. I've been working with the stim designed Jeff Clarke to correct this oversight with the newer stim. There will be a new design to correct the lack of proper function when a 12v ignition input pullup is in place, but in the meantime we found a workaround. First off you need D1 in place and not jumpered out in your MegaSquirt. Secondly, on your Stim, replace R4 with a 180-200 ohm, 1W resistor. Don't use less than 1W as even the 1W gets a bit warm. (about 110f) I've not tested this on a 2.1 yet but on a 2.2 it works just fine and seems to be a decent mod for you guys using a pullup on the ignition input. I'm continuing to work with Jeff for a 'one size fits all' solution stimulator though... the challenge is to meet all of the needs while keeping the part-count, and therefore the cost down. People keep talking themselves out of buying a stim all the time to save a few bucks, and then they don't have what I'd consider to be a critical diagnostic tool, especially if you're building your own ECU up from a kit....

Thanks jerry, I dont have any miata specific mods. I simply followed all the directions in the manual to make a hall/opt setup without the VR or negative coil trigger options. I then stopped at step 55 to test with the stim and discovered that i could create an rpm signal in megatune by flipping the stims RPM pot switch, but not by turning the pot. I tried this on the standard code that comes loaded on the chip and the bowling and grippo codebase in megatune. It did the same with ms&se btw and wheel decoder setting was off.

btw my stim is v2.2

v2.0 stim here.

akaryrye -- If you haven't modded the board for the Miata yet, and you haven't setup the code for wheel decoding, then you should absolutely have an RPM reading... and I'd recommend stopping where you're at and posting on the MSEFI.COM forums with the details of what's going on to get to the bottom of things before continuing. It's usually simpler to troubleshoot the assembly in stages rather than noticing a problem and continuing until the end and then trying to troubleshoot it. If you work the problem as soon as you notice it there are less components on the board, and less possible sources of the issue... The support guys on the forum are usually pretty good about helping you get to the bottom of it either way, but the sooner the better.