MS1 losing CAS signal
 

MS1 3.0
(spec in sig)
29y4


So when driving, both in boost and cruising, tooth logger will show the signal disappear randomly, at the same time the tach drops and the car pops
ive went throw timing/dwell/injector pwm/diff cas

any ideas?

EDIT
now on HiRes 10g, with 330ohm resistors, and .1uf cap

This seems to be a common issue around here due to the unreliable CAS we have in these cars. I've spent lots of time trying to correct this issue myself and have yet to be successful, although I have been able to make it happen less ofter by running dedicated grounds and adjusting the timing belt for less slop. The only real cure seems to be to ditch the cas and run some form of Crankshaft trigger instead.

This is not a common issue, and we have very reliable CAS units...there's nothing to them.


they can start to degade considering they are pushing 23years old...so you just get a new used one, and go one with life...no need to upgrade to a crankshaft trigger.

Im going off of what I've read in posts made by joe perez. I've tried 3 different cas units all with the same effect. Rather than spending money on additional Cas units it just seems more worthwhile in my opinion to upgrade to a crank trigger, especially considereing there is an OE 36-1 trigger wheel that can be had from a junkyard for next to nothing.

then I blame shotty wiring.

It very well may be considering the wiring is now about 23 years old, but I've exhausted my efforts on this issue short of running all new shielded wiring from the cas to megasquirt. Funny thing is it could drop out 100 times on the highway I'll shut the car off and turn it back on and it wont do it again until the next restart.

that's odd a hell.

mine will keep doing it

you could try using the VR circuit for the crank trigger and opto circuit for the cam trigger...see if that improves the signal. but I've never heard of or had tihs issue with the hundred of MSs I've built.

now i did get the ms unit from a member on here, and it is ran parallel to the stock ecu
might that effect it?

1 more thing, the p/o of the car had a safcII in the car, very crappy job of wiring it in too, could one of the wires the safc feeds off of be the culprit?
i think the safc wires are power/map in/map out/tps/tach/ground/ground/o2
now, i dont have a stock o2 anymore either, i eliminated it, my powerdex feeds the MS (did same thing with my AEM ugo)

no, i ran parallel for years to no ill effects; never lost the CAS signal.

but sometimes the spark gap and spark output method could cause oddities and blowout. running boost and stock coils?

but yeah, shotty wiring like i said could be some issue...but I'd look into the CAS and ground wires if anything

alright will do.
ill try adding a ground directly to the CAS and run it down by the ecu first. heck, i got cat6 here, if anything, i can build me a jumper harness from the cas to the ecu and see if that fixes it, if it does ill just rewire the car, i want to eliminate the stock ecu anyway

its possible the harness has fatigued. I've had the actually pins snap off, where the solder held fine. they appeared to be fine, but you could feel the connection felt "loose." wiggling it just a bit and the pin snaps...those connections in the meantime are not solid and intermittent.

im still wondering if its the way the ecu is setup
i got it off Devin, kingof133t made it. the MS ecu is wired into the stock ecu, 2 toggle switches that switch between stock fuel to ms fuel, and stock spark to ms spark
i attempted to eliminate to just the MS, when i found that the resisters for the ignition out are in the stock ecu case with the toggle switch

no prongs on the stock ecu are cut, so im wondering if the stock ecu is messing up the signal

He didn't use the most ideal spark outputs, IIRC, they caused havok. I remember running them and always having the singals cut out in boost around 6K or something.

If you can post pics of the board and your msq we can see.

well here is the msq, ill get pics a little bit later when i make it outside

i dont have MS installed in the machine. is your spark output set to normal or inverted?

inverted

https://www.miataturbo.net/attachmen...ine=1338921254
https://www.miataturbo.net/attachmen...ine=1338921254

i care more about the ECU (ms) side of things...but god i hated how he did this.