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Old 09-07-2015, 11:17 AM   #1
Asx
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Default CAS weirdness

I've picked up a 323 gtx that had an aborted MS install. It's using a miata CAS (the hall style, not optical, if it matters) and a v3.57 MS2. I cannot get a CMP signal.

Composite log shows great CKP no CMP at all. I verified the wheel decoder settings. I verified the mods. Everything goes to the right pads and the components are of correct value. With the Jimstim set for 4G63 I get a beautiful CMP and CKP waveform in the logger and proper sync/RPM on the TS dashboard. Cas wiring is Correct now (CMP was miswired in the DB-15 originally because the PO didn't know how to connector good) verified by Ohming out the connectors plug to plug. I found a spare 1.8 CAS (also hall style) and swapped it. No change. I plugged the loose CAS into the harness and spun the wheel by hand. CKP pulls down to ground as it should, but CMP is only pulling down about 10mV (from 4.92V to 4.82V w.r.t. battery ground). I have not swapped the CAS's back and hand tested the newer one, but I'd expect the same.

How likely is it that I happened to have 2 bad CAS's or are the mods per DIYautotune's article not compatible with the Hall style Cas (unlikely right? I think the Hall was the much more common one?).

schematic of CMP input circuit attached
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CAS weirdness-diyautotunecmpmods.gif  
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Old 09-08-2015, 11:55 AM   #2
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The Hall effect CAS gives the same signal as the optical and our article should work for both. How exactly is the board set up?
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Old 09-08-2015, 12:15 PM   #3
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CMP to db15-7, 1k from db15-7 to js10, 470 from 5v to db15-7, .1uF from js10 to gnd

Edit: i also found a post where the PO said he sent it to you all to do/redo the mods. Cleanliness of the wiring suggests that to be the case.
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Old 09-11-2015, 09:54 AM   #4
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Can you post an MSQ and composite log of an attempted start?
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Old 09-17-2015, 12:22 AM   #5
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simulator is hooked up to the jimstim, the other is cranking
Attached Files
File Type: msq CurrentTune.msq (110.5 KB, 92 views)
File Type: csv simulator.csv (11.6 KB, 38 views)
File Type: csv 2015-09-07_07.50.08.csv (20.2 KB, 38 views)
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Old 12-15-2015, 12:14 PM   #6
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For closure, the cmp wire was lightly broken internally, or something. Didn't show up with the multimeter. On a hunch (read: wild *** guess) I cut out the wire, ran a new one, and got a happy ending.
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