Greetings. Just introducing my self. Here in California with a '99 Miata (automatic transmission) that’s been in my family for 23 years. I’m waiting for a DET3+ unit to arrive. I recently installed a Flyin Miata turbo kit. I’m committed to maintaining the invisible serial communications between the PCM and Aisin 03-70LE transmission’s control module. Everything works great except for low speed, low RPM throttle transition (lifting off/declerating), at which point it seems the “Voodoo Box” piggyback unit’s O2 sensor spoofing is causing AFRs to go way too rich (~9:1 as seen via AEM UEGO gauge)…and the Mazda PCM can’t “see” it (due to spoofing), so the car stubles and stalls out. Since the Voodoo Box isn’t adjustable, I bought a DET3+ and am reading everything I can find. It’ll be installed in FIT mode, with ignition control. My first challenge: Determine how to integrate the DET3+ to the PCM, for the purpose of ignition control. What I know: 4-tooth trigger wheel, open collector Hall’s sensor, two coils/wasted spark…and a cam angle sensor for phase information. What I don’t know: PCM to DET3+ pin 9 ignition in w/ pull-up pin 3, then ignition out pin 6 to both coil connectors (11.4 in DET manual) or, Ignition out pin 6 to the Miata PCM’s “2J” crank angle sensor in pin (11.3 in the manual). Anyway…one step a time. I’ve just discovered these OEM forums…so now it’s time to search, read, search, read. I can’t be the first person to integrate one of these things with a '99-'00 Miata. Warmest regards to all chronic tinkerers out there. Enjoy your weekend of tinkering.
First roadblock: I’m hoping to replace the '99 Miata’s 4-tooth trigger wheel with a 36-1 (Mazda part ZM0111408) and then configure the DET3 to modify the signal before passing it to the Miata “PCM” (ECU). The Miata’s trigger wheel’s teeth are separated by an alternating 70 and 110 degrees. To configure the DET3 to spoof the stock 4-tooth signal using the 36-1 trigger wheel, I would need to:
- Connect the Miata’s Hall Sensor to Pin 9 (ign. in), with the pullup on Pin 8
- Configure the Input Trigger Pattern to 36-1 (easy peasy)
- Configure the Spoofed Output Signal (NOT easy peasy, aside of telling the DET3 to provide 8 pulses per 720 deg of crank rotation)
The NOT-easy-peasy part: Defining the Uneven Tooth Spacing. This is critical, as the stock Miata ECU relies on the specific, uneven timing of these pulses. The manual indicates that the DET3+ supports various ignition types and allows defining the “Num signals per 720”. However, the provided sections of the manual do not explicitly detail the software interface for programming custom angular positions for each pulse when the pattern is uneven (like the 70 and 110-degree alternating separation). To accurately spoof the signal, the DET3+ needs to output pulses at the exact angular positions the stock ECU expects. The pattern over 360 degrees is:
First tooth: 0 degrees (reference)
Second tooth: 70 degrees after the first
Third tooth: 110 degrees after the second (total 70 + 110 = 180 degrees from reference)
Fourth tooth: 70 degrees after the third (total 180 + 70 = 250 degrees from reference)
Then, 110 degrees back to the start of the next cycle (250 + 110 = 360 degrees).
While the manual confirms the device’s capability to support various ignition modes, it does not show a screen or method for entering custom angular offsets. And I don’t see in the wiring diagrams any reference to any Miata, which suggests early Miata ignition control is not yet supported.
Alternatively, under, “11. Controlling ignition angle” in the DET3+ manual, it says, “10. retard of two signals controlling dual ignition modules” is an option. However, this setup and configuration is not explained anywhere in the manual, and available I/O labeling and descriptions don’t provide any indication as to how this would be possible e.g., there’s only one Pin 9, 9 Uni- and bi-polar ign in. Perhaps two of the Analog inputs are used (Pins 13-16)? Perahps Pin 10, frequency in can be used for the second coilpack signal? But this relies on the fuel table…?? In any case, I clearly don’t understand the DET3+ enough…yet.
Anybody know how to implement DET3+ 99-00 Miata ignition control? Or, is this not possible with the current DET3+ version?
I’m going to reply to my own thread…because I’m hoping this learning process will help influence the next version of the DET3 user manual. I think I’m near the answer. The preferred approach is NOT to provide the DET3 with the crank sensor (CKP) signal, and potentially the cam sensor signal (CAS). Instead, we want to implement, “…retard…two signals controlling dual ignition modules,”. Why do I suggest this? Because, there’s no description of a method for turning a 4-pulse crank and cam sensors’ signals into an ignition signal in the manual and, in the DIGITAL ECU TUNER software, under “Setup” > “Ignition configuration…”, the option, “Retard two ignition module signals” is listed (as indicated in the manual). Under this selection, it says, “This ignition mode is suitable for retarding two ignition module signals [OK, great! How?]. Using this mode freqency input/output is used [Perfect!] for second signal. All freqency functions are disable.”
However, it’s not clear what option must be chosen under, “Ignition input configuration”. If we implement this method, we’re going to provide the DET3 with the Mazda ECU’s 3G (coils 1&4) and 3H (coils 2&3) signal.
Here’s another “However”: The software’s, “Ignition input type” options includes only, “VR Sensor adaptive threshold”, “VR Sensor fixed threshold”, “Hall effect or optical sensor”, and “Other sensors”. Obviously, coilpack trigger signals are not VR or Hall, and they’re not “sensor” signals. Shall I assume the DET3+ knows what to do with a coilpack trigger signal, if I choose, “Other sensors”?
I’ve done a bunch more reading. Here’s the plan. If ECU Master engineers (or anyone who has a DET3 running on a '99 Miata) reads these posts, a review of this proposed '99 Miata integration plan would sure be appreciated. A few notes: Notice the injectors aren’t connected to the Miata ECU, and the Miata’s ECU injector leads are instead connected to resitors with the same rating as the Miata injectors (intended purpose: prevent CEL and DTCs). Notice crank and cam sensors aren’t connected to the DET3. I have the Miata ECU’s coil-trigger signals going to the DET3, instead of to the two coil-packs; we’re using DET3 pins 6 and 7 to fire the coil-packs instead. The Miata’s MAF is no longer connected to the Miata’s ECU. Intead, it’s connected to the DET3’s pin 2 “Map Switch”. And the Miata’s ECU gets a modified MAF signal from the DET3’s Analog Out pin 17. Will this work? “CLT” is coolant temp; “AIT” is air intake temp.