UPDATE 25SEP2015
6 Attachment(s)
I've been in contact w/ DIYAutotune for some help on this issue. I've confirmed the following:
I continued to play w/ dwell settings as a part of troubleshooting. Reduced dwell duration to 2.5 ms, keeping spark duration between 1.0 and 1.5 ms, and added fuel between 2.5-4.5k where it appeared slightly lean before. These settings seem to be closer to how the engine was running before removing the MS3X to measure and adjust the VR circuits (14SEP update post)...but it's still misfiring... Tach behavior during "misfire" (Dropbox link) While confirming base timing, w/ TunerStudio still in Fixed Timing = 10 deg, I slowly rotated the throttle plate w/ the timing light still on the crank pulley to determine if timing was retarding. I was expecting a gradual change if it truly was retarding as rpm increased, though what I saw was a sudden step-change. The crank pulley TDC mark suddenly ADVANCES from 10-deg BTDC w/ Fixed Timing (900-2600 rpm) to 0-deg TDC between 2700-3300 rpm. I checked this last night and also saw that the mark went back to 10-deg BTDC from 3300-4100 rpm then started retarding ~5-deg at ~4100 rpm (spark hardware latency = 20 usec). Crank pulley (Dropbox link) The .msq's spark map doesn't have any sudden changes that would retard suddenly through the powerband. If this retardation of spark timing is occurring when the spark map is being used, that would explain the loss of torque I've noticed along w/ the misfires. Trouble is TunerStudio only logs what spark timing is commanded vs. actual, otherwise it could be useful to log spark timing through these occurrences. VR Circuits I haven't ruled out the Cam and Crank inputs yet. Testing (can share measurements if needed) showed the output pins of the U7s on each input NOT providing the voltages DIY cites (mentioned in the 14SEP update). Is this worth investigating?? |
UPDATE 03JAN2016 (The FIX!)
4 Attachment(s)
The warmer and not-so-snowy weather has been a treat and allowed for additional troubleshooting of this misfire issue I've documented here.
Discussions w/ Joe Perez and DIYAutotune left me w/ the symptom of a poor CKP signal causing a loss of spark at above 4.5k. If the signal was bad from the stock CAS, then it needed to be filtered. I'm not into making circuits, so I arranged a Dual VR v2.1 from JBPerf (Jean Belanger). It arrived last week, so this past weekend, I reviewed the latest (2015-10-12) MS3X V3.57 hardware manual as Jean's instructions detailed needing a pull-up resistor for the input, which sounded similar to what I had read in the MS3X setup documentation (https://www.diyautotune.com/tech_art...azda_miata.htm). I determined that my DIYAutotune MS3X did not have the internal 1k pull-up at R57 on the main board, so I installed one early December since Jean's instructions also called for it. I reinstalled the MS3X w/o adjusting the VR pots and logged this: https://www.miataturbo.net/attachmen...ine=1451856612 Since I was losing sync above 5k, I was fairly certain I wasn't meeting the voltage threshold required to create a CKP pulse to fire the coils. Adjusted Main and Expander pots to get 2.5V w/ 5V applied (at top of R54 and ZC test point, respectively), I got the following (log was huge, so just a screenshot): https://www.miataturbo.net/attachmen...ine=1451856612 Nothing crazy, just shows pulls to 7000 rpm…but after months of not being able to do this and not being able to figure out why, it feels like a small win! This allowed me to continue tuning the VE Table (as you can see, I had conservatively WAY too much fuel above 5.5k) and start exploring closed-loop idle tuning and AE for throttle tip-in. I appreciate the help along the way in troubleshooting this issue. The solution forced a much deeper understanding of the MS3 and how it triggers the Miata’s coils via the CAS, but in the end, the idea was to better understand engine management…so another win! Key words: MS3, MS3X, high-rpm misfire, no tach signal, no rpm signal, no sync loss, R57, pull-up resistor, VR circuit, crank input, CKP |
You have a sync loss. Can you post a composite log of it?
|
Originally Posted by Matt Cramer
(Post 1296529)
You have a sync loss. Can you post a composite log of it?
The curve colors are washed out on those screenshots, but I have not logged any sync loss since the R57 + setting pots. I simply wanted to document what happened to me here for anyone in the future. |
Originally Posted by mkrazit
(Post 1270097)
I've been in contact w/ DIYAutotune for some help on this issue. I've confirmed the following:
I continued to play w/ dwell settings as a part of troubleshooting. Reduced dwell duration to 2.5 ms, keeping spark duration between 1.0 and 1.5 ms, and added fuel between 2.5-4.5k where it appeared slightly lean before. These settings seem to be closer to how the engine was running before removing the MS3X to measure and adjust the VR circuits (14SEP update post)...but it's still misfiring... Tach behavior during "misfire" (Dropbox link) While confirming base timing, w/ TunerStudio still in Fixed Timing = 10 deg, I slowly rotated the throttle plate w/ the timing light still on the crank pulley to determine if timing was retarding. I was expecting a gradual change if it truly was retarding as rpm increased, though what I saw was a sudden step-change. The crank pulley TDC mark suddenly ADVANCES from 10-deg BTDC w/ Fixed Timing (900-2600 rpm) to 0-deg TDC between 2700-3300 rpm. I checked this last night and also saw that the mark went back to 10-deg BTDC from 3300-4100 rpm then started retarding ~5-deg at ~4100 rpm (spark hardware latency = 20 usec). Crank pulley (Dropbox link) The .msq's spark map doesn't have any sudden changes that would retard suddenly through the powerband. If this retardation of spark timing is occurring when the spark map is being used, that would explain the loss of torque I've noticed along w/ the misfires. Trouble is TunerStudio only logs what spark timing is commanded vs. actual, otherwise it could be useful to log spark timing through these occurrences. VR Circuits I haven't ruled out the Cam and Crank inputs yet. Testing (can share measurements if needed) showed the output pins of the U7s on each input NOT providing the voltages DIY cites (mentioned in the 14SEP update). Is this worth investigating?? I had a similar issue, turned out to be a slack timing belt |
All times are GMT -4. The time now is 08:01 AM. |
© 2024 MH Sub I, LLC dba Internet Brands