Hello all,
I recently bought a 2003 mx5 Miata and i'm trying to get it running on megasquirt. Currently everything is stock on the car accept for MS. I'm using the DIY MS3 kit with a MS3X expansion card. The car will idle on MS just fine but once I rev it past 4k it looses sync and cuts fuel. I've tuned the VR input pots with my scope and ensured the signal is clean. Looking at the composite log it shows the RPM and CAS signal are normal and no missing or extra pulses are present. I'm not a MS expert and I don't know why MS is loosing sync for seemly no reason? I have attached a snapshot of the comp log and data log at the moment where it looses sync. If you want more info or a full log let me know and I will upload it.

Thanks!

 

It looks like the cam teeth are very close to the crank teeth, when this happens, usually the crank trigger wheel is inserted the wrong way (facing backwards instead of forward), but then again, when it happens it usually never syncs and backfires during cranking.

 

I also noticed how close the cam and crank signals are but I wasn't sure if this is normal or not? The car ran great on oem ECU so I assumed that the the crank wheel was good. I had a very difficult time getting the car to even start. I had to add a 0.47uF capacitor on the crank input and tune the VR pots before it would even try to start. Now it has a solid sync until I hit 4k RPM. Once I hit 4k it will bonce off it like a rev limiter. Another thing to note is my VVT is not working. It seems like the VVT PID doesn't even try to do anything. It is always fully retarded unless I manually change the VVT PWM Signal.

 

A 0.47uF capacitor on the crank input will only cause huge problems, especially on the higher rev range - remove it and try again.

 

I wouldn't have added it unless I needed it. If I remove it the car won't start and gets massive sync loss on crank. The comp log will show a ton of noise on the crank input without it and yes I have checked my grounds. I haven't tried a smaller input capacitor but maybe the capacitor is delaying the signal and causing a sync loss? What size pullup resistor do you use on the crank signal? I think i'm using a 1K right now but maybe a 470 ohm would help reduce noise?

 

There is zero need for a capacitor on the input. Zero. If you must have a capacitor, try something a lot lower, like 0.1uF or 0.01uF.

 

I will try a 0.1uF cap and see if it makes a change. Also should I try a different pullup resistor or leave it at 1k?

 

Ok I just tried it with 0.1uF, 0.01uF and NO capacitor at all. Absolutly nothing changed on each run. Oddly the car ran without the capacitor BUT would still lose sync at 4k. In case your wondering I don't have any other mods on the crank input. What should I try next? Do I need to check the crank wheel? The comp log still looks the same without the capacitor.

 

I just took a picture of my crank pulley showing the TDC mark and one of the trigger wheel teeth. I'm not sure how they are suppose to relate so maybe someone could tell me if it looks right or not.

Update:
I have been trying all day long to get this working with no success. I'm starting to wonder if this is a glitch/bug in the firmware. Here is what I've tried so far;
Enabling/Disabling VVT - no change
Changing Ignition capture edge Rising/Falling - no change
Moving TSEL to VR-out-inverted - no change
Manually changing the VVT PWM signal to advance the cam - no change
Inverting the cam signal - car wouldn't even start.
Tried forcing the car to rev past 4k with more gas - didn't work
Changed ignition trigger angle - no change
Changed firmware version from 1.5.1 to 1.5.0 - no change

I can't even think of anything else to try at this point. It would be interesting to know if anyone here is running a NB Miata on MS with a stock 4 tooth trigger wheel?

 

With cyl 1 at TDC, do you have a trigger tooth under or extremely near the crank sensor?

 

Just put cyl 1 at TDC and pulled the spark plug. Cly 1 was at TDC and aligned with the timing marks. Also looked at the trigger wheel with cyl 1 at TDC. The tooth painted white was directly under the crank hall sensor.

 

That means the crank wheel is installed correctly (I would be surprised if it wasn't, the car shouldn't even start). Disable the noise filters if you have them enabled.

 

I thought I had noise filtering disable but I just double checked and it is actually enabled. I'm going to disable it and try again. I bet that is the problem.

 

Problem solved! I disabled noise filtering and it revved up to redline with no sync loss. Thank you Reverant very much. Can't believe I forgot to check that.