MS3 Ignition Issues

[SleeperZ]

I'm running MS3 on my L28ET with the turbo distributor, the DIY 12-1 wheel, and a single coil fired with the MS3 BIP373.  I have been experiencing intermittent misfires at idle with no sync loss, and I've looked at the distributor trigger input to MS3 with an oscilloscope and it it quite clean.

 

I went through the entire ignition system from the plugs back to the coil, checked gaps and tightened connections as much as I could.  The cap and rotor look good, and they should since they are a new, same brand, bought at the same time.  I verified I located the distributor properly so I will get a spark to the proper plug from just before TDC to 40 degrees BTC.  Then I tried to verify the trigger position with MS, and found it was off.  With the base offset at 345, it was about 10 degrees retarded, but when I would add that much to the offset, the trigger would jump to 20 degrees more advanced.  The Megasquirt forums informed me my MS3 firmware was out of date, so I updated Tuner Studio and the MS3 to the latest, and now I have been able to get the trigger on solid.

 

So this brings me to my latest issue that my ignition is now momentarily and seemingly randomly dropping out.  I replaced my plug wires with a brand new set that fits the cap terminals and the plugs much better, but the problem remains.  I have configured the coil driver to a 3.0mS maximum dwell and a 1.2mS maximum spark duration.  Are those appropriate values for a standard coil?  I am using a MSD Blaster 2, which has the same characteristics as a factory L28ET coil.  What are folks using in their MS systems?

 

My coil does not get hot, so I don't think I am overdriving it, but it seems as though the MS3 coil driver may be thermally shutting off as the cars stars from cold well and does not start missing for a few minutes.  And it's not just like a random misfire, it's like the whole ignition turns off, loses a few sparks in a row, then catches itself before the engine dies.  And this also started with the new firmware update.

 

I am thinking I need to wire the factory ignitor and coil in, and just drive it with a low current output from the MS3.  But what is the experience level at HybridZ with the single coil ignition?

[Metro]

According to DIYautotune's article on it "The thermal shutdown range is between 185 and 210 degrees C with a typical shutdown at 195C."

 

I would think your case should be very warm if the ignitor was cutting out.

 

A few years back when I thought I had an ignition problem, I tried various dwell settings, high and low, and could barely get the ignitor warm. With an MSD blaster coil it worked down to 1.6ms before it started cutting out. It should work fine at 3ms, I don't remember what I used exactly, I think I just used the stock values MSNS-extra was loaded with (chevy v8?). I'm using GM DIS coils now, but I still think I'm running close to the default settings without any issues up to 6800rpm.

 

If you think something is overheating, I would just run it with the case open and feel around. I've never used it, but an old trick for overheating components would be blast the board with an upside down can of compressed air to instantly drop the temperatures.

Edited September 30, 2013 by Metro

[mobythevan]

I never had many noise problems with my MS installs until my LSx RX7.  I am in the process of completely rewiring this car because of the noise issues.  One of the major contributors was having the harness run right next to the coils and injectors.  I've had so many noise problems on the LSx that I decided to throw everything at it, all new wiring, grounding, better locations, better shielding, you name it.  I was seeing a lot of noise coupled into the coil control wires and injector control wires.  I also saw a lot coupled into the trigger wires.  Installing caps was not good enough to filter this out.  It should be noted that I was not using the factory routing for the LSx harness so I ended up with my harness real close to the coil and injectors.  I know this is not specific to your problem, but misery loves company.

[skirkland1980]

I wasn't having any ignition problems until I changed to the diy 12-1 wheel. Seems like a lot of folks experience problems while using it.

[loy]

Do you have both crank and inner wired up? When i had only the crank (one coil) I had no problem but once I wired the cam (COP)  I had all sorts of issues. Turned out to be the electronics in the distributor. Also having it on rising or falling will make a difference also. Need to look at trigger log.

[motomanmike]

A tune file might help us too. Maybe an engine running data log?

[SleeperZ]

I thought I posted my tune file on MSExtra, but I don't see it anymore.  http://www.msextra.com/forums/viewtopic.php?f=131&t=51553#p378559  I will probably repost on there, and make sure my current tune goes up too.

 

I am now unsure whether I wired the cam signal in or not,  I will look at that. I don't see the signal on the composite logger.

 

My coil is wired to fire on rising edge, of course, as it is firing it directly.  If I rewire to use the 280ZXT ignitor, I know I will need to change it to falling edge.

 

I can also check the box for heat when I check to see if the cam signal is wired in.

 

When I was checking the tooth logger, I never saw any dropouts.  I also never saw any sync loss.  Is there a log file I can run or check that would show if Megasquirt was deliberately dropping the ignition out?

 

Edit:  Tried to upload my .MSQ file, but I am not allowed?  WTF?

Edited October 1, 2013 by SleeperZ

[Chris83zxt]

Edit:  Tried to upload my .MSQ file, but I am not allowed?  WTF?

 

Try putting it in a zip.

[SleeperZ]

Alright, here is a fairly recent .msq in a .zip.  I have not changed anything but the firmware version and my trigger reference since I captured this.

sleeper78z_10degreesoff.zip

[loy]

You should upload a msl (log) with a tooth log. I just read there is no sync loss? Any voltage spike?

Edited October 3, 2013 by loy

[SleeperZ]

I take it back.  I hooked the scope up to the ignition last night, and every ignition dropout (quite visible on the scope) was accompanied with a sync loss.  My dwell time is good, right on 3mS, and the discharge waveform looked to be about 2mS, so I changed that in the .MSQ (not that it affects the dropout).

 

What I do see is a very fast edge on the discharge that spikes to 80-100V, so I pulled my condensor and will test it at work today.  I suspect it's ok, so I think I will try to control the coil with the L28ET ignitor and try to get more of this ignition noise out of my MS3 box.

[FricFrac]

I never had many noise problems with my MS installs until my LSx RX7.  I am in the process of completely rewiring this car because of the noise issues.  One of the major contributors was having the harness run right next to the coils and injectors.  I've had so many noise problems on the LSx that I decided to throw everything at it, all new wiring, grounding, better locations, better shielding, you name it.  I was seeing a lot of noise coupled into the coil control wires and injector control wires.  I also saw a lot coupled into the trigger wires.  Installing caps was not good enough to filter this out.  It should be noted that I was not using the factory routing for the LSx harness so I ended up with my harness real close to the coil and injectors.  I know this is not specific to your problem, but misery loves company.

What about running a secondary board with opto couplers to drive the coils? What are you doing for shielding/grounding on those lines?

Edited October 12, 2013 by FricFrac

[Matt Cramer]

Do you have a data log? If not, try making one and pressing the space bar when the engine misses. I can look at the log and see if anything's amiss at that point.

[SleeperZ]

My garage has been filled with kitchen cabinets for almost a month now, so nothing has happened with the car.  Kitchen remodeling is a PITA even if you hire a contractor to do it....

 

 I do not want to get fancy with the ignition circuits here, I am already running the crank signal (distributor, DIY wheel) through the opto interface in the MS3 and it is shielded.  But the coil current is being sunk by the MS3 and returning into the ground point at the starter.  I do not like that configuration and think it may be upsetting the sync, so I am about to modify the BIP373 circuit with an internal current-limiting pullup and connect it to the ignitor base (NPN bipolar) at the factory L28ET ignition coil.  That way I can limit the current to about 100mA, filter it better and keep the ignition current out of the MS3.

 

I appreciate the feedback, and if anyone has already done this I am interested in reviewing that work.  If/when I fire up the car with the original configuration, I will log it.

[loy]

I had better luck running the trigger via vr. Also have you tried a cap on H1 boot?

[SleeperZ]

I had better luck running the trigger via vr. Also have you tried a cap on H1 boot?

 

I have not tried a cap on H1 boot.  Are you suggesting that somehow noise (presumably from the ignition or injector drivers) would be rebooting the MS3?  I can't see in the schematic how that cap would hurt anything, maybe I will try that when I get my cabinets out of the garage.  Since I still have the oscilloscope, I may just do some probing in the MS3 while the car is idling, that could give some insight into this issue.

[SleeperZ]

Man, it's been a while.  I re-read this thread and see some opportunity to get to the bottom of this issue, which strangely, has not gone away despite me ignoring for so long.

 

- I rewired my ignition so I am using the factory L28ET coil and ignitor, and just using the MS output to trigger it, keeping the coil current out of the MS box.  Although the ignition signal is quieter, I still have the periodic miss.  

-I pulled my distributor and ensured the DIY wheel and sensor were functioning as designed, with a 1k resistor pullup to the battery voltage.  I spun it with a drill and watched the signal on my eBay oscilloscope - perfect.

- Last night I hooked my scope up to the PCB of my MSIII, tach in and the VR output.  Interestingly, it ran like a whole bunch of crap with the scope probe on the VR output (the distributor signal still looked good), improved back to normal periodic miss when I took the probe off.

- Then I re-wired the tach input through the optical input and looked at the output.  I got better and cleaner signal out to the MSIII, so I will keep it that way, but it still has the periodic miss.  One thing I see now that I did not before, is this periodic miss is not caused by the tach input.  Whatever is upsetting the MS, it is not the tach signal, which is very clean and not upset when the miss happens.  I see the tach signal widen (slow down) during a miss, but the signal is not disturbed, so I need to look elsewhere.

 

So now, reviewing the suggestions, I think I will try the cap on the H1 boot.  Perhaps the noise level in general is causing a reboot.  But maybe before that, I can try moving where my Megasquirt ground is bonded.  Currently it is connected to the starter bolt, the same place as the battery ground.  I can't see how connecting that to the body would be an improvement, but at least if it makes the problem worse or better I will know I'm on the right track.

 

And Matt, I will see if I can capture a data log during this miss.  As with all software, I do not often explore the details or understand the options, but I will see if I can capture anything of note.

[NewZed]

Are you running batch fire, six at a time?  My plain old NA stock EFI L6 has always had some degree of periodic miss.  I can affect it by adjusting the mixture via fuel pressure or cooling temp. circuit resistance, or AFM idle bypass screw.  Seems like very lean on the idle gives the least missing.  In short, maybe it's not electronic, maybe it's idle mixture.  The problem with batch fire at idle is that there are six different fuel timing scenarios, with each pair of cylinders getting fuel at a different time in one crankshaft rotation, and each individual in a pair alternating between two of those scenarios.  It can hurt your head to ponder.  Might be an inherent problem with EFI batch fire and why the manufacturers all use sequential at idle.  Every miss is an emissions burp.

[SleeperZ]

I am running batch injector fire per the MS wiring diagram, 2 banks of 3.  The miss is enough to badly fail emissions testing and my wideband goes full lean.  It may be missing more than just one spark, raising the possibility the MS unit itself is periodically shutting down.

[SleeperZ]

Had a few minutes last night, so I took apart my MS3 box.  It already has the capacitor on the H1 boot pins.  But I read a lot of this thread on the MS Extra forums, and it is worth the read, very enlightening...

 

http://www.msextra.com/forums/viewtopic.php?f=101&t=28178

 

Apparently this circuit board was not designed with any substantial current carrying capacity.  I work as an electrical engineer and have designed many switching power circuits, so I know the importance of not only how one routes return currents, but how much copper one should put in for the amount of current being supported.  Needless to say, it appears that the modifications people are having to make are due to these issues with the board.

 

Now that I have determined my tach input is not the cause, and I have already re-designed the coil trigger, now I need to focus on the batch injector firing, as I have 6 low impedance injectors, 3 per bank, using the PWM for keeping the injector open.  It looks like I need to disconnect the ground connection from the FETs that fire the injectors, and wire it directly to the DB37 connector pins for the main ground, and keep all that current out of the circuit board.  It also looks like a substantial amount of noise from the PWM circuits is also being routed into the +12V that operates the MS3.  I don't think I will try to route that out of the box, although that is the best solution, but will simply add the capacitance to the +12V at the transistor pins.

 

Hopefully those mods will fix this issue.