Tracing down my last bit of reset issue

[opethmike]

Still have an occasional reset/sync loss issue. After some poking around, I think this may be due to a voltage drop issue; most likely for the 12v switched feed into the Megasquirt ECU. I spent quite a bit of time probing around with my multimeter today. Reset usually only happens at idle when an electrical "spike" occurs - such as locking the doors, the A/C compressor cycling, etc. It doesn't always happen with those events. Sometimes it will happen without any of those events happening.

I have attached a VERY crudely done drawing showing what the voltages were at the various places I probed today. I think I may have either a bad capacitor or bad solder joint on the 12v switched line. These measurements were taken with the key on run, but the car not started, so that is why the readings are in the 11s. Please let me know what you think.

[Spittybug]

Mike, I have a hard time reading your diagram, too small.... The two guys that I've been helping to get their stock EFI conversion working are experiencing some sync loss issues that have been at the higher RPMs. I haven't had any similar issues at all however. It would appear that the issue manifests itself only on the ignition portion of Megasquirt, not fuel only. Both were running just fine fuel only, but when converted to full spark control they started losing sync about about 3500 RPM. Trimming the pots helped move that up, but also caused some problems at lower RPM. Ian has now reverted to fuel only. Shannon I think has got the issue to be at a high enough RPM that it doesn't impact his driving. Like I said, I have no issues at all.

What board do you have? They have the 3.57 while I have the 3.0. Maybe theirs are just more sensitive to voltage fluctuations. I know that my electrical system is in good shape. I've cleaned fuses, connectors, grounds, removed harnesses and replaced with home built ones, etc...

When we tested the MS unit and the dizzy mounted in the drill press, we got a nice clean VR wave form. We did however get no-so-nice squared off teeth after the conditioner. That was using a stim to drive the MS unit on the bench, so that doesn't lend credence to the problem being in the car. We sent it back to DIY and they said that they were able to get it nice and clean by just trimming a pot. Their log shows no sync loss. Lot's of confusing, contradictory issues, but it would appear to be a case of the MS 3.57 boards being more sensitive to incoming power fluctuations than mine.

Maybe we need nice big capacitors or other conditioning on our power coming in? We need Dave M.'s help.

[opethmike]

Not sure why the diagram uploaded so small. Its nice and big on my machine locally. But basically what it shows is:

11.4 volts at the battery
11.4 volts at the green wire from the RPM relay (switched 12v source)
11.4 volts at the live 12v pad on the relay board
11.0 volts at the switched 12v pad on the relay board

I have a resistor & capacitor pair installed in-line for both the switched and live 12v wires to the relay board. I found that the voltage was the same in front of and behind the capacitor for the live feed wire, but not for the switched wire.

Makes me thing that I either have a faulty capacitor/resistor, or more likely, a bad soldering job. I'm going to try running a fresh wire for the 12v switched to eliminate the possibility. At worst, that will cost me a little bit of wiring.

Yes, I do have the 3.57 board. Trying another board sure would be a heck of a lot of money, so I'm going to try everything I can to fix the issue without having to go to another board.

[Bitsyncmaster]

If it's DC voltage with noise, use a large capacitor and diode feeding that capacitor. I would suggest a 1000 uf. 16 volt or higher capacitor and a 1 amp or larger, 200 volt or higher diode to feed the power.

It may be your ignition sensing circuit has noise. This is a common problem with lots of designs reading RPM off the coil wire. It took me a few designs to get that working clean. I use a filtered coil signal driving an optical coupler on my idle ECU. My first try would get an occasional miss. What Bosch did was use the ringing voltage levels (threshold of about 18 volts) to get clean signal. My circuit runs about a 7 volt threshold voltage.

[opethmike]

I just resolved this (hopefully). I had my ignition input setting set to basic trigger. As I am fuel only, I changed it to 'fuel only'. I did everything I could for a good stretch of time to try to cause a reset, but none occurred. Hopefully this is finally over and done with.

[AdmiralSenn]

That's weird, I had the same issue in reverse. Mine wouldn't run on fuel only but suddenly cooperated on basic trigger.

If I have any issues with the ignition when I finally tackle that, I'll update here with any relevant info.

[lazabby]

You mentioned that you have the 3.57 box. Texas Twister and I are having the sync loss issue with the 3.57 box when running both fuel and spark. It really looks like there is something in the Deloreans that the 3.57 box does not like. The 3.0 boxes seem to work fine though.

[opethmike]

You mentioned that you have the 3.57 box. Texas Twister and I are having the sync loss issue with the 3.57 box when running both fuel and spark. It really looks like there is something in the Deloreans that the 3.57 box does not like. The 3.0 boxes seem to work fine though.

Considering that is several of us experiencing that issue now, I am inclined to agree. Should I decide to go spark control at some point, I'm just going to go with a 3.0 box.

[dustybarn]

This is good to know. I'm probably going to upgrade 1776 to an MS2 to get spark control in the near future.

[opethmike]

I'm not skilled with the spark control portion, but I am pretty good with the fueling. I would love to help you out. One of the nice things about MS2 is that the AFR & Fuel tables are larger, so you can get a better tune done.

Definitely go with the 3.0 board; it seems to be less problematic. I'd also like to have you drive my car; so I can get your opinion on my current tune.

[opethmike]

I wanted to update this thread that I've driven ~500 miles since making this change, and have not experienced one single sync loss or reset since. When I do eventually go spark control, I will be switching to a 3.0 box.