Voltage spikes and Sags with MS II V3.0

[zul8r]

Hi guys,
I'm having some major voltage spike and sag issues with MSII V3.0. I originally thought the issue was my tune until I started data logging. Upon closer inspection when the voltage spikes the car leans out immediately after, when the voltage sags the car goes rich. You feel the car shutter for a brief moment as well when this happens. This happens during all driving conditions as well as when im crusing at a steady rpm with constant light throttle. I was wondering if anyone has had any similar issues or if theres something else I can try for a fix.

For info on my car its a 1982 280zx Datsun and for Megasquirt im running MSII V3.0 with a relay board that a friend and I put together. I am also running version 2.6 of the firmware on Megasquirt. The battery has been mounted in the trunk of my car and I've got a thick (2-4 gauge) power wire running from the battery to the starter. The ground wire (2-4 gauge) for the battery is grounded to the trunk of the car. Originally the relay board was pulling power from the factory ECU wire, and was grounded to 3 spots. It was wired with aproximately 16-18 gauge wire for both power and ground. The switched power on the relay board is coming from a 16-18 gauge wire that powered the original ECU.

To try and remedy the problem of the voltage sags and spikes last night we re wired the relay board's power and ground wires with 12 gauge wire. The relay board now pulls power directly from the starter where the battery and alternator connect. The relay board also has one 12 gauge ground now that grounds on the starter where there is a thick (4-6 gauge) factory wire that grounds to the frame. The switched power (16-18 gauge) wire from the factory ecu is still in place. After re wiring the issue doesn't seem to have improved at all unfortunately...

I'm just wondering what I should try next?
I have read that the battery can act like a capacitor and that running power off that may help to reduce the highs and lows?
Would updating the firmware on the ECU help remedy anything?
Could the switched 12 wire be causing anything like this?
I've thought about running a ground wire from the battery up to the starter but we did some tests and were able to find little to no resistance between the battery ground and the starter so haven't done that as of yet.
Could something be acting up on my megasquirt or relay board that would be causing this? We double checked and made sure the power,ground and switched 12 connections are nice and tight on the relay board and that nothing is loose.
If something on the board could be causing the issue is there anything I can check to make sure its working well? The board was originally built by me and a friend a couple years ago. I should add that I had the luck of living next to an electrical engineer who looked over the MS board and relay after we put it together and touched up any solders that he thought looked weak.

I've included some screen shots of the voltage sags and spikes. I tried to upload the datalog but its too large if its if any help let me know and I'll see if I can make it smaller. You'll notice my AFR's follow the trend of the voltage spikes and sags when throttle is constant as is RPM. (im running an AEM wideband sensor as well).

[my_mad_z]

Just wondering if you found a solution to this problem? I'm experiencing a very similar problem in my 240Z (running an injected L28) and am getting the odd voltage spike of 21.6 volts and down to 7.3 volts. I'm running MS-II with 2.886 firmware. I'm not using the standard alternator; ending using an alternator out of a Lancer that is internally regulated. I've had the alternator tested and everything came back fine.

I'm waiting to resolve the issue before I install my turbo setup; don't want it running lean under boost!

Interested to know if you got to the bottom of this.

Marc.

[Matt Cramer]

High or low impedance injectors?

[my_mad_z]

Hi Matt,

I'm running 440cc low impedance injectors off a supra. All of my cabling is screened and shielded with the shield (one end only) tied to ground at one common point.

I've attached a screen shot of the spikes; not sure if you need any more info regarding my setup.

Thanks in advance.

Marc.

[Matt Cramer]

Ok. What board are you running? Are you using injector resistors?

[my_mad_z]

Sorry, forgot to mention it's a version 3.0 board. I'm not using any resistors; I've got 3 injectors per bank. It's been a while since I did the install, from memory I think the injectors are approximately 2.5ohm. I configured the board for low impedance injectors when assembling. Sorry if it's a silly question but am I supposed to use resistors with my setup?

[Matt Cramer]

It's not mandatory, but it can cut down on noise. Or you could use this mod:

1. Cut the center leg on Q9 and Q12 or desolder it so it does not reach the PCB.
2. Run a length of jumper wire from the center leg of Q9 and Q12 to an unused pin on the DB37 connector.
3. Wire this pin to a 12 volt source in the wiring harness, separate from the Megasquirt's power supply wire.

[my_mad_z]

Thanks Matt; I came across that mod in the documentation last night. I will make the mods and post the results as soon as I can.

Once again, thanks for the advice, much appreciated!

Marc.

[my_mad_z]

Hi Matt, just wanted to say thank you; my voltage spike issue seems to have disappeared since I modified Q9 & Q12. Thanks again!

Merry Christmas.

Marc.

[Matt Cramer]

You're welcome, glad to hear it's fixed.

[my_mad_z]

Hi Matt,

Sorry to bother you, just wondering if you can shed some light on a problem I'm experiencing.

I'm not sure if I have a bad batch of fuel or if it's the high temperature we have at the moment but my Z seems to stumble between 3500-4500rpm under WOT. I've attached a screen shot of where the rpm suddenly drops to 0rpm. It's never done this before so I'm baffled as to why it just started happening. Just before this happened, my MSII suddenly stopped working; after some investigation, I found the main 20A fuse (which was still intact) had a poor connection - the metal cap at one end of the glass fuse was loose. I replace the fuse but still had the same issued. I ended up making a new fuse box and getting rid of the old school glass fuses and replacing them with blade fuses; I rewired my MSII and I also ended up replacing Q9 and Q12 as one of the middle legs snapped off after I ran a separate 12V feed to the center legs. I took it out for a run and it stumbled again, with the same symptoms.

There appears to be no noise on the tach signal. I found that if I slowly accelerate it will rev ok passed 3500rpm without stumbling - not all of the time though. It seems to happen more under load; I've also noticed it's started to ping which leads me to believe I got a bad batch of fuel...... or the problem is causing it to ping. I haven't changed my ignition table; if anything I backed the timing off when I heard it ping. I'm waiting till the fuel tank is empty and I'll try a fresh batch of fuel. I'm not sure what else it could be??? The strange thing is the car was running like a dream after I supplied a separate 12V feed to Q9 and Q12 as it got rid of my voltage spike issue.

Summary of my setup:
MSII V3.0 running 2.886
460cc low impedance injectors
I have wired my ignition as per http://www.DIYAutoTune.com/jwplayer_vir ... wiring.jpg
With Q9 and Q12, I had to go for the next size up as they didn't have any in stock; I ended up using 100V 8A transistors.

If you can lead me in the right direction, would greatly appreciate your advise.

Sorry for the long post, thanks for your time.

Marc.

[my_mad_z]

Just wondering if it could be my coil or plugs? Might try a new set of plugs tomorrow and see if it makes a difference.

[my_mad_z]

Replaced the plugs, no love! I normally don't give the car a hard time when it's cold but today I opened her up before WUE cycle was complete and there was no hesitation/pinging. As soon as it was close to operating temperature, it started to cut out at 4500rpm...... correct me if I'm wrong but coils tend to play up when they get warm??? I'm enjoying the beers too much right now, so I'll get stuck into replacing the coil tomorrow after work.

Open to suggestions.

Thanks in advance,

Marc.

[my_mad_z]

Just had a 'light-bulb' moment...... I think I might know why I'm having this problem. On the initial setup of the MSII many years ago, I had a VR signal from the distributor; I recently changed this to an optical signal distributor and being such a long time since the MSII assembly, I forgot about the jumper changes

I visited the assembly manual and I'm hoping step 52 solves my problem! I really hope this is it, can't wait to get home from work and check it.

[my_mad_z]

Hi all,

Ok, I've gone through and changed my MSII to accept hall/optical trigger and put it all back together...... I am no longer getting a tach signal to the MSII my tacho responds while cranking but there is no rpm feedback while viewing in TunerStudio. Also noticed that the fuel pump doesn't run while cranking. When the key is in the ignition position, the fuel pump primes and when I start cranking, nothing..... I'm obviously missing something here.

My ignition options are:

Trigger offset: 65 deg
Skip Pulses: 3
Predictor Algorithm: Last Interval
Time Mask: 1ms
Percentage Mask: 50%
Cranking: 75%
After Start: 50%
Normal Running: 15%
Check Tach Sync Options: Check Always
Ignition Input Capture: Rising Edge
Cranking Trigger: Trigger Rise
Coil Charging Scheme: Standard Coil Charge
Spark Output: Going High (Inverted)

I set all of the correct jumpers according to the assembly manual and removed the jumpers that I had for the VR configuration; I'm stumped and don't know where to go from here??? Is it possible that I damaged something having MSII configured for VR rather than hall/optical?

If someone can point me in the right direction, would really appreciate it.

Thanks guys.

Marc.

[my_mad_z]

Just a quick update:

My problem with no rpm signal is now sorted Had a look over the MSII board and found a bit of wire between D1 and D2 jumpers.... must have come off the soldering iron tip or when I was putting the cover back on..... Thank god that's all it was! It's a little late so I can't take her out for a test run, a bit too loud. I'm hoping that this has solved my rpm spike; I'll update tomorrow after work.

Marc.

[my_mad_z]

Problem solved; car has never pulled so hard..... loving it!

Megasquirt rocks!!!