A little background first...

Purchased Ms2 v3.0 back in April or so, and spent a few months on and off constructing the board. Read all I could, which I guess wasn't enough , and went ahead with a basic install. By basic I mean that I am not running anything with the ms yet. I tapped into TPS, Crank Angle, stock o2(did I even need to?), installed both GM sensors, and wired into power and established ground. I am eventually going to go turbo, as I have already rebuilt for it, and wanted to get the ms installed before doing so. Now the issue...

Everything ms seems to be fine as far as the readings that I am getting while in MT, except the damn tach. My first mistake was when I built the ms, I had read the posts by Corbin, Wicked and Gil about the tach spikes that they experienced with the 3.0 board, so I wired my board with this in mind and followed Corbin's fix for the situation found here:

MSnS V3 Board Tach Spikes Fixed!

No go. I still saw jumps in the tach reading. So I continued searching and came across Wicked/Gil's fix:

Running MSnS v3 Board as FULL Standalone (No Spikes)!

Now with this setup, I was able to get a steady tach signal, however, it seemed too far under what my stock tach was reporting( stock tach was at 950 or so and ms was in the high 600's/low 700's and as I would rev the gap would grow until it was around 1k apart up in the 4000's), so I continued to adjust the pots, and when The tach reading on the ms was VERY close to the stock reading, the spikes were evident again. It would spike from @950 up to @1300. I tried even finer tuning the pots, however to no avail. After searching more indepth on the ms2 site, I stumbled across what I thought was going to be my answer:

MS2-Extra Neon/420A Manual

I followed this setup and now my tach is up in the high 3000's and low 4000's. Also, it is still spiking. I was hoping that some of the ms guru's would have some suggestions?




One quick question about the wiring schematic. In this picture, are D1 and D2 supposed to be open? That is how I have them now. I had them both jumped before. At this point, the only thing that I can think of doing is increasing the value of the c12 capacitor. Thanks for any responses in advance.

DirtMegirt
Wiki Contributor

A few guys tried to increase the value of the ED capacitor but claimed it didnt help. I never went any further into this problem. I chose the easy way and stayed with the older board. In fact the spare 3.0 i have still isnt built.

Another thing to try and make sure the MS case isnt touching the vehicle chassis at all.

DirtMegirt
Wiki Contributor

How stable is your battery voltage at the Megasquirt? Can you post a datalog of it with the car running? Did you clean all the solder flux off real good?

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

DirtMegirt
Wiki Contributor

If those are your min/max volts from you datalogs than that is good, I was just looking for spikes there. Are you running 8v regulated power to the crank sensor as suggested in my writeup? Does the crank ground go to the Megasquirt? Is the signal wire shielded? If all is true, then have you noticed my comment about soldering in those extra capacitors to greatly stiffen up the overly sensitive MS1 processor maybe the MS2 needs the same capacitors.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

No Joel, i'm really not doing anything that is suggested in your write-up except what Gil suggests to do about halfway down in your post. I noticed that you run MS standalone, and now that I think about it, Gil does too, doesn't he? For some reason, I thought he was piggyback like Corbin. Looks like i'm going back to your post. I just tapped into the blue/white crank wire at the ECU for my connection. The wire in my db37 harness is shielded. Also, maybe you could let me know how to get those datalogs you are talking about?

DirtMegirt
Wiki Contributor

I was just talking about a datalog from MegaTune, then looking at it with MegaLogViewer, people in the Megasquirt forums usually just post screenshots of the areas of logs they are concerned with, and then attach the complete datalog.

I don't know of anyone who's been able to run the v3 board with spark without taking the stock ECU out of the picture. It's just too sensitive to all the noise that gets induced with all that extra wiring everywhere.

I'm pretty sure you're going to have to run a dedicated power, ground, and signal line from your MS to the crank sensor.

This was what made my car drivable with the MS1 processor v3 board, although, I did have to add some additional capacitors on top of that to eliminate some seldom spikes thereafter.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

DirtMegirt
Wiki Contributor

Those are the caps, but they are soldered onto the processor pins, not the db37.

Battery voltage shows up as battvolts I think. If it's not in the list, you need may be using an older version, and will have to add it as a logged parameter.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

Alright, just a little update. Nothing good however. I have tried every setup that I have come across, and continued to read as to hopefully not miss anything that might help. Just to clear something up, I do not have the ms installed and it is not running anything at this point. I have made the connections and am still in the process of wiring a harness for the injectors. The issue that I am having is that I cannot find a tach signal that is both accurate and stable, it's either one or the other. After reading Corbin's post, I realized that he says that he only got tach spikes at a certain rpm range, and only after adding spark duties to the megasquirt. At this point, I must have done something wrong. Terry, in your experimentation with the ms2 v3 board, were you able to get it to run fuel successfully? That is all I am trying to do. It seems to me that I will need a stable tach signal nomatter what setup I run, but am I looking at this wrong. I have even tried to connect the ms wire to the white ecu tach wire, but the megatune rpm's seem to be about 1/2 of what the stock gauge reads. Anymore info you guys can give me will be very appreciated!

DirtMegirt
Wiki Contributor