This is somewhat of an offshoot of my other thread in the -extra part of the forum. I am getting resets under boost and higher rpm (8psi at +3500rpm usually). Here is that thread http://www.msefi.com/viewtopic.php?t=20585. Here is another thing I noticed any opinions are greatly appreciated.
Since I wired it in the beginning, I had the 2 extra vb921s wired to the jumper for R43, and have leads that connect that jumper to a DB9 connector with 3 pins for ground (for more grounding ability), and 3 pairs of pins for the 3 coils.
I tried isolating all of the vb921 grounds (including the onboard one that came with ms), so it wasn't grounding through the board at all. I tried firing it up and it was resetting the ecu every few seconds during idle, and the vb921s were getting hot really quick, so I shut it off. I rewired the onboard one to go through the board again, and fired it up and it didnt reset at idle anymore, but still resets under load at higher rpm.
Does the board itself have enough grounding capability to ground the 3 coil ignitors on its own? Should I try to ground all 3 ignitors through the jumper for R43, without the external DB9 helping out?
I'm going to buy NGK BPR7ES resistor plugs and see if it helps out the higher rpm resets. If all else fails, I'll splurge for the MSD DIS 4 box to amplify the outputs. It had no resets with my single VB921 outputing to the MSD 6BTM box that went to my distributer, so maybe the VBs are drawing too much from the MS board to fire the 3 coils on their own. Otherwise it runs great for cruising around town, 22mpg on the highway and 17 in the city with 80lb/hr injectors. I'm using MSI-extra 029q2 code, v3.0 board.
Thanks for the input.
matt
VB921 grounding issues.
Moderators: jsmcortina, muythaibxr
Matt - I ran dedicated grounds to the VB921s via 16 or 18 gauge wire. I was told that in theory the MS could ground all the VB921s internally but to not risk it. Then I was all suggested not to use the DB37 or the DB9 I had added because the pins did not have enough amperage to support the grounding. Go to radioshack, get the "power connectors" they are 4, 6, 9 or 12 pin, get those the pins hold like 8 amp or more I think... I have yet to really drive the car but those are working for me!