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Megasquirt MS3X BIP373 ignition tuning

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hi guys,

yes you read correctly. I have a MS3X and Im using a BIP373 installed on the MS3 mainboard for my ignition for now. Later if my budget allows it, Ill move over to LS truck coils, but no budget currently. I attached my MSQ for reference, but here is my setup:

1977 GMC C15 Suburban

454 Chevy Big Block MKIV, stock, except for the Edelbrock Performer cam and Air gap intake

FAST dual sync distributor for cam and crank signal + MSD 5526 streetfire coil

fuel: IMPCO 300A LPG mixer on thethrottle body (will change that to LPG vapour port injection later)

I had all kinds of trouble getting this FAST dizzy setup, because the hall sensor broke and the phasing of the distributor seems to off from what its supposed to be from factory. Fast couldnt confirm so far and havent been a lot of help in trying to solve it. But got it running with help of the Megasquirt community.

I am now tuning my ignition timing and its my first time doing so. So Im new to al the stuff Im noticing on how the engine responds to my changes.

I attached two log files. One with data where I experienced hesitation/hickups during cruise at about 80km/h. And one after dropping the timing a little in those cells and now the hesitation is gone. The thing is I would have thought these cells would take a lot more advance, since Im running LPG and its at low load and I have a low compression engine.

I also took some data at 100 kph and then I sense no hesitation or hickups (or whatever you call that) under cruise. Ill also add that log.

At first I had a lot of added vacuum advance at low loads and low rpm (by mistake) and also noticed the same hesitation trying to take of at around 40 degrees of advance. taking some advance out solved that too.

So I was hoping you guys could look in my log files and tell me what you see?

And what could cause this hesiation (feels like dropping sparks/cilinders) at this advanced timings at cruise?

weird...I cant share MSQ nor log files?

Attached Files
  • 38-vs-36-degree-advance-knock-visible-in-datalogs.jpg
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

can you confirm you have locked the dust internal advance and disconnected the vacuum advance or locked it

the ECU should handle all advance the phasing of the rotor can be checked by cutting a hole in the distributor cap and using a timing light to see the position of the rotor while reving the engine

Hi Ross

yes I have. The FAST dual sync is a off the shelf product:

I'd rather not drill a hole in my cap, cause I dont have a spare I can use for that. Is there another way other then by eyeballing it like I did doing my setup video?

setup video I made for reference: [url=]