MSefi.com read only forum (Jan.15,2018)

I have MS2 ver3 2.89 on 454 with a tunnel ram and 2 gm tbi, msd dist and gm 8 pin module. I am running fuel and ignition. The tunnel ram likes lots of idle advance. I am currently running on a run stand and have the initial advance and the offset at 20 degrees. When running on computer advance I run 25 degrees at idle. Although I don't get to the high load low rpm on the run stand I have 100/1000 rpm on the advance table at 10 degrees. I have read that the computer would not be able to command an advance any lower than the offset. Is that true. If so I will have to lower my initial and offset but would leave it as is if no problem as it provides limp home that the motor is happy with.

I have read that the computer would not be able to command an advance any lower than the offset

355vette,

I don't believe it says that anywhere in the manual.

Lance.

355vette,

That may be true for older, more primitive ECUs that basically delayed off the trigger value NOW, but a large portion of the software in the various models of MS is the tracking and prediction systems - where is the crank NOW, how fast is it going NOW, how fast is it accelerating / decelerating, when will the various sparking points come, and when do(es) the coil(s) need to start charging for each sparking point. Within reason, the more teeth on the wheel the more accurate picture the ECU has - the "offset" may be at 20 degrees, but if you have 8 reference points crossing the sensor every rotation, the processor has a pretty good idea of when that next cylinder should be firing, and is quite capable of firing anywhere from +0-90BTDC (numbers may need correcting by wiser heads).

You are right about the manual, I read it in some non manual talk but being a little slow on the take up I could have just typed 10 degrees into TS while running and would have known the answer which is it works just fine whatever the offset is. Thanks Lance