MEFI 1 basic and total timing?
07-15-2018, 12:28 PM
#1
Registered
Thread Starter
MEFI 1 basic and total timing?
97 502-MAG all stock. Got a few general questions
1- Spec calls for 8 BTDC when setting timing per factory(Rinda) how much is added when going from basic back to normal mode at idle.
2- From what I found total timing is 30* but not sure what RPM that is at
3- From my past younger days 30* seems low
4- Running 89 octane can more timing be used and if so what... or not worth any gains?
thanks
1- Spec calls for 8 BTDC when setting timing per factory(Rinda) how much is added when going from basic back to normal mode at idle.
2- From what I found total timing is 30* but not sure what RPM that is at
3- From my past younger days 30* seems low
4- Running 89 octane can more timing be used and if so what... or not worth any gains?
thanks
07-16-2018, 07:00 AM
#2
Platinum Member
Platinum Member
iTrader: (1)
Maybe trash will reply but its been said that mefi1 looks for kock upon startup or at somepoint thru its knock module than does something w the timing then runs w reduced timing if it doesnt see it hit the threshold w high octane fuel plus theres some kind of multiplier for timing once it reaches the top of tables. I just rooted all that knock module crap out of two of them i converted to mefi3, Smitty
07-16-2018, 11:57 AM
#3
Woodchuck,
To your question in general, 8 deg BTDC in base timing mode (A-B pins jumpered on the DLC) is what the distributor should be set to mechanically. This value should match what is stored in the MEFI 1 assuming a stock profile. I do not recommend simply advancing the base timing.
How did you find total advance to be 30 degrees?
Typically I've found Merc tables to have highest advance in the midrange rpm and MAP settings. They tend to taper off at high MAP and RPM points, likely to better warranty the motor.
I don't have a 502 MAG/EFI/MP file but do have a 454 MAG EFI/MP file WOT advance is 27.8 degrees. BUT!!! That is not peak advance. Peak advance is 38 degrees 2400-3200 rpm in the 80 kPa column. It tapers off at higher rpm and MAP settings.
It is unlikely you will gain any "measurable" in the boat difference in max speed by changing the advance a1-2 degrees at WOT. Where you would feel the difference is coming on plane and midrange IF the advance was insufficient by a large margin in that regime.
If you are stock I would leave it alone. You are likely worrying about a problem that doesn't exist.
To your question in general, 8 deg BTDC in base timing mode (A-B pins jumpered on the DLC) is what the distributor should be set to mechanically. This value should match what is stored in the MEFI 1 assuming a stock profile. I do not recommend simply advancing the base timing.
How did you find total advance to be 30 degrees?
Typically I've found Merc tables to have highest advance in the midrange rpm and MAP settings. They tend to taper off at high MAP and RPM points, likely to better warranty the motor.
I don't have a 502 MAG/EFI/MP file but do have a 454 MAG EFI/MP file WOT advance is 27.8 degrees. BUT!!! That is not peak advance. Peak advance is 38 degrees 2400-3200 rpm in the 80 kPa column. It tapers off at higher rpm and MAP settings.
It is unlikely you will gain any "measurable" in the boat difference in max speed by changing the advance a1-2 degrees at WOT. Where you would feel the difference is coming on plane and midrange IF the advance was insufficient by a large margin in that regime.
If you are stock I would leave it alone. You are likely worrying about a problem that doesn't exist.
