Actual Spark vs MBT & BDL
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- Posts: 92
- Joined: 2021 May 15, 15:59
- Location: Edmonton, Alberta, Canada
- Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185
Actual Spark vs MBT & BDL
Looking for clarification when datalogging, if we are watching the actual spark value and it is dropping compared to the MBT or BDL spark values is the actual spark value what the engine is getting for ignition timing.
At any given time the actual spark delivered is the lowest spark the ecu calculates.
With that being said if I'm commanding 17 degrees in the Borderline table but only getting 14 degrees actual what is causing this. Surfed the timing write up as well as all retard functions that I could find and not seeing reason to be losing actual spark. Log and file attached, mid range the actual spark drops and doesn't follow the BDL table.
At any given time the actual spark delivered is the lowest spark the ecu calculates.
With that being said if I'm commanding 17 degrees in the Borderline table but only getting 14 degrees actual what is causing this. Surfed the timing write up as well as all retard functions that I could find and not seeing reason to be losing actual spark. Log and file attached, mid range the actual spark drops and doesn't follow the BDL table.
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- Posts: 5126
- Joined: 2021 Feb 15, 12:23
- Location: Metairie, LA
- Vehicle Information: Work Truck
'19 F-150 3.3L
Re: Actual Spark vs MBT & BDL
actual spark is reverse calculated from the cam sensor
did u look at ect and act retard functions?
did u look at ect and act retard functions?
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- Posts: 92
- Joined: 2021 May 15, 15:59
- Location: Edmonton, Alberta, Canada
- Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185
Re: Actual Spark vs MBT & BDL
Yea I think I've found the right ones, They don't look like they would be limiting anything the way there set up. When I had ACT sitting around 100-120
deg f I lowered the 130deg cell value then also found out those cells get divided by 10 which would be 0.2 and I'm seeing a bit more then that.
I also found this list of spark source values online, Guessing this is accurate data when looking at actual spark.
deg f I lowered the 130deg cell value then also found out those cells get divided by 10 which would be 0.2 and I'm seeing a bit more then that.
I also found this list of spark source values online, Guessing this is accurate data when looking at actual spark.
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- Posts: 92
- Joined: 2021 May 15, 15:59
- Location: Edmonton, Alberta, Canada
- Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185
Re: Actual Spark vs MBT & BDL
So with that being said what value is more important to watch on the datalogger, Actual or Borderline. I mean if actual is actual and I'm only actually getting x amount of spark ignition timing then is that where I'm lacking in the power production department. What would be removing a few degrees of spark, I read it uses the lowest values and it looks like the Borderline spark table is lower then the MBT table, MBT table looks healthy and I can't see that coming into play, also read your cals should be using the borderline table and obviously adders and subtractors.
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- Posts: 5126
- Joined: 2021 Feb 15, 12:23
- Location: Metairie, LA
- Vehicle Information: Work Truck
'19 F-150 3.3L
Re: Actual Spark vs MBT & BDL
Neither.
actual is what the cam sensor says you have, it could be wrong though.
borderline is what you should be commanding.
saftot is the actual commanded spark and what you should be looking at.
actual is what the cam sensor says you have, it could be wrong though.
borderline is what you should be commanding.
saftot is the actual commanded spark and what you should be looking at.
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- Posts: 92
- Joined: 2021 May 15, 15:59
- Location: Edmonton, Alberta, Canada
- Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185
Re: Actual Spark vs MBT & BDL
Mint, so if actual is lets say correct, then is that what were theoretically getting?
In this Calibration I'm using is it pretty much on the ECT and ACT retard functions that should be modifying timing or is there a bit more to it?
In this Calibration I'm using is it pretty much on the ECT and ACT retard functions that should be modifying timing or is there a bit more to it?
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- Posts: 5126
- Joined: 2021 Feb 15, 12:23
- Location: Metairie, LA
- Vehicle Information: Work Truck
'19 F-150 3.3L
Re: Actual Spark vs MBT & BDL
correct
no, the ect and act retard are already setup you shouldn't need to mess with that just the borderline table
no, the ect and act retard are already setup you shouldn't need to mess with that just the borderline table
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- Posts: 92
- Joined: 2021 May 15, 15:59
- Location: Edmonton, Alberta, Canada
- Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185
Re: Actual Spark vs MBT & BDL
So why would I be losing some spark advance compared to what is being commanded. Like you were saying its either not accurate or is there something modifying the commanded spark ?
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- Posts: 5126
- Joined: 2021 Feb 15, 12:23
- Location: Metairie, LA
- Vehicle Information: Work Truck
'19 F-150 3.3L
Re: Actual Spark vs MBT & BDL
could be some timing chain stretch
commanded spark is saftot, no such thing as modifying commanded spark its the lowest calculated spark. You have modifiers to individual spark sources that are modifiers but not actual commanded spark.
it looks perfect to me in the log, there will always be some slight variation
commanded spark is saftot, no such thing as modifying commanded spark its the lowest calculated spark. You have modifiers to individual spark sources that are modifiers but not actual commanded spark.
it looks perfect to me in the log, there will always be some slight variation
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- Posts: 92
- Joined: 2021 May 15, 15:59
- Location: Edmonton, Alberta, Canada
- Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185
Re: Actual Spark vs MBT & BDL
Good point on the timing chain stretch and I figured a bit of variation was normal but just wasn't sure if this was excessive or not.