Actual Spark vs MBT & BDL

[Brewster]

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.

BREWSTER_230519a-V11.bin

(256 KiB) Downloaded 157 times

WOT-V11.xdl

(17.64 KiB) Downloaded 151 times

[decipha]

actual spark is reverse calculated from the cam sensor

did u look at ect and act retard functions?

[Brewster]

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.

[Brewster]

actual spark is reverse calculated from the cam sensor

did u look at ect and act retard functions?

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.

[decipha]

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.

[Brewster]

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?

[decipha]

correct

no, the ect and act retard are already setup you shouldn't need to mess with that just the borderline table

[Brewster]

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 ?

[decipha]

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

[Brewster]

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.