ERL 430 w/ LS7 top end questions. HELP!
05-08-2018, 04:48 PM
#21
Maybe I was informed wrong long ago, but I've always been under the impression that you need to retard the timing above peak torque because the "window/time" to burn fuel is less/shorter as RPM goes up. The timing demands of an IC engine should follow the torque curve pretty closely.
I've also seen a drop of 50 HP when going from 24 to 26 degrees on a healthy LS7 N/A combo on an engine dyno.
The combustion chamber design is going to dictate a lot of the burn rate and subsequent timing requirements. The small efficient chambers in most LS heads will require less timing. Also, as compression increases, timing requirements typically go down. The fuel type and octane will have an effect on the timing requirements as well.
I've also seen a drop of 50 HP when going from 24 to 26 degrees on a healthy LS7 N/A combo on an engine dyno.
The combustion chamber design is going to dictate a lot of the burn rate and subsequent timing requirements. The small efficient chambers in most LS heads will require less timing. Also, as compression increases, timing requirements typically go down. The fuel type and octane will have an effect on the timing requirements as well.
If you lost 50hp by going from 24 to 26 degrees there was certainly abnormal combustion going on.
My experience with LS engines is that when you get in the right ballpark they're incredibly insensitive to both fuel and spark.
Last edited by spanks13; 05-08-2018 at 05:59 PM.
05-09-2018, 10:25 AM
#24
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Max BMEP = Spark Instant Hi Spanks, I have worked with Large Cam engines.
The Spark Instant can be MUCH GREATER when the engine is OFF SONG, then at peak BMEP the Spark advance is LOWERED, then increased/decreased as RPM increases.
The art of best engine timing is FOUND AT Peak Torque then as RPM is increased that Torque value is maintained as best as possible.
MY OBSERVATION is when the advance is too great the RPM/Torque will DROP over time.
My OBSERVATION is when the advance is too low the RPM/Torque will INCREASE over time.
MY OBSERVATION is when the advance is correct the RPM/Torque will be STABLE over time.
Lance
The Spark Instant can be MUCH GREATER when the engine is OFF SONG, then at peak BMEP the Spark advance is LOWERED, then increased/decreased as RPM increases.
The art of best engine timing is FOUND AT Peak Torque then as RPM is increased that Torque value is maintained as best as possible.
MY OBSERVATION is when the advance is too great the RPM/Torque will DROP over time.
My OBSERVATION is when the advance is too low the RPM/Torque will INCREASE over time.
MY OBSERVATION is when the advance is correct the RPM/Torque will be STABLE over time.
Lance