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662 Posts
Discussion Starter · #1 ·
tunning book
First, get and read Greg Banish's book Engine Management: Advanced Tuning, then proceed to tweaking the tune.

I have no idea what initial changes Diablo makes to their canned "xx octane" tunes, however an increase of 5° to 10° in the Global Spark Adder ranges from pretty aggressive to scary.

Most canned "93 octane" tunes add 4° to 7° to the overall timing by various combinations of bumping the Spark Borderline Table (SBT) at higher loads (>70%) by 2°-3°, and/or bumping the Global Spark Adder (GSA) by the same.

FWIW--the relationship between the SBT and GSA is that the PCM will calculate ignition timing (using load, TPS, rpm, IAT, etc.) and then compare that calculated value to the SBT value at the current load and rpm. It will then select the lower of the two values (the calculated and that from the SBT). With this done the GSA is added to the selected value to determine the actual timing to be applied.

I.e. the SBT limits the calculated timing if needed, the GSA is always added to the calculated timing value...
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