I was comparing the stock P72 map which has a timing of "negative 4" (i.e 4 ATDC) at 500 rpm/3kpa.
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I used a another after market ECU before and the timing at 500rpm/3kpa is way different 8 degree BTDC.
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I just want to understand or confirm that in S300, that on firing (500 rpm) does the S300 ECU use a hidden cranking timing table* or is it using the ignition map at 500rpm/3kpa. At what point does the ECU switch to the main ignition map (from the hidden cranking map)
* I changed timing at 500rpm/3kpa and the engine still cranked at -4.SO ia m wondering what are those cells for and what should be the range of acceptable values
From my S300 datalog I can see that immediately after firing at 500 rpm the ghost traces the 500 rpm.3kpa cell.
I also want to know - does the cranking timing vary with ECT and if so that is the hardcoded values is cranking retarded 4 degree across all ECT?
As I using race cams i cant get the distributor/timing using "set timing" at 16 degrees
i also read this - Some programmable engine management systems have a default cranking advance of 15 degrees, a value about midway through the range of appropriate cranking advances. Smaller engines with faster cranking speeds need a greater ignition advance (up to 20 degrees), while slower cranking speeds of a high compression engine will require less advance (down to 10 degrees). The compression ratio of the engine will also determine the likelihood of kickback on starting. Engines with a low static compression ratio of 8:1 will accept an ignition advance of anything from 0-20 degrees without kick-back. A 10:1 compression ratio will reduce this to 15 degrees, 11:1 to around 10-12 degrees, while race engines using very high compression ratios of 12-13:1 can sometimes tolerate no cranking ignition advance at all.
Can cranking ignition be changed by rotating the distributor?
The above is from Flash Pro...guess you would change it is you radically upped the compression.