isx 870

[Rawze]

(05-28-2020 )ynot Wrote:  ...
It sounds like who ever turned it was trying to tune the 870 to be a 570, that SOI map looks a lot like a 570 ish map.
...

They were not even close. Here is the pre-2000 CM570 Sig.-600 (API/APX) finalized start of injection timing map for all 4 (denoted as "4D") engine modes...




The older engines used ATDC offsets and the newer engines use BTDC offsets. So to get a proper visual representation, I had to flip the 3d chart below ( used "zero-{mapped values}" ) to correct for ATDC vs the newer BTDC so that it can be compared visually.


Granted, it is not as smooth as newer maps, but nowhere is there +12 degrees offsets at high fuelling output or crazy and whacky jumps like seen above.

the trouble is that too many idiots will copy paste parameter tables form one engine to another with no reference or clue of its use, or even what compensations may be done to it before it is applied. - I see it all the time, and it is downright shameful how little most of those people who dig around inside other people's ecms really know.