I am new to tuning fuel timing, so please forgive anything that might seem otherwise obvious. My understanding is that the fuel should be hitting the back of valve just as it's about to open. I have a cam profile similar to the 944/924S data shown here, with the intake lobe center 115 deg. ATDC: http://members.rennlist.org/951_racerx/CamProfiles.pdf
Setting the fixed timing to 110 degrees seems to run the car fine, although I am posting this because I am not sure what that fixed timing is relative to. It's semi sequential, so it all happens every 360 crank degrees. I have read posts on here where people are saying it's relative to spark timing - is that true in the latest MSExtra firmware I'm running? Is that fixed timing degrees BTDC, or ATDC?
My other area of interest is in tweaking the injector timing table. I made a spreadsheet that takes into account the VE table, head and runner geometry, displacement, cam lift and duration, and injector dead time to calculate (roughly) the degrees by which an injection should be advanced in order to maintain a point in the cycle where the fuel always reaches the port at the same time. This is just to give a rough idea of how the timing should vary with respect to RPM and fuel load. Is this consistent with reality/theory concerning injection timing? Note that these degrees are all relative to a fixed point in the cycle, not relative to spark timing or anything else.
