Magnitude of the Effect of Airflow Correction on Timing

Quote:

Originally Posted by KeithMac

If you have a look at the timing maps, a small change in percieved load (2 row change) can have a massive effect with timing.

Where does your knock start? worste point for me is 4250 rpm where I thinng maximum torque sits.

Silly as it sounds if you bump your boost up to 10 psi (to alter the load row) and trim fuel to gt 11.2:1 you may not encounter any knock, that`s how people size their injectors for use with an AFC.

I was thinking that timing didn't change much after looking at the maps. Am I looking at them wrong? If you look at ~6,000 RPM when it goes from 400 load to 160 there is actually no change (at least on this maximum timing map). Doesn't really coincide with what I am observing on the logs though (how timing jumps 10* when I go from positive correction to negative).

My knock starts around 5,500 RPM (right where I go from positive correction to negative - therefore right where timing jumps from ~15* to ~24*). Maybe it's the sudden change in timing and I should just leave the airflow correction at near zero for lower RPM? The ECU wants like 13.5 AFR at 3,000 RPM and 6 psi which I thought was a little lean so I added correction down low.

That does sound wierd that turning up the boost would help but I see what your saying - higher load will make the ECU lower timing, correct? So at 6 PSI I would be best to just pull back a bit of timing and move on to higher boost levels?

I was shocked the ECU wanted such a rich AFR at only 6 PSI at redline (10.4:1!). This does make it seem that the correction made the big timing jump, but doesn't go alone with what Pete posted..