Ported MAF ends causing incorrect load readings and KR?
Ported MAF ends causing incorrect load readings and KR? I have had ported MAF ends on my car for about two months. I recently started tuning the spark advance with LS1Edit and discovered that the MAF ends may be causing KR at certain RPM's, and that further, they cause incorrect engine load readings.
I noticed on EFIlive that I would experience high KR at 20-51% throttle in 4th after the converter locks RPM was between 1500-2000. Typically when trying to go up a hill or accelerate. Calculated engine load (using the formula 15*MAF(gm/s)/RPM) was between .3200 and .5250.
EFILive shows timing advance just before the KR to be 35 or above. I would get as much as 8 degrees of KR before I let off the throttle when I realized this. If I gave the car enough throttle to unlock the converter or shift to 3rd, the KR would go away.
I thought I would just adjust the timing advance in LS1Edit and fix it.
When I looked at the tables, the advance shown on EFILive was much more for the given load and RPM than what was programmed in.
I was very suprised at this. I then looked at the advance values for the given RPM's, but with lesser engine load, and voila! those are the values at which I was getting KR.
I am thinking that the ported MAF ends are flowing more air than the computer thinks, so therefore the PCM's calculated engine load would be too lower than the actual load, and subsequently result in excessive spark advance and KR.
I plan to put back on stock descreened MAF ends this weekend and see what happens.
Anyone else have these findings?
Comments?
I noticed on EFIlive that I would experience high KR at 20-51% throttle in 4th after the converter locks RPM was between 1500-2000. Typically when trying to go up a hill or accelerate. Calculated engine load (using the formula 15*MAF(gm/s)/RPM) was between .3200 and .5250.
EFILive shows timing advance just before the KR to be 35 or above. I would get as much as 8 degrees of KR before I let off the throttle when I realized this. If I gave the car enough throttle to unlock the converter or shift to 3rd, the KR would go away.
I thought I would just adjust the timing advance in LS1Edit and fix it.
When I looked at the tables, the advance shown on EFILive was much more for the given load and RPM than what was programmed in.
I was very suprised at this. I then looked at the advance values for the given RPM's, but with lesser engine load, and voila! those are the values at which I was getting KR.
I am thinking that the ported MAF ends are flowing more air than the computer thinks, so therefore the PCM's calculated engine load would be too lower than the actual load, and subsequently result in excessive spark advance and KR.
I plan to put back on stock descreened MAF ends this weekend and see what happens.
Anyone else have these findings?
Comments?
