I took the car for a dyno tune and for some reason the car consistently misfires from between 5-6k rpm then smooths out again. This was for every run. The tuner couldn't figure it out. Pulled the plugs and gapped to .025. Plugs looks good. 3k miles old

Could it be because of the butterflies opening on the 99 head?
Car runs real smooth from 5k rpm down.


Thanks

 

Datalog? Losing sync?

 

I've had this kind of thing with my DIYPNP.

First of all with the 1st Deriv prediction enabled in the ignition settings I get mis firing around this rpm. I disabled this and things were strong up to 6500rpm where it hit a flat spot.

This was with a spark duration of 1ms and max dwell of 3ms. After reading that DIYPNP recommended 4.5-5ms dwell for my '90 miata I tried 5ms and got a bit flat spot around 4-5krpm

After this I reduced the dwell to 2.6ms and there were no flat spots throughout the rev range but the low end seemed sluggish.

I changed the max spark duration to 0.7ms and max dwell to 2.7ms (yes random changes ftw..) and now the car has no flat spots anywhere and feels torquey and strong everywhere.

Might be worth experimenting with. SpookyFish was having a similar issue and it seems that he noticed an improvement with a lower dwell setting before spinning a bearing.