I have a problem with missfires on a Volvo S60 R machine.

It runs with VAG 115 coils and it runs fine up till 1.6 bars boost, 420bhp.

But when it boost more, up to 1.8 bar, it starts to studder, one or more cylinders misfires.

We run NGK BCP7RES plugs, with 0.5mm gap. The coils are all new, and ao is the plugs. The injectors have been checked for flow and were within 5%. The compression os also good on all cylinders.

And the problem only appears on full load on 4th and 5th gear at max torque.

I suspect that because we run on 4 stepper outputs, the 5th coil runs on a logic output this might be the problem.

And my question is, could a to low pull-up be the problem?

How much do the VAG115F coils need to give good opperation?

The VAG 115F should work without problems on both stepper and logic out outputs but when using logic out make sure you have applied the double 510 ohm resistor series (resulting in ~255 ohm resistance between hc259 and logic output pin).