"Breaking up" when in boost?

[DrX]

Engine is running nice and smooth idling or cruising, but when I get into boost it wants to break up badly. No misfires logged. Taking a look at this log I think this corresponds to intermittent AFR dips into the 9's on WO2AFR1 which I think is actually on bank 2. Not that I trust the accuracy of the dual LC1s, but it looks like there is a correlation here. A free air cal was done immediately prior to this log.

Motor has fresh coils, wires, plugs which definitely improved how it runs otherwise, but didn't help with this issue. Injectors are also new this year - ID1000 high Z. Current plugs are 8's gapped at .025. Any ideas? Take a look the spots where I give it some throttle and check out the WO2 traces. Didn't have this issue last year before the rebuild.

[joecar]

Hi DrX,

Not only does measured AFR dip excessively rich, but ignition timing pretty much goes to zero.

I can tell by DYNCYLAIR that the VE table is off, I think this is the problem, correcting the VE will get the AFR correct and ignition timing correct.

Can you log SPARKADV...?

[DrX]

I will get that(base spark) next log - deleted it to make room for state00. It was basically identical to run spark except in boost where I am pulling around 4* with A0010. Started tuning with VE scaled 50% and spark tables shifted accordingly from where I was last year. Didn't need scaling last year due to higher FP in boost with the dual FPR fuel system I was running. If VE is off now, one or both widebands are screwed up. To make it even more intersting, in today's log that wide band was dropping to 9 intermittently just cruising!

[DrX]

Here is a new log with A0010 zeroed out. Still get the "popping" from the exhaust in boost (actually sounds more like rapid fire shotgun blasts).

[joecar]

Spark timing is being pulled down alot during boost... do any of the EST_xxxx_DMA pids show the reason...?

[swingtan]

Any chance you have a loose plug lead? looks like the rich spikes occur even when cruising.

Simon.

[nevinsb]

Were the spark plug wires melted? It seems to be a re-occurring issue with mine.

[DrX]

The timing appears to be exactly what is being commanded by the High Octane table.

I replaced the plug wires without any improvement. No misfires logged even though it is obvious.

[DrX]

Looking at the rich spikes logged on WB1 which occur both cruising(more so at MAP values below 60 kPa) and always when into boost(multiple spikes at short intervals- .1 -.3 sec), what could cause this?

1. A bad wideband
2. A sticky injector
3. Intermittent loss of spark on 1 or more cylinders
Any others?

Now which is most likely and why would it get worse in boost?

Injectors, plugs, coils, wires are new. Plugs are gapped at .025"

[slows10]

Looking at the rich spikes logged on WB1 which occur both cruising(more so at MAP values below 60 kPa) and always when into boost(multiple spikes at short intervals- .1 -.3 sec), what could cause this?

1. A bad wideband
2. A sticky injector
3. Intermittent loss of spark on 1 or more cylinders
Any others?

Now which is most likely and why would it get worse in boost?

Injectors, plugs, coils, wires are new. Plugs are gapped at .025"

When you figure out the extremly rich condition under boost, you will have fixed your misfire. Imo it is spark blowout. Did not look at your logs extensively but are you as rich as 9:1 - 10:1 during boost?