Fixing hesitation on boost

After having the car for a while, I started to notice a kind of surging / hesitation when on boost. Some times the engine would feel fine, other times the performance would feel noticeably blunt.

Once when I got the car back from the mechanic, it felt absolutely terrible the whole time. On that occasion it turned out to be that they had disconnected one of the knock sensors and left it unplugged. I ran a ECU diagnostic using my paper clip method - it alerted me to a knock sensor issue.

The hesitation issue was nowhere near as drastic as the unugged knock sensor, so I was considering a few things that may have caused the problem :

• Spark - lots of RB25 and RB26 hesitation issues are caused by faulty coil packs or other ignition issues like cross firing to the head. I am running stock coils, so these could be a problem.
• Fuel - insufficient fuel could be a problem. However I think I have my fuel pump and return line issues resolved at the moment, running a Walbro 460lph pump, with upgraded wiring and the return line restrictor removed.
• Timing / ecu related. This was actually something I could check just by plugging in a laptop, what is the ECU doing with the timing?

So I went for a drive with Nissan Datascan running, logging the ECU data as I drove. A quick full throttle run would give me the data I needed, and I could compare the ignition timing data to some stock timing maps to see where it was running on the maps.

Reviewing the logs gave a clear diagnosis - the ECU was deliberately pulling timing, leading to the hesitation. Also - when comparing the actual ignition timing values logged, it was clear that this was not a rich and retard scenario, the ECU was instead jumping from the normal ignition timing map to the knock maps!

Now - I always run with P98 premium petrol, so fuel quality shouldn't be the issue causing the sensors to pick up knock. The engine has probably done plenty of kms, and also I have a twin plate clutch which seems to transfer a fair amount of chatter to and from the gearbox, even with it's sprung centre hub, perhaps the knock sensing is a bit pessimistic. After reading some posts on Nistune forums, it seems a few people will disable the knock map switching on high kilometre cars, so perhaps it is time to disable the stock knock sensors to get my ignition timing and power back, and to fit the K-mon with headphones to listen for knock instead!