Flat power delivery

[Dale FZ1]

After finally solving the coil-related misfire with a set of Splitfires, my test run revealed that there still remains a problem with the power delivery of my s1 R33. Previously running the original coils with insulating tape, I was aware of it, but put the sensation down to weak/inconsistent spark.

The engine pulls quite strongly from off-idle to about 5000, before hitting a plateau (maybe even declining) up to 6000. At that point it takes off and willingly smacks into the 7200 limiter in the lower gears because it builds revs so fast. The flattening out of the power is something akin to hitting a massive ignition retard.

There are no misfires, and the new coils seem to make the engine feel more lively everywhere but that 5-6000 band.

Mods are 3" full exhaust + split dump, FMIC. Std ECU, std boost, std airbox, std platinum plugs 1.05mm gap.

I initially suspected a weak fuel pump, but the way it zings once past the flat spot makes it seem unlikely.

Ignition timing is unchecked, with the CAS returned to the factory sticker-locked position when I replaced the timing belt.

Any ideas?

[JaFF]

it's the standard ecu

[caminperth]

Jaff could be right here. I had the same sort of problem and changed the factory ecu out for another and it fixed it. It could be that the VVT solenoid is not being given the correct signal by the ecu, hence causing the flat spot. It was for mine anyhow...

[Robo's]

Standard ECU, more dips and peaks than Mt. Everest

[Dale FZ1]

So there is a possibility that the ECU has a glitch?

I accept that factory tuning will result in slight dips (impact of tuning around emissions requirements), but this is a major flattening out as described previously.

Why would an essentially unlockable ECU develop a problem like this, assuming that it is the cause of my problem? Any others with like experiences?

cheers

[The Mafia]

yeap, exactly the same with mine. Its the stock ECU, is flat spot city at 5000rpm.

As soon as I installed the PFC, ****en awesomenes.

[Sydneykid]

Standard ECU rich and retard strategy:cheers:

[PlasticStan]

Why would an essentially unlockable ECU develop a problem like this, assuming that it is the cause of my problem?

Because with intake and exhause mods, the engine breathes more efficiently. This means your running in a different part of the fuel and ignition maps than Nissan thought a 'normal' car would be in. So in these areas the ignition is retarted and fuel increased for safety reasons.