Dwell time not stable during quick acceleration

[vtfvaldir]

Hi everyone,

I'm facing a problem with the dwell time in my setup, and I’m hoping someone can help me troubleshoot. Here are the details of my configuration:

Engine: VW AP 1.8-liter, 4 cylinders
Distributor: Hall sensor with an internal 4-0 toothed wheel
Fuel Injection: Four injectors pulsing simultaneously
Dwell Time: Set to 3.6 ms across all RPM ranges
Firmware: Running the firmware for the Discovery F407 board

The issue occurs when the engine is at idle (around 1000 RPM) and I accelerate rapidly. In this situation, the dwell time decreases significantly, even reaching zero momentarily. However, if the engine is at 2000 RPM and I accelerate quickly, the problem does not occur, and the dwell remains stable.

This behavior is causing ignition instability during rapid throttle changes at low RPM.

Has anyone experienced a similar issue or knows what might cause the dwell time to drop like this? Are there specific settings or configurations I should double-check to ensure consistent dwell time in this scenario?

image.png

image.png

WhatsApp Video 2025-01-08 at 12.02.29.mp4

CurrentTune.zip

Any advice or suggestions would be greatly appreciated!

Thanks in advance for your help!

[AndreyB]

https://github.com/rusefi/rusefi/wiki/rusEFI-Quick-Start-PDF#log-it

[vtfvaldir]

Sorry Andrey, I forgot to attach the log.

2025-01-08_16.22.15.mlg.zip