The old v3 was very non-standard.
Originally low voltage flyback.
~10 Ohm injectors so the replacement ECU has 30V flyback which is better. But you need to increase VE table especially at low kPA to get appr +500 usec longer pulsewidth.
Without tuning the VE table the engine can be lean, undrivable, and misfire. The USB-RS232 can indicate misfire by disconnecting.
solution: Increase fuel pulsewidth
You can get an idea of the direction of required changes:
- in the VE-table we increased the lowest-kPa row by +32, than gradually only +24, +16, +8, +4, +2... import VE table by saving [this vemscfg] to disk and dragging over the VemsTune VE table (VE tuning)
- this is just very approximate, to show the direction of changes, the engine must be fine-tuned for proper lambda 0.96 .. 1.00 at low load (that's why the wideband lambda sensor is installed)
- and in "Engine setup" dialog increase req_fuel slightly (eg from 3.0 to 3.1 msec)
Alternatively, in injector settings "injector opening" can be increased (eg. from 208 to 720 usec).
See tutorial videos under [vems.hu/vt].