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Ideas for improvements:
I've made and installed a circuit in my car which could hold the power supply to the ECU even when the ignition is turned off. It's possible by holding the relay from one P259-output. The circuit works great but some functions in the firmware would be needed to make it work as thought.
This circiut makes it possible to:
- Improve coldstarts
- Cooling fan, water pump (and so on) controlled by VEMS can operate even if ignition is turned off
Functions requested:
- When ignition turns on, VEMS activates the P259 output.
- When the analog output goes high (ignition is off):
- Cut the fuel to kill the engine (or do it a while after as a turbo-timer)
- Start a timer which counts down to zero, then deactivate the P259 output and cut the power to VEMS.
Idea how to improve coldstarts:
- If the engine stops just a while after a coldstart it doesn't need as much fuel-enrichment as the very first start. (For me which runs on E85, this becomes a problem because the engine requires very large fuel-amounts the first cold-start) The timer(described above) could be used as some kind of scaling value for the enrichment..
- For example the afterstart enrichment could be a 8x8(or something more suitable) table with temperature on y-axis and engine-revs on x-axis and let the timer decide where on the x-axis to read from when restarting the engine. The crancing enrichment would need to be scaled too at somehow..
Saab DI-Ignition
I did some changes in the old open-source code(r027) to drive a saab with DI-ignition system, and it worked good! The changes and problem I solved was following (summary):
- The DI-casette fires the spark on the rising edge of the dwell, instead of falling edge like usual ignition-coils does.
- Function requested: An option in ignition settings which decides if the sparks should fire on rising edge(saab DI) or falling(usual ignition coil). Then I can upgrade from stone-age firmware r027 to the newer and at least run with waste-fire.
- The sync signal which uses the ion-current from the sparkplug (cyl 1+4) or (cyl 2+3) to sync, is quite noisy and needed some filtering(software). A reliable signal is more than 1,9 to 2,3millioseconds long.
- Note: I've seen that the newest firmware have a similar option for the secondary trigger settings. A firmware request would be to wait for x similar positioned(at the same position in ref-tooth table for example) signal to entering seauential ignition and require y lost signals to exit sequential and only run waste-fire.
- When no combustion occurs during start, engin braking (or just a noisy signal in low loads) no sync-signal is detected. Then it runs waste-fire. As soon as it detects a good sync-signal it goes to sequential again!
- Note: Maybe it would be nice to include this in ordinary cam position-sensor installs too, if the sensor fails.
[clean sync signal cyl 2+3]
[noisy sync signal cyl 2+3]
