1993 Audi USA B4 90 quattro with 4.2 ABZ V8.
60-2 TTV flywheel
Audi OEM cam sensor
OEM injectors (220cc) quite small, should be easy to tune
when I blip the throttle from idle under no load - VERY light throttle and also when pulling away very gently from a stop, the lambda swings very lean as revs climb the very rich as revs fall and engine stumbles badly. I have been fiddling with the VE map and it does not seem to help. This is VERY light throttle blips and slow take-off. Which setting is most likely to cause that?
Also, when I use the timing light to check static timing, should I make an ignition map with 0 degrees in all cells?
It was the ~10% alpha-N setting I inherited from the member who gave me his config. Made it 0% and now idle is stable.
Out of nowhere the idle began oscillating and A/F swings from .8 to 1.4 and engine dies. A/F under load is fine. Just idle is messed up. I did not change anything, but now the beast is untamed again.
quite lean lambda (1.04) in idle range configured, causing some hunting on return to idle
Good tuning strategy:
- much simpler to tune with target a bit rich, than target a bit too lean
- especially near idle
- and especially with big injectors compared to cylinder displacement - not the case with factory injectors;
- even more so if injector opening time differs between injectors (mostly a concern at idle with large injectors fuel pw~1.2 .. 1.6 msec )
- tune slightly richer than target, and only allow EGO to remove some fuel (eg. ego limits: -15% .. +1%).
- rationale: inj or ign problems show up as too lean reading, but adding more fuel will not fix it, rather make it worse.
- rich reading is usually correct, so it is common practice to let EGO remove a small % and do the small final adjustments
- needless to say: tuning should be consistent: the % to be removed should not wildly deviate between loadsites
Obtained good config from member Dangerrous, spent some hours verifying pinouts and calibration, then VROOM!
Discovered that main problem was TDC after trigger was 30 degrees too high, as suggested by anonymous member. I suspected this but was too dumb to make the math with the engine installed - no access to sensor, but invented a way last night. Still need timing light to fine tune.
Right now there is strange behavior from the ISV in that it won't go below 1300 rpm and attempts to lower the rpm result in HIGHER rpm. So... carefully reading the documentation (rtfm). Ah yes... INVERT the output! Sometimes I wonder how I can even tie my shoes.
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