This Mitsubishi has a HALL trigger on the camsync.
unfortunately
- precision is trash (due to cambelt sloppyness)
- period is same as if it was on crank (less information than normal cam signal: not enough for fully sequential, but enough for wasted spark)
The trigger is Coil type (one pulse per event ), but alternating positive and negative to distinguish 1-4 and 2-3 cylinders (are you sure?).
Somewhere we apparently have a a series capacitor (input highpass filter !!! ) that causes the very characteristic sharktooth signal.
- maybe in the notebook: I recorded the trigger signal with a notebook. Almost sure that this is the case since the signal measured (with DVM) DC=2.5V amplitude: ~2.5V which suggests a normal 0/5V signal. Once measured with engine off it was 5V.
The signal is currently processed with LM1815 and series condenser so it is theoretically universal considering trigger type (hall and VR). In 50% of cases, LCD displays right value, otherwise rough half of proper RPM.
if we reconstruct the original signal, we can see that
- pulse for cyl1,4 has a longer width
- pulse for cyl2,3 has a shorter width
Note that
- falling edges are equidistant
- good for triggering
- store timestamp in ptrig_capturedtime_prev
- rising edges are not equidistant (only useful for checking cyl1,4 vs cyl2,3 and updating igncount). pulsewidth=time since ptrig_capturedtime_prev (last falling edge)
- if this pulsewidth is (significantly, or with any amount) longer/shorter than previous pulsewidth than igncount=ignchmax
Find the correct cyl:
- camsync
- using bothedge ( LM1815 not suitable) and consider signal length: firmware modification
- modify primary_trigger_init() so IC1 initialized (similar to IC3 in secondary_trigger_init() ) that both edge triggers. Maybe setting just one edge and changing to falling/rising in interrupt is necessary
- detect edge in PRIM..TRIGGER interrupt
Any ideas, how to condition the signal?
- remove the 10k pullup on trig1 input inside v3.x (if not already removed)
Setup is not VR anymore, but the symptoms are the same
I converted the TRIG1 input to hall setup and removed 10k pullup as well, but I don't have stable RPM signal yet as I described above.
This must be something trivial. Eg. if you configure falling edge (primary_trigger bit0=0), RPM reading should be rock stable. Maybe you accidentally configured rising edge (primary_trigger bit0=1) ?
On the other hand I found an other trigger:
An other trigger found
I've found an other trigger probably from crank-shaft HALL because 3 wires are coming from the bottom of engine (I will check it soon). Wires: 0V, 12V, signal (0V or 5V).
Notes:
- I don't understand why 12V and why not 5V is on feed.
- Observation: AC and DC voltages are measurable between the trigger described here and above. (unfortunately this info is of little use).
- Signal levels are almost the same than in the previous case. DC=2-2.5V, AC=2-2.5V, same frequency (measured by DVM).
- Since I use this trigger I have stable RPM signal. It is good for setting up injectors, but not enough for ignition.
- coil type setup in config. TODO: the other relevant config, eg. rpmk[] and config13, etc..
- Does this facilitate to get the trigger needed for wasted spark?
- Is it worth to connect both triggers to primary and secondary inputs, and try to determine which cylinder to ignite with alien which is already implemented in the firmware?
We know too little about this. Scope snapshots would be nice. particularly, with 2 channel snapshot together with the CAM-HALL. Maybe connecting the
- crank-HALL to primary trigger and
- CAM-HALL to secondary trigger (configured for both edges or falling edge)
- simpler firmware modification and
- better ignition precision
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