Q: Can someone give some good info about turbo Eclipse Gen1 4G63T DOHC trigger pattern? Use optical sensor on cam with 2 signal wires and 2 for supply. It must be simple trigger.

This is NOT about "engine", but about a "trigger" setup (HALL/HALL where sectrig =camsync HIGH/LOW pulse length varies)

This Mitsubishi has a HALL trigger on the camsync.


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?).

The trigger signal was recorded with a notebook, that's why the squarewave looks distorted (to sharktooth signal) by the highpass filter (series capacitor) on the notebook audio input.

With DVM DC=2.5V amplitude: AC ~2.5V is measured that you expect for a normal 0/5V signal with 50% duty. With engine off, 5V (DC) is measured.


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

(or the other way around)

Note that

Find the correct cyl:

Any ideas, how to condition the signal?

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).


We know too little about this. Scope snapshots would be nice. particularly, with 2 channel snapshot together with the CAM-HALL. Maybe connecting the

and measuiring "alien dwell" would work to sync to CAM. This would mean than without the crank signal.

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