tach indicates half actual rpm

[TimT]

Using the recommended settings, the tach is off by a factor of two. Half what
it should be. The only setup for TS that will give the correct reading is one
cylinder, two stroke.
My test setup produces one pulse per revolution, 33 ms apart.

Is it possible to change the code for the tach to correct this?



Equipment:
two rotor rotary eng.
MSII, V3.0, code 2.889, Hall circuit
Honeywell Bipolar Hall sensor 103SR17A-1
8 pin GM HEI module
MSD 8207 coil
Dell dual core, vista
Tunerstudio MS
Belkin F5U409 usb - serial adapter

[Matt Cramer]

If you want to control ignition on a rotary engine correctly, you'd need at least two pulses per eccentric shaft revolution anyway. Usually the MS would be set to a four cylinder four stroke in that case.

[TimT]

The ignition control for the second rotor is a complete and separate system (for me). A second hall sensor, hei module and coil. The difference b/w the two ign. is the magnets
are offset by 180 degree.
Is it possible to combine the two pulses into MS to give the needed two pulse per rev.?

[Matt Cramer]

It should work if you wire them in parallel - however, you'd only be able to run the ignition in wasted spark like that. Is the MS controlling spark or is it not?

[TimT]

Matt,
Is the MS controlling the timing? Good question. I have pin E of the module connected to pin 36, pin R to pin 24, and pin B to pin 6 as suggested in the hei manual.
The coil is connected to the module coil pins as usual.
The test setup is running at a constant 1818 rpm (33 ms pulse rate). I know the firing is following the pulses from the hall because I see the firing rate slow as the motor slows to a stop. TS indicates the timing is around 16 degree advance at full speed. There is no O2 sensor feedback. I can only assume the module is controlling the firing. Is there a better way
for one to determine?
I just remembered that the test setup was operating as stated above without pins B,R,E connected to the MS so I think the module is controlling. The only thing I'm not sure about
is the advance.

I follow your thinking on the pulses in parallel and wasted spark scheme but you can see the problem with doing this on a rotary. I'm using a dual post coil so both plugs fire at the same
time for one rotor. At low speeds (low advance) you may have the trailing plug firing into the oncoming charge (firing at or just after the apex) on the wasted spark. Besides redundancy that was my reasoning for going with a separate ign. for the second rotor.
I would rather find where I can insert a *2 for the tach code in TS.

Tim

[Matt Cramer]

So, if I'm reading this correctly, you've wired the MS to control timing on one rotor but not the other?