Until see Curt's hair stand on end when he gets shocked by his experiment I stand by the previous posts ... the R* is single fire and only fires on the compression stroke.
With the advent of computerized ignitions systems, in our case the ICU, things are not as obvious as they seem. The ICU controls a lot of functions that in previous mechinized engines was controlled by gears, levers and such ... magic.
If you examine the pickup rotor you'll see lobes on it, some with marks. Clockwise, the first mark is on the 4th lobe and is the advance at 10 degrees BTDC of piston #1, the next mark is TDC of piston #1 (let's call this 0 degrees) and the last is TDC of piston #2 (rotationally 402 degrees after #1). The additional lobes prior to the 10 degree advance lobe are to signal the 40 degree advance at 4000
rpm. Only three areas on the lobe are marked because those are the only ones a tech would need when working on the engine.
The lobes trigger the pickup coil on/off sending pulses to the ICU, which then sends a signal to the coil appropriate coil so fire one cylinder. How does the pickup coil know which cylinder is at TDC? ... it doesn't, the ICU counts the pulses. The first rotation of the engine fires #1; the second rotation fires #2.
That's the reason the timing on the R* is not adjustable because if it was, it would screw up the messages received by the ICU.
That's my take ...
Doc
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