Sandro

iTrader: (1)

I understand (e.g. re. page F-34 of the Service Highlights Manual) that one of the two crank sensors is used to reference the TDC. I also understand that the two spark plugs are physically located to a certain degree difference relative to the TDC (like +5 for the L and -15 for the T, if I am not mistaken).

How do the advance timing in the IGL and IGT maps relate to the physical location of the spark plugs?

In particular:

1. If you have e.g. 15 deg advance in your IGL map, would that include the 5 deg physical distance between TDC and the leading plug hole, or not?

2. If you have 0 deg in your IGT map, would the two sparks fire at the same time, still leaving a 20 deg "physical" difference in between, or else?

Thanks.

- Sandro

cewrx7r1

iTrader: (2)

Same as for a piston engine except instead of vertical, ours is horizontal.

Sandro

iTrader: (1)

Thanks.

- Sandro

arghx

iTrader: (3)

Yes. That's partly why from the factory there is 0 split (FD) or negative split (Rx-8) in a lot of low load areas.

You have to remember that the leading plugs are waste sparked on the FC and the FD. So both rotors fire at the same time on the leading, and then the trailings fire one after the other. The Rx-8 uses 4 separate coils that can fire independently (hence the crazy firing order at idle). This provides much better control over combustion, although the Rx-8 coils have had major build quality problems.

as an important side note... most modern EFI ignition system have two basic signals: a G signal and an Ne signal.

The G signal senses top dead center and helps the ECU figure out which cylinder/rotor is in the compression stroke. On the FD this is mounted to the pulley. On the FC it is integrated into the top part of the drop-in crank angle sensor. On a piston motor, this signal comes from the cam shaft position sensor(s) if there is no distributor. This signal relies on only a couple teeth (depends on the design).

The G signal is very important for timing the firing of the fuel injectors themselves. During cranking and during tip-in, fuel injectors are batch fired (all fire at the same time). During normal running they are fired sequentially. This is covered in the FD service highlights but also the Rx-8 service highlights.

The Ne signal actually senses engine speed. It tells the ECU how fast the engine is going and is important for calculating engine load for spark timing and fuel injector pulsewidth. This sensor usually uses a bunch of teeth.

On the FC and FD, there is 1 G signal tooth for every 12 Ne signal tooth. So 2 + 24 teeth. More modern crank angle sensors use Hall Effect sensors which rely on magnets.