You're learning about ignition compromises and "tuning". It's an interesting exercise in physics IMHO. The basic variables are cylinder pressure and voltage. The wider gap literally raises the spark voltage, makes a later hotter spark, but one thats more delicate: closer to not being able to happen at all. When the pressures raise or the voltage drops, the spark goes out. Higher RPM raises the current requirement proportionally, and thus lowers the spark voltage because the coil can't charge itself fast enough.



Scene 1: Wide gap, factory timing. This is essentially a retarded timing, probably misfiring because of the wide gap, not preigniting.

Scene 2: Wide gap, further retarded timing: makes the more delicate spark stable, but produced heat more than power.

Scene 3: Factory gap, retarded timing: essentially this is a tune for high boost. Again, trend is towards heat not power.

Scene 4: Factory gap, factory timing: APC limits boost to keep engine from pinging. Maximum performance is obtained from the fuel and atmospheric conditions available (within static timing limitations anyway)

Decreasing the gap improves spark quality under high ambient temperatures and high boost and high rpm, because it lowers the minimum-voltage requirement to strike a spark!

The optimal setting for factory hardware really is basically the factory spec, and premium gas, maybe slightly advanced like 18-BTDC instead of 16.

This starts the rabbit hole of tuning old technology - the timing control of this car consists of a vacuum bottle that retards timing a little at slight boost. The next bandaid is the MSD Boost Timing Master, which allows you to retard timing based on boost, so you can run more advanced timing off boost…but pretty soon you’ll realize it’s cheaper to update to Trionic 5. You also have a delicate gearbox, don’t push it, but thats just my .02.

posted by 76.105.241...

• Plug gap, timing, and boost, Oh my! (long), steven W, Fri, 14 Apr 2017 05:24:54
  • Plug gap, timing, and boost, Oh my! (long), SWEDISHDYNAMICS, Fri, 14 Apr 2017 13:27:561
    • Re: Plug gap, timing, Saabina , Fri, 14 Apr 2017 13:55:06
      • Re: Plug gap, timing, SWEDISHDYNAMICS, Sat, 15 Apr 2017 11:48:22
  • Re: Plug gap, timing, and boost, Oh my! (long), Simon S, Fri, 14 Apr 2017 11:09:54 <-- Viewing This Message
    • Re: Plug gap, timing, and boost, Oh my! (long), Landjet , Fri, 14 Apr 2017 14:42:431
    • timing under boost, Notnoel , Fri, 14 Apr 2017 14:00:08

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