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I'm confused whether I should advance or retard my scooter ignition timing on higher RPM (> 7000 rpm).

When I open the default stock ECU settings, it seems retard the timing excessively on wide-open throttle, but the principle said that I should advance my ignition timing on high RPM.

So, which one is correct?

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  • Welcome to Motor Vehicle Maintenance & Repair! Oct 16, 2023 at 9:59

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Because there is less time for ignition events to occur at higher RPM, the timing should be advanced. If you retard the timing at higher RPM, the ignition event will be happening too late in the combustion cycle and a lot of power will be lost due to this. The engine would basically "fall on its face" as they say.

Mind you, the ignition can only be advanced so much before it starts working against itself. Every engine is going to be different as to what its needs are and therefore will need to be treated differently. Also, there are different types of ignition advance, such as programmatically (through a tune), mechanically (through shifted weights in a distributor), and initial timing (where the distributor is set during setup). Each one of these will make a difference as to what the timing will be at any given RPM. Your scooter might have any of these, so before you jump to conclusions as to where your ignition timing is set, make sure you understand how any or all of these come together to form the overall timing curve.

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    Added to which, it takes about the same time for the spark to ignite the fuel/air mixture and propagate through it regardless of the rpm. So at higher rpm it needs to happen a bit earlier for the best efficiency. Oct 16, 2023 at 16:37
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    @WeatherVane - You stated that much better than I tried to (ie: I alluded, you concluded!). Nice add :o) Oct 16, 2023 at 17:23
  • Thanks for the answer @Pᴀᴜʟsᴛᴇʀ2, Does engine load affect ignition timing? I'm tuning on a 'racing' ECU, and the only axis I can adjust for ignition timing is the RPM vs. TPS for each degree of timing. Oct 17, 2023 at 1:14

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