Spark timing - Low Octane, how does the car know?

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hsv08
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Re: Spark timing - Low Octane, how does the car know?

Post by hsv08 »

delcowizzid wrote:Some subarus just rely on the knock sensors fully they just take timing out and readd it over and over to keep it in the max timing zone lol
The LS1 HSVs were similar. I think it may have been VY that had so much timing in the high octane table, that it would actually knock more often then not, when on anything less them 98, therefore the ecu was always interpolation between the high and low maps.
They seemed to use the knock system as a crude way to deliver "optimum" timing when using a higher octane fuel.
The system majority of the time was reactive.
They always felt alot more flatter when a low grade fuel was used as the reactiveness of the knock system would pull huge amounts of timing.
Which is something you try and stop when tuned correctly for the grade of fuel you want to run.

In HPT there is actually a PID that shows what percentage of the high octane map your running in. So for eg if it was less then 1 you were running more toward the low octane table then the high.

For some stupid reason they flipped that for the 6L stuff where 1 is low octane and 0 was high.
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