Originally Posted by McNastyGT
Your good as long as you are not getting any knock
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That's not very helpful.....
He is getting knock which is why his car is pulling timing.
There are a few things to consider when discussing timing:
1. Quality of fuel being used
2. Commanded timing
3. Detonation
4. Cylinder pressure
Certainly not the whole picture but most of it.
Basically what happens is you command a certain amount of spark advance in the tune which can be RPM based. There is also a global spark advance modifier that works towards overall timing. When you hear of someone taking a few degrees out running nitrous for example, they are doing so on a global scale generally.
The knock sensors work to detect detonation. If they detect it, spark advance will be reduced and then ramp back in when it is back under control. Knock sensors can also allow timing to be added in vs. just for reduction.
Using a fuel such as e85 will allow for a greater amount of timing to be used as it is highly resistant to pre-ignition causing detonation. There are much deeper conversations that can be had about e85 and it's ability to resist detonation.
Then comes the whole discussion on octane rating and fuel. IMO you want to use the lowest octane fuel possible before detonation occurs. This ensures a more complete burn.
Cylinder pressure and dynamic vs. static compression have a lot to do with the detonation, timing, fuel discussion as well.
Not a cookbook by any means but a high level overview of what is happening.
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