I have a question regarding ignition advance.

since the combustion mixture in a gasoline engine always burns at the same rate, as RPM goes up so does the amount you can advance the ignition timing. my question is, what is that rate of advance? i know that every engine has different requirements. but lets say all things being equal and cylinder pressure didn't change with RPM, if an engine runs 10? of advance at 1,000rpm, what would the linear advance be?

The mixture doesn't always burn at the same rate, so you can't just plug a flame front velocity and cylinder diameter into a spreadsheet and work from there.  Historical advance curves suggest that that may not even make a good starting point.

For one thing, you've got acoustic effects and turbulence interacting with what would otherwise not be a steady flow anyway.

For another thing, some really odd stuff can happen in a cylinder.  More than ten years ago, someone at Yamaha published (probably available as SAE papers) results that started as a study of the burbling noise in two-strokes.  Briefly, they found that a plasma existed in some speed ranges, which autoignited the incoming charge without regard to spark timing ... and the engine ran better when the plasma was present, and didn't even need a spark.  Then they found they could make the plasma stable over a wider speed range with a sort of throttle valve(Bellow Seal Valves) in the exhaust port.  Yamaha went on to mass- produce a two- stroke motorcycle with computer controlled exhaust throttling, and decent emissions and efficiency, for a couple of years.

In a gasoline engine the speed of combustion does change with engine speed. However, the relationship is in no way linear.

For a given AFR & air mass per stroke (Load) increasing the engine speed will not only change the speed of combustion (ie 0-100% mass fraction burnt) but it will also change the ratios of 0-10 (ignition phase) :10-90 (flame front phase) :90-100% (post flame phase) MFB

Consider this; with a constant AFR & Load, the propensity of the engine to knock is affected thus: -

At low speed, where combustion speed is also low, the flame front will still be progressing through the charge when the end gases reach their Auto Ignition point & detonation will, therefore, occur. In this condition the position of Maximum Advance for Best Torque (MBT) may not be achievable before knocking occurs and the engine is said to be knock limited.

However, at higher engine speeds detonation may never occur because the charge is consumed by the quickly moving flame front before the end gases ever get near their AI point. In this condition it is often quite possible to continue to wind spark in until misfire occurs (because of the reduced residency time of the charge)

The change in speed of combustion is totally to do with the mixture preparation being improved by the increase in gas speed.

As mentioned above, squish & swirl do their part to improve matters at higher speed whereas a more useful mechanism at lower engine speed is tumble. An optimised combustion system makes use of all three in different areas of the engines operating range.

"Ignition advance in a diesel is accomplished by advancing the fuel injection start point"

This isn