Boost versus timing

[mituc]

Now we all know that power comes from a combination of both these things: boost and timing.
However, we are somehow limited on both of them: we can't run too much boost because we run too hot and we can't run too much timing either because of the limitations of the fuel we're using (let's say we're using 93 octane pump gas). So there must be a balance.

There are side effects of taking any of these approaches to extreme for making more power:
- if we run more advance and we happen to have filled with a gas less resistant to knock an aggressive timing may lead to severe detonations;
- if we run too much boost the BAT's will be a bit higher and therefore we may need to run less timing to prevent detonation, and less timing may not get us the power we're after at those boost levels.

The gas in my area seems to take more boost easier than even slight increases in timing, especially below 6k rpm, so I chose to give it a bit more boost and make very small steps with timing after I was happy with the boost.
However, I wonder if anybody can give us an idea about the difference in added power between one more PSI of boost versus one more degree of timing, at the same BAT values.

[Steve @ VersaTune]

It's dependent on a lot of other things. There is an ideal maximum timing. If you exceed that, you start to lose power because your pressure wave peaks too soon. Max timing can be roughly calculated based on engine operating parameters. It's hard to know the exact chamber turbulance and other complex parameters though. The OEMs use in cylinder pressure transducers during development to determine optimal timing. Advance timing so long as there is no knock and there is a power increase. Then, up the boost and back off timing if you get knock. Compare the power and see which yields more. These changes are subtle, so a real dyno may be needed to measure them.

[YuraL]

Use VirtualDyno and logs of different tunes (max boost, max ign, poor mix, ...)

[YuraL]

Increase the absolute pressure equal increase the power, all other things being equal.
For example, boost 1 bar (2 bar absolute pressure) match 300 HP, then for boost 1.5 bar (2.5bar AP) you'll get 300*2.5/2.0=375 HP (If the timing, BAT and AFR will remain constant.

About timing, I know that 1 degree of ignition timing approximately equal 1% of power.