I figured out how to advance timing past 29 degrees.
There's a setting in the software to allow going past the timing lobe on the crankshaft.
I'm running 93 Octane during these tests. I should be able to go back to 87 Octane when I'm done, since all my advancements are at part throttle operation. I'm a little scared to try it though.
I ran some more tests with my new air setup (anti-pulse valve).
I slowly ran the RPM up from idle to just over 8000 RPM, and measured engine vacuum.
Then I bumped the timing up 1 degree and ran it again.
First run was 5 (1100) to 25 (3500) degree timing, second 6-26, then 7-27, 8-28, and 9-29.
At each setting, I ran the test 3 times to get an average.
The goal was to find what timing gave the lowest reading (highest vacuum).
I found that with more timing, the engine is able to maintain a given RPM with less throttle.
And this is the resulting graph.
It's kinda a mess like that, so I broke it down into pieces.
This shows 5-25 (blue) vs 8-28 (black), from 1500-5000
I saw about a 2 kPa improvement across this range (0.6 inHg).
This shows 8-28 (black) vs 9-29 (red)
At 4500-5000 RPM, 29 degrees showed an improvement as compared to 28 degrees.
Otherwise, 8-28 was the same or better than 9-29.
No advantage to 9-29 below 4500 RPM.
From 5000-8500, there was a big improvement going from 25 (blue) to 29 (red) degrees.
Look especially at the 5000-6200 range! About 10 kPa (3 inHg)!
Comparing 28 (black) to 29 (red), you can see that improvements were starting to diminish.
However, it's possible 30 degrees will show further improvements.
So now a full scale comparison of 5-25 vs 9-29 timing.
I'm excited because of the big improvements in the 5000-6000 range.
This equates to 70-80 mph.
Even the 4500-5000 showed some improvements (~63-70 mph).
This is my resulting table.
WOT is the bottom line, and that's the stock timing.
Anything above that is interpolated to the values on my graphs, based on engine vacuum.
I HAVE NOT run this table yet.
I need to log a ride on stock timing first, to double check IAP values to see how they compare to my slow rev tests.
I had no indications of engine knock at any point.
I checked the spark plugs and they look like the top picture on this site.
Spark Plug Reading Information
www.seadoosource.com
The manual suggests that timing between 4-6 at idle, and 24-26 at 3500+ RPM is acceptable.
I extended the horizontal lines over to the side of the graph, found in the service manual section 15.
I'm guessing that that's a safe timing then, even at WOT.
Otherwise the manual wouldn't put tolerances on the timing chart.