SDS CPI Users: curve advice requested.

[j-red]

I'm running a single CPI and a slick on an o-360. Just looking to find out whether those of you who are running this ignition have been pleased with the stock curve shown in the installation instructions for 100LL, or whether you would suggest modifications? I ask because I'm pretty new to the concept of an ignition curve and am not sure I understand the way that manifold pressure advance/retard functions alongside the rpm advance, and thus don't really know how to tune the system for best performance if that is even necessary. Just want to make sure I'm making the most of the system.
Thx.

[Toobuilder]

Can't comment on the published curve, but it has been my experience that dialing in the system isn't tough. I think there are only 4 points that you need to hit to have a highly optimized system:

1 Idle
2 100%
3. Best power cruise
4. LOP cruise

These 4 points will require you to burn some avgas, but once established the points in between can just be filled in with a natural slope.

One of the confusing things about having this much adjustability is that there are several ways to play with the MP and RPM settings to arrive at the same outcome. Personally, I use the basic logic employed by automotive engines with centrifugal (RPM) and vacuum (MP) distributor ignition systems because thats what I grew up with. In this scheme, my RPM slope is "all in" by 1800 RPM, and any additional advance is governed by engine load (MP). As I have essentially a fixed RPM engine with a C/S prop, the vast majority of my power changes are seen as a change in MP, so that becomes my primary tuning parameter. Again, not the only way to do it, but it works for me.

If you do a search on my username and "CPI", you should be able to see what I've done in more detail. If you need more, shoot me a PM and we'll work through it.