If you go to full throttle for tuning data observe the peak EGT rule. Stay well rich of peak EGT and not above 1650 degrees. Best power is about 50 degrees rich of peak. So the method for idle and off idle is not used.

Peak EGT is a function of cylinder filling, mixture strength, lubrication availability, intake air temps and timing. The reasoning is that peak EGT can be well over 1900 degrees, and you may get into overheated apex seals. Best power is just rich of peak, but we must NOT go there unless you have ceramic seals.

.

 

So make any changes you like with each pass but stop at 1600 EGT.

Adding advance past about 26 degrees usually does not add much power unless you are using very high octane fuel. You can get up to 30 degrees, but you are making more heat rather than power.

The engines produce more power on lower octane faster burning fuel,

so less advance can be used, thus less cylinder pressure before TDC which subtracts from torque. Mistral had it working on Jet A.

 

All of this is for normally aspirated engines. Boosted engines are very

much different. Because you are screwing with over 100% cylinder filling. So you are increasing the swept volume ingested while keeping the same headspace. So, the effective compression ratio is going up with boost. So, timing is pulled out at the boost comes up. A more complex tuning issue. You still want peak cylinder pressure at about 50 degrees, but the mixture is now tightly packed and very fast burning.

So you roll back the timing and at best power may see near zero degrees of advance. No split timing on boosted engines. It looks like

detonation. Rewind detonation definition.

 

This will all seem obvious after a while.

 

Lynn E. Hanover 

 

 

 

In a message dated 7/18/2012 12:02:46 A.M. Eastern Daylight Time, echristley@att.net writes:

I discovered the log viewer's scatter plots this evening.  It's a way to visualize how various parameters affect each other.  It is fairly obvious that I can add in a lot more advance.

The task for the next session is to set the whole table to 20*.  Run the throttle up and down a couple times, increase 2* and repeat.  The end of the day should find me with a graph showing RPM against advance for a range of throttle positions.