Can someone please check my thinking...engine efficiency, cyl mass and timing

[angrygoat]

Okay so I'm reading about timing and engine efficiency and I think I have put two more things together. From reading the tuning grail, i.e. Greg's book, I gather that engine efficiency is at its best at peak torque. Also that as efficiency increases you want to decrease timing, then as efficiency falls off, i.e. higher rpm past peak torque, you want to increase that timing again.

Now for my TT aplication, I would assume that efficincy would not fall off due to the turbos. Would I monitor dynamic cyl air (SD gr/cyl measurement) to verify if my efficiency is decresing, shown by my dynamic cylinder air (gr/cyl) value lowering as rpm increases? My thinking is that if my dynamic cylinder air is flat lined around say peak torque and does not trail off all the way to redline that my "efficiency" is flatlined and I could actually use the same timing from peak torque all the way to redline.

Does any of that make sense? Comments?

[EaglePerformance]

One thing to keep in mind as far as timing is concerned, not only does efficiency, cylinder filling, drop off, (N/A), the time required from spark to full burn out to the edge of the combustion chamber, is pretty much a set time, of course it varies a bit depending on A/F ratio, since the window from spark to peak pressure is a set time, things happen mechanically much faster at 6,000 rpm than they do at say, 4,000 rpm. So in order to get peak pressure to hit at approx 15* or so ATDC, timing needs to be advanced to keep up. S/C engines generally have a rising boost pressure as rpm goes up, if dynamic cyl air increases, less timing is needed because a more densely packed cylinder burns faster. If it flatlines, even if boost increases, then timing should be increased, I would ASSume!

[angrygoat]

So even though my efficiency (VE) may not trail of at the higher rpms, I still need to advance the timing above peak torque to acount for the engine spinning faster. That makes sense

[Ironmancan]

interesting...