340 Static Compression Numbers and Test Procedure
Wouldn’t a higher timing point be BETTER for idle as opposed to a “disadvantage “?
Like Goldilocks. need to find the timing that is just right for the conditions.
Idle should be relatively rich for maximum efficiency powerwise. Lots of testing for military and civilian applications establishes this pretty well.
With high compression, there is good heat input and combustion should burn relatively quickly.
So these two factors mean less lead time is needed to develop pressure.
On the other hand, cam designed for higher rpm is going to have overlap at idle that will cause exhaust dilution and may even cause reversion into the intake.
This will reduce the mixture density and slow the burn - therefore requiring more lead time to build pressure for maximum leverage of the crank.
With no load on the engine, timing can be advanced more and more and the engine will seem to like it. Because under light loads the engine can run very lean.
But as soon as the engine is put in drive, it wants to die. It has no power. Just the load of turning the trans TC and pump takes all it has.
The goal is to come up with an initial timing and fuel mix that will produce maximum torque. The way to check this with an auto is by putting into gear at idle. The smallest rpm drop between N and D is the goal.
