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I like to call it effective compression, which is the actual amount of atmospheric pressure in the cylinder at BDC on the compression stroke (although it may be slightly higher due to the inertia of the incoming air at slightly after BDC).
It is directly related to manifold vacuum, with full load enrichment applying an additional effect.
Your best BSFC, as a general rule (certainly with exceptions) is about 1500-2000 RPM with the minimal manifold vacuum, without enrichment.
To the OP, reducing the inefficiency of light load operation is the key component of P&G.
An example is a dyno test of the 4 cylinder (GM 2.5 liter) where the 20 HP load applied used 1 unit of fuel. Increasing the load to 50 HP required 1.5 units of fuel.
20 HP per unit situation A
33 HP per unit situation B
The ideal use of situation B in a P&G scenario would theoretically increase fuel consumption by a factor of 33/20 percentage if that load operation tactic was employed (B).
I would accelerate at higher loads than 35, more like 80, and possible shifting earlier if that was possible, with a manual transmission.
If it is an automatic then you want the highest load that does not keep the transmission in lower gears.
regards
Mech
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