[aerohead]

If you could magically perform back-to-back tests,simultaneously,you could easily measure the difference.----------- One thing to consider.The alternator load may have been a design criteria for the cars powerplant design and may effect it's BSFC.----------------------------- By arbitrarily lowering the "load" on the engine,you could actually move it into a regime of lower efficiency.-----------------------------------------------I lost an alternator in Amarillo,Texas,in the CRX.It was going to be two days to get a part.I went to Walmart,bought a spare battery and battery charger.I drove,in two days,to Phoenix,Arizona,running constant-loss off the battery I charged in the motel room.I'd topped off the tank in Amarillo,and by Phoenix,I'd showed no measurable gain in MPG.------------------------------------ I have also purposefully removed the alternator belt and conducted mpg tests,and never showed any measureable difference.--------------------------- The CRX alt drops field exitation during acceleration,then resumes with manifold vacuum increase.--------------------- Also,cheap,adjustable,normally-closed vacuum switches can be adjusted to open-circuit the field,while under acceleration.----------------------- I've found the manufacturers systems so efficient,reliable and of little load,I no longer consider modifications to them for a daily driver.Just my opinion.