I believe the vacuum range will apply to all throttle managed engines regardless of the number of cylinders but the ones with few cylinders might show a pulsating vacuum if the revs were low enough.
The engines with radical valve timing show lower vacuum at reduced revs because of leakage out the exhaust valve during the increased/longer overlap period when both valves are open.As the revs come up this leakage doesn't have time to effect much on the faster flowing inlet charge.
Vacuum readings are higher when the throttle plate restricts the engine from getting all the mixture it wants so the same throttle plate position will give increasingly higher vacuum readings as the rpms come up.
The carb power circuits are designed to richen up as the vacuum decreases/throttle opens so a vacuum guage visable and used by the driver can help increase fuel economy.
Basically we can say that driving to always give the highest vacuum reading will give the highest economy---and drive your passenger and motorists around you crazy.You will be driving like "old folks"-crawling away from stops-dropping speed on hills,etc.But seriously it is a useful driving tool probably more effective for the average driver than a tach. and adds a new challenge in driving.
One thing more before the arguement starts.I am considering lower vacuum a lower number on the normal vacuum guage but actually the higher number is a lower vacuum.
Vacuum is the condition when pressure is reduced below zero on the pressure guage.So zero would be no pressure-no vacuum and 10 on the vacuum guage would be a minus on the pressure guage.
