FGT, You ought to hear the tales we here in the lowland hear from our tourists returning from your area after tackling pikes peak etc. with their motor home or hauler.Baro pressure has everything to do w/charging an IC engine and pumps and people.here's the way the people in Hydraulics school taught us to think concerning fluid flow(did we know that gases are considered a fluid);as Harvester was saying:a vacuum is not---anything, just a lack of air pressure stacked up above us in the atmosphere and totalling approx 14.7 PSI @ sea level.Higher elev=taller stack/higher pressure and lowr elev=lower stack/lower pressure.A pump/engine/human are pumps-something in them in operation makes a void wanting to be filled by fluid and the needed fluid (liquid or gas) is pushed in by the available baro pressure.
The most urgent need for the supercharger was not only for power nuts but to increase the power/efficiency of aircraft which in normal operation have drastic pressure changes and the need for fuel/air mixture compensation.
One common major use for the supercharger/turbosupercharger was in diesel engines used at higher elev and Cat,Cummins,Murphy,and all the big players had kits or original equipment to make their engine produce the SAME power as the naturally aspirated one @ lower elevations.And their advertising performance charts usually gave power ratings based on an elevation standard.After all it wouldn't be good for the reputation if a product didn't do the job because of an overlooked detail.Even Breaks&Scrapum, in their small engines list and probably originally furnish different jetting for different elevation operation--has anyone else cussed and mourned that we don't have adjustable mainjets for our small engines now?I had a relative who on moving to the Colo area had to retune their lawnmower(carried from here) with a different carb jet before it would "do right".
Sorry for the long post.Now lets hear other testamony.
