Posted for "terrence o'neill" <troneill@charter.net>:

 Morss,
    Interesting.
    I think of supercharging as a device to bring or keep engines up to their
max design power.... limited by detonation, ability to dissapate heat, and
mechanical stress.  It can't help a n engine running at sea level already at
it's maximum potential, but will just sap a little HP.
    When that engine is moved to altitude where there isn;t enough manifold
pressure to max the output, a supercharger or turbo can bring it up to max...
as you example shows.
     My belt-driven VS-57 McCulloch (now Paxton) gave me about 8 to 10 HP for
each HP used.  My blow-through supercharged  Ford 351 Windsor with Dart heads
and other mods had a lot of extra potential without overheating or failing.
  I ran it in the Magnum for an hour one day tethered, at 45-in. MP and about
4200 rpm, as I recall, with no overheating or other probems... putting out
about 9 boost HP for each horsepower belted into the blower's drive pulley.
 This was on 93 octane premium Marathon auto gas.  Probably could have run
more manifold pressure on 100LL.
    I think supercharging's a good tradeoff, IF the basic engine can stand
it... an d that's the real question.  I'd like to put a belt-drive
supercharger on our LNC2/IO320, if I can find room somewhere....and if the FAA
ever clears the registration.
 Terrence
 
"""
  From: morss
  To: Lancair Mailing List
  Sent: Friday, March 18, 2005 04:23 PM
  Subject: [LML] superchargers
 
  for those that like real data not guesses, I tested the same plane eng and
prop combination on the same day with and without a supercharger. The higher I
went the faster I went and the bigger the difference between normally
aspirated and supercharged.at 5000 norm 24.5" 2300rpm true 205 at 12 gph. SC
27 " 2300 12.6 gph 208 true. At 15000 normal 16.4 " 2500 216 true at 12.5 gph
SC 27"2500 245 true at 15.6 gph. All mixtures were 50 lop (im cheap)
  Interestingly if you don't want to go over 30" at reno the speed of my plane
was the same normally aspirated 25" as supercharged 30".The big difference is
if you run the boost up or climb .
  I removed the supercharger as the legacy at 215 true can get over 20 mpg.
and thats fast enough for me . I can get up to 240 true normally aspirated but
dont want the fuel burn . the supercharger can install in a day .the weight
penalty is only a few pounds and doesn't show any big heat changes in the
cowl. Unless you start building from scratch I dont think a turbocharger is
even an option especially if you include an inter-cooler.
"""