Paul,

   The twin-screw supercharger is sometimes generically referred to as the
   "Lysholm supercharger," in honor of the Swede who invented it in the
   1920s.

   It's kind of a convoluted story, but apparently the company called
   Lysholm
   is now owned by Autorotor, and they continue to make both product lines.
    From what I've heard, the Autorotor is the higher-end product, with
   some
   subtle refinements in the aerodynamics of the rotors, the gearbox, etc.

   The Kenne Bell website has an article on Lysholm versus Autorotor:

   http://tinyurl.com/f8m6o

   In that comparison, KB claims about 10 percent less power required for
   similar cfm output. Not huge, but still a nice little improvement,
   if it's
   true.

   I just want to clarify for the record the power consumption issue. The
   normally aspirated Mazda rotary displaces 1300 cc, so at 3500 rpm it
   would
   consume exactly 4.55 cubic meters [160 CF] of air, provided it had a
   VE of 100
   percent. (1300 x 3500 / 1 million)

   If you boosted the engine by a ratio of 1.7 (10 psi boost), you
   would have a
   maximum airflow into the engine of 7.735 cubic meters [273 CF].
   According to the
   Lysholm chart, that would require a power consumption of just over
   10 kw [13.4 HP] and
   would give a discharge temperature of just over 90 degrees
   Celsius[200 F]. It would
   place you in the 63 percent adiabatic efficiency island.

   That does not sound bad. Cool enough to not require an inter cooler
   and would
   give about 155 hp net. Fuel efficiency would not be much worse than a
   geared, normally aspirated engine spinning 6000 rpm. I'd guess maybe
   five
   percent, so a fuel flow of .5 let's say.

   Engine weight would be about 30 pounds less than a geared engine.

   Btw, how much does the RX8 engine weigh, stripped of intake manifold and
   exhaust, since you would have to fabricate those anyway?



   Regards,

   Gordon.

Gordon,
You lose the weight of the gearbox but gain the weight of the
SUPERCHARGER and all it's plumbing and mounting hardware. I'd bet it
would be close to a wash on weight, and the wear aspect would be MUCH
higher. Paul hammers on this all the time but I'll take over this time.
The rotary is NOT a piston engine! There is no reciprocating motion, and
higher e-shaft RPMs are NOT a wear problem. As has been said many times
Mazda instrumented the engine and found that bearing load at 6000 RPM
was NIL, ZERO, NADA, NOTHING. The compression and power loads balanced
out. I plan to cruise at or slightly below that figure using a 2.85:1 PSRU.
Secondary item: Paul the figures on the screw Lysholm supercharger are
true. The efficiency improvement lead to the NHRA banning them at one
time. I don't know it that is still true or not.
Bill Jepson


The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.