Greetings all,

For a Renesis 4 port (non-priph  intake)  using Premix in fuel, what is the
consensus of redline RPM  for aircraft  (before PRSU) for best
power/longevity--   .

Also, if I decide  to switch to peripheral porting What kind of  HP increase
and what kind of  fuel burn per HP, as well as longevity  decrease can one
expect  (all  other things being  equal).

Thanks,

Rich


The RPM red line is the same as  any other rotary. Limited by the prop
to about 7500 RPM. The street RX8 is  9000 RPM

Paul Lamar


Thanks for the reply.

Am I to infer by your last answer that the maxRPM is limited by prop RPM
(to a max of 9000) and that the  7500 limit is in reference to the prop tip
speed (redced by the PRSU).

Are there any downside effects (longevity, severe increase in fuel used per
HP developed, etc) that would prevent me from running T.O. higher than
7500. The  prop is 68"

Thanks

Rich


With a prop load and a four port the HP will be way down from
it peak due to breathing limitations so you may not reach
9000 RPM in any event with a practical fixed prop pitch.
To reach peak power at 9000 RPM you will probably need
a P-port.

Assuming you are going to change the gear ratio as even a 68" is not
going to go 9000 RPM and you only use it for takeoff for a max
of 5 minutes I think it might work :)

dia =  68
 RPM    Tip FPS  Vel FPS    Vel MPH    Mach
 2200      653      716      488       0.70
 2250      668      729      497       0.71
 2300      682      743      506       0.72
 2350      697      756      516       0.74
 2400      712      770      525       0.75
 2450      727      784      534       0.76
 2500      742      798      544       0.78
 2550      757      811      553       0.79
 2600      771      825      563       0.80
 2650      786      839      572       0.82
 2700      801      853      582       0.83
 2750      816      867      591       0.84
 2800      831      881      601       0.86

2800 times 2.85 is 7980 engine RPM.

Here is a handy QB program. If you need QB let me know
I can send it to you. Will run under the command line in XP.

CLS
PSRUratio = 4!
pi = 3.1416

HPrat = .033
OPEN "tipspee4.dat" FOR OUTPUT AS #1
PRINT #1, "RPM  HP  PROP 72  74  76  78  80  82  84  86  88  90  92  94  96  98  100"


FOR RPM = 6000 TO 8500 STEP 100
PRINT #1, USING "####"; RPM;
HP = RPM * HPrat
PRINT #1, USING "####"; HP;
PropRPM = RPM / PSRUratio
PRINT #1, USING "#####"; PropRPM;

FOR dia = 72 TO 100 STEP 2
DiaFt = dia / 12
tipspeed = (DiaFt * pi * PropRPM) / 60
IF tipspeed > 1000 THEN GOTO skipit
PRINT #1, USING "####"; tipspeed;
skipit:
NEXT dia
PRINT #1,
NEXT RPM
CLOSE
SYSTEM

Paul Lamar