Thread: 80 mph @ 4500 feet?
03-22-2011, 01:32 PM #1
80 mph @ 4500 feet?
What will you guys say will it take to get to 80 @ 4500 feet, 30 degrees Celsius and 20-30% humidity? I have done it at sea level but can't seem to get even close at 4500 feet.... staying around 76mph.
03-22-2011, 01:43 PM #2
I think forum member Skoepp also rides in higher elevation and is well over 80 with a RXP. He prob will chime in.
03-22-2011, 03:25 PM #3
Even at 4500 ft you should be over 80 with you mods. What rpm's are you turning. Running a stock 15/20?
03-22-2011, 03:48 PM #4
Alot of power, time and very fine tune ski!!!!!!!!!!
You will loose 100 rpm (1 MPH) for ever 1000 ft above sea level even with rpm dialed in.
Will even be more speed loss if down on rpm.
I bet your RAD is 7-8,000 ft at that temp.
Get your rpm and boost back up and good luck!
Welcome to altitude.
03-22-2011, 07:00 PM #5
- Join Date
- Apr 2006
- panama city beach 'fl
ya might what to give woody a buzz, he has same problem with his ski @ high elevation
03-23-2011, 01:09 AM #6
Thanks for the feedback, found a small boost leak in the intake manifold!
My RPM is 8100 - 8150 and boost was around with the leak 11psi! With a stock 15/20R.
03-23-2011, 01:15 AM #7
03-23-2011, 02:02 AM #8
Ok at sea level it's up to 8500 - 8550 think it's on the limiter (Rotax ECU), nozzle used was 81mm and 15/20R. But to get a really accurate speed at sea level is quite difficult as our seas have quite hight swells (4m+), but my absolute top speed was 129 kmp/h (80.1 mph/h).
Now I have a stock nozzle and a 15/19R prop. I tried the 81mm and 15/20R but then only 7900rpm at best. Thats with the 11psi.
With the 15/19R I got 8100 and maybe 11.5psi....
03-23-2011, 12:15 PM #9
Are you speaking of a 15/19 skat 3 blade?
If so, I would go back to the 4 blade and maybe slightly take some pitch out of it.
Also I would try the 4 blade with stock nozzle (83.3mm) or even put pro nozzle back in and try a 84 ring to even a 85 ring.
What air intake system are you using?
Be sure you are not running too rich or you will be robbing hp and rpm.
How healthy and strong is your motor, hours, compression/leakdown?
What your slip on your super charger?
You need to get your rpm back up to gain speed back.
Last edited by skoepp; 04-10-2011 at 10:10 PM.
04-10-2011, 04:25 PM #10
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