10-06-2013, 09:53 PM #1
Accel and prop testing using a VTech logger
Here is a few screen shots.
Here is Idle - 60 mph in 3.5 sec
Here is an accel rate of 14.4 MPH/sec as the ski pulls thru 50 MPH
Here is the prop slip as the ski accelerates up to top speed. I defined prop slip as RPM/MPH
vs this curve for the other ski
And the most interesting plot is comparing hundreds of pulls up thru 50 MPH on two different skis. The one on the left is averaging 10 MPH/sec accel rates as it pulls thru 50 MPH and tends to top out at 68 MPH. The one on the right is averaging closer to 14.1 MPH/sec as it pulls thru 50 MPH and tops out closer to 74 MPH.
These skis are both at near 700 ft elevation but tested thousands of miles apart. Both skis are 2012 RXPX skis running VTech loggers and tuned with a VTech and Autotuned with the newest VTech software. Graphing was done with MegalogviewerHD.
Have fun tuning
10-07-2013, 06:33 AM #2
We need to get into the conversation regarding prop slip out of the hole and what yields the best true acceleration. That motor is hitting 9300 RPM .7 sec after the finger throttle moves. I simply am not seeing it as a short term issue but who knows haw often the pump would need rebuilding. Note that the rev limiter is set to 9000.
Last edited by whittlebeast; 10-07-2013 at 06:59 AM.
10-08-2013, 08:36 PM #3
- Join Date
- Jul 2009
Am I reading this graph correctly?
The prop slip delayed is reading about 110 at max speed of 74 MPH.
This would indicate the prop never gets fully efficient and is always slipping.
10-08-2013, 08:44 PM #4
110 is not an efficiency, like 100 is 100% efficient. Think of it as the motor is pulling 110 RPM for each MPH. It is true that the prop is slipping less or more "hooked up" are speed increases.
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