Thread: Prop Testing
09-06-2013, 06:57 AM #1
Many of you know I am a big data guy. I like getting as much repeatable data on your ski as you can get type thing. I have found a way to compare impellers. Evey Impeller has two basic things to test. With the motor accept full power without blowing out the prop. This is when the motor has the ability to boil water in front of the prop by pulling too much vacuum in the water intake. This is hard to document but normally shows up when the motor wants to over-rev as you punch the motor out of the hole.
On the top end is a little easier to prove with math and testing. I happen to have a CMD/Autotune2/LCD-200 setup and a Jegs GPS device feeding a calibrated speed input into the LCD-200. This can also be done with a VTech data logger. What I do is create a new field in a graphing program that I call Propslip. It is defined as engine RPM/MPH. I then scatter plot MPH on the X axis, prop slip on the Y and have RPM or throttle position in color. Here is what you get.
The top line indicates just how well the prop locks in at speed. The point at the bottom right shows that this setup is pulling 8233 rpm at 70.7 MPH and averaging 115.9 RPM/MPH at WOT. In that plot you can see the RPM that the motor is pulling at every point in the curve. The rep in the upper left of the curve is the hole shot.
Have fun testing
Last edited by whittlebeast; 09-06-2013 at 08:25 AM.
09-06-2013, 07:34 AM #2
09-06-2013, 02:03 PM #3
09-06-2013, 06:11 PM #4
I learn something new every time a talk to you or read your posts.
Keep up the good work! And thanks!
09-06-2013, 06:29 PM #5
09-06-2013, 07:15 PM #6
Andy, very nice analysis!
Here is a Motec webinar that discusses Launch Control using the M1 ECU software. There is an excellent discussion on impeller cavitation, the Drive By Wire throttle on the 2010 & newer Doo's and Yamaha's, and shows how you can overlay logged data for comparisons of throttle control tunes. This overlay can be used for impeller comparisons on hole shots also. I found this topic very interesting.
06:50 instruction starts
24:50 Testing with Data - shows hole shot logs and how tune can be adjusted
28:00 Overlays of 2 hole shot runs
09-06-2013, 08:28 PM #7
Cool video. I wish I was at the Motec meeting when that was being designed....
09-06-2013, 11:39 PM #8
09-07-2013, 11:37 AM #9
09-07-2013, 12:23 PM #10
Andy can you run my log I sent you for prop spin.
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