1. ## How to measure acceleration with your GPS

Everyone has a GPS and uses it to quote top speed but acceleration seems to be more subjective. This isn't going to be as accurate as a radar gun but I find it to be good enough to detect changes in acceleration performance and it's a lot more accurate than the seat of your pants.
I set my Garmin GPSMAP60csx to the fastest sample rate which is once per second. After the ride I open the GPS with Garmin MapSource and then open the Active Log (see attached). A ctrl-A and ctrl-C will copy all of the track points. Open a spreadsheet in Excel and a ctrl-V will paste the copied data into the spreadsheet.
I added a column to the spreadsheet to calculate the MPH change between samples (see column P). Since all of the samples are at one second intervals the MPH difference is MPH/SEC. Column Q converts MPH/SEC to G's. 1G=(MPH/SEC*1.47)/32
You can then use the Excel LARGE function or just scan down column P to find the Peak acceleration.
My Stage1 SHO was between 15 and 17 MPH/SEC with a MAX speed of 70.5 MPH with the stock prop at 14/20. After adding an Intercooler and re-pitching to 14/18 I am seeing 21 to 23 MPH/SEC with a MAX of 69.5MPH. So I lost 1mph top end and gained .25Gs acceleration.
If you have a GPS you can easily get max MPH/SEC. Post your best here.

2. awesome!!! I'll try it out next time I ride. Thanks for sharing.

3. Great IDEA ! ! !

4. Originally Posted by philip_gpr
Great IDEA ! ! !
If I get enough response I will compile a list of mods and acceleration data.

5. I have the same gps unit....how do you set the sampling rate?

6. Nice, i need to get me a new unit...how easy is this one to use?
Thanks for sharing!!!

7. I still think the Garmin GPSMAP 60/62 series is the best GPS out there for what we do. It has all the right features, is rugged, has a 19hour battery life and its waterproof. It also has a magnetic compass and will support Marine maps. Because of its rich feature set it sometimes gets dinged for being hard to use but once you use it you won't pu up with anything else.

For those with a similar unit here is how I setup my GPS to collect the data.
There are two things you need to setup. The track buffer size is on the Setup Maps menu and the sample rate is on the Track Log page Setup.

Press Menu a couple times, Select SETUP then MAPS from the menu options. Use the right arrow to get to the Track Setup. Arrow down to Track Points field and enter 10000 which is the largest number you can enter.

Now press Page a few times until you get to the TRACK Log page (the one that lists all of your Tracks) and Select SETUP.
Set the Record Method to TIME.
Make the Interval 00hrs 00min 01sec

I also set the Track Log to Wrap and be sure to clear the Track log before you start your acceleration runs and turn off the GPS when you are thru. 10000 samples at a 1 second sample rate will fill the buffer in 2hours and 45minutes.

8. Thanks

9. Originally Posted by philip_gpr
Great IDEA ! ! !
+1

10. Bumped up.

Just curious if anyone has tried this? I am really interested in understanding the acceleration potential of these ski's.