[Paid Software Announcement and Discussion] dakdroid:
Playstore Link:

https://play.google.com/store/apps/...siphorsepowerdyno&feature=more_from_developer

Updates in second post: http://xdaforums.com/showpost.php?p=29938013&postcount=2

This is a dyno app, for scooters, motorcycles or cars.

I have only tested it on my vespa, but people told me it works good on other vehicles, aslong the engines sound can be recorded and IT IS NOT AN AUTOMATIC SCOOTER !

Unlike all other dyno apps, I don't use the GPS signal or the accelerometer to measure your speed, but i use the sound.

Ok, I know what you are thinking:

"Dude this wont work or do you really think: The louder the faster ?"

Here is how it works:

Each sound has its specific frequency, consider someone whistling low or high.

The frequency is always the same, let's say you run your engine at 2000 RPM or 2100 RPM, i can measure 2 different frequencies there and i can exactly say at which RPM the engine runs.

From the RPM i can calculate the EXACT speed (GPS or accelerometer just isn't exact, it's a mess).

From the speed difference at 2 points of time i can calculate the power that is needed to get from speed1 to speed2.

Done, thats it.​

There are a couple of important things you should be aware of, before you download the app:

1. Not all devices support the recording quality, therefore i uploaded a test app. Please download it, record sound (speak or something else, doesn't matter). Then replay the sound. If it doesn't force close, you are good to go. Link: https://play.google.com/store/apps/...29tLnBsZWRsc3RlZmFuLmhvcnNlcG93ZXJ0ZXN0ZXIiXQ..

2. In order to get the measurement right you need to know these values (it is a very technical app):

Overall Weight (vehicle + you + gas + backpack + helmet + trousers + shoes ...)

Gear Ratio (this needs to be as exact as possible as well, i use the overall gear ratio, which is your gear ratio divided by your tire-circumference in meter, i have an option to calculate the gear ratio by using the GPS speed, but as said before the GPS isn't exact enough)

Cw-Value (if you dont know what this is, please google it. I could fill a whole thread with information on this. If you don't enter the exact value here, you will still get comparable results for different dyno runs and engine setups aslong you leave this value the same)

Frontarea in squaremeter: (either measure it, or just leave the value, like the Cw-Value to get comparable results)

Temperature + air pressure: (can be get online, within the app)

One thing i didn't consider yet is how the tire changes during the run, the faster it spins the higher the tire circumference gets.

I compared my measurements to real dyno runs and its usually only about 0.5 horsepower off.

The displayed horsepower is "power on the ground". I know americans have some other fancy methods to measure this, but to be honest, "power on the ground" is the only measurement that is worth measuring.

Unlike power on the crank it is the real value which your engine has on the street.

Maybe you might have noticed that i am not native english speaking, so here are a couple of copy/pastes from other users, which i think help to explain what is going on:​

Text Tutorial which i wrote here:

http://modernvespa.com/forum/topic101980?page=1

Either watch this thread or follow me on Google+ for updates:

https://plus.google.com/105280101829289526269/posts

or:

https://plus.google.com/109720416927515295704/posts

If there are apple fanboys around here:

I am working on an iphone version.