I am posting this here because I feel it fits the "Performance" title. I installed this app on my iTouch and it seems to work well. I'm just not sold on it being acurate to 100%. My '87 300D runs pretty well but I didn't think it was capable of 9.8 second 0-60 times. The app shows 137rwhp which translates to 171 sae net hp. (assuming a 20% drive line loss). I know I've seen some others post using this app, just wondering what the opinion general opinion is. Graphs look pretty cool.

I've used it a few times and its accurate enough for the casual user.
Actual dyno tests on my car showed power to be above what was shown by dynolicious. (120whp dyno vs 100whp dynolicious)

If you want something thats more accurate you need a tool thats GPS based. The iPhone/iPodT accelerometer is heavily influenced by suspension flex, so a car with bad shocks will show as more powerful than one with new shocks.

It also relies on how accurate the weight of the car you set in the app. Go to a truck stop with a scale and get your car weighed, then just add yourself to it, and run the tests, ive gotten as low +-3% difference between dyno and dyno app.
The condition of the suspension doesn't matter if you go in a straight line because the total work measured by the accelerometer by the end of the run would be the same (unless you are getting nasty wheel-hop).

Assuming you have a good mount.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42