Wanted: data for vehicle performance app

[skier219]

I develop the gMeter performance app for iPhone/iPod/iPad, and just put out version 2.0:




More info: gMeter Website

I'd love to get some data from a Z4 with DCT, since it should dramatically reduce power loss during upshifts (see above for example -- that was a leisurely run with my manual transmission Z4 while fine tuning the calibration last week). If anybody has an iPhone or iPod Touch with iOS 4.1 or later and wants to try this out, send me a PM. I will provide you with a coupon code to download the app from iTunes for free. Come back here and post your 0-60 or 1/4 mile results so that we can see them (don't do anything dangerous or illegal of course).

Though I am most interested in DCT, I'd be glad to give a coupon to anyone else who wants to try the app (Z4 or otherwise), while the coupons last.

Thanks,
219

[KCSchoey]

Very cool. Wish I could download this for Android!

[Mr. ///M3 RD]

Question, will you be working on a similar application for the ///M3 and the Z4M ?

Thanks,

Rolf-Dieter

PS. I drive a M3 and plan to purchase a lightly low milage 2008 Z4 M

[bjarne]

skier, sounds really cool, I would love to try it.

[skier219]

Originally Posted by Rolf-Dieter

Question, will you be working on a similar application for the ///M3 and the Z4M ?

Thanks,

Rolf-Dieter

PS. I drive a M3 and plan to purchase a lightly low milage 2008 Z4 M

Rolf, it works on any car.

[skier219]

A couple of you asked about what vehicle specs to put into the app for the Z4. Here's what I would recommend. Most taken from the 2011 Z4 brochure, but others are my estimate.

Weight: 3250 lb (s30i) or 3500 lb (s35i/is) + driver weight + fuel weight
Drivetrain Loss: 0.15 (manual or dct) or 0.2 (auto)
Rolling Resistance: 0.013
Drag Coefficient: 0.34 (s30i) or 0.35 (s35i/is)
Frontal Area: 19.5 square feet
Pitch Correction: 2 deg/g (approx for sport mode, tweak as needed)
Roll Correction: 2.5 deg/g (approx for sport mode, tweak as needed)
Weather: enter pressure and temperature for your location (or default to 29.92 and 70F)

Note 1: you can enter these inputs with US/English units as shown here, and then if you switch the app to metric mode in settings, the dimensional quantities will automatically be converted to their metric equivalents.

Note 2: the pitch correction is the only variable relevant to velocity and distance computation (which is obtained via integration of accelerometer data). Pitch correction can be used to tweak the observed speed into agreement with a known/trusted calibration speed across the speed range. The speedo in our cars reads a little high according to a recent thread, so expect the app to be about 2-5mph below the speedometer at the tail end of a 0-60 run -- so it will take a bit longer for the app to read a proper 60mph than the speedometer (falsely) indicates.

Note 3: with the exception of the roll correction (which only applies to the lateral g), all the inputs factor into the power computation. Among other things, the inputs are used to account for losses (tire/drivetrain friction and aero drag) in order to compute the engine power. See the app's manual for details on how to tweak the inputs if you'd rather measure wheel horsepower.

[mash11]

I've an iPhone 4 and a Z4 sDrive35i with DCT.

Happy to have a go with your app if your still looking for volunteers.

[bmw-nj]

I HAVE A 2011 Z4 35I DCT AND WOULD ALSO LOVE TO TRY YOUR APP AND SEND YOU THE DATA.

PM ME THE CODE PLEASE

[Z4-2023 Mike]

I have a 2010 Z4 30I so would love to try your app! Pls send coupon.

Mike

[skier219]

OK, I am out of coupons. Thanks for the interest all. Be sure to post your results here when you get something to share.