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      12-17-2008, 09:52 AM   #1
Second Lieutenant

Drives: 2008 135 (sold), 2017 M2
Join Date: Jul 2008
Location: Australia

iTrader: (0)

iPhone Dynolicious vs Dragstrip

You might have seen my post last week about Wednesday night drags at Willowbank. I wasn't planning on going again for a while but the wife is away tonight so I thought "what the hell". Same setup as last week. JB3 v1.1 with all else stock. Very slightly cooler (about 25-26 deg) and noticeably less humid.

Anyway, good news is I ran a PB. Second run of the night 13.065 @ 109.28 mph. Happy, yes, but I want that 12 badly now. I can see how this becomes addictive. 60' time was 2.125.

The reason for the post is I ran my iPhone "Dynolicious" application while on the strip. On the run above, the iPhone dyno gave an ET of 13.06 @ 116.2 mph. It got the ET exactly right to the 1/100th of a second. Amazing. The trap speed is out a bit. This may be partly because at the strip, the trap speed is calculated via sensors placed 66' before the finish and on the finish itself. This means cars are moving slightly quicker across the line than the time slip indicates but it certainly isn't enough to account for 7 mph. Still, for a simple application it's remarkably accurate.

The first run I iPhone dyno'd showed 13.50 @ 109.5 vs the time slip of 13.378 @ 108.85 mph. Not quite as close on the ET but almost perfect on the trap this time.

Here is a download of the performance graph from the PB run:

There are a couple of bugs in the program still. The Y axis is labelled MPH and HP but the data plotted is actually KPH and KW. I told the application to use metric - it just didn't adjust the graph legend. The power output at the wheels seems about right (peak 224) considering I was using the published weight of the car - actual weight might be a bit more meaning I have more power than it thinks. I've had the car dyno'd at 238kW at the wheels.

I'm fairly sure the blips on the yellow power curve in second and third gear represent wheelspin and DTC functioning, since it occurs just after the clutch is released.

Cheers guys!