Brad has an iPhone, so he downloaded the free iTSX app. At the track, we plugged the dongle into the car's OBD-II port and synced it to Brad's iPhone. Before flashing the PCM, we made a couple of passes to test the iTSX's accuracy and to get a baseline. To perform the test, you simply open the app, select the performance test option, come to a complete stop, and push the start button. We simply staged fully, then pressed the start button; the clock doesn't start until your vehicle's PCM sees that the vehicle has begun moving.
A couple of baseline runs yielded a best of 12.80 at 107.72 mph with a second best of 12.96 at 107.59, according to our timeslips. We were launching at 3,800 rpm and shifting just before it hit the rev limiter at 7,000 rpm. We were going through the traps just after completing the 4-5 shift. On the 12.80 run, our performance test on the iTSX said we went 13.0 at 111.2 mph.
The variances between the two can certainly be attributed to the way the dragstrip measures e.t. and mph. The clocks at the track don't start your run until your front tires completely clear the beams at the start line. Called Rollout, this allows you to get the car moving before your run actually starts. Depending on how shallow (or deep) you stage, Rollout could account for two-tenths of a second of your e.t. The iTSX starts your run immediately when the car begins to move, so you don't get the advantage of Rollout. Also, the clocks on track calculate your speed by timing how long it takes you to get to the finish line from a beam 66 feet before the finish. The iTSX uses the vehicle speed sensor to measure actual miles-per-hour at the quarter-mile mark instead of the "speed trap."
Though different, the results were similar. Would we see the same after the tune? Back in the staging lanes, we uploaded the SCT tune to Brad's GT through his iPhone. On track, we went a full two-tenths quicker and four mph faster, 12.56 at 111.73. According to the iTSX, we went 12.7 at 113.9 mph. Launching at the same 3,800 rpm, we were now shifting at 7,500 rpm. And since we could wind each gear out longer, we went through the traps just above 7,000 in Fourth.
Though we always enjoy a day at the track, admittedly, this was surprisingly enjoyable. It was a blast testing out the new gadget, and even though it doesn't measure exactly the same way the dragstrip does, it was exciting to see such close and consistent results. We did test out the virtual gauges, as we monitored coolant temp in between runs (see photo). But we didn't get a chance to even touch the 60-0 mph braking test or g-meter. We'll save that for next time.
iTSX vs. Gainsville Raceway
Here's a look at the performance...
Here's a look at the performance test results. Not only does it give you a quarter-mile e.t. and mph, but it also simultaneously logs top speed, braking time, and estimated horsepower and torque output. Horsepower and torque were higher than they should have been, but Johnson attributed that to a little wheelspin off the line.
Between runs, we used the...
Between runs, we used the virtual gauges mode to monitor coolant temp between runs, so we could make all of our runs at consistent engine temps.
After our baseline tests,...
After our baseline tests, we flashed the PCM with the SCT tune, which is included. This is also done remotely through your decive-in our case, Brad's iPhone.
After flashing the PCM, we ran a best of 12.56 at 111.73 mph-over two-tenths quicker than our baseline of 12.80 at 107.72. And the iTSX logged a 12.7 at 113.9 mph on the same best run. We'll call that accurate enough, considering the radically different methods of obtaining the data.