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The G-Tech Accelerometer - Dashtop Dragstrip

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So you've just installed that new cam and headers, and you're sure the thing's running in the 12s. You take it to your favorite back road to try it out-sure feels faster.

Face it-other than taking it to the strip, it's all guesswork. Chrondeks don't lie, and sometimes the truth can hurt, but you'll always be better off with bruised pride and real numbers. Impromptu testing in any kind of serious way has been out of the realm of the average enthusiast, until now. We were intrigued, if not a little skeptical, when we saw the low-buck G-Tech accelerometer from Tesla Electronics. Being familiar with these kinds of devices, we knew that most are sophisticated high-dollar gadgets about as realistic for the average street enthusiast as bolting on a fifth wheel. The G-Tech, at a tariff of about a bill and a half and the size of a pager, seemed cute, but we were more interested in serious numbers.

Taking delivery of the G-Tech and talking to the man behind it's development, Jovo Majstorovic, it was clear that the G-Tech's sophistication belies its low cost. The key to making the G-Tech possible was the development of highly precise, low-cost electronic accelerometers that were initially an outgrowth of airbag research technology. With a means of accurately measuring acceleration force and an electronic timer, the G-Tech was designed with various circuits to perform complex mathematical algorithms, integrating the data and calculating velocity or speed. From there, calculating distance or even road horsepower can be done by the G-Tech's computer. Calculus buffs realize that an integration calculation becomes more precise as the interval becomes smaller. The G-Tech's accelerometer refreshes the value for acceleration used in the computation 400 times a second, which is virtually continuous input. The G-Tech is programmed to calculate 0-60 mph acceleration, 60-0 braking, quarter-mile speed and e.t., horsepower, instantaneous and continuous g-force, and even lateral g-force.

You don't need an engineering degree to hook-up the G-Tech-just plug it into the car's cigarette lighter, mount it to the windshield with the suction cup, and go. Adjusting the unit so that it is level (or perpendicular for lateral g's) and inline with the car's centerline is critical for accurate operation. Leveling is easy; just set it so that the g-force display reads zero. Getting it straight is a matter of careful eyeballing. Jovo recommends sighting it from outside the car.

We worked through all of the G-Tech's functions and were amazed by the repeatability. Using the 60-0 braking function, we were able to practice pedal modulation for the shortest stops. The acceleration mode was used for dialing carb jetting in our daily driver 318 Dart. By telling us if various modifications had us running better or worse, the value of the comparative numbers was obvious, but we were eager to see how it stacked up against those cruel Chrondeks.

We brought the G-Tech to Bakersfield's Famoso Raceway for some actual drag runs in the Dart. The results are shown above. Quarter-mile e.t. was surprisingly accurate and consistent, bettering the claimed accuracy of one tenth in our test by holding within half a tenth. This is real data. On the mph side, our readings were consistently about 2 1/2 mph faster. Not quite on the mark, but the repeatability was extremely good. Bear in mind that on the dragstrip the timing system averages trap speed between the lights over the last 60 feet of the quarter. The G-Tech is designed to read the speed at the precise moment that it calculates reaching the end of the quarter-mile, and this will certainly account for the discrepancy. It's significant that the mph numbers are repeated within a narrow range, and this precision is a tremendous aide to tuning for more horsepower, making the G-Tech one the most useful and fun items in our toolbox.

G-Tech Features and Manufacturer's Specs
Measurement Resolution Accuracy +/-
0-60 mph 1/100 sec. 1/10 sec.
60-0 braking 1 foot 2 ft.
Quarter-mile speed 0.1 mph 1 mph
Quarter-mile e.t. 1/100 sec. 1/10 sec.
Horsepower* 1hp 3hp
Instantaneous g's 1/100 g 2/100 g
Continuous g's 1/100 g 2/100 g
*Horsepower calculation is rear wheel and includes the effects of aerodynamic and mechanical drag.
DRAG TEST RESULTS
RUN E.T. CLOCKS E.T. G-TECH DIFF MPH TRACK MPH G-TECH DIFF
1 16.661 16.62 -.041 83.61 86.2 +2.59
Easy run; Off idle launch; Auto shift 4,500 rpm; two passengers
2 16.512 16.50 -.012 85.93 88.5 +2.57
Off idle launch; Manual shift 5,200; two passengers
3 16.32 16.28 -.040 83.93 86.7 +2.77
1,200 rpm launch; Manual shift 6,200; two passengers; High rpm fuel delivery problem
4 17.242 17.23 -.012 88.20 90.52 +2.32
1,800 RPM launch; incinerated tire (open diff); Manual 6,000 rpm shift; Driver only
5 15.926 15.89 -.036 90.03 92.6 +2.57
1,200 RPM launch; Manual shift 6,000; Driver only

SOURCES
Tesla Electronics
881 Alma Real Drive
Suite T-09
Pacific Palisades
CA  90272
310-230-0040
www.gtechpro.com
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