There are a number of dash-top units that give good and accurate, ET's, trap speeds, and horsepower readings. Those devices contain an accelerometer and a GPS unit built in. By measuring time over distance via the GPS and at the same time, acceleration over a fixed distance, they will get your times and be accurate with the best 1/4 mile measurements. G-Tech is still the premier unit but there are a number of other devices that have come on the market that do the same thing. There is even an iPhone application that offers some of the best features of the dash top units. As for Aterra, I believe it works by tracking RPMs over time.
BTW, G-Tech readings have been compared with 1/4 mile times and speeds on the track and they agree perfectly. There are You Tube videos on it.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
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