does anyone in here own a Gtech performance tester or whatever??
09-28-2006, 11:18 AM
#1
does anyone in here own a Gtech performance tester or whatever?? Ok the Gtech thing its supposed to be able to tell you your 0-60 mph and 1/4 and 1/8 mile times and all this stuff, has anyone tested these things to see actually how accurate they are?? i was just wondering about them, they also supposedly tell you HP ratings and what not is this thing a load of 
or is it actually worth the money 
or is it actually worth the money 
09-29-2006, 11:32 AM
#5
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Originally Posted by bjamick
quik show of hands
suck
or dont suck??
suck
or dont suck??
It measures acceleration continuously and incrementally figures out if you are speeding up or slowing down. After each acceleration sampling it adds or subtracts to its current estimate of your speed. Then it updates your cumulative distance.
It has to have a starting point. From a dead stop over a distance of maybe a mile it will have a pretty good idea of your distance and speed but the totals will continuously drift further from the real values.
The biggest problem is people eyeball a flat road and expect that it is in fact flat. You absolutely have to run in both directions and average the results. The manual tells you this but people don't bother and blame the unit. Going up a slight hill makes your car look more powerful and vice versa.
The new high end one can measure RPM by reading the alternator output ripple (alternators produce 3 phase power and rectify it into something close to DC), my new stereo does this too and displays a techometer on the display. Knowing RPM, it can back out a torque value from the power calculation.
The actual math is grade school level, the physics is high school level. The smoothing it does is huge and this is where the smarts are. The new ones use a multi-axis accelerometer which alleviates the need to level the unit but adds only a little accuracy. The new one provides a nice little graph that the old one does not.
If you want to see the raw acceleration data, check this thread out, I cracked my unit open and did my own math instead.
09-29-2006, 11:49 AM
#6
^ what he said.
I have one of the original ones, probably 8 years old by now. Cost about $120 back then, and I've seen them on clearances sites for like $30 not too long ago.
Per what BJM said, I found mine to be very good with respect to the time measurements. 0-60 and the 1/4 seem were within 0.1-0.2 of strip results, which I think is fine considering weather and launch surface variations. If you understand how the unit works and always do your runs in the same place in similar conditions, it is a great tool for casual comparisons.
I don't think I'd drop the cash on the newer units but if you can find one of the cheapies at a closeout around still... good deal for $20 or $30.
I have one of the original ones, probably 8 years old by now. Cost about $120 back then, and I've seen them on clearances sites for like $30 not too long ago.
Per what BJM said, I found mine to be very good with respect to the time measurements. 0-60 and the 1/4 seem were within 0.1-0.2 of strip results, which I think is fine considering weather and launch surface variations. If you understand how the unit works and always do your runs in the same place in similar conditions, it is a great tool for casual comparisons.
I don't think I'd drop the cash on the newer units but if you can find one of the cheapies at a closeout around still... good deal for $20 or $30.
09-29-2006, 06:35 PM
#7
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I had one wehn i had my truck, used it as a tach, tested the HP TQ function on just about every friends car i know, they all seemed close but the only one who had real dyno result was a buddys 99' camaro...dyno said 410HP Gtech said 412 not bad?
