G-Tech Pro
Sep 29, 2003, 08:16 AM
#16
long!
Hey all,
I've had a GTECH Pro for several years. I used to go out at lunch and try to get into the 14s with my N/A GSR, heh.
Anyway, there has been a lot of debate on their accuracy on various forums on the Net, and here's my take. First, in terms of precision, they are very good, referring to the consistency and relativity of the measurements. For example, if you do a 14.2 quarter mile on the GTECH, then add a mod and run a 13.9 using consistent methods (same stretch of road, calibrate to 0.0 +/- .01, similar atmospheric conditions, etc.), then you can probably conclude that the car is faster. If you do 14.5, under the same circumstances, you probably got slower.
In terms of a thermometer, precision would show that it's hotter or colder, but it may not necessarily be accurate, or close to the "actual" value.
If you use somewhat "scientific" methods with the GTECH, you can get precision and pretty good accuracy. For example, run on the same stretch of road, in both directions. Do several runs, throw out high and low, then average. Precision alone is valuable, since you can gauge improvements or lack thereof to some extent. The road needs to be quite flat, since inclines read as more accel and declines read as less accel. Also, the GTECH should be set to 0.0 at the start to make sure it gets a decent reading.
The ET will probably be fairly close to the ET at the drag strip. The trap speed is always high, either subtract 3-5 MPH or just ignore it. The manufacturer (tesla) claims this is because the strip averages your trap over a fixed distance while the GTECH reports it instantaneously, however, it's still just too high.
I haven't used it for the HP, TQ, or any handling recordings. Turning the thing sideways just seems kind of hoky.
BTW, for those unfamiliar, it just plugs into the cigarette lighter and sticks to the windshield like a radar detector. The unit itself is just an accelerometer and DSP to take instantaneous acceleration reading (either + or -) and measure time in seconds, then calculate position. As you tilt it forward or backwards it reads + or - accel.
I would think is uses Newtonian projectile motion like formulas and calculus, something like:
position = (initial position) + (initial velocity) *(time) + 1/2 (acceleration) (time*time)
or
x = x0 + vot + 1/2att
Does that sound right? You are constantly measuring a and plugging in t, so you can solve for x and v to figure out when you have hit 60 mph or when you have covered 1/4 mile and at what speed. Pretty cool.
Finally (if anyone is still reading), you can use it as a rough tuning aid. If you keep it in instantaneous accel mode, you can see what kind of "gs" you pull in various gears at various rpm. Can't really plot it over time very well, but it can give you somewhat of a idea. If you get higher peak "gs" or hold gs higher into rpm, it's probably working better.
Don't know much about the newer unit, but I think it has logging or some sort of graphical displays?
Oh well, sorry for the novel.
Take care,
FB
I've had a GTECH Pro for several years. I used to go out at lunch and try to get into the 14s with my N/A GSR, heh.
Anyway, there has been a lot of debate on their accuracy on various forums on the Net, and here's my take. First, in terms of precision, they are very good, referring to the consistency and relativity of the measurements. For example, if you do a 14.2 quarter mile on the GTECH, then add a mod and run a 13.9 using consistent methods (same stretch of road, calibrate to 0.0 +/- .01, similar atmospheric conditions, etc.), then you can probably conclude that the car is faster. If you do 14.5, under the same circumstances, you probably got slower.
In terms of a thermometer, precision would show that it's hotter or colder, but it may not necessarily be accurate, or close to the "actual" value.
If you use somewhat "scientific" methods with the GTECH, you can get precision and pretty good accuracy. For example, run on the same stretch of road, in both directions. Do several runs, throw out high and low, then average. Precision alone is valuable, since you can gauge improvements or lack thereof to some extent. The road needs to be quite flat, since inclines read as more accel and declines read as less accel. Also, the GTECH should be set to 0.0 at the start to make sure it gets a decent reading.
The ET will probably be fairly close to the ET at the drag strip. The trap speed is always high, either subtract 3-5 MPH or just ignore it. The manufacturer (tesla) claims this is because the strip averages your trap over a fixed distance while the GTECH reports it instantaneously, however, it's still just too high.
I haven't used it for the HP, TQ, or any handling recordings. Turning the thing sideways just seems kind of hoky.
BTW, for those unfamiliar, it just plugs into the cigarette lighter and sticks to the windshield like a radar detector. The unit itself is just an accelerometer and DSP to take instantaneous acceleration reading (either + or -) and measure time in seconds, then calculate position. As you tilt it forward or backwards it reads + or - accel.
I would think is uses Newtonian projectile motion like formulas and calculus, something like:
position = (initial position) + (initial velocity) *(time) + 1/2 (acceleration) (time*time)
or
x = x0 + vot + 1/2att
Does that sound right? You are constantly measuring a and plugging in t, so you can solve for x and v to figure out when you have hit 60 mph or when you have covered 1/4 mile and at what speed. Pretty cool.
Finally (if anyone is still reading), you can use it as a rough tuning aid. If you keep it in instantaneous accel mode, you can see what kind of "gs" you pull in various gears at various rpm. Can't really plot it over time very well, but it can give you somewhat of a idea. If you get higher peak "gs" or hold gs higher into rpm, it's probably working better.
Don't know much about the newer unit, but I think it has logging or some sort of graphical displays?
Oh well, sorry for the novel.
Take care,
FB
Sep 29, 2003, 08:21 AM
#17
Forgot to mention,
A couple of my coworkers and I have run my GTECH at lunch, but just 0-60 since there isn't a suitable road for the 1/4 close by. Overall, my EVO runs right around 5 (s) flat with my 200 lbs anchor/friend (I'm a buck 60 ). I've ranged from 4.6 with a killer clutch smelling launch to mid 5(s). The same guy's automatic Maxima runs right around mid 7 (s) under same conditions.. Another coworker with a 350Z runs mid 5 (s) or so, same conditions. This seems to agree pretty well with expected relative performance.
Take care,
FB
A couple of my coworkers and I have run my GTECH at lunch, but just 0-60 since there isn't a suitable road for the 1/4 close by. Overall, my EVO runs right around 5 (s) flat with my 200 lbs anchor/friend (I'm a buck 60
). I've ranged from 4.6 with a killer clutch smelling launch to mid 5(s). The same guy's automatic Maxima runs right around mid 7 (s) under same conditions.. Another coworker with a 350Z runs mid 5 (s) or so, same conditions. This seems to agree pretty well with expected relative performance.Take care,
FB
Sep 29, 2003, 12:58 PM
#18
Evolving Member
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Join Date: Aug 2003
Location: Seattle, WA
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Just an update... My order has been processed and shipped since ordering yesterday. Although I purchased mine via an ebay ad, the company is actually www.avionicsgps.com. They have a website with the g-tech listed for $49.95:
http://avionicsgps.com/avionics_gps....oductNum=GTECH
They seem to have excellent customer service. (I'm not affiliated with them.)
http://avionicsgps.com/avionics_gps....oductNum=GTECH
They seem to have excellent customer service. (I'm not affiliated with them.)
