I went out today and ran a test run to see where i was at. I haven't used my G-tech for over a year (don't ever lend your G-tech to a buddy).. I had some stored runs on there averaging 13.4-.5's with 103 trap speeds. I have tested the G-tech at the track and it seems very consistant, but about .1-.2 seconds faster than the timers. My car is consistantly around 13.60-13.80 at the track depending on where i go, with 60' in the 1.9's.. It was cool today (55F), and i eased it out of the hole with very little tire spin. The tires have very little tread left (1/8") and i left the psi at 30. After watching the vid a few times i thought there was a slight bog at the lower RPM's after a shift.. Listen for yourself. I was also wondering what you guys think a 2200 stall and drag-radials would do for me... Thanks. Video - 91 Z28 G-tech test

It makes me nervous watching you mess around with the camera doing over 100 mph in all your videos.

don't worry Stu, i extended the tripod handle on the dash mount. Its as close to my hand as the center vent. I also make sure im on a straight road and i don't look at the camera.....
I appreciate the concern though. I can see the distraction it could cause...

I dunno if your g-tech does the estimate horsepower like some, but you could probably "g-dyno" 700 HP by driving in reverse and throwing it back into drive. This will probably kill your tranny though.

where can you get those things?

and how do they work anyway?

I'm not totally sure, but I'd imagine Summit and other vendors have them. They measure how many Gs you pull accelerating...it's more complex than just that, but beyond that I don't know. The old ones were pretty innaccurate, but I guess the new ones aren't that bad.

I hear the new ones E.T's are almost right on. Just the mph is usually a bit too high.

but what about wheel spin, does it count for that? cause if i just floor it on street tires on the street, i'll just spin...till i don't feel like spinning anymore. which is kinda fun...cruisin' around at 20mph, then dropping the hammer and going sideways to 60-70+mph (yes, that's what the speedo reads after i lift) is alot of fun. haven't held it out till it quit spinning yet...kinda scary at 70mph. i mean, i can roll into it, but launching on the street is nearly impossible...i even spin the 275/60/15 mt et Street Radials on 15x10 welds pretty good on the street (not so much on the track with me 1.64 60' times)

The G-tech works by sensing the g-forces of your car as it accelerates. It uses a mathmatical fomula equating the g-force over time. Its all physics. The technology was used in helicopters before gps speedometers were around.
For accuracy you need to calibrate it often. Its real easy to use and you can store 5 different vehicles in it and 15 runs. It just plugs into your lighter and sunctions to the windshield. It does measure your wheel HP, but it is very inaccurate because it cant take into account wind-resistance. You enter the weight of the vehicle and calibrate the tach (it can sense your RPM's through the lighter socket) It says my car has like 210hp to the wheels, i don't pay attention to that. What i really like about it is the replay mode which will go over your run in real time with a graph showing your shift point's etc...and it will show the graph @ the 60', 1/8, 1000', 1/4 mile with the mph... The mph is off a bit because its not a trap speed like a track but the exact top speed through the lights (you are still accelerating through the trap)
It works great as a tuning tool to see if the mods you have done really worked. You just have to test on a flat piece of road or the same piece of road to get good before and after results. I use it all the time, it is very consistant...
As far as tire spin, it will still read accurately because you wont be getting as good of g-force as hooking would get you.
Its kind of like a scientific measuring stick for the seat of the pants feel...
They retail for around $200 i think, don't let ppl borrow it