I fail to see how something that just plugs into your cigarette lighter can tell you your acceleration, hp, etc. How in tarnation does it do that? If I buy it, can I expect consistancy from it? What I mean is, if the numbers themselves are not accurate, are small changes (i.e. as mods are added or things malfunction) going to be noticeable? If this thing really works why would anyone want to dyno anymore?

 

It's fairly accurate on most calculations (maybe +/-5%). It's just an accelerometer. Knowing your cars acceleration, it can calculate your cars torque based on other information you have given it like the weight of your car, etc. It can do this because your car's torque curve matches its acceleration curve. By knowing torque, it can then calculate your HP (again, HP = torque x rpm/5252). Also by knowing your cars acceleration, it can integrate over time and calculate what speed you are going (useful in calculating 0-60 times). Doing this again, it can calculate the distance you have travelled (useful in calculating 1/4mi times). It's a fairly simple tool with a bunch of math/physics to spit out some pretty decent info.

Contrary to how this post may sound, I don't have one of these. Others may be able to provide more info on what data the G-Tech asks for when you set it up. If I could get a list of this info, I'm sure I could explain why it needs it. (Sorry, I'm a math geek!)

 

My G-Tech is very consistent. When I go out to do multiple 0-60 test I very often get times with in .01's of each other. The only time you have to put your vehicles weight in is when you do a HP test. I got a indicated 244 HP when I had my SC on my I30 and now I get 174 HP{to the wheels}. Those #'s are dead on. I also did some 0-60 runs with my SC and with out, my best time with was 0-60 in 5.44 and with out the SC I have goten 7.1's.

 

a G-Tech is just an accelerometer that measures your car's acceleration, and from that it can get other things.

In English, it can detect how fast you're accelerating, and do some cool stuff from that. Like if it can detect that your car is accelerating at 10mph per second (10mph/s) and that acceleration remains constant, then it'll be able to tell you that you did 0-60mph in 6 seconds.

So it'll do that, and also integrate your velocity over time to get distance vs. time as well, like a 1/4 mile time. Basically, it just measures acceleration. It integrates acceleration over time to get you a velocity, and then it integrates velocity over time to get distance vs. time.

In the real world however, it's not really all that accurate (much more than 5% error!), and there are TONS of ways to trick the thing out so that you can get it to say that your stock Maxima (or Accord V6) is pulling 9 second quarter miles!!!

Even when they are properly set up and you're not trying to trick it out, they can still be off by like 0.5-1.0s in the 1/4 mile, which is A LOT. And simple little things like the rear of the car diving under hard acceleration, and rough pavement can completely mess i up too. All the time over on the SHO Accord boards we get these stupid morons in 4-cylinders saying they're pulling flat-15 quarters and we're like WTF - you're full of it, so we ask to see a time slip and they go, oh..umm...it was a G-Tech.

yeah, uh-huh!

One of our Accord V6'ers that goes to the track too much has done some comparisons between his slip and his G-Tech and the thing is off by a lot 99% of the time.

G-Tech user

It's just a toy at best, and not anything you could use to make any serious performance claims. For that you still need a 1/4 mile track and a time slip

 

Check out these sites:

http://www.gtechpro.com/
http://integra.vtec.net/geeser/gtech.html
http://www.flash.net/~duetto/gtechpro.htm

There is more info if you need. Just do a search on 'Gtech performance meter' in yahoo.