Hi, on another forum just heard of these $200, HP/G force/ GPS devices.

Put in your vehicle weight and it will do the sums in real time, for speed , braking etc and the RR one does sectional lap times, so you can work on your driving.
You can tell exactly whether the shiny rocker cover added HP or the rubber bushes make cornering faster ( you get the drift)

Anyone have experience with them $199 for the base one

blurb from the website link http://www.gtechpro.com/ss_fanatic.html

G-TECH is the easiest, most effective way to measure the performance of your car before and after modifications. It's a dedicated-hardware device specificaly designed for vehicle-dynamics testing.
There is nothing, and I mean nothing, that comes close to the same "bang for buck" when you want to know the truth about your car. Sure, you can go to the dyno or to the track. But not whenever you want to. Not to mention, everytime you go, you pay.

With this new High-Frequency GPS Technology the accuracy and the consistency is so superb that we encourage you to compare the results to your favorite track or dyno. If you are not blown away by how great it is, just send it back, no questions asked.

I had one for a couple of years. Yes they are quite good, but I would investigate Apps for your phone or notebook as well. The same inertial measurement is built into many devices (iphones for example).

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I see the problem with the iPhones ones etc is though, how do you mount it so vibration doesn't affect the repeatability?
Most of the phone cradles these days seem to be suction cup or vent clip type.

Having said that, I haven't seen how the Gtech's mount.

_________________

I have an early G-tech, it mounts on the screen with a suction cup. I don't currently use it.
My concern is that it uses tilt angles not just G force, so how accurate it is in my hydro car when it pitches under acceleration is anybody's guess.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

The inertial measuring uses all three axis' to measure the acceleration, so in my understanding a tilt won't be a problem for the mathematics, and they are relative to your own car only.

The vibrations I thought would come up in the acceleration graph as well. It shows in the HP Vs Time graph, but didn't affect the overall, as all is added and subtracted at once. Integral under the curve stuff.

I've got an old graph here somewhere I'll try to find. But it is relative to your own car, like dynos are relative to the installation.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.