G-tech meter, got it!, How many g's can you pull???? Options

[TimT]

Rich,

I take it you feel the same way that I do about street racing.

The data logger I use calculates rolling resistance, and CdA, its up to you to input vehicle mass.. the more accurate the info in, the more accurate the output.. as would be expected.. I dont really give a crap about 0-60

I want to preserve as much speed as I can, and use the brakes as little as necessary and always have my foot holding the accelerator pedal on the floor.. all on the track of course..

[Charles Deutsch]

You did say "it can only approximate a 0-60 time" which is true but it can approximate this time with great accuracy. And, you're safe since Philadelphia is much too far away for me to drive there anyway.

[mskala]

The idea that an accelerometer-based device needs to
have any idea of the weight of your vehicle to determine
time-to-speed or -distance, is false.

[ss6]

The G-tech derives its speed readings by mathematically integrating its accelerometer outputs. Their accelerometers are good, but not perfect, and they add error to the integration. The longer you look, the bigger the error. That's why they talk about the drag strip (short time frames) not road courses (long time frames). For accurate speed on a road course, you need either a wheel sensor or GPS. The DL90 supports both, but they advertise the GPS because it saves you the trouble of installing sensors (which can be a royal PITA). The GTech FAQ promised "road course software" "later this summer". Don't hold your breath.

Mark, I think they were talking about needing the car's weight to get HP figures, not times.

[ArtechnikA]

The idea that an accelerometer-based device needs to
have any idea of the weight of your vehicle to determine
time-to-speed or -distance, is false.

did i say that? i don't think so... i agree of course.

for a power approximation, obviously a mass estimate is required.
how the device can tell the difference between mass and drag (aero and mechanical) is beyond me...

i just think this particular device is a SWAP - a Solution Without A Problem.
assuming your mass is invariant (?) it can tell you -- ahh -- pretty much what a stopwatch will tell you over the same repeated stretch of road ... if you were determined to do this kind of thing on a road.

which is also what a couple of pulls on a chassis dyno will tell you, or a couple of runs on the local dragstrip.

the lateral accel is interesting and probably worth the $50 it's actually selling for.

Your Mileage May Vary, your HP may vary, your mass may vary, and as long as they do it in a safe, sanctioned location, i'm okay with that ...

[TimT]

sometimes I just love when threads take these turns.... people state their positions, and defend them no matter what...others could have some enlightening input..

[mskala]

Rich I may have been reading your post wrong, whatever as
long as conclusion is the same.
SS6, I agree the errors will accumulate, and this type of thing
is more a toy. I've been into the cheapo logger concept for
a while since I like monkeying with electronics, but even for
short autocross I can't see getting the data to line up
enough to help you (without radio start-finish and/or GPS).
Like I'm going to wade through 6 or 8 runs of an AX course
and try to plot the stuff, and then remember what I was
doing each time through (IMG:style_emoticons/default/blink.gif)

[Charles Deutsch]

for a power approximation, obviously a mass estimate is required.
how the device can tell the difference between mass and drag (aero and mechanical) is beyond me...

Your point is perfectly valid. A reduction in drag (all else remaining the same) would increase the acceleration of the car and this would be calculated as an increase in power at the driving wheels. Made me go back and look at my old physics book. Apparently they measure acceleration on a "frictionless table". A chassis dyno would also have some drag associated with it and this may be the same as the drag produced by the road. The difference would be the aerodynamic drag. If I'm not mistaken, the power that the G-TECH Pro records should be the same as the chassis dyno minus the power lost due to aerodynamic drag.