First 0-100 run on G-Tech

mrx · Post by **mrx** » Mon May 03, 2004 11:07 pm

Had a quick run on the way to work this morning for a 0-100 dash. No launch at all, just got moving and buried it. Ended up running 7.04s, which given I had no revs on board to start with, I was quite happy with. It actually felt quicker than that, but that was the figure. Could easily run a few tenths quicker with optimal launch etc.

Getting the car put on the dyno next Monday. Will be interesting to see what it returns. Just want to make sure that all is in order. Will post my figures next week.

thecook · Post by **thecook** » Tue May 04, 2004 2:50 am

thats pretty good, but gtech devices have been said to be inaccurate..

if u want more accurate times, take it to the track

mrx · Post by **mrx** » Tue May 04, 2004 7:02 pm

Well, it depends on who you believe.

But I am not arguing - it is just that there is no track that is terribly close. Will have to make a treck to eastern creek one day to see for sure.

It is more a bit of interest - a bit like dyno results!

Post by **smorison** » Tue May 04, 2004 7:26 pm

the best "mobile" units for this purpose are the ones that use G force sensors to gauge your acceleration and the like. Why? because it automatically excludes wheel spin!

ruchi · Post by **ruchi** » Wed May 05, 2004 12:20 am

mrx wrote:Well, it depends on who you believe.

So as to be unbiased and biting my lip to restrain myself, I'll let the manufacturer of the product speak for themselves.

The following quote is from the G-Tech website and explains the difference between the standard / Pro unit and the competition model. As they openly admit that the competition model has a "a huge improvement in accuracy", this would suggest that the standard / Pro model is hugely inaccurate

"There are several significant improvements over the original G-TECH/Pro Performance Meter that have been implemented in the new COMPETITION model. First of all, there are 3 accelerometers and they are fully temperature compensated. This in itself is a huge improvement in accuracy. Secondly there is a very sophisticated new calibration algorithm that allows much higher precision. Also the system now has 32 times higher resolution which speaks for itself. New Noise-Correction algorithms have improved overall accuracy as well."

...remember, this is their words, not mine

FTO338 · Post by **FTO338** » Wed May 05, 2004 11:12 am

This is the full write up of the product I found from the website.

How accurate is it?
There are several significant improvements over the original G-TECH/Pro Performance Meter that have been implemented in the new COMPETITION model. First of all, there are 3 accelerometers and they are fully temperature compensated. This in itself is a huge improvement in accuracy. Secondly there is a very sophisticated new calibration algorithm that allows much higher precision. Also the system now has 32 times higher resolution which speaks for itself. New Noise-Correction algorithms have improved overall accuracy as well. With all of these valuable features we are very proud to announce that the accuracy is now within 5/100 second. With the consistency at 5/1000 of a second! Absolute Horsepower and Torque measurements are within 3% and consistency within .5%!

So in the real world how much would 5/100 of a second would make to the accuracy in all the models of G-Tech.

salacious · Post by **salacious** » Wed May 05, 2004 11:27 am

My friend was using his GTech Pro Competition on a 1/4 mile strip and sometimes it was within 0.1s and 0.5mph in the terminal speed. But one result was 0.8s out!

Brian

ruchi · Post by **ruchi** » Wed May 05, 2004 2:10 pm

FTO338 wrote:So in the real world how much would 5/100 of a second would make to the accuracy in all the models of G-Tech.

Kev, it's not all the models, the figures quoted are only for the competition model. They do not publish the figures for the standard / Pro unit. But at their own admission they state that the competition model has a "huge improvement in accuracy" over the standard / Pro unit which suggests that the standard / Pro unit is hugely inaccurate.

GPXXX · Post by **GPXXX** » Wed May 05, 2004 4:31 pm

this reminds me, we should have a track day at Heathcote soon... hopefully the weather improves, coz it doesn't look ideal lately...

mrx · Post by **mrx** » Wed May 05, 2004 10:38 pm

But at their own admission they state that the competition model has a "huge improvement in accuracy" over the standard / Pro unit which suggests that the standard / Pro unit is hugely inaccurate.

Don't you think that is a bit of an extreme viewpoint? So if (say) Ferrari claim to make a "huge improvement" in the wind tunnel, does this mean that before they were pathetically slow? Their "big improvement" may amount to 2 or 3 tenths a lap! That is a long way in F1, but in the real world...

As I said before, it is just a bit of fun, nothing too serious. Oh, and with a launch I got a 6.83 (for what it is worth).

ruchi · Post by **ruchi** » Wed May 05, 2004 10:49 pm

mrx wrote:Don't you think that is a bit of an extreme viewpoint?

Nope. They're inaccurate, 'nuf said.

Post by **smorison** » Wed May 05, 2004 11:42 pm

mrx

i think you need to bring your car to wakefield next week

who knows it could be a monday car and blow us all away

G1 · Post by G1 » Thu May 06, 2004 10:37 am

i doubt it would give an error of more than 5% (this is just a guess), more important would be how consistent it's output is - just like you wouldnt read your dyno test reading like the bible you wouldnt use this to claim your car's performance figures - only as a very rough idea though... it can be used to quantify gains from mods, and compare performance to other cars (on the same day)

just like any form of measuring, you wouldnt wanna rely on just one run either and throw out the readings that have deviated way off the average etc...

ruchi · Post by **ruchi** » Thu May 06, 2004 12:12 pm

Spot on G1, figures from anything like a G-Tech unit or Dyno mean jack-sh*t unless they are consistant and there is a benchmark to compare them to.

Dyno
With a Dyno, their accuracy is pretty good, and some have closed rooms which allow you to control the environmental aspects, however there is no benchmark and as such two different dynos will give you two different results. If however, you keep to using just the one dyno and keep all the variables the same, then you can use it as a reasonably accurate tool for tuning and modifications.

G-Tech
Aside from its internal (in)accuracy, the G-Tech is also suseptible to calibration and environmental issues, which compound the inaccuracies. In terms of calibration, the manufacturer allows for a deviation of 0.96g to 1.04g which provides a total range of deviation of 8% (-4% to +4%) from the standard of 1g. In a 0-100kmh time, 8% is more than half a second and over a 1/4 mile is more than 1 second. Whether this is considered a "huge" inaccuracy is personal opinion

Even if you can calibrate it to a perfect 1g, environmental issues and vibration will cause errors.

In short, if you want to use a G-Tech unit, make sure it is calibrated and test its consistency by doing multiple runs. If it is providing reasonable consistency then you can use it to note the differences modifications make, but in terms of using it to compare against other cars the data is useless unless you are using the same G-Tech unit in their car, doing the same run and with virtually the same environmental factors.

Measurement
It is interesting to note that both a Dyno and G-Tech unit only measure one item, they then use mathematical formulae to calculate the rest of the figures they provide. As some of these calculations include variables, any changes in these variables such as calibration or environmental issues, will increase the error of the readings.

Dynos measure torque while G-Tech units measure gravity, all the other readings such as speed, power and 0-100kmh times etc. are all calculated from either a change in torque or a change in gravity, respectively.

Sorry
Sorry to burst your bubble mrx, but posting performance figures to a public website using an inaccurate tool like the G-Tech unit is just asking for trouble. The figures don't mean anything, due to inaccuracies, and others can't compare their figures to yours as there is no common benchmark to go by.

TheSentry · Post by **TheSentry** » Thu May 06, 2004 12:28 pm

For those interested, Autospeed did a write up on the G-Tech: http://www.autospeed.com.au/cms/A_0022/article.html

G1 · Post by G1 » Thu May 06, 2004 1:36 pm

so mrx i wouldnt feel bad about providing those figures, just dont expect anyone to accept them as true figures, but you could accompany the figure with a before/after-adding-such-and-such-mods figure, or my-friend's-integra-tyre-r figure, see my point?

i personally would interpret your figure as roughly 7 seconds, which is about right for a gpx manual i assume, i would be worried if you were getting something like 7.5-8 seconds at which point you would suspect either the g-tech or your car. even now it would be good to re-affirm with a dyno test, or run the same g-tech on another car down the same strip, whose true figures you know, this will tell you how accurate your g-tech is.

all in all if you can prove that you can get consistent readings from it, then it is no doubt a very valuable tool for measuring performance gains/losses and comparing figures with other cars.

like autospeed said, it sure beats using your stop watch.

Post by **smorison** » Thu May 06, 2004 1:45 pm

ruchi wrote: Measurement
It is interesting to note that both a Dyno and G-Tech unit only measure one

Ruchi this is incorrect. with current dyno's you can measure many different things and basically it's only limited to the amount you want to spend on a dyno some things you can measure are:

A/F ratio
Boost
Vacuum
Intake Temp
Exhaust Temp

sensors can be purchased to measure just about anything these days

ruchi · Post by **ruchi** » Thu May 06, 2004 3:24 pm

Steve, the factors you've mentioned are more or less incidental as none of them measure performance.

But if it will help, I'm happy to reword my statement to say "they only measure one performance factor, they then use mathematical formulae to calculate the rest".

(is that better?)

As you said yourself "sensors can be purchased to measure just about anything these days" and while those sensor may provide additional information that could be of interest or may even help in tuning the car, they don't measure performance nor are they used in the performance calculations.

The performance factor that is the basis of a dyno is the measurement of the change in torque over time, while the performance factor that is the basis of the G-Tech unit is measurement of the change in g-forces over time. The other performance figures are calculated from this information or plotted against other inputs such as revs etc.

Theremin · Post by **Theremin** » Thu May 06, 2004 4:28 pm

Ruchi
Much to my dismay, in your dissertation on performance measuring devices you didn't cover rev/speed meters. These measure speed (based on the same signal that drives the speedo, so depends on accuracy of your speedo and will be affected by wheel size, etc), revs (which is connected to the ignition wire so should be 100% accurate) and time (again, should be pretty close to 100% accurate). From that they calculate 0-100km/h times, quarter mile times and power (the latter of which I suspect is an approximation seeing as there are many other variables such as weight, resistance etc). The thing about these devices is, as I think Steve mentioned earlier, they "count" wheel spin (ie. the device thinks you are moving even though you're not) and they don't count reaction time (ie. they usually start measuring once the car starts moving). Have I covered it?

Theremin.

ruchi · Post by **ruchi** » Thu May 06, 2004 5:30 pm

LOL!

OK, you're right a RSM will give you a more accurate reading, in fact the reading they provide should be more accurate than what your speedo and rev dials show and hence there can be a difference.

Wheel spin is only an issue if you are measuring over a distance (1/4 mile time) not when measuring over time (0-100kmh), but even that can be overcome if you get one which has a g-sensor in it. However dyno's will also provide an incorrect reading if the wheels are slipping too.

I'd have a lot more faith in a RSM reading than a G-Tech one.