Aaron

[2ML67]

Was fooling around with my buddy's G tech today, so just how accurate is it.
0-60 4.71, 1/4 13.16@105.7mph, hp 187@5048rpm, tq 206@4241rpm, and g's 0.81@1.141s
How does that compare with your car if you don't mind me asking remember this is basically a stock 3800SC powered Fiero. Dan

[Rob]

Dan, that HP rating is about what I got with my stock car too..

[aaron88]

You ask a loaded question Dan.  The accuracy depends on a lot of factors.  The main one being which G-Tech meter you are using.  Is it a pro comp, an ss or rr.

The calibration of the meter and the flatness of the road are of paramount importance.  Your results could be off by more than 20% if not calibrated properly.

The meter it’s self will be within .5% to 2%, however; with the human factor of calibrating you can easily add 5% to that figure.  The more accurate you can calibrate the closer you will get to that .5 to 2 percent.

If you want the short answer scroll down to the last paragraph.

It’s easiest to break thins down into percentages.  So take all the things you have to calibrate and brake them down into accumulative percentages and then find the root-mean-square of that and assume it to be your accuracy.  This will not be the most accurate but it will be consistent, so for comparing runs it will be reliable but only in that capacity and to the accuracy aforementioned.

Let’s look at a few factors, rpm, vehicle weight, pitch correction, road flatness, unit accuracy, and vibration.

RPM
For arguments sake lets say that you have an accurate way of reading the rpm and you manage to calibrate your rpm with the unit within 100 rpm at 4000 rpm.  That’s still an error of 2.5%, and it’s only fair to assume that this is about as close as you can get it without having software to calibrate with.

Vehicle weight
You go the scales to have your car weighted but the scale is only accurate to 10 lb and you have a half tank of gas, but when you are testing you might have a full tank of gas (but that’s only at first) from full to empty the gas will change the vehicle weight by about 80 lb, and this time you have a buddy with you and he said he weighed 185 lbs but neglects to tell you that his cloths weight an additional 7 lb.  These are all factors that will affect your results.  So lets say you make your best guess and the car weighs 2880 plus driver, passenger, equipment, gas et cetera, you are feeling confident that you got the weight within 30 lbs.  This means that your hard work makes you about 1% accurate with a 2% floating gas weight.

Pitch correction
Pitch correction is something that the newer ss and rr models have on top of self calibrating level ground.  I’m assuming at this point that you don’t have this newer ss model.  With this feature your results should be within .5% but without you can expect to be off by 2.5% if you can calibrate level within the computer (g-tech) to .01.  You can do it but it takes a while.  Otherwise you can expect result to be off an additional 2%.

Road fatness
If the road isn’t perfectly flat and with relatively little wind, you can expect a wildly ranging accuracy to result.  What I do for consistency is use the same stretch of road exactly run for run and in the same direction.  This will give you good result to compare run to run, but will decrease the overall accuracy.  At this point I’m going to just assume you have a nice flat piece of road and call it 1% accurate.

Unit accuracy
The unit it’s self claims to have an accuracy (depending on model) of better than 1%, so you can take this number and add it to your overall accuracy

Vibration
If there is any vibration acting on the unit, this will adversely affect the results anywhere up to and over 20%.  The idea here is to make sure that the way you have this thing mounted is nicely insulated. You don’t want it to move and you don’t want it to vibrate.  I use a nice soft piece of foam to dampen any vibration (noticeable vibration anyway).  I put the foam between the unit and the dash (but only when I’m tuning).  Don’t overlook this step, it really helps improve the results if your car experiences any noticeable vibration wile at idle or acceleration.

I know all this looks bad for accuracy but even though the accuracy may be off the unit is still about 1% accurate.  So if you add up all these accuracy discrepancies and use the root-mean-square your accuracy is off by 6%.  On a bad day you could be off by more than 11 %. But your consistency run to run is about 1%, or .5% if using a newer ss or rr model.

Dose that take a short answer and make it long?  I didn’t even get into all the factors (I could go on and on), but the sort answer is that your results should be consistent but only 6 to 11% accurate if using the G-Tech Pro Comp.  Also, if all you want is ¼ mile times the meter should be much more accurate for that than it will be for hp, simply because there are a number of variable you must enter that are affected by other variables.


Aaron

.

[aaron88]

Was fooling around with my buddy's G tech today, so just how accurate is it.
0-60 4.71, 1/4 13.16@105.7mph, hp 187@5048rpm, tq 206@4241rpm, and g's 0.81@1.141s
How does that compare with your car if you don't mind me asking remember this is basically a stock 3800SC powered Fiero. Dan

The 1/4 mile time and trap speed are almost identical to mine, but you must be making more hp than indicated to get to that speed in that time.  Probably closer to 230 at the wheels.

However; as I stated above you may be off by a good percent.  The speed and time should be fairly accurate (whithin .5 sec) but you have something wrong with your other calibrations.

Aaron

.

[2ML67]

Its a pro SS if that helps and I did not program it a friend of mine who owns it did. The road is as flat and level as I could find it actually has a slight upgrade to it. I don't care about the hp or tq readings its the 1/4 and g's that I am curious about. Hoping next shannonville is not rained out so I can get a true test before modding the crap out of this engine. Dan

[aaron88]

Its a pro SS if that helps

In that case, the 1/4 mile time will be within .2 sec, you can get that to .1 or less if you have the pitch properly figured out.  G’s in acceleration and deceleration will be within 2% (if not calibrated for pitch), but lateral G’s might be off by 10%.


Aaron

.

[Slammed Fiero]

Why don't you guys just race??? The fastest N/A 5spd N* is Will lucke's @ a documented 12.86. That was with a GM computer running a 300hp motor on a 275 Chip. Gtec's shouldn't be used for a comparison on a forum between 2 different cars , there good for personal testing and mods...


Just my 2 cents

[aaron88]

I agree.  That's all I got mine for and all I use it for, tuning.
My intensions were to never post such inaccurate results, but at the time someone was being rather amusing, so the cat’s out of the bag now.

Anyone that knows what they are talking about, also knows what the deal is G-Techs anyway.