gtech

[awe25gt]

was wondering about the accuracy of the 1/4 mile with the gtech pro. Ran a 13.2 tonight at 5280ft elev. with an APstg2 and uppipe. I've seen the debates on the hp/tq numbers and would seem to me the 1/4 measurement would be most accurate. Any thoughts?

[Magowin]

Mine was .5 seconds off for the 1/4 when I was at Etown. I did a 13.7's and it showed me a 13.2's. Not sure how others Gtech's compare with our car.

I never tried it when I started getting my lower times. I'll have to wait till Feb when Atco reopens because I don't think E-Town reopens till March.

 

 

[Fallschirmjaeger]

I remember hearing somewhere that most NHRA drag strips used a 1 foot rollout, which typically took about .3 secs to travel). Could that account for the discrepency?

 

Okay, I just remembered, R&T Mag December 05.

[rporter]

What G-Tech calls a quarter mile is not like a measured quarter mile on a track. Using a G-Tech at the track will generally give ETs that range from better to worse, and virtually always give trap speeds that are high by 4-6 mph. Always a good way to tel when someone is trying to pass off a G-Tech time as a 1/4-mile time. Then, when you move you car to a stretch of road, who knows how things can compare?

 

G-Tech is a great testing tool if you are careful and use it to compare to changes that you make. Attempting to use the G-tech to calculate HP or 1/4-mile times against other standard measurements is not realy a valid use.

[deimos]

What G-Tech calls a quarter mile is not like a measured quarter mile on a track. Using a G-Tech at the track will generally give ETs that range from better to worse, and virtually always give trap speeds that are high by 4-6 mph. Always a good way to tel when someone is trying to pass off a G-Tech time as a 1/4-mile time. Then, when you move you car to a stretch of road, who knows how things can compare?

 

G-Tech is a great testing tool if you are careful and use it to compare to changes that you make. Attempting to use the G-tech to calculate HP or 1/4-mile times against other standard measurements is not realy a valid use.

+1

 

That said 13.2 in the 1/4 for a stage II MT LGT is pretty close to what many people are getting at the track.

 

Best thing to do is to make sure you have the gtech set properly, in the right place and you are on level ground etc. Next time you go to the track g-tech your runs and youll have a pretty good idea whats going on.

 

Edit: just noticed your elevation, the gtech might be off a bit then not sure..

[NHLEG]

Mine is very accurate. While my times were not very good as I couldn't get traction off the line, slip vs gtech were VERY close. See: http://www.legacygt.com/forums/showthread.php?t=17943&page=10 post 146

So much depends if you get it calibrated right. I know my car's exact weight which helps alot.

[schwinn]

GTechs are generally of varying accuracy because of the critical nature of mounting - it must be totally horizontal (though newer units may be better in this regard).

 

In addition, as I recall, the dragways measure "trap speed" by measuring your time during the last 60' (I think) of track... hence, it's an averaged speed over that distance. Gtech reports your g-force calculated speed at the end of the 1/4 mile point, and hence reports slightly higher speeds.

 

1/4 mile times should match, but can still be somewhat off. C&D had done a test of many of these devices, and found that none were "perfect" even when you followed the directions to the T.

[rporter]

GTechs are generally of varying accuracy because of the critical nature of mounting - it must be totally horizontal (though newer units may be better in this regard).

 

In addition, as I recall, the dragways measure "trap speed" by measuring your time during the last 60' (I think) of track... hence, it's an averaged speed over that distance. Gtech reports your g-force calculated speed at the end of the 1/4 mile point, and hence reports slightly higher speeds.

 

1/4 mile times should match, but can still be somewhat off. C&D had done a test of many of these devices, and found that none were "perfect" even when you followed the directions to the T.

 

The dragstrip measures averages speeds, as you say. the ETs are also different, as your ET starts when you pass out of the "stage" lights.

 

The key issue is that the G-Tech is a tool to use for your own testing, and it does that very well (if you use it properly). it is NOT a substitute for measured 1/4-mile times at a dragstrip. It measures a 1/4-mile, but that's a "G-Tech 1/4".

 

In case I seem touchy about this, it has been a big issue of contention on car forums over the years (and even on this one awhile back) as folks try to pass off G-Tech times as being "real" 1/4-mile times from an official dragstrip. It gets a bunch of us '"really cranky" when you try & do that!! :laugh:

[deimos]

In case I seem touchy about this, it has been a big issue of contention on car forums over the years (and even on this one awhile back) as folks try to pass off G-Tech times as being "real" 1/4-mile times from an official dragstrip. It gets a bunch of us '"really cranky" when you try & do that!! :laugh:

 

This is the key, gtech is great and pretty accurate if used correctly but a gtech 1/4 will never = a dragstrip 1/4 100% so as long as people are honest when making power claims its all good.

[ThatGuyDownUnder]

What about reaction time? Would that count? Say a reaction time is .5 but your gtech does not account for that because it only accounts from the second you stomp the pedal. Which would make sense if you ran a 13.7 on the track and a 13.2 on the gtech, just check your RT to see if it comes close (Track Quarter Time Minus Reaction Time Equals Gtech Quarter Time?)(TQT - RT = GQT) <====homebrewed equation :-P

[BDII]

very, very accurate when tuned properly to your car. 1/100 of a second accurate.

[Magowin]

What about reaction time? Would that count? Say a reaction time is .5 but your gtech does not account for that because it only accounts from the second you stomp the pedal. Which would make sense if you ran a 13.7 on the track and a 13.2 on the gtech, just check your RT to see if it comes close (Track Quarter Time Minus Reaction Time Equals Gtech Quarter Time?)(TQT - RT = GQT) <====homebrewed equation :-P

 

Hmm true I never thought of that but I think that run my RT was .8 something or other because I was a newbie at the track didn't know you had to start going on the last yellow. I'll try to look for that time slip to make sure.

[rporter]

Reaction Time has NO effect on your ET.

 

R/T just determines who gets started first.

 

If a 10-second car races a 14-second car, and the 14-second car has a 5-second better R/T, it will still run a 14-second ET, the 10-second car will still turn a 10-second ET, but the 14-second car will get to the finsh line 1 second before the 10-second car.

 

But....this is one of the reasons why the G-Tech doesn't exactly mimic a real 1/4-mile run. The G-tech will meaure the initial roll, but on a dragstrip, you will get some roll (if you shallow-stage) before you trip the lights.

[rporter]

very, very accurate when tuned properly to your car. 1/100 of a second accurate.

 

I would need to see that. The "best" Ive seen is when someone ran is G-tech at the strip, and came within a tenth. By their design, they ca't match a dragstrip ET. And they won't be close on trap speed, again by how the two venues (G-Tech vs dragstrip) measure speed.

[Shmike]

I was about to start a thread about this actually. I've got a Gtech SS and today i ran 5.48 to 60 , 1.9 60ft. and 13.7 @ 98.8 in a stage 1 + intake and tune 05 wagon 5sp. It sounds pretty generous to me. I've got the thing Gtech tuned in pretty right too. Weighed the car at the dump with me in it and everything...

I'd be laughing if this was a 13.7 car but honestly i really doubt it. Any thoughts?

 

Oh, plus it gives net hp and torque estimates. HP 202, TQ apparently 0.00 It says it couldnt get a reading because there wasnt enough time in gear. LOL