talljosh85

iTrader: (3)

Well, my dad bought the expensive G-Tech accelerometer for testing his Supra and other asundry things, and since the seven's motor compartment and drivetrain were stock tonight, I figured I should give it a shot. I calibrated it for the car and headed out with my buddy to a long, deserted straight. My first couple of runs were pathetic, I didn't boost much, and bogged the launches something awful. I ended up with a couple of mid 14s and a high 15, which occured when I bogged, missed third and didn't boost well. SO, I decided to reset the ecu and cool it off a bit, then I tried again. I ended pulling two 13 second runs, the first was a 13.858 at 102.46, my reaction was 1.334 and my 60' was 2.114s, and my 0-60mph was 5.715s. I guess I kinda jumped the start a bit. The second was a bog (again) and subsequently a 14s run. The third and final run for the night was a 13.845s at 102.15mph with a reaction time of 1.076, which may or may not be legal for drag racing, truth be told I'm not sure. The 60' time was 2.190s, and 0-60mph was 5.785s. So, assuming I calibrated correctly and didn't screw up the controls too much, I was able to hit a high thirteen on cheap kumhos in about 80 degree (fahrenheit) temperature with another person in the car. I'm pretty pleased with seven, now I need my damn upgrades. Josh

T88NosRx7

iTrader: (1)

sounds good, how do you like the G-Tech, I was thinking about getting one to see how accurate they were.

talljosh85

iTrader: (3)

I love it, as does my dad. Its super easy to use, mounts easily, and you can set it up for four different cars and save the info. For about $250, I would suggest getting one. I can't say that its super accurate, but the numbers seem to match up and coincide with how the car performs and how it is driven. To us, the accuracy seemed rather good on both the Supra and the Seven. The only problem with it is the connecting line to the computer uses an archaic plug, which hasn't been put on a Mac in years, so we have to find an adaptor. It also estimates horsepower and torque, gives other drag related info, and can calculate lateral-Gs. Josh

T88NosRx7

iTrader: (1)

Just out of curiosity, what kind of hp did the gtech say you had?

talljosh85

iTrader: (3)

It said I was putting to the ground 199 and 197hp, and like 160-170 ft/lbs of torque. I'm not sure if this is right or not, but it seemed accurate on the Supra, when traction control was on, A/C, and low boost it made about 300 to the ground on a shitty run with just full exhaust BCC, cam gears and a profec-b. Josh

cavellm

Josh, looks like it's accurate in at least the times and ET's.

Last night I had a pathetic run at the track. Somehow my Profec B II had gotten reset to 0, and I ran down the track @ 6 psi with a 13.8 @ 102 or 103.

Be damn sure I'll hit 120 today.

911GT2

Your 0-60 time looks waaaay off. Stock it should be 5.0 or so, is this just a G-Tech thing? Are they known to always be off? Especially if you're pulling high 13s 1/4 mile times, the 0-60 should be much lower.

60' times look pretty decent for a stock car though. And the 1/4 mile time and MPH look good too, the 0-60 is just bugging me...

Kento

Any "numbers" that you cull from gadgets like the G-Tech are useful only in a relative sense at best. Using an inertial accelerometer to accurately measure any type of specific time/distance equation such as a quarter-mile (or even 0-60 mph times) is like selecting your next date by going into some divey bar blindfolded.

T88NosRx7

iTrader: (1)

yeah, I agree with Kento, its just a guess. BTW your hp readings seem a little off to.

Kento

Oh man...horsepower and torque? From an inertial accelerometer?

talljosh85

iTrader: (3)

I'm just posting what the g-tech told me. And remember, force=mass(x)acceleration, so by programing in weight (which it uses to calculate mass), it should be able to use acceleration and time, and from there, using the definite integral, calculate velocity(in this case just speed). I agree the 0-60mph times seemed a bit slow, as does horsepower and torque to run those times. And also recall, horsepower is a function of torque and rpm, and since you calibrate the g-tech using engine rpm and plugging it into the cigarette lighter, a horsepower calculation is not all that impossible. I'm not a physicist, I only took two years in high school, and I'm not saying its perfectly accurate or precise, I'm just explaining what happened. Its more for entertainment and fun, it is not a replacement for a true race track or a dyno when it comes to tuning and practicing. Josh

talljosh85

iTrader: (3)

Sorry that kinda ran on in my reasoning and my language was a little weird. Thats probably why I didn't do so great on physics tests. Accurate or a little less then that, its still fun to play with, and I would suggest getting one to play around with; now I have to try the lateral-g meter, see if it will read somewhat accurately, or way off (does 1.5g seem a little high?) Josh

Kento

Sorry Josh, didn't mean anything personal by flaming the G-Tech. I understand you're just posting numbers, and I'm sure they're fun to play with, but a minor problem arises in that some people see these numbers on the forum and take them for gospel, thinking that the G-Tech will give them accurate readings on quarter-mile, hp, etc. The magic word when using a gadget like this is GUESSTIMATE. Yes, force = mass x acceleration, but there are a ton of variables in that equation not easily accounted for.

Again, nothing personal. Perhaps if you change some mods, then compare and post numbers in a relative/comparative sense, they will have more realistic value.

ebb

I have used the g tech original model at the track. Staged up and started the g tech at the same time, after 3 runs it was never off more than .1 sec from what the track was telling me. It was not mine, just borrowed it and wanted to see how accurate it was. Pain in the *** getting that thing started when you are thinking about everything else and getting ready to launch.

that is not as accurate as the mfg claim, but is good enough for a check on performance.

donny

I used the old g-tech model at the track last year to compare it to the times the track was giving me and it was consistently only .001 seconds different in the eta. and 5mph faster on the trap speed. I was surprised, they are extremely accurate. I dont know about the HP numbers or g-force numbers, but the ETA's are right on, just deduct 5mph from your trap speed on the g-tech..

Kento

I watched as a friend tried out a G-Tech, on a his modded Camaro on both the dragstrip and on an asphalt strip with timing lights similar to street conditions (not a prepped concrete launch pad like the strip). His results varied wildly, especially on the asphalt. True, at the strip, we were surprised that it was able to get within 0.10 to 0.30 sec and 2-4 mph of the dragstrip's clocks, but when we tried it on less than perfect pavement, the results averaged from 0.10 to 0.5 sec (!) and 3-5 mph.

To each his own, but I'd rather spend $250 getting timing slips with accuracy that no one can dispute.

donny

If you had the same timing light set-up on the street as on the track, your times would still read very close. you cant compare times you got from the track to times you are getting on the street. you will almost always get a better launch on the track because there is so much traction compound sprayed onto the concrete.

Kento

The lights were basically the same as a purpose-built dragstrip. It was just on regular asphalt without the concrete launch pad, like I said. This was two different days, obviously, but the results we saw were right there for all to see.

turbojeff

iTrader: (30)

The old G-tech was pretty decent at giving ETs, mph was off though. Best I ran with the G-tech was a 13.4, at the strip the same car ran a 13.58. On a TII it showed a best of 13.4 and the car actually ran a 13.4 at the strip. I'd say that the OLD model was decent. I imagine the new G-Tech is better.

supracosworth

I ran the old GTech simultaneously with my Apex RSM on the Supra and the GTech reads 0.2 to 0.5 faster than the RSM. Since the RSM reads off the rpm signal feeding to the ECU, I'd trust the Apex more than the GTech. Have yet to try it out on the Rx7. Incidentally, what sort of times was your father getting for the Supra and with what mods?

SpeedracerRX7

Just to clear something up the reason the G-Tech was 5 mph faster in the traps is because at the track it uses the average speed of the last 100 ft (I think) as a measurement of trap speed where as the G-Tech is supposed to be instantanious. I know I have one and it is rarely off more than .01. It is the G-Tech Pro and it is neat but the all the stuff it does. It gives you shift points of what you should shift at in each gear based on acceleration information. It reads your RPM similarly to the way inspection stations do (Don't know how it will work on a rotary). It is pretty neat looking.

racerfoo

A kid I know has a stock Golf VR6 gti or somethin like that....and after turning a 13.9 on his g-tech he bragged to everyone how fast he was. We all laughed when he got totally destroyed by mid 14 second cars

Houdini

iTrader: (3)

I had the original G-tech and now the competition and I'm happy with both. Luckily, I know something about the physics of this device since I studied engineering. The original used a single axis accelerometer and the new competiton uses a more precise temperature corrected 3-axis. It's just a matter of physics. Accelerometer get syou the accelaration. Integrate acceration with time and you get velocity. Integrate the velocity and you get distance. Also since force = mass X acceleration, then if you know the mass and acceleration, you get the force produced at the wheels. The G-tech doesn't actually integrate though, it takes the acceleration it gets for a given time and multiplies it by the length of time it took to measure it(sampling rate). There's only 2 real reasons the unit would be off. #1, if it was calibrated improperly by the user(you have to carefully calibrate the unit). #2, if the weight of the car was off. When you enter the weight, you have to be careful to include things you've added(stereo equipment, wheels, gas) and things you've removed(spare, stock seats...) and make sure to include the driver's weight.

As far as your times go, 5.7 to 60 is pretty bad. Also, your 60' distance was long also. Try launching with the RPMs higher but spin the tires, not the clutch. That'll keep the car in higher RPMs so you get more power. That brought me from 5.0 secs to 4.7s on only a straight pipe catback system. You should also be hitting low 13s if you launch right and shift quickly. If you want a real low 0-60, don't lift on the shift between 1st and 2nd, that'll shave another 3 or 4 tenths. It keeps boost up and the turbos at full spool. I got the 0-60 down to 4.37sec doin that. After a while, the clutch won't grab any more. With the PFC and boos at about 12.5PSI on the stock IC, I could get high 12s on the 1/4 mile. Lets see what I get when I get my Stage 2s and my new clutch/FW.

Looks like they finally have the PC software released so I can start download my results. Pretty cool, well designed little toy. I especially like ignition pulse sensing feature that lets you read your RPMs off the cigarette lighter you plug it into. They've come a long ways since the first version.

supracosworth

That's all fine Houdini but can you explain why the GTech needs to be so painstakingly set up to horizontal before launch? If that's to make sure that the accelerometer is measuring accleration parallel to the road, then surely, the heads up posture of the car at launch MUST upset the assumption that the accelerometer is horizontal throughout the trip. For this reason, I'll trust the Apexi RSM more than the GTech.

poss

iTrader: (5)

deleted