I've only got the PRO model, but here's my experience with it. Before the headers I could run 20 times and 18 times run withing .03. My car ran 13.46-13.49 very conistent with a 4.8x 0-60. Mph was around 108-109. After the headers I ran consistently 13.26-13.29 at 110-111 with a 4.7x 0-60. I gained exactly .2 from the slp shorties. I then sold my 315's and welds, and switched to 275's on 15" telstars and skinnies up front and pulled out the rear seats. I then ran a 13.09-13.16 at 111-112 with 4.65-4.7 0-60's(not as consistent since it's harder to hook on the 275's). I always make sure to run when it's between 65-75 degrees out, and I never heat up the tires. I do also run both ways on a level road.

Right now I've got a bad exhaust leak and am running really rich. When I went to the track, I didn't use the gtech at the track since it was my first time at the track. I spun badly compared to how I hook on the streets, and ran a 13.68 at 101 mph. When I went home that night I ran on the g-tech (just hours after running at the track), and ran 13.30, 13.30, 13.32, and 13.32 all at around 109mph. Also I got in a street race with a supra that I've raced several times before and always beat him by 2 1/2 - 3 cars, but only beat him by 1 1/2 cars, so I now my car isn't running what it should. It's now too cold out to accurately compare to my old times, but I can do mods/remove mods and compare my times.

I believe its very good and a cheap way to compare mods and see how much they improve your et without going to the track.

 

I don't have any experience with the new unit but the older model was quite accurate. Usually found to read 1-2 tenths fast. and about 3 MPH fast. the MPH difference is because it calculates MPH at the end of the 1/4 and an actual track has lights 60 foot before the finish. Your speed is an average run between those lights. So the speed the track gives you is actually the speed you were running about 30 ft before the finish.

Carcraft tested the old unit at the track and found simular numbers.

It's a hell of a lot better than nothing. Even if it's off, at least you can see if your making progress.

By the way. Dropping the clutch at 7000RPM in a 300Z = destroyed IFS rear

 

My tazzo is pretty accurate..within a tenth at track and 2.5 mph high but it can be calibrated to be dead on.Remember track mph is low its an average of last 60ft like g tech manual says. MY 60 was right on the track.
So not sure I had the cheap gtech and thought is was pretty accurate for et and high for mph about 5 I thought.Once we ran g tech and tazzo in same car.The gtech basic was within tenth of the tazzo and was at least several mph higher.
I would think its possibe for your car to run in the 13's with
decent 60fts and 2.20 aren 't bad at lower altitude with good density air.MY 97 ta ws6 with mild bolts ons could hit the 14.0 and dip into the 13s even at my 1900 ft but that was an m6 with 3.42 gears although later tried 4.10 without much improvement on street tires.
Anyway I guess take it to track to really see whats up.But remember there are always lots of variables in racing.temp,humdity,bar,altitude,traction conditions ,etc.
Up here its rare for stock lt1s or lightly modded ones to break into the 13s on street tires.

 

Popular misonception, actually spread by the manufacturers of the g-Tech. The difference in MPH can NOT be attributed to the "average over the last 60-feet" vs. "the actual mph at the finish line". It can be easilly demonstrated that for a vehicle running about 100mph, and pulling 0.20G's at the end of the track ( a very generous assumption.... it is typically quite a bit less), there is LESS THAN 1mph DIFFERENCE between the average speed over the last 60-feet and the actual speed at 1,320-feet.

The error appears to result from the method the g-Tech uses to arrive at MPH and distance travelled. The g-Tech only measures two things.... time from start, and G's (accelleration) at that point in time. It then integrates time and G's to derive speed, and then integrates time and speed to get distance travelled. The accuracy of this method is obviously very sensitive to the sampling frequency, and the accuracy of the timer and G-sensor. The low sampling rate and itterative nature of the calculations appears to cause the error.

Since this error is very well documented, I don't consider "3mph fast" to qualify as "quite accurate". There is a similar unit made by Vericom, and it appears to be significantly more accurate, because of its higher sampling frequency. It's disappointing to see that when g-Tech upgraded the "capabilities" of the unit, they didn't bother to correct the optimistic MPH error.

JMHO.

 

From what I have read else where, the G-TECH Pro Comp is accurate to + 3% compared to a real track time. However, it does appear to have extremely good repeatability. So, it is an excellent tool for measuring changes made by mods. But, not so good for comparing track times.

 

For the cost of Vericom's unit (898$) I would expect it to be significantly better.

 

Well at any rate my tazzo was closer to track mph than the gtech basic.But my tazzo has capability to also be calibrated to nearest hundreth for et,mph and 60ft to more exactly match track ,just ddn't get around to it yet.Wanted to maybe make like a 5 runs and double check next year only got a couple runs at track with it.
So the new gtech comp doesn't have the capability to do this correction.?? Thought it would.
I am pretty pleased with my tazzo but wish it would give a bit more detail,it don't give anything besides 60ft in a run and it will do 1/8 and 1/4 but won't give all the detail that some other units do.I had a very expensive vericom like a few years ago and it did seem pretty close to track mph I think but it was just a bit too big and awkward so sold it off.I should have actually kept it though.
The new units coming out like mr dyno do seem to do more and more.My tazzo is at least consistent it seems.

 

Just for reference. With the same 60' time you got(2.21), I ran a 14.4 at 98mph at the track. That was at 86g degree weather and 80% humididy at sea level. I have a '97 M6 with a K&N FIPK, that's all. With a cutout, you might gain a few tenths. The mph on the g-tech is high, like others state because it's the speed at the actual 1/4 mile point, not the average of the last 60 ft. You are probably capable of sub 14's with your setup. I bet it's fairly close. I'm guessing you would run about a 13.9 at 99 at the track. It's good for comparisons in any case.

Dan

 

it would be nice if it could log the RPMs vs Gravity through the gears.

I saw in TV the interior of one of those 18 wheelers trucks that had been all fixed with computers and they showed one that had on screen the RPMs and gravity pull of a Top Fueler. that was awesome. They could log all wheather conditions and engine RPMs plus acceleration all at once.....

Now who needs a dyno test when every pull they make at the track is a dyno pull in itself!!

I am sure they have fuel compsuption somwhere in their computers too... I was like Dam I gotta get me one of those!!!



Marvin

 

One remark about the G-Tech accelerometers.
The keyword here is ROLLOUT. The old (basic) G-tech and the Tazzo unit is calibrated with a 12 in. (30cm) rollout, which appears to be a baseline value at most NHRA tracks. It cannot be changed on the unit, so if you run at a track which has, let's say 8 in. rollout your times will be down compared to the Gtech or Tazzo. Rollout makes slight difference in trap speeds, but makes a huge impact on ETs. For instance, I run 13.786 w/ zero rollout and 13.3xx with 12" of rollout!
Now, the new G-Tech unit (Pro Comp) can be set up from zero to 16" rollout. You should really consider this.
I think the new G-Tech ProComp is really a very good unit, as far as it is calibrated properly! The first (2002) Pro Comps had to be calibrated at the very first start up, and of course it requires major care and attention! The 2003 Gtech ProComps are calibrated from the factory, so they are dead accurate, if you attach it to the windshield FIRMLY!
Oh, and the old units (Tazzo, etc) had only 2 gyroscopes (not 3, like the new ones), so basically if they weren't positioned (leveled) correctly, they were useless.
Sorry for the long post I thought I might share some info

 

Well as stated my tazzo was within a tenth at the track so must be ok for rollout.Its supposed to be self levelling don't need to adjust like the old g techs.It also is correctable to nearest 100th for et,mph and 60ft but the only thing out was mph 2.5 high and et was one tenth quicker or slower forget now than track.I would have thought the g tech prol would let you calibrate to match track times also..? But if the newest ones are dead on then thats ok so are you saying the new pros read same as tracks for mph too..???

 

hungry T/A i too was thinking about this...............so i reset everything then calibrated it all again and set my ROLLOUT distance to 2 inches................once i did this i ran a 13.8 @ 103

I MAD SURE I DID EVERYTHING CORRECT.

when i made the earlier posted runs i had a rollout distance of 12 inches...................and it was cool outside...........and i had a little below a quarter of a tank of gas.

when i pulled the 13.8 i had a FULL tank of gas..............it was hotter outside than before...........and the roll out distance was only 2 inches.

KEEP IN MIND I LIVE MISSISSPPI..............HUMIDITY!!!!!!!!!!!!!

I pulled 4 runs with the ROLLOUT distance set at 2 inches and everytime i pulled a 13.7 or a 13.8................(3 runs were low 13.8xx......and the other one was a 13.7xx)

If you said most NHRA tracks have a basline rollout distance of 12-8 inches then wouldnt i be running quicker than a 13.8 at the track??? (I know i calibrated it properly........and by what Hungry T/A said is they are right if they are done correctly)


so now all that said what do you guys think??????

Scott