How accurate is the G-Tech Pro?
Thread Starter
Racer
Joined: Aug 2003
Posts: 403
Likes: 1
From: Cotati Ca
How accurate is the G-Tech Pro?
I hesitate to ask this for fear the answer will negate my results. I purchased one a bit ago and just pulled it out of the box and installed it per the instructions. After a couple of HP runs and minimizing the wheel spin, the car's averaging 322 to the rear. With a 15% loss through the drivetrain (an estimate, I know) that equates to 370 at the crank! Can this be? Only mods are Airfoil, Elims, K&N, Power Programmer, cut lid, and TB bypass. Any thoughts? Should I be happy and not look a gift horse in the mouth?
Race Director
Joined: Sep 2004
Posts: 13,793
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From: St. Peters MO Sometimes you have to prove yourself by doing alot of killing or alot of dying...
They claim they are within 2% of accuracy. I agree that it sounds optimistic, but I think it is the airfoil that did it 
Just playin'.
Just playin'.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
A G-Tech is an accelerometer that mounts within the car to give acceleration, 0-60, and 1/4 mile data.
Are you sure that the G-Tech isn't reporting crank HP?? To check, look at your trap speed and use the launch weight of your Vette to calculate crank HP.
Are you sure that the G-Tech isn't reporting crank HP?? To check, look at your trap speed and use the launch weight of your Vette to calculate crank HP.
Race Director
Joined: Feb 2003
Posts: 18,484
Likes: 1
From: Everyday you must choose between the pain of discipline and the pain of regret. Fredericktown, OH
My LT-4 with comparable mods made 305 at the wheels. Just as a point of comparison. I'd say 370 at the crank is a bit optimistic.
What 1/4 mile time did it give you? I've gone 12.90s with mine.
What 1/4 mile time did it give you? I've gone 12.90s with mine.
Thread Starter
Racer
Joined: Aug 2003
Posts: 403
Likes: 1
From: Cotati Ca
Originally Posted by LT-4 CE
My LT-4 with comparable mods made 305 at the wheels. Just as a point of comparison. I'd say 370 at the crank is a bit optimistic.
What 1/4 mile time did it give you? I've gone 12.90s with mine.
What 1/4 mile time did it give you? I've gone 12.90s with mine.
what is a g tech pro
Melting Slicks
Joined: Dec 2001
Posts: 2,049
Likes: 0
From: Texas
Originally Posted by kwik_ta
They claim they are within 2% of accuracy. I agree that it sounds optimistic, but I think it is the airfoil that did it
Just playin'.
Just playin'.
No doubt about it, it's the airfoil. Just think if you would have slapped on some of those 50 hp catback systems!!!!!!
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Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Your launch weight will vary. For example, my launch weight with 1/4 tank of fuel, no spare nor jack and a 170lb driver is about 3,370lbs.
You can use time slip data or get 1/4 mile data from your G-tech. Trap speed on the G-tech will be 1-2mph higher than on time slips due to the way trap speed is measured by the track timers. So you can use G-tech data & launch weight estimate to calc chp.
You can use time slip data or get 1/4 mile data from your G-tech. Trap speed on the G-tech will be 1-2mph higher than on time slips due to the way trap speed is measured by the track timers. So you can use G-tech data & launch weight estimate to calc chp.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Gtech measures actual acceleration. So it's output is RWHP minus a little for aero drag (which is why you should do your HP runs in 1st or 2nd)
I have a hard enough time finding a level road to use it on... I think most of the accuracy is lost in not getting it level and the cars tilt when accelerating, which will boost your numbers.
I used it twice at the track, and it was off about a tenth and a half both times.
MPH was way high though. I've even gotten a 107 mph 1/4 mile run out of it with my stock L98, which is total b.s.
As for the trap speed vs 1/4 mile instantaneous speed, Gtech says thats why their mph reads 5 mph high, but its b.s., those values don't vary by more than 1 or 2 mph in reality, unless you're powered by thrust from a jet engine.
I have a hard enough time finding a level road to use it on... I think most of the accuracy is lost in not getting it level and the cars tilt when accelerating, which will boost your numbers.
I used it twice at the track, and it was off about a tenth and a half both times.
MPH was way high though. I've even gotten a 107 mph 1/4 mile run out of it with my stock L98, which is total b.s.
As for the trap speed vs 1/4 mile instantaneous speed, Gtech says thats why their mph reads 5 mph high, but its b.s., those values don't vary by more than 1 or 2 mph in reality, unless you're powered by thrust from a jet engine.
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
G-Tech should be used to compare performance when you do some modification.
I never used for HP calculation.
I found that it is very VERY accurate on the same road, and that you can obtain the same results (in the same road with the same weather contition..)
So if you bump the fuel prssure (just for test) and you perform a run (0-60) and you obtain a better time, you can be SURE that your mod is fine.
I don't care if the time of 5.39 sec is right, but I'm happy to see that with a mod i can lower this time to 5.20 sec and see that if I return to the original setting the time return to 5.40 range.
-Beppe-
I never used for HP calculation.
I found that it is very VERY accurate on the same road, and that you can obtain the same results (in the same road with the same weather contition..)
So if you bump the fuel prssure (just for test) and you perform a run (0-60) and you obtain a better time, you can be SURE that your mod is fine.
I don't care if the time of 5.39 sec is right, but I'm happy to see that with a mod i can lower this time to 5.20 sec and see that if I return to the original setting the time return to 5.40 range.
-Beppe-
Burning Brakes
Joined: Jul 2002
Posts: 871
Likes: 0
From: Costa Mesa CA
You need the G-Tech Competition Pro...
A good price for it is about $275.00. You can't get anything accurate for $49.95. The GTCP has 3 accelerometers and is accurate to 1% and repeatable within 5%. So says the instructions anyway.
I haven't hooked mine up yet pending some other mods. I will report when it's functional.
BIG JIM
A good price for it is about $275.00. You can't get anything accurate for $49.95. The GTCP has 3 accelerometers and is accurate to 1% and repeatable within 5%. So says the instructions anyway.
I haven't hooked mine up yet pending some other mods. I will report when it's functional.
BIG JIM
Thread Starter
Racer
Joined: Aug 2003
Posts: 403
Likes: 1
From: Cotati Ca
Originally Posted by chriswtx
My car weighs 3470 with me(150lb) and 1/2 tank of gas. What was your mph...My experience with the Gtec was it was pretty accurate in the 1/4mile time and mph...
. Don't know where else I can weigh the car.
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
I've got one (G Tech).....
I don't know about the HP test but the 0-60 and 1/4 mile and 60-0 runs are quite accurate. Had it for about two months and use it for testing new parts, ie. brakes--pads and rotors and new tune-up--plugs wires etc.
