: G-tech 1/4 run



bryce3
07-24-04, 10:11 PM
I followed all the tips from the forum group on the these units and their installation and all the onsreen set up instructions including the RPM recalibration mode. I got both the cars tach and the G-tech tach to be within a couple of hundred R's apart. Then I took the V out for a 1/4 mile run and the results were pretty good but i feel not right on, a 13.034 @ 112.73 crazy I know.
-Sean

StealthV
07-24-04, 10:24 PM
Great run. Does your driver's license say "John Heinricy"?

What HP does the G-Tech come up with? According to my calculations, to turn a 13.0, a V needs 415 HP at the flywheel.

wildwhl
07-24-04, 10:29 PM
What weight did you load into the G-tech? Pro or Competition model (sorry if this was already answered)? I have had one run prior to the new differential that was like a 13.02/113 mph but I throw it out because it was much higher than my other "passes" that day. I might have to get off the couch and go makes some passes :)

StealthV
07-24-04, 10:50 PM
My mathematical calcs are done with a weight of 4150 lbs. The 415 flywheel horsepower equates to 340 rear wheel (18% driveline loss).

bryce3
07-25-04, 01:28 AM
The weight that I entered was 3890 lbs. and the unit is a G-TECH /Pro Competition. I tried to upload an image of the tech sheet but it didn't appear on my earlier post. The run that I made felt good, I mean I didn't miss any gears and the I was on a pretty flat road but like I said earlier how accurate are these units?
-Sean

StealthV
07-25-04, 01:45 AM
The curb weight I've been using is 3949 (from Car and Driver) + 201 pounds for a driver and a little extra fuel ~ 4150.

The G-techs are within a few tenths on 1/4 mile times. Even if they don't match exactly, they are repeatable so you can verify the gains from any mods you perform.

Z06CADY
07-25-04, 01:50 AM
Not much fuel..

wildwhl
07-25-04, 01:53 AM
Not much fuel..

Agreed, I've been using 4150 previously but just tonight reentered at 4132 as I weighed the vehicle at the salvage yard next to my shop with a full tank and my ass in it this week. I haven't made any runs but intend to try some horsepower run calculations in the morning since they are not really abusive (gentle launch, 2nd gear, then WOT through 2nd, shift into 3rd and you're done). I'll leave the 1/4 mile and 0-60 stuff alone until I'm sure the new rearend is going to hold :)

bryce3
07-25-04, 01:56 AM
Originally I was going to use a weight of about 4100 lbs to account for me and any fuel in the tank. I try to make any passes on a 1/4 tank or a little less to not add so much in weight. So I guess I need to recalibrate the vehicle weight and give it a go again. I don't have any mods as of yet but I did order a set Taylor 10mm spark plug wires and a BMR wheel hop kit. I am still waiting for someone put out a good set of headers and maybe supercharger if I can get it done localy (S.F. Bay Area).
-Sean

wildwhl
07-25-04, 02:01 AM
I could be wrong, but I read the manual on the competition model again tonight and I don't think the vehicle weight entered will change the recorded 0-60 or 1/4 mile calculations as this is simply activated by the accelerometers. The weight is critical for the hp/torque calcs, but, and again correct me if I'm wrong, I don't think it matters for accelerationmeasurements?

StealthV
07-25-04, 02:02 AM
To give you a ballpark - from my calculations a stock V with 400 hp at the flywheel and 18% driveline loss will put 328 horsepower to the wheels. With a perfect launch @ 2000 rpm, a 4150 pound V will run the quarter at 13.23 seconds with a trap speed of 108 mph.

Since your weight was a little light, there's probably around two tenths difference which looks to be right on the money to me.

StealthV
07-25-04, 02:04 AM
Wild, I think the G-tech needs an accurate weight since Newton's laws of motion have mass in the equations. The G-tech has accelerometers to measure acceleration, but can't directly measure the mass.

wildwhl
07-25-04, 02:06 AM
One more Gtech note. I looked through my saved runs and had some HP tests in there with the 4150 weight. The numbers were 332, 337, and 339. The manual states that the unit records NET hp, which will be lower than RWHP as recorded on a chassis dyno. So, again, this seems to confirm the power is there...but that's that other discussion, right? :)

wildwhl
07-25-04, 02:08 AM
Wild, I think the G-tech needs an accurate weight since Newton's laws of motion have mass in the equations. The G-tech has accelerometers to measure acceleration, but can't directly measure the mass.

Fair enough, I'm certainly no expert on the matter and I believe you, but I thought Newton had something to do with defining when an apple was ripe? OK, lame reference.

I've been using 4150 lbs up until now, including my one 4.7 something run IIRC, so no worries.

bryce3
07-25-04, 02:12 AM
I just checked my G-tech for the HP rating for my run and it registered 406.9hp.
-Sean

wildwhl
07-25-04, 02:21 AM
I just checked my G-tech for the HP rating for my run and it registered 406.9hp.
-Sean

Sean -

If you read the manual it will indicate that the method for measuring HP is different than 1/4 acceleration runs. Basically, they suggest using 2nd gear, but you start in the drag strip mode, perform a mild launch, accelerate to say 3,000 rpm mildly, shift to second, then floor it to redline or about, shift to third and you're done. It does stress that RPM readings and entered weight need to be accurate. It also indicates that it will record net figures, therefore, your torque will be somewhat higher due to the fact that you're multiplying it I guess. I believe the reason for the 2nd gear suggestion in the manual is to reduce the effects of aerodynamic drag, but it may also be so that we remain in a speed range closer to the legal speed limit(s). The HP measurement can be performed in any gear, but in my experience, 2nd and 3rd gears work pretty darn well.

For the last week or so the Gtech was at a friends house while he played with his newest creation which uses an Edelbrock crate motor. He used the HP measurement quite a bit, and guess what? It is REAL CLOSE to what Edelbrock advertises their motor to produce (420 hp if I recall correctly) if you use, I think he said, 18% driveline loss (Ford 9", Muncie M21?or22?, 65 Chevelle, sort of a restorod/drag car).

I have to believe that these units are reasonably accurate, sometimes optimistic, but have certainly been consistent with our experiences.

6104696
07-25-04, 01:01 PM
4150 sound like a pretty good ballpark weight; I think that the dry weight is 3850? So c&d's curb weight of 3949 makes sense if you figure about 6-7 (?) lbs per gallon of gas, then 4150 makes sense with a 200 pound driver (give or take), unless you left your barbells in the trunk.....


Doug

2004ctsv
07-25-04, 02:45 PM
I just checked my G-tech for the HP rating for my run and it registered 406.9hp.
-Sean

OH SH*T
If the hp is over 400, will GM sue us???????
Wrong thread?

Shinkaze
07-25-04, 05:17 PM
OH SH*T
If the hp is over 400, will GM sue us???????
Wrong thread?No no no the board has no problem if results show more power than advertised, it's when you bring up the fact that a 320 RWHP isn't a 400 crank hp car that folks freak out!

BTW, G-Tech times are estimates based on an accelerometer. Much less precise than actual timing lights, typically the ET is close to actual and the MPH is way over-estimated. That said ET is more a function of traction and gearing than actual power. Increased HP tends to show more in the MPH rating. FWIW I know of more than a few sub-300hp Mustangs that are deep in the 12s on slicks and gears. A buddy of mine with no weight reduction has his non-Cobra SOHC 4.6 Liter Mustang GT pulling 12.70s. According to an ET calculator his car would have to make more power than a DOHC Supercharged 4.6 Liter Cobra!

BTW in no way am I saying a G-Tech is junk, it's actually a very effective inexpensive way to do basic tuning and before/after results, but as far as repeatability it's only helpful to compare any given G-Tech's results to it's own.

-Adam

Shinkaze
07-25-04, 05:20 PM
I followed all the tips from the forum group on the these units and their installation and all the onsreen set up instructions including the RPM recalibration mode. I got both the cars tach and the G-tech tach to be within a couple of hundred R's apart. Then I took the V out for a 1/4 mile run and the results were pretty good but i feel not right on, a 13.034 @ 112.73 crazy I know.
-SeanBTW, regarding your times..
:D :D :D :D :D :D :D Kick-ass!

StealthV
07-25-04, 05:22 PM
No no no the board has no problem if results show more power than advertised, it's when you bring up the fact that a 320 RWHP isn't a 400 crank hp car that folks freak out!

You are right, 328 RWHP is 400 FWHP in a V. :yawn:

Shinkaze
07-25-04, 09:39 PM
You are right, 328 RWHP is 400 FWHP in a V. :yawn:
:helpless: The emperor has no clothes.

bryce3
07-26-04, 06:11 AM
I tried another go at it late last night with the new weight factored in (4190 is with my fat ass) and I ran faster. Same stretch of road same temp outside. According to the G-tech I tunred a 12.78 @ 117 mph with a 4.9 zero to sixty time. Now I didn't do a RPM recalibration but the R's looked good. Should I recalibrate the RPM's before each run? :hmm:
I also did a HP run before the 1/4 run and produced 328 hp's. :bonkers:
-Sean

Shinkaze
07-26-04, 08:56 AM
I tried another go at it late last night with the new weight factored in (4190 is with my fat ass) and I ran faster. Same stretch of road same temp outside. According to the G-tech I tunred a 12.78 @ 117 mph with a 4.9 zero to sixty time. Now I didn't do a RPM recalibration but the R's looked good. Should I recalibrate the RPM's before each run? :hmm:
I also did a HP run before the 1/4 run and produced 328 hp's. :bonkers:
-Sean
Yea, I doubt that a 12.78@117mph V is only making 328 hp :D
This is why I feel a G-Tech is only good for tuning inisde of itself. That said I'm curious to see waht your actual Qtr Mile times are since the G-Tech tends to only be a couple tenths off.

wildwhl
07-26-04, 02:22 PM
Yea, I doubt that a 12.78@117mph V is only making 328 hp :D
This is why I feel a G-Tech is only good for tuning inisde of itself. That said I'm curious to see waht your actual Qtr Mile times are since the G-Tech tends to only be a couple tenths off.

Well, for what it is worth, with my old unit (the Gtech Pro) in my friends '66 Mustang drag car, the Gtech was "generally" 1 to 2 tenths more optimistic then his slips were. He kept it in the car for a whole season and used it to tune on a secret stretch of highway near his house (not a street legal vehicle). While the car was only a low 12 second car he found it invaluable and I had to wrestle it away from him. I experienced runs at the track where the Gtech and time slip were darn close...so I think they do pretty good, but not perfect, IMHO.

bryce3
07-26-04, 03:34 PM
Like I said earlier, does anyone feel that a RPM recalibration before each new test is needed????
Sean