Gtech vs Reality (track)....again VERIFIED....new data! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-27-2004, 10:50 AM   #1
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Default Gtech vs Reality (track)....again VERIFIED....new data!

As many of you know, I have a Gtech Pro Competition meter. I've had varying results in the past, simply comparing run to run. Allmachtige also has one, and has had slightly better results, I think.

I didn't have the opportunity to run it at the track for a direct comparison at WCBF (Woodburn Dragstrip), as I had my hands full with someone in the other lane each time. But based on the discrepancies I found between my OLD Gtech times and my new Woodburn times, I dug it out and hit the book again last night.

I have the latest firmware version that'* supposed to be calibrated before it leaves the factory. They sent a warning that you shouldn't go through the accellerometer cal on my version UNLESS you have a problem. Since my intent was to verify the accuracy of the meter by simulating the same conditions we had at Woodburn (100+, no humidiity, street trim with half a tank), I tried to make a run yesterday afternoon. The meter wouldn't stage.

Checking Gtech'* forum, I found my Accellerometer calibration was at fault. I'm now in the lab doing a hot and cold calibration on it.

The best 1/4 I ever recorded on it was 14.7. This is optomistic for a 93 SSEi modded like mine, but the question I have is how bad did the conditions at Woodburn hurt us, and how much can the Gtech tell me about it? The Gtech can also tell me whether I should simply hold 2nd gear to the traps, or let the car shift to third for me. Where is my power now? HP and Torque peaks? I need to know the most efficient way to drive the car with the modified curves from my hardware upgrades and PCM. The Gtech can tell me this.

I'll use the Gtech to:
Establish hp and tq peaks to determine my 3rd gear shift, if needed.
Determine the best tire pressure to launch with.
Determine the effects of tricked ELC, or leaving it alone.
Determine the effects of higher octane fuel on ignition timing and E/T.
Determine the effects of outside temperature on E/T.
Practice my launches for more consistent R/T.

So what does an E/T do as the temperature drops every 10F? How does humidity affect your E/T? Vehicle weight? How much is each 10 pounds 'worth' in E/T? I'd like to make some predictions, and see if the Gtech will back that up. Next time I go to the track, the Gtech will be on for the final comparison.
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Old 07-27-2004, 11:01 AM   #2
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Default Re: Gtech vs Reality (track)....again.

Quote:
Originally Posted by willwren
So what does an E/T do as the temperature drops every 10F? How does humidity affect your E/T? Vehicle weight? How much is each 10 pounds 'worth' in E/T? I'd like to make some predictions, and see if the Gtech will back that up. Next time I go to the track, the Gtech will be on for the final comparison.
Doesn't matter the temperature unless you are susceptible to KR in which case cooler temps may reduce KR. Humidity will cause the blower not to compress the air charge as much (more water vapor which doesnt compress well). I have found that the launch is what really changes ET'*. Every .1 you drop in the launch equates to about .2 drop in ET. There is also a rule of thumb that every 100 lb is a .1 off the ET and that every 10HP increase is good for a .1 reduction in ET.
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Old 07-27-2004, 11:08 AM   #3
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being a new guy to this type of tech talk . . . what is this GTec? is it an in car performance monitor?
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Old 07-27-2004, 11:14 AM   #4
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www.gtechpro.com

1/4 mile E/T and speed
Braking 60-0
horsepower
torque
PC compatible for graphing/analysis...
Cornering and accelleration G'*

Think of it as a poor-man'* dragstrip and dyno in a little box.

Here'* my setup:

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Old 07-27-2004, 11:32 AM   #5
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so, it gives you stats . . . but it does it allow you to adjust set points?
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Old 07-27-2004, 11:36 AM   #6
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Default Re: Gtech vs Reality (track)....again.

Quote:
Originally Posted by willwren
So what does an E/T do as the temperature drops every 10F? How does humidity affect your E/T? Vehicle weight? How much is each 10 pounds 'worth' in E/T? I'd like to make some predictions, and see if the Gtech will back that up. Next time I go to the track, the Gtech will be on for the final comparison.
you need to find out how temp and KR are related. Humidity is a bad thing (water doesnt burn well in a cylinder. Isnt 10*=2-3* of timing?
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Old 07-27-2004, 11:37 AM   #7
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What set points?

I can set my shift lights based on my power curves (that I get from it), and set my cornering G limits to warn me.....is that what you mean?
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Old 07-27-2004, 11:53 AM   #8
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No, i meant can you adjust the actual car settings. Like, shift points or rev limit. is GTec like the Auto tap?

I guess the only way to change what i am thinking is a new pcm burn, eh?
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Old 07-27-2004, 11:54 AM   #9
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Quote:
Originally Posted by Xac Xado
No, i meant can you adjust the actual car settings. Like, shift points or rev limit. is GTec like the Auto tap?

I guess the only way to change what i am thinking is a new pcm burn, eh?
The Gtech doesn't interface with the car at all except for 12V power and sensing the Tach signal.

The Gtech can TELL you what your shift points should be based on hp and tq curves, then you burn those values to a PCM. I'd rely on Dyno info for that, though.
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Old 07-27-2004, 12:30 PM   #10
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The autotap is also read only. You can not change car parameters without a chip or pcm flash. You CAN try to fool the computer by having external electronics change what the PCM thinks a sensor is sending it, an AFC for example, however I have found that the PCM will compensate for the changes quickly giving a net result of nothing.
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