G-Tech accuracy: 2 data points

[treynor]

While at the dragstrip on Wednesday, I hooked up my G-tech to get a measure of its accuracy. I remembered to turn it on for two of my three runs, with the following results:

Run 1:
Dragstrip reported 12.42 @ 116.8
G-tech reported 12.71 @ 117.9

Run 2:
Dragstrip reported 12.32 @ 116.9
G-tech reported 12.51 @ 119.1

Obviously two data points do not a complete picture make, but I tentatively conclude that the G-tech is a pretty accurate gauge for 1/4 mile runs. I should note that the G-tech records slower times and higher MPH because it starts timing at the initial movement of the car and records MPH at the very end of the run, while the dragstrip starts timing after the car has moved 2-3 feet (through the staging lights) and measures average MPH over the last 60 (?) feet of the strip.

 

[Venom Lover]

Ben,

I don't have the exact numbers with me here at the office, but I did 3 runs at Pomona last summer with the G-Tech and got similar results, though my ET numbers were closer.

ET as measured on the G-Tech was 0.1-0.2 sec slower than reported by the drag strip, and G-Tech mph was ~3 higher than reported by the drag strip, for the reasons you noted.

Bottom line is, if you do a 1/4 mile run on the street with the G-Tech, subtract 0.1 sec from the ET and subtract 2 mph to get a conservative estimate of how you would've done at a drag strip.

I wonder if different drag strips have different geometries (e.g., different distance car moves before timing starts), or if there is some NHRA or other standard. Anyway, such differences could account for differences in "accuracy" reported by different people at different drag strips. I'll post my exact results over the weekend.

 

[9 seconds]

G-tech = Time starts on first movement and MPH is speed at exactly 1/4 mile.

Track time = Time starts when line crossed (car already moving slightly) and MPH is an average over a distance.


This would acount for the higher times and MPH with the G-tech. If you use Mikes factors you will be very close each time.

 

[SoCal Rebell]

Ben, what dragstrip were you at? Elevation? Nice times!!!

 

[Bill 96 GTS]

Another factor in drag race terminology is called "rollout". You can stage (stop in the stage beam) for a run as soon as the second light comes on or you can creep forward till the "pre-stage'(first stage light) goes out. It will have an effect on reaction time and ET. There is a lot more to consistent drag racing than "stab it and steer"

 

[Bill/APEX Motorsports]

Sears Point's drag strip is actually _uphill_, if you can believe it. There's also usually a headwind, which doesn't help any.
One of the scary things about Sears' road course is that it crosses over the drag strip. You can imagine going 100mph in a sweeping left hand turn and hitting all the drag racers' rubber! It's pretty scary, especially in the rain. That's one of the things that's going to be changed when the track gets redone.

 

[Bill/APEX Motorsports]

Sears Point's drag strip is actually _uphill_, if you can believe it. There's also usually a headwind, which doesn't help any.
One of the scary things about Sears' road course is that it crosses over the drag strip. You can imagine going 100mph in a sweeping left hand turn and hitting all the drag racers' rubber! It's pretty scary, especially in the rain. That's one of the things that's going to be changed when the track gets redone.

 

[Venom Lover]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Bill/APEX Motorsports:

One of the scary things about Sears' road course is that it crosses over the drag strip. You can imagine going 100mph in a sweeping left hand turn and hitting all the drag racers' rubber!
<HR></BLOCKQUOTE>

Or hitting a drag racer! I guess if you're going 100 mph and they're going 100 mph orthogonal to you, the chance of collision is small. (Let me guess, they try to avoid this by not having road racing on the same day as drag racing???)

 

[treynor]

"Scary" doesn't begin to describe it. When wet, that dragstrip is worse than an oil slick. Seriously. For extra fun, try riding a motorcycle at Sears in the wet

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I'm interested to hear the 'strip is *UPHILL*. How much slower do cars run there compared with a flat dragstrip?

Ben "need a correction factor for my bragging rights" Treynor