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      09-16-2007, 03:11 PM   #20
hotrod182's Avatar

Drives: 07 335i, 06 M3
Join Date: Dec 2006
Location: California

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Originally Posted by Driver72 View Post
BTW guys, I volunteered to drive to his place.
This meeting was more for us to compare the GTech PRO to the Vbox for accuracy reasons. The VBox by Racelogic is a consumer version of the same technology that is used by most of the car mags. Yes, magazines like Car and Driver use a Racelogic GPS based unit similiar to this VBox to record their times.

This wasn't intended to be a JB2 vs PROcede v1.47 comparo.
It just became that when we realized we got basically dead nuts same time on both cars....mine was at the slight disadvantage of running later when it was a bit hotter outside, and having a really hot engine, getting that time after doing 3-4 straight runs, "cooling" off for about 5 minutes, then doing 4 back to back runs and recording the 12.9 @ 110.5 on that last run.
Even before this meet, I said to Hotrod, "I don't think I'll get the best of times with my car, and I also knew his car was an exceptionally strong runner, so it didn't surprise me that even though the JB2 has dynoed 20 hp and 25 tq less in ONE test, that our two cars ran neck in neck.
His car stock ran like it had an extra 20 hp from the factory, basically keeping up (with 1/2 CL in the 1/4 miles) with Turbo Tuned cars.

I also know Hotrod's intent with this post was not to compare the two cars either, but rather, validate that his GTech PRO RR is quite accurate in his car.
Surprisingly so.
What we can't figure out is, why when we put it in my car it consistently read .05-.1 and 1+ mph slower than the VBox???
In his car it was within .05 and .3 mph each and every time.

No need to flame him for being excited that his GTech PRO RR is (at least in his car) extremely accurate.
His car is also extremely consistent in it's runs.
He also noted that he doesn't have the second oil cooler, yet his car runs just as cool, if not cooler than 335i's with the 2nd oil cooler. He never got up to 270-280 degree temps in his sedan like other early build sedans (without the second oil cooler) WILL quite quickly with repeated hard 1/4 mile runs. We don't know why either his particular car runs so cool, but again, his car is definitely blessed.
I did some more testing on my GTech Pro RR this morning also, because I was curious what happened to make the readings 1mph slow on your car. I think it had to do with the fact that it fell off of your windshield. The reason why is I made three runs this morning. As usual, they were all within hundreths of a second of each other. But in the 1st run, my MPH was almost exactly 1mph slower. Furthermore, before that 1st run, the unit was measuring .60g up, and I could not get it to zero out. I don't know if you remember if the unit would not get within .01-.02g of level when you made your runs. So interestingly enough, during my 2nd and 3rd runs, the unit was no longer acting up, and was within .01g of level. And of course my MPH was back to normal again. Interesting. After using it in you car, seems it took a run in my car to get it back to normal! LOL. Actually, I really think it had to do with the unit falling off of your windshield. That subjected it to some "unusual" G forces. But I think since this morning it has recalibrated and all is fine. The Gtech ETs of all of our runs seemed to be accurate nonetheless. The great thing about the GTECH, you WILL be able to see and graph even the slightest changes in horsepower, launch techniques, etc. Nonetheless, it was great to have you bring your Vbox down to substantiate our times. If I could have just acheived .10mph faster than my 110.9 on the Vbox, then I would have had a 111mph run just like Shivs personal car. Thanks again.

FYI...I was very curious what makes the GTech tick. So I took it apart and examined it. As you can see it is not just some cheap toy, rather a well engineered piece of equipment with some sophisticated electronic processors on board. Now take apart the Vbox for us...JK.
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