Awesome, did you run a 9 second pass? Can you please post the link to the timeslip/video, I must have missed it.

 

Thanks....You did not miss anything that I posted... All the car info including the runs along with a video dedicated to Todd and Cynthia will be posted at the 996tt retirement party on January 6th...

 

The 60-130mph seems to be catching on at the Corvette forums...
http://forums.corvetteforum.com/show....php?t=1557634

 

Looks like some of them are trying to extrapolate 60-130 times from their 1/4 mile timeslips. Someone needs to tell them those times are not in any way accurate. That's akin to timing your 1/4 mile runs using a stopwatch.

 

Someone (I don't remember who) requested that I post my 50-150mph run at full boost...i finally found it and here it is:

Powershifted 3rd-4th

 

So does anyone bother to reply and post the graph and information about that 6.15s run?

 

The performance of these cars is really improving,
DMK's car (6.15) will be at Scottsdale Drags this weekend,
from EVOMS website, it has back seats removed and different bodyparts
(non stock), and is one of the best looking 996TT I have ever seen.
I do not know how the mods EVOMS did to the car have effected its weight.
What is weight of car ?
What is gearing in car?

I cannot wait to see these guys run this Saturday!!!!!!!!!!!!

MK

 

I imagine if you give KPG some time to come online and reply, he'll be happy too.

 

Thanks Scott. Looking forward to see the graph.

Hoping to hear from the owner what is the weight of the car, gearing and numbers of gears used.

 

Have you PM'd the owner, DMK?

 

No.. But I will wait to see the graph when KPG posts it.

 

Unfortunately this thread may turn ugly..lets try to keep it civil. In the spirit of full disclosure, Jean is a friend and has shared much data privately. I respect his opinion greatly. He has forgotten more than I will know. The problem we have is we are speaking 2 different languages... he AX22.... I Dbox. They both arrive at their numbers in decidedly different manners. I am NOT an expert in any of this. Period.Common sense will go a long way in this thread. I do have some software that most Dbox users do not have that makes it easier to look at data. First a quick lesson in these units and how they calculate numbers. AX22 is a 5mhz( 5 times per sec) satellite gps that uses accelerometres to calculate speed and distance. It is susceptible to leveling errors ie: VRalex's previous runs. Dbox is a 10mhz satellite unit (10 times per sec) that measures speed and distance with no accelerometer help, but has its own bugs. Todd sent some data from DMK and Renntech's vehicles a week or so ago. DMK's vehicle posted roughly the same numbers as those posted ,but had some very strange issues with times and long G's. He had a 3.9 sec run with wildly oscillating long G's. Clearly this car cannot do 3.9 sec. Some other data sent on his others vehicles was showing the same issues, some numbers in the ballpark, and then one in left field. His 997 TT did 8.25 and then 6.xx, again the 6.xx was not correct. I shared this data with Jean, and he has some proprietary calculations that break these runs down to the .01 sec and calculated a theoretical speed based on G's to the datalogger(DBox/AX22). I do not have the calculations, but Jean shared the results. Basically, it shows a deviation from the dbox speed to his calculated speed. So in a perfect world, the ax22/dbox speeds would be the same at every .01 sec line with actual and calculated speed. Jean stated there is room for error. So the 130mph terminal speed of the datalogger should be 130mph calculated speed. None of Todd's data was close according to Jean.My 7.93 run was sent to Jean as well and the terminal speed was dead on, but there were issues in the middle run, more on that later. I sent off some emails to Racelogic/VBox and here is their response:

Kevin,


let me answer your questions individually:

DriftBox's speed is measured, not calculated, using doppler shift of the carrier frequency from as many GPS satellites as it can see. It is using the concept of triangulation, but with an average six to ten GPS satellites as reference points, measures a very accurate speed, within 0.1 km/h of actual vehicle speed. The accelerometers have literally no effect on the speed, straight-line performance, and lap timing results from the DriftBox. This is the same speed measurement method used in all of our professional level VBOX devices, and has been proven time and again against radar guns, optical and microwave sensors, and fifth-wheel instruments. One caveat to this is an old firmware bug in DriftBox which I'll explain later on.


The requirement is that the antenna can see at least four GPS satellites for accurate speed measurement in three axes. If the GPS signal is lost or interfered with (by driving under a bridge or between close, tall buildings for example), then this can cause temporary jumps in speed and position information, and can sometimes affect distance-based tests like 1/4 mile runs.

The accelerometers are not even used in G-force or drift information. G-forces are calculated from GPS, which inherently makes them corrected for body pitch and roll, and provides more repeatable results than accelerometers. The calculated lateral acceleration is used in calculating the drift "score" in Drift Mode, just to avoid someone driving at 70MPH from rotating the DriftBox in their hand and having that create a high score. The accelerometers are only present in the DriftBox to align the yaw rate sensor, which is used in calculating vehicle slip angle.


The only way I can foresee someone manipulating results with the DriftBox would be to move the antenna (if using an external) or the DriftBox itself. All of the unit's measurements and calculations are based on GPS, so if the antenna were to be moved faster than the vehicle somehow, that is what the DriftBox would report. The only parameter that would be affected by changing the way the unit is mounted (assuming here that it has a clear view of the sky and a good number of satellites) is slip angle, since the yaw information is based the unit being flat. Even with changing the mounting, the unit would only report less slip angle being off-axis, so there is no benefit to someone trying to skew data.

As long as the DriftBox can see the sky, the mounting (or any angle at which it is mounted) has no effect at all on the performance numbers.

I have a theory about what is happening here. The first few versions of DriftBox firmware had a bug where if the unit saw more than ten GPS satellites, this would overflow the bandwidth between the GPS engine and firmware, and cause samples to be dropped from calculations. This would manifest itself by a tenth of a second less time per run or lap for every sample dropped. If this has happened, there will be dropouts in the data file, which can be repaired using the latest version of DriftBoxTools (or VBoxTools). The new "repair" feature is designed to address these dropouts, as well as those you might see from driving under bridges and the like. To check if a user's file has dropouts, load the file and click the "Summary" button in DriftBoxTools and it will list the dropouts in the file, and where they occur. To fix the problem for the future, make sure that people are keeping their DriftBox firmware up to date. The bug was fixed in firmware 1.01 build 22, and the current version is 2.0 build 17. Firmware 2.0 also adds several new features, including a horsepower estimator.
It would make sense if you never saw issues with yours if you keep your own DriftBox up to date better than others, or just have a newer unit that came with the newer firmware from us.


If there is a track or dragstrip where a DriftBox cannot reliably see satellites, then data gathered there is also unreliable. Using an external antenna can help the DriftBox lock onto satellites, having a bigger view of the sky than the internal antenna inside a vehicle, but I have successfully used DriftBoxes without external antennas in a great many cars with reliable and accurate results.


I hope this answers your questions, and feel free to ask more if it doesn't. Also, if you have specific data files that look suspicious to you, please send them to me and I'll have a look and see what we're dealing with.


Thanks,


-jim

Jim Lau| Customer Support Manager
________________________________________



VBOX USA
1368 Anderson Rd
Clawson, MI 48017
248-655-0557 | office
248-953-3251 | mobile
248-246-1797 | fax
jiml@vboxusa.com
http://vboxusa.com



OK, now Jim from Vbox told me to load Todds data and check for summary errors, basically time/distance sampling errors where the unit drops data. Todd had hundreds of them because he was suffering from the firmware bug that was described in the email. He has updated his dbox's firmware that fixed the bug and sent the current file, which had ZERO summary errors. Also, his previous 3.9 sec run is explainable. The errors logged by the unit before the firmware update had a Universal Coordinated Time stamp that could be used to find where on the graph the errors occured. All the time/distance sample errors were on the 3.9 sec run....hence the 3.9sec run.That is the extent of my validating his run.
Now , here is where my good friend Jean and I part ways. I stated above that Jean claimed my run was correct, but had some issues. The terminal speed of 130 was equal to the calculated speed..great. The only problem is that in the core of the run, say 70-120 the deviation was in the 20% range..quite alot, but it came in on the numbers in the end. Here is my problem with Jeans calculations. 1: I do not run on the street doing these 60-130's. Every 60-130 run I have was done at a sanctioned dragstrip. I dont trap 130, so I just keep my foot in it past the traps and I have my legal, do not go to jail, 60-130. This means I have a timeslip to compare all my 60-130 runs and the the middle of the runs do not show the deviation that Jean has calculated.This means the track, the Dbox, or Jeans calculations or a combo of all are wrong. I think we will all agree the track timing isnt open for debate. So although Jeans calculations are spot on for the AX22, they dont seem to work as well for the dbox. All of the dbox runs have some sort of error in his calculations, but some do come out correct in terminal speed.Part of the problem is Jean needs the data in a certain format, and I tried to provide it ,but we realized it was in the wrong format for his formula. He needs .01 sec and all I can get is .1mph... it ends up being close to .01 but not exactly... how this affects his calculations, I do not know. The problem is his formula needs long G's to be used and the units calculate them in different ways. Here is a Car and Driver review of the Dbox:
http://www.caranddriver.com/features...-driftbox.html . Where does this leave us? I believe in the unit. My drag times are dead on with NHRA tracks and my roadcourse times are dead on with a stopwatch. Jean has some issues with the shifting or lack thereof in the run.I have a feeling Jean may post his thoughts on the matter rather quickly. Jean... your microphone OH , almost forgot the graphs. I think a real quick and easy solution to this matter is this: Some believe in GPS, some 1/4 mile dragslips... myself both. Run this car at the Dec 2nd drag date with the gPS onboard that Renntech has advertised and compare GPS data and timeslip data. Simple and effective. Kevin BTW....DMK's run was uphill!

 

Thanks Kevin,
and for what its worth, I am bring my AX-22 to the Drag day
12-2 and I am happy to let anyone use it!!

MK

 

Marty, what are you doing in the land of the eternal sun.... are you running? Kevin

 

also Kevin:
did your driftbox have the same software bug the Todd (EVOMS), had?
Are you 100% confident that your #'s (60-130) are correct on your car?
I believe you are at a almost unbelievable 7.93 (I said almost!)

thanks again for the amazing effort you have put into and helping seek the
truth.

AX in hand and heading to warmer weather... Just to recreate, hang with my beautiful wife
and check out some super fast Porsches...