M-Phibian

He told me they are positively not related. He was adamant about it. He said that the Vbox uses an entirely different method of measuring acceleration than it does elevation. He said I could literally remove the elevation measurement feature and it would not effect the acceleration measurements. Feel free to contact him directly for more info. His mobile number is listed above. Don't forget, my car also traps 148 mph in the 1/4 mile (at only 830 rwhp). This is the same as other cars that run in the 4.5-4.8 range.

Felix

The absolute altitude data reported by a commercial non-differential GPS is not very accurate; this is a result of the deliberate "jitter" in the data supplied by the satellites and the geometry involved. It has nothing to do with the datum (WGS 84 or otherwise). Over a short period of time and reasonably short distance the change in altitude reported by a commercial GPS is sufficent for most purposes. Just do a google on gps altitude accuracy; here are a couple of links http://gpsinformation.net/main/altitude.htm and http://docs.controlvision.com/pages/gps_altimetry.php I particularly like the last sentence in the first link

TB993tt

Here is a clip illustrating the inaccuracy of the "height" function - the DB thinks the same part of the track has grown 3 metres on the second lap !

From the graphs I have looked at the height function is pretty useless - I have seen graphs where the guy swore the roads were flat and it looked like he was testing in the alps !
It seems to me that "verifying" slope using the DB/PB is worthless - I guess you just have to trust people - most people know if the road they are using has a slope or not and for those that fool themselves - at least it makes them feel good

Jean

Interesting last few posts.

Now that Virginia's altitude has been established as being at or above sea level we know that the altitude shown by the device is wrong. I had mentioned this before, not only the altitude, but also the long Gs are out of whack..

The question is whether this has an impact on the run itself. IMO the answer is yes and no, it depends. If the device is showing this as a result of miscalibration (not given enough time to calibrate before the run or other) then the whole run can be wrong. If this is as a result of blind GPS spot, then maybe not.

I have seen the exact same problem in a run that was sent to me, where the 60-130mph was in less than 5 seconds. Altitude was screwed up, long Gs were screwed up, obviously the run, which was for a 520bhp stock weight car, was also screwed up. And if I am not mistaken the run was with an AX22 in this instance. I can get as many of those miscalibrated runs as needed.

A much more accurate measure of altitude is through calculations made off the data extracted and on excel. In most instances it is not needed, but when there is doubt, it certainly is needed.

I would hope that any validation of a run is taking all of this into consideration, and looking closely at inconsistencies such as positive Gs during a shift or negative Gs while the car is accelerating... Clear indications of a speed vs time problem as well, and therefore worth looking at beyond the graphs that the device shows.

There is a calculation that can validate the slope vs the acceleration, time and speed, since this is pure motion physics, the results cannot lie, unlike a GPS that are prone to blindness when it comes to altitude.

As TB is saying and has clearly showed in his graph, measuring the validity of a result based on altitude on this device or the AX22, is not accurate. long gs, and sharp looking speed vs time curves are much more indicative. As far as I am concerned, both devices have given me excellent results during my runs, with very accurate altitude and long Gs, I live in a good spot I guess

All of the above is irrespective of whether Scott's car is capable of those numbers, I think (rather I am sure) it is, but those graphs do not look good and seem to have a lot of reception issues.

M-Phibian

The elevation errors are due to inherent innaccuracies within the WGS-84 GPS Datum. Not the P-box. It has zero effect on acceleration times.

Here's further info from Gulfstream Aerospace.

M-Phibian

Okay guys,

So KPG told me that the 5.7 graph that I gave him was way too strange to validate (you were right TB). So, I did some more runs today.

I'm still on 93 octane, but I swapped out my BOV springs for stiffer ones to help me stay under boost longer between shifts. I ran a 5.52 with 2-shifts. I peaked at 1.15 BAR this time. The graph shows my shifts clearly. I sent it to KPG for validation. I'll post it once he validates it. I also have an in-car video of the run here: http://media.putfile.com/553-run

M-Phibian

KPG validated this 93 octane run at 5.52 with 2-shifts.

JBL930

I've just done a quick run and thought i'd share, two people in the car with full tank of petrol, i can verify that the car weighed 1381kgs with the 930 lump in there and a full tank, this engine must be a bit heavier but i don't suppose it would be much, add the combined weight of me and her 145kg and you have a total of roughly 1530kg. I have a four speed box and this was done with one shift, 2nd to 3rd, and it took 7.75 seconds.
Can i send you the file Jean so you can have a look, PM me with your e-mail, i recently changed computers and now don't have it, cheers

eclou

Nice run JBL. That should equate roughly to 550+hp.

VRAlexander

I just spoke with Bobby and it appears that we have a new 60-130mph record for the 996tt. Congrats Markski...great driving Bobby.

Now go out and get that quarter mile time

Congrats again buddy...

Jean

Let's see them. I hope no funny fuzzy lines and the runs are non debatable. I have been hearing for ages about Bobby and know he is a motorhead but haven't seen anything tangible at all, zero, zilch, nada, niente, ma chi yet.

If anyone deserves to be the fastest, it definitely is Markski with all the effort he put!

VRAlexander

I believe that Markski will send a copy to KPG for verification....

KPG

No he won't. To my knowledge, this run never happened....Although I have no doubt he will break the record in the near future.

vincentdds

I am confused.

Freak997tt

Cant wait for Bobby results !!