Super Chevy and DSE Test

[alcino]

Just guessing, but I think the Vbox could map(plot) out the path of the car going through the cones. But that’s all that you would see, a line going straight, then wiggling, then going straight again. No start/finish lines or cones. I guess you could estimate the entrance of the slalom and measure out to 420', then see what time that took.



So if you really pester DSE, I guess they could give you an "estimated time". I don't think that classifies as apples to apples but close.

[Steve1968LS2]

I'm in contact with the guys at VBOX... The unit used in the test is the VBOX Pro Lite. The head guy for VBox USA is sending me over the software so I can check it out. After talking with him I have a much better understanding of how this equipment works. It's pretty high end stuff. They will also loan us a box so we can use it in some of tests as a comparrison to our timing lights.

http://www.vboxusa.com/datasheets/vbprolite-data.pdf

The results given in the DSE were exit speeds. The plot graphs for the tests are givn on page 48 of SC, but are a bit hard to figure out.

<-- on the case

[Steve1968LS2]

So if you really pester DSE, I guess they could give you an "estimated time". I don't think that classifies as apples to apples but close.

No pestering needed.. Kyle has been very forthcoming every time I have asked him for info.. In future testing they will data log for average speed as well as exit speed

[Mkelcy]

Maybe it has the capability, but wasn't used that way.. why don't you hold off judgement till we find out..

If you look closely at the picture of them removing the differential it appears to be stock leaf sprung rear end with stock shocks (and even drum brakes). So it was not some super fancy modified leaf spring deal from what I can see.

As much as you would see that we are somehow giving DSE "a free pass".. others could see that you are taking a "guilty until proven innocent" approach..

I will detective it out a bit more..

Just a few responses:

1) My comments and questions about the Vbox are in response to the apparent insistence that the system is INCAPABLE of getting the data that corresponds to the PriMedia method of testing. I believe, based on my own review of the Vbox site and literature, is that the equipment is fully capable of timing a vehicle from point A to Point B.

2) I've asked a series of questions about the test methodology and the decision to report the results in a way that couldn't be compared to a huge database of comparable test results. If asking questions about test methodology and the atypical format for reporting the test results is taking a "guilty until proven innocent" approach, I guess I don't understand why we need test results at all; we could just take DSE's word for it that their 4 link out-performs a stock leaf spring rear suspension and move on.

3) All I've said in a conclusory fashion was that the DSE test doesn't "prove" anything useful to me. Again a test that shows the DSE 4 link out-performing a "stock leaf sprung rear end with stock shocks" doesn't, frankly, surprise me. Perhaps others in this thread are impressed.

4) What does surprise me is the, so far as I can see, uncritical acceptance of the significance of this test vis a' vis the performance of the DSE 4 link. I would think the relevant comparison is the 4 link versus aftermarket leaf spring/shock setups available from DSE, GW, Hotchkis and others rather than against the OEM setup.

4) I have no beef with DSE. I'm sure they reported accurate test results for the tests they did. What I do have a beef with is the apparent insistence that this test tells us anything useful. I sincerely doubt people on this board struggle to decide between the DSE 4 link or the OEM spring/shock combo. Rather, my guess is people who are looking for performance (and not "bling") are evaluating the DSE setup against performance aftermarket leaf spring/shock setups, other 4 links and perhaps even the new Lateral Dynamics 3 link. In making that decision, this test appears to be useless.

[Mkelcy]

<-- on the case

Boy, Steve, you act as if you have an actual job to do beyond posting on this board.

[Steve1968LS2]

Boy, Steve, you act as if you have an actual job to do beyond posting on this board.

I am a multi-tasker.. lol

Right now I am writing a story on the Super Chevy drag races las weekend. Compiling the next set of Hometown Hotrodding cars, chasing down parts for my LS2 dyno testing in a week, compiling New Products for the August issue and typing this post..

[Damn True]

I am a multi-tasker.. lol

Right now I am writing a story on the Super Chevy drag races las weekend. Compiling the next set of Hometown Hotrodding car, chasing down parts for my LS2 dyno testing in a week, compiling New Products for the August issue and typing this post..

I'm having a cup of coffee.

Things at Initech are a little dull.

[Mkelcy]

I'm having a cup of coffee.

Things at Initech are a little dull.

I'm pulling my '68 apart trying to get it ready for a cross-country road trip. Need to swap in an LS1 T56 for the after market T56 that's in there (lower numerical first and 6th; will work better with my 4.11's); install the C4 seats i've had sitting around for a while, install the DSE wiper kit and subframe connectors, chase down some electrical gremlins and do some wiring, cut the front springs to drop the front end about 0.5" to 1.0", install a radio, amp, etc., realign doors, fenders and windows from when I threw it together 2 years ago, etc., etc., etc. All this rain hasn't helped.

[Damn True]

Well I'd much prefer to be in the garage working on my car. As dull as things are here at Initech (I think I do 15min of "Actual work" per day) they still want me to be here in exchange for a paycheck.

[DJW32]

Things at Initech are a little dull.[/quote]


LOL!!!

[bretcopsey]

Damn True,

You better get cracking on those TPS reports. The end of the day is fast approaching!! Oh yeah, don't forget to use the new coversheet-you did get the memo on that, right?

[harshman]

So it seems you kids have been busy while I was at Disneyland.


My opinion: While to the common guy the PHR test looks way more accurate, to compare suspension changes and the likes and to only attain a given 1 mph using PHR's testing method, the common reader will see no point in taking these bolt-ons seriously. But to show the layman reader what a more seat of the pants feel it is to upgrade to these items the Vbox test appears better.


Unless you have seen these tests you can't comprehend how fast these cars are zipping through the cones physics major or not. My car ran a dismal 42.1 mph but compared to a 48 mph that the high end cars ran, well, it just doesn't show up well on paper. Now change that for the reader to a 42 to a 58 mph change using the Vbox and they will see the picture rather clearly.


There are a lot of factors that can change these test as well. Temp, humidity, altitude, sunny or cloudy, cold or hot tires. PHR tries their best to adjust their settings to make them the most accurate. Does the other machine do this? Don't care and it is pointless to debate this unless it's your car.

[JV69z/28]

One point that seems to have gotten lost in this is DSE improvements are also retaining ride comfort not aimed at nothing but all out performance.
Maybe one of the magazines (PHR - Steve) could set up a suspension shoot out. Way back when Herb Adams and **** Gulstrand were battling for street supremacy there were more than one magazine doing shootouts where they pitted Camaro Vs Firebird. Set up a loose set of rules like no aftermarket sub frame and the biggest tires that fit in the stock wheel wells or even limit the tire size or one step further supply the tires so there is no advantage in the rubber choise. Then invite DSE - Global West - Heights - Fatman - Hotchkis - air ride and any other company to supply a 1st gen F-body to test (skid pad - 420 cones - autocross or lap time - 0-60 or 1/4 mile if space permits) and then you would have numbers to compare were the conditions are not a variable. You could also have subjective opinions on ride and handling. It maybe hard to set this up and the manufactures may not be able to supply the vehicles but maybe some people would be willing to volunteer (like when Carl C did the tire test for Camaro Performers).

[chicane67]

"The VBOX communicates with the U.S. government's global positioning system, a constellation of 24 satellites that orbit the earth 10,600 miles overhead. At least four of the satellites are above the horizon at all times, and each sends a carrier signal that is picked up by the VBOX's antenna (a small magnetic unit that you affix to a test vehicle's roof). As a vehicle travels, it draws nearer to some satellites and farther from others. As this happens, the frequency of the carrier signal shifts minutely. The VBOX senses this frequency shift, which is also known as the Doppler effect, and calculates the velocity, acceleration, and distance traveled."

VBOX communicates with the SPS system, not the NSB-PPS system. The difference here is that the SPS system is the 'civilian network' and the NSB-PPS.... is the 'USDOD network'. The difference here is roughly...... uh..... yeah. Right about 26%. That 26% is "purposeful" error.

FOC 19960428 Block II/IIA: DOT-VNTSC-RSPA-95-1/DOD-4650.5

The SPS system has a predictable position accuracy of 100m horizontally and 156m vertically with a TTA of 340 nanoseconds.

The PPS system has a predictable position accuracy of 22m horizontally and 27.7m vertically with a TTA of 200ns.

As the math works out, that is roughly 4.627m for the SPS system and right about 0.5m for the PPS system.

Let's see here..... 4.627m is right about 14' for the SPS system (and about 19.9 inches for the PPS). So now there is a 14fps error in the elapsed time. Which is right (about) where the USGOV keeps the civilian error tracking. Wow.

Considering that the specified MPH was 58.39... would mean that the car traveled the distance in roughly 4.9 seconds..... without making any lateral transfer to scrub any speed...... in 420'.

Uhm.... no.

Taking into consideration the 14fps error would place that same car in that same distance in at 44.44mph. Which will be around 6.5 seconds. Now, that I believe.

So, you're convinced the Vbox technology has no ability to measure how long it takes to go from point A to point B, say the beginning of a 420 foot slalom course and the end of that same course? That hardly seems like technology that would cost $10,000 plus.

You would need an "IRIG" clock signal to make the correlation of the start of the data point, to the actual time at the beginning and the end of the 420'. You are correct.... its about $10k for the time code generators alone (and that doesnt include the network) and it isnt available in cililian GPS units.

All in all.... for this to even be a considerable "DATA set" all other vehicles in comparison would have to use the same equipment under the same conditions..... or you will have introduced "the measurement of uncertainty". You can not fool timing lights..... (unless you hang a spoiler out there to trip the beams quicker)..... so 'like' data isnt necessarily 'like' data in this example. Nor is using a 125' skid pad and a slalom (with a collection device that has computable error, but wasnt done, obviously)....... as a comparison to everything else that has been tested, on a 200' skid pad using lights.

And yes..... that would mean that the big three have this same error. Unless they have done the correction factors for the NAVSTAR offsets..... which I doubt that the USGOV has given them that information.

[Steve1968LS2]

All in all.... for this to even be a considerable "DATA set" all other vehicles in comparison would have to use the same equipment under the same conditions.....

Uh.. they did use the same equipment under the exact same conditions... the show gain is valid.

The guy at VBOX said that the built in error was turned off on GPS (I think).. and that that even if you exact specific location was off the distance traveled between two points would be exact to within less than an inch. So if you went to a mile marker and drove a mile (going by GPS) you would stop at the 1mile marker almost exactly.

I'm sure the GPS egghead at VBOX could explain it better, nice guy and very willing to discuss the technology.

[chicane67]

Uh.. they did use the same equipment under the exact same conditions... the show gain is valid.

The guy at VBOX said that the built in error was turned off on GPS (I think).. and that that even if you exact specific location was off the distance traveled between two points would be exact to within less than an inch. So if you went to a mile marker and drove a mile (going by GPS) you would stop at the 1mile marker almost exactly.

I'm sure the GPS egghead at VBOX could explain it better, nice guy and very willing to discuss the technology.

Uhm.....Steve. I am talking about every test that is to be or will be compared to the results, of the DSE testing, from here on out. I am aware that their testing was done using the same equipment and under similar conditions for their data collection in this article.

The gain is representative of their collected data and how they interpret it. But, it still doesnt represent the factual error in the data not being measured or compensated. I too can measure a given parameter of a certain object. And then ask you to do the same thing..... now, weather or not you performed the test the same way as I have, there is a 99.9% probability that error has just been introduced into a data set.

I would really like to hear what VBOX's "built in error" is all about. It can only be as good as the SAT that is being used and the error % of the SAT's included in the triangulation (which is actually about 10 or so total SAT's, not just the four for the instantaneous segment.) The GPS/SPS system still has a rough +/- 4.627m smear in tracking in any instantaneous segment.

Then again, bit subframes are every six seconds or so. So I would imagine that their "built in error" is from the "Selective Availability" of the SPS system.

• Bias errors result from Selective Availability and other factors
  • Selective Availability (SA)
    • SA is the intentional degradation of the SPS signals by a time varying bias. SA is controlled by the DOD to limit accuracy for non-U. S. military and government users. The potential accuracy of the C/A code of around 30 meters is reduced to 100 meters (two standard deviations).
    • The SA bias on each satellite signal is different, and so the resulting position solution is a function of the combined SA bias from each SV used in the navigation solution. Because SA is a changing bias with low frequency terms in excess of a few hours, position solutions or individual SV pseudo-ranges cannot be effectively averaged over periods shorter than a few hours. Differential corrections must be updated at a rate less than the correlation time of SA (and other bias errors).
• Differential Correction (DC)
  • The idea behind all differential positioning is to correct bias errors at one location with measured bias errors at a known position. A reference receiver, or base station, computes corrections for each satellite signal.
  • Because individual pseudo-ranges must be corrected prior to the formation of a navigation solution, DGPS implementations require software in the reference receiver that can track all SVs in view and form individual pseudo-range corrections for each SV. These corrections are passed to the remote, or rover, receiver which must be capable of applying these individual pseudo-range corrections to each SV used in the navigation solution. Applying a simple position correction from the reference receiver to the remote receiver has limited effect at useful ranges because both receivers would have to be using the same set of SVs in their navigation solutions and have identical GDOP terms (not possible at different locations) to be identically affected by bias errors.

For the non GPS savy crowd, the term "SV" means space vehicle.

Anyway, my whole point was in reference to the data collected from 'here on out' needs to be the same points collected, the same way, for it to be comparable.