Originally Posted by PencilGeek

I have a couple of questions:
1) Why was your vehicle weight about 300 pounds heavier than the CTS-V in the database? The database shows 4108 pounds for the CTS-V. Everywhere I google "2009 CTS-V weight", it comes back 4222lbs, plus I'm unfortunately 200lbs myself, so I figured 4225 going down the track.
2) Were you at 30 PSI tire pressure? I know lots of drag strip guys will lower pressure. I just want to double check. I used MT Drag Radials that DO NOT SPIN, and I had them at 18-20psi, but my fronts PSS2's were about 45-50psi of course, so I averaged them at 30psi.



I re-ran your results with the following changes.

1. I changed the vehicle weight to 4108 pounds. This will decrease your calculated power.
2. I changed the tire type to "Performance" from "Racing." I'm not saying this is right, we're all experimenting here. :-) But I changed this because I'm wondering if full blown racing tires are even sticker than DR's. I honestly don't know the answer. This will decrease your calculated power.
3. I increased the frontal area to 25.1 sq-ft. I looked this up, and it seems to be correct for the CTS, so I used it on the CTS-V. This will increase your calculated power.
4. I didn't make any changes to tire pressure. But if I increase it, it will decrease your calculated power.

I ran with these changes and it decreased the horsepower by about 35-40 whp. So that's getting much closer to your Superflow dyno results I would think. The horsepower spike at the end of your run is pretty interesting. I'll dig into the data logs a little later and see if I can isolate the spike to one thing or a combination of things.

Thanks for giving your feedback. Here's another feature I haven't mentioned before that you might find useful. Now that you've entered your vehicle data, you can recall it and tweak it if you like. Here's how you do it. When you load the web page, use the very first pull-down menu and change it from "Search the vehicle database" to "Search by vehicle record ID." The record ID saved with your runs was 790064939. This was the number that appeared in the "Save as record ID" field when you first used the program. The program generates a random number, but you can type in anything you want here; anything from your cell phone number to your email address. Then the next time you use the program, just use the search feature using that same value and it will pull up the same data.

If you enter this number (790064939) and click the search button, the vBoxDyno will pull up all of your data just as you originally entered it. (I'll be explaining all of this in the HowTo video.) From there, you can tweak the input data and submit the file again to get a new set of results.

Originally Posted by Fadi

I tried a 5.1s 100-200km/h (6.0 60-130) run from my gtr on pump, but showed only 430whp, dont know what was wrong. I dont have a dyno from this setup, but estimate somewhere 750-800whp, and was really interested to see some data

Originally Posted by PencilGeek

I didn't get a chance to fix the bug, so I've temporarily disabled the vBoxDyno. I actually found two bugs: 1) the sample rate thing I already mentioned, and 2) was calculating whp due to acceleration 1.8% too high (long, complicated story on that). I'll need a few hours to fix it, and didn't have time today. Hopefully I can get it finished tomorrow.

Originally Posted by BlackHorseTurbo

I ran a calculation on a 60-130 pull of mine and it spit out 3400HP.

Originally Posted by PencilGeek

I looked in the database of results and didn't see anything that matched the descriptions (nothing "60-130 & >2000 whp" was found). Do you have a link to the graph or send me the first 8 digits of the "Test ID" string that appears on the graph? I'll look into this one if you can give me a little more info to help me find it.

But even without looking at it, I can tell you the two most common reasons why this happens:
1) The vBox file is unusually short and starts only a few samples before the 60-130 run itself. Horsepower is calculated based on a change in velocity. Some people trim their files to the bare minimum (not sure why), and sometimes add a "0 MPH" entry at the beginning. So when the vBox Dyno (or G-Force calculator) sees this, it see a 60 MPH change in velocity in 1/10th of a second. This massive change in velocity causes a very large spike in horsepower calculations. I've toyed with the idea of adding a filter for this, but never went too far with the idea.

2) The vBox file contains bogus data. For example, one file uploaded contained a velocity change from 15 MPH - 270 MPH in about 3/10 seconds. That caused a 50000 whp spike. Most likely the file contains some bogus data. I never really looked into this any further because it's an example of bogus data. The program already flags bogus data when it can detect it and marks that on the graph.

Originally Posted by Fadi

775whp sounds like it should be.

I have just verified an old run from 2014 - 4.9s 60-130s on my rwd 996tt, had it dynoed two days before that run at 916whp on a lower reading dyno than dynojet and ran a bit more boost on the street than at the dyno,

I estimated 950-970whp or so for that street pull as did 0.1bar more than on the dyno, results from vbox dyno were first 1015rwhp (forgot the drag coef to
at 0.34 like the gt2), put drag to 0.31 and result was 995whp, so seems right as my dyno reads a bit lower than dynojet!

Thanks for this great tool, looking forward to trying new runs on my GTR with way more power than before (20Hz version)

Originally Posted by PencilGeek

Since I forgot to mention it: the vBoxDyno is now back online and ready to use.

http://www.vboxdyno.com

Originally Posted by BlackHorseTurbo

I ran some very old runs as well
More data

1. Tiptronic 996TT 197mph Texas Mile 622hp May 2009
2. BHT: 10.4 ET 1/4 Mile 913hp Feb 2012
3. BHT: Texas Mile 226mph 941hp 2013
4. BHT: TX2K14 March 2014 921hp
5. BHT: TI June 2015 1128hp

Originally Posted by PencilGeek

What's the difference between #4 and #5? Where did the extra 200 whp come from?