Virtual Dyno by Brad Barnhill is a stand-alone software program that analyzes and presents data captures in the form of a virtual dyno graph.  It can work with a variety of datalogging formats.

I have been interested in Virtual Dyno and have read a bit about it.  Today made a good day to grab several data runs, slice them up, and compare.

Virtual Dyno data capture

I used my normal 20 minute test drive route.  I ensured that I added several 2nd gear pulls from 30 mph to 60+ mph, as I wanted to check that range at the top of 2nd gear.  I am unfortunately far from Mexico, where all true internet speed captures are done (lol), so a true 4th gear pull to 144+ mph is not in the cards today.

Virtual Dyno data preparation

To capture the data, I used HP Tuners VCM Scanner.  I exported the data file with all runs to a .csv comma delimited file.  I used VCM Scanner gauge review to find the 0-60 runs and noted the sample range for each run.  Then I used Open Office Calc to edit the .csv file, creating new .csv files with only the acceleration run of interest in the .csv file.  I renumbered the sample for each run from 1..n within that file, and named the file by the sample file name and sample range.

Although Virtual Dyno includes a file for the STS-V, it treats them as if the weight were constant for all model years, although it was not. The correct weights are 4,343 lb in 2006, 4,295 lbs in 2007, and 4,233 lbs in 08/09.  I created a custom file in the app data section for the 08 STS-V.

in addition, my STS-V has an extra inline intercooler tank (12 lb with coolant) and a ZZP front mounted heat exchanger (6.4 lbs). So my curb weight would be 4,251.

Today my car was at 1/2 fuel, so 9×6=54 lbs of fuel missing; 4251-53=4199 lbs.

Virtual Dyno includes a few different dyno settings and adjustments.  Since my actual dyno was done on a dynojet I selected it.

Virtual Dyno Screen Shot

This screen capture shows Virtual Dyno crunching 3 different datalog runs from the same day. The data run file info is shown to the left, and the data runs are graphed to the right.

I wanted to compare them side by side to decide repeatability.  With many modern cars this in itself is troublesome — my 2008 Cadillac STS-V will tend to run quite differently from one run to the next.  So determining what variability is due to the software and what variability is due to the vehicle performance is tricky.

Virtual Dyno Summary

Virtual Dyno exports the graphic output into an image file, which makes it easy to use and reference.  What my runs seem to show is that the first run, while the STS-V was up to temperature, but still relatively cool, the V made the most power at 485 whp.

The other 2 runs had relatively more wheelspin, and made relatively less power, at 363 and 349 whp, although within a relatively close range of each other.

Here is the HPTuners Gauge output for the max hp run:

Hot on the dyno before the cooling additions my STS-V made 394 whp on a dynojet dyno in 4th gear.  Assuming the virtual dyno is setup properly and interpreting the data presented, what we may see here is that there is a lot of variability in the power the STS-V produces.  Even with traction off, a lot of wheelspin in 1 causes early shift to 2nd and a longer pull with the intake temps heating up, and power reduced.

HPTuners Gauge snapshot for the lower HP [blue] run:

Virtual Dyno Smoothing

Virtual Dyno offers a range of smoothing.  Smoothing is averaging of the values relative to their surrounding values.  It has the effect of better showing average or trend information out of relatively bumpy real life data.  A smoothing choice that shows smooth data trend lines but no more than needed seems best — and consistent from run to run and day-to-day.  The upper graph has smoothing 4; the lower graph has smoothing 3.  I plan to stick with Smoothing 3.

Virtual Dyno — What does it all mean?

Virtual Dyno gives you another input to try to measure how your vehicle is performing.  It has the advantage that you can use it on the street at your leisure.  It has the disadvantage that you have to exercise more care to isolate and eliminate variables in your test method.  Otherwise you won’t have comparable tests from one day to the next.  As software I find Virtual Dyno easy to use and pretty consistent.    It is another tool in my toolbox of car metrics.  I will continue to work on repeatability.