I had a go at measuring horse power and torque today using Virtual Dyno and the Dyno function in the MazdaEdit LogViewer.
Both are based on the same method; measuring the time it takes to accelerate between RPM points and then calculate hp and tq based on weight and gearing ( gear, final drive and driven wheel diameter)
The source is a log file that included at least TPS (to detect 100% throttle), RPM and TIME. VD supports a huge amount of EMS and OBDII loggers including MazdaEdit, ECUTek etc.
IND over at m.net has a nice writeup with results for both VD and actual Mustang dyno numbers here :
It is essential to get all the parameters 100% to get credible readings:
- A long stretch of straight and flat road. Measure both ways and average the results.
- Actual measured weight of the car + driver
- Actual distance from the surface to the center of the driven wheel x 2. Calculated size using tire width,profile,rim will not be 100% correct.
- Gear ratios for both the diff and trans.
- In which gear you did the pull.
For my car this resulted in :
Weight car + driver 1160kg + 80kg = 1240 kg (full tank, some gear in the trunk)
Gear ratios for 6 speed box (EU):
Just for fun I tried to use the same numbers and log on the MazdaEdit Logviewer Dyno function and got this:
About correction factor.... The Dynojet correction factor is 1.09 in VD which results in 220whp at the wheels for the exact same log and data... 28 whp difference. This makes it hard to believe dyno claims from vendors that only publishes hp and tq numbers.
I think VD and similar is a really valuable as a tuning tool to verify changes in the tune. The only real downside is that it can be hard to find a good stretch of road suitable for doing pulls.
I can't wait to play with this more and get a final base line that I'll use for further tuning.