RomRaider

Did you clear the results between runs? If not the second will be run 1 & 2 averaged together and you may see odd results if the conditions and run length are not identical.

I did press record again. Thanks, will trying clearing that or will just use this feature to do an average run. Appreciate the help on this.

Are the HP on the Dyno WHP or crankshaft HP?

I've noticed that despite entering the temperature, pressure, altitude and relative humidity I always seem to get default figures in those boxes once I have done a run as shown below - anyone else experience this?

If you did the run in real-time, the pressure and temperature are updated from the ECU sensors to be the ATM and IAT values at the current time. The humidity is the only one not automatically updated.

What was the temp during your pull?

it would have been about 32 F and about 600 feet above sea level. I created a new definition for the vehicle in the xml file but would not have thought this would have an influence on these calculations?

No a new vehicle entry would not affect those values. As I said, they are read from the ECU at the end of the pull. So is your IAT temp 40F above the ambient temperature?
Try a pull and log IAT just to see how the IAT changes during your pull.

As an alternate, make a log of only RPM and TPS for your pull. Then load (Load From File) the log to see how it plots. Then you should be able to play with the temp and pressure values and click recalculate to see the change.

thanks - in that case IAT would have been about right i.e. the temp of the air at the maf (I was thinking this was the ambient temp outside the car) but the altitude does seem to stick at that shown on the plot across a number of different cars.

The elevation is calculated from the ATM pressure read from the ECU. It's for information only and eventually I'll try and incorporate the elevation and altitude in for a correction factor function. The elevation is not used in any calculation but the ATM pressure from the ECU is.
It's odd that your IAT is that much higher than ambient at the end of the pull. That's when the IAT should be closest to ambient. You need colder air!

I did not realise that altitude was not included in the calculation so it's not an issue.

I have to say that you really have done some incredible work getting this software to where it currently is.

I use DataLog Lab, VirtualDyno, and AirBoy's spreadsheet and come up with results varying from 300whp to ~340whp between the different programs using the same logs...

Just wondering where the RR Dyno program would sit in accuracy....has anyone done a comparison using RR dyno on a car with a known Dyno'd WHP rating?

BTW, AirBoy's spreadsheet is giving the lowest at just over 300WHP (~ 285 torque) and VirtualDyno on Mustang Dyno settings is about the highest using the same logs....RR dyno is close to or a tad higher than the VirtualDyno result at 338 or 339 whp (torque ~320). So what I've read in earlier entries indicating that AirBoy spreadsheet results and RR dyno results being very close is not holding true for what I've found and I have been doing comparisons for several months as I have been tuned from stage 2 thru stage 4 and finally now in the final days of 93 octane map on stage 4.

Les

At what RPM do you see the peak HP/TQ in the curves of the various programs for the same log?
I don't think a comparison to a real dyno would be useful.

Maybe I'm missing something but isn't the whole point of a "software dyno" to be as close in results as a 'real' dyno for comparison reasons?

I realize there are given variables and factors in both the virtual versions and the mechanical versions so neither is likely to be exact and the virtual v. mechanical will likely not match HP to HP exactly but if a given dyno program is just shooting out some number without any expectation of it being an accurate rating compared to a 'real' dyno then what is the purpose?
(Taking into account that there are other uses for the software versions - as tools - such as map revision to revision comparisons on a given car, however, wouldn't one still want a reasonable expectation of result accuracy compared to "the real thing")

Maybe not - am I just not getting something???

As far as RPM at peak hp, I don't have the graphs in front of me but all appear to be realistic with peak numbers ranging from 6200 to maybe 6500 rpm running the 20G on my 2.0. The least likely candidate would probably be DataLog Lab which most of the time peaks HP out very near or at redline (I can feel power starting to drop just a bit by then).

Please don't take me wrong...I appreciate your time and effort into this project and it is definitely a useful tool. I'm not trying to burn or run down ANY version, just curious about the accuracy compared to what I could expect when I get it dyno'd.

I suppose it's rather like in my world where someone calls 911 because their automatic B/P machines are showing dangerously high or low B/Ps and we scream to the scene only to find , once again, an inaccurate machine with a B/P within normal range. (The automated machines are well known to be less than accurate a good portion of the time.) The automated readings sometimes are also within "normal" range when in reality they are dangerously high.

My point: What is the use of checking one's B/P (HP/torque) with an automated machine (software dyno) if the results are not even close to accurate?
False expectations and undue concern or confidence??

I was just wondering.

I understand what your saying. Although measuring B/P is much easier than HP/TQ.

I think the comparison between various programs is going to be difficult as each may use a different method of smoothing and interpolation of the speed and acceleration. And if there's no correction factor (as with the Airboy Spreadsheet & RR Logger dyno tab) then results from one day to the next may vary with temperature, air pressure and wind. If you are making changes within the same day then comparisons maybe more valid.
With a mechanical dyno you have an environment in which some of the variables are more consistent or controlled and they have the corrections built in for temperature and pressure. Also, you can't take a log made on a mechanical dyno and run it through a software dyno program and expect accurate results as some things will not be interpreted correctly. Like the drag that the car should be experiencing with speed.

Now whether you use a mechanical or software dyno, I think it's best to pick one and stick with it such that at least the calculation method and comparison is always based on something that's the same.

I asked about the RPM for max HP best sometimes the smoothing chosen with cause the HP curve to dip and then go up at the top of the trace. This my not reflect where the actual max HP is. With the RR Logger dyno at least you can limit the upper RPM to remove this affect.

I'm just doing an update to my car defs for this. Sorry if this sounds like a stupid question but when we say 'final drive' can I just double check that we are referring to the rear diff ratio? I'm aware that the front and rear diff ratios can vary depending on the ratio of the transfer gear in the gearbox. For example, a front diff with ratio 3.9 and a 1.11 transfer gear in the gearbox requires a rear diff ratio of 3.545 (i.e. 3.9/1.1:1)

Thanks