0-60, 60 ft, 1/4 mile calculations......

[arthansen]

A few years ago, I developed an Excel spreadsheet to help me tune my 2001 Firebird V6. Bellow is a link to one of the files from one of my "runs". I would do a 3rd gear run on a long flat stretch of road and make a log. I would then import the data into this spreadsheet to calculate HP. The formulas take into account HP needed for acceleration, wind resistance and tire rolling resistance. The first row of the calculations tab is where you enter your cars parameters (weight, frontal area, coefficient of drag, tire pressure) and atmospheric conditions (Temperature and Atmospheric pressure). Those are the bold values. the rest of the row contain results. Column "U" is the most important. It calculates HP using a variety of smoothing functions (mainly to account for the poor resolution of the Speed PID). The graphs are pulling data from the section that is highlighted in yellow (Rows 197 to 155).

Just for comparison, this car dynoed at 322 RWHP.


http://home.tampabay.rr.com/jakerace/HP40.xls

If it askes for a passwoerd, just click "cancel".

Hope this helps.

[TiredGXP]

I've built a similar spreadsheet, just to play around with numbers. I guess the concept is using the vehicle's mass and acceleration as an inertial dyno. Someday I'll actually get the vehicle weighed and compare the results to an actual dyno run.

Problem is that the log data is "jittery" but you can run a trendline through the data in a graph and come up with a graph that looks somewhat reasonable. My spreadsheet only needs two PIDs - RPM and Transmission output shaft speed in RPM (on the FWD, this is the same as wheel speed in RPM but provides much higher resolution than the speedometer PID), and a number of constants for the calculations. With only 2 PIDs the resolution is pretty high, just jittery.

[redhardsupra]

yea you need much higher resolution device, and one that's not based off wheel speed, as that's not gonna do much in case of wheelspin. GPS would be good, but the resolution and the scanning frequency would have to be improved.

mychron 3 gold has a 200hz scanning, which is like 1.5in resolution at 120mph, which would be great, but i'm not sure how they achieve it.

[Brice]

A friend of mine is using Powerdyn
http://www.powerdyn.fr/

It's a french company, it's a dyno via obd2.
He seems happy with it.
I have to try it