Imprecise Auterra palm-based "dyno"
 

I really should take this to a real dyno and have it done... but for now I thought I'd share the potentially inaccurate results of my Palm-based Auterra OBD-II Dyno-Scan scantool.

I did 2 3rd-gear runs.
It does note that you need a feature called "Fast Sampling" enabled for good accuracy, however the Nissan ECU doesn't work right with this, so I have to settle with the standard (slow-azz) data rate. I'm pretty sure this trashes the accuracy by a lot.

Anyway, here's the parameters (many assumed):

Weight: 3600lbs (roughly educated guess)
Gear Ratio: 5.087 (this was actually measured in 3rd gear with cruise control on)
Tire Diameter: 25.32" (computed based on 235/45-17)
Temp: 75F (I think that was a little high... my climate control said 59F after I was done)
Elevation: 1000ft (assumed)
Humidity: 25% (assumed)
Pressure: 29.24 inHg (assumed)
Drag: 0.32 (assumed based on the fact that I read the '99 is 0.32, although this might be off since the 2000 is a different body style...)
Frontal area: 20.0 sqft (assumed)

MODS-
Place Racing CAI with a fairly new K&N cone filter
Warpspeed 2.5" B-pipe w/ resonator. Stock Y-pipe, and a brand new OEM (variable capacity) muffler.

Run#1:
Shows a torque curve that peaks around 4000, then around 6200 or so it shows the same torque reading as 2000 RPM.
Stats-
Peak Power: 173HP
Peak Power RPM: 5500
Peak Torque: 193 ft/lbs
Peak Torque RPM: 4000

Run#2:
I started this one at 2000 RPM instead of ~1500 like the first one. This torque curve looks similar... peaking around 4000, but at 6200 it is actually LOWER than the torque value at 2000 RPM.
Stats-
Peak Power: 162HP
Peak Power RPM: 5700
Peak Torque: 186 ft/lbs
Peak Torque RPM: 4000

I am going to see if there's a way to download the Palm data to my PC and generate "dyno graphs" out of it for illustration. Plus I'm going to read up about the compatibility between this scantool's "Fast Sampling" mode and Nissan ECUs.

lol... okay, this thing allows you to grab specific data points from the graph, although you can't download it directly to the PC. So I used gnuplot to generate some graphs (HP graph is calculated based on torque graph)-

Run#1
torque data horsepower data
http://spirilis.net/stuff/auterra/09262004/run1.png

Run#2
torque data horsepower data
http://spirilis.net/stuff/auterra/09262004/run2.png

The graph utility on the Auterra software lets you view data points by hundred-RPM increments. I seriously doubt the unit actually received data that often, so it's obviously doing some heavy interpolation. I guess that's why you need the "Fast Sampling" feature for accuracy.

He used this on my car while at a local meet. The tool is pretty cool and gives a crude estimation of the power your car is making.

lol I think the torque dropoff and then rise at the end of the 2nd run was me getting light-footed on the accelerator at 85+ MPH :D

have you done the 1/4 mile, 0-60 runs yet using the program...how accurate are they? I have the same thing...but have yet to use the program for other than sensor read-outs and tuning/diagnostic purposes...

MaximaTodd....I believe there was a rather large thread on the auterra software back in the day....on the forums somewhere here which drove me to buy it....I will tell you that I have not used the dyno or acceleration features yet...but absolutely love the power to see what all the sensors are doing and so easily reset the check engine light...it also computes real time gas mileage which is nice to have like all of our luxury car bretheren!!! after a few months of using it, it has turned out to be an absolute god-send in every form of the word!!! has never let me down and has proven invaluable in so many situations!

or, let me just sum it up for you...it's an amazing, powerful, full-featured software! BUY IT!!!

I've never tried the accelerometer on mine, and I wouldn't know how accurate it is since I haven't run mine on a track yet. The problem with this tool is that its accuracy is killed by the slow samplerate of the OBD-II serial interface, and the Auterra product's "Fast Sampling" feature doesn't seem to work on our Nissan ECUs (on a 4th gen, it won't connect at all, on a 5th gen it'll connect but it'll sample SLOWER)

thanks for the info michaelnyden. i think i will get it now.

spirilis, now im confused, it wont work on my 4th gen? or it will just at the slow rate?

thanks for all the help!

on our 4th gen's the data will update every 0.5-1 second....as opposed to newer cars, which update almost instantly...

Those parameters are way off. A 5th gen weighs 3200-3240lbs so add your weight to that figure. Now for the elevation, you'd probably have to keep the assumed value, unless you find out the elevation of where you do your testing at. For the weather conditions just plug in what the conditions are that day before testing. The drag is correct but the frontal area is off I calculated it at 25.5 sqft.
I too have the auterra dynoscan software plus I have road dyno. The auterra is usually off compared to road dyno but its no less reliable. As long as you use the same specs and account for weather it should produce repeatable results.

I have the Auterra and fast sampling seems to works on my 97. I haven't done any of the dyno features yet but I love the tool. Sprillis, if you open up the disk that came w/ the Auterra there is a folder called "Windows Software", open that up and then use the PDBExport program. It will allow you to save the info into Excel or a similar spreadsheet. It's covered in the users PDF.