Dyno Maths Library

[FWombat]

All right everybody, I've created a Maths library for AEMLog that will create dyno-style HP and Torque curves.  All you have to do is open the library, run the calcs, and HP and Torque will be data channels that you can overlay on your Log windows.  Very cool stuff.  It includes corrections for rollling and aerodynamic loss.  I did some testing against another dynoing device, and the results were very accurate. 

The only requirement is that you have Engine Speed as one of the channels in your log.  The filtering in the library is optimized for Engine Speed being logged at the maximum possible rate (250 times/sec), but it should still work with lower sampling rates.  For max accuracy, the highest sampling rate is recommended.

You'll get the most useful information if you do a long, straight pull on flat ground from low RPM's to redline.  This library can only calculate HP/Tq for one gear, so make sure you put in the gear you want to use.  Again, the area you pull in must be straight and flat. 

At the top of the library are a number of car-specific variables.  Right now they're set up for my car (6-speed VR-4 in 2nd gear).  After you open the library, you'll need to enter some information about your car.  Change the first value in the following equations.

WHEEL_SIZE:  Wheel size, in inches.  In 245/45 17, this is the 17.
TIRE_WIDTH:  Tire width, in mm.  In 245/45 17, this is the 245.
TIRE_ASPECT:  Tire aspect ratio.  In 245/45 17, this is the 45.
GEAR_RATIO:  Gear ratio of the gear you're doing pulls in.
DRIVE_RATIO:  Final drive ratio of your car.
CD_DRAG:  Coefficient of drag for your car. 
CD_AREA:  Frontal area of your car, in square feet.
WEIGHT:  Weight of your car, in pounds.

In each of these equations, make sure the "+ _ZERO" remains after the number you enter.  You can see how I did it for my car when you first open the library.  The WEIGHT is particularly important to get accurate; I'd suggest going to a truck scales and weighing your car with you in it.

Once the Library is calculated, you're going to see a ton of new data channels.  Most of these are for internal calculations, and can be ignored.  The ones you care about are:

_Wheel_HP:  Horsepower at the wheels, corrected for aero drag and rolling loss.
_Wheel_Torque:  Torque (in ft*lb) at the wheels, corrected for aero drag and rolling loss.

Give it a try.  Let me know how it works for you.  I haven't had a chance to try this on any other cars, so if you're willing please post a log of a pull in your car, and give me the values I listed above so I can see if the filters need any tweaking

Oh, and please treat this like Freeware.  You can give it to anyone to use, just give me credit for creating it. 

Have fun!

- Brian

http://ErichMoraga.com/Eclipse/AEM/3rdgear.mth

[FWombat]

I tried it and it says "No Equations Have Been Created"...

Did you import the Library?  Do this:

1) Open up the Log file in AEMLog.
2) Maths -> Open Library
3) Select the FWombat_Dyno_Library.mth
4) The List of equations will come up.  Enter the necessary values as I mentioned in the previous post.
5) Click Close
6) Maths -> Recalculate
7) Select All, then click OK
8) You'll see a little progress bar calculating the equations.
9) Right click on your log graph and Select Overlays, and select _Wheel_HP and_Wheel_Torque.


Note on editing the equations:[/i]  The Equation editor is... well... buggy.  There's no other way to say it.  When editing the constants to put in the values for your car, DO NOT USE THE BACKSPACE KEY!!!  I found that this often triggers incorrect edits.  Also, do not click the cursor to the middle of the equation.  Click at the beginning to put the cursor there, and then use ONLY the left and right keys to move the cursor.  Use the ONLY the delete key to delete.  

Even with these tips, sometimes equations get mangled by the editor.  When you close the equation, look at it on the list to make sure it's still what you're expecting.  If it's not, edit it again.

- Brian

[TDtrader]

Nope, I still come up with "no equations" upon opening the library.  
Tried this on 2 computers now, one running w2k, one running xp pro...<sigh>

[BLKMGK]

Looks to be working for me too but I need to edit the fixed values for my car. Just had to open, set it to calc on read, close my current log, and reopen. Once reopened I went to the menu and told it to calc, then added the values as an overlay. Now I just need a good log Have to hunt around for my dyno logs to do some comparison!

[eslai]

Hehehe, I must've screwed something up, because it's telling me I only make 141.5 horses in third gear.

I don't know what my frontal area is though (2G DSM) so I left it with your 3000GT settings.  Maybe I screwed up a gear ratio or something, because second gear seems to have a more appropriate number of 268.3.

Thanks for the math!!

[FWombat]

Hehehe, I must've screwed something up, because it's telling me I only make 141.5 horses in third gear.

Note that it will only give accurate numbers for the gear you enter at the top.  So, if you enter the gear ratio for 2nd gear, only 2nd gear pulls will give you accurate number.  1st gear will read high, and 3rd and up will read low.  

Use the ratios for whatever gear you can do a pull from low RPMs (1500ish) to redline in.  For me with all-wheel-drive, 2nd gear works well.  For you 2 wheel drive guys, you may have to use 3rd so you can get traction.  

- Brian

[RCABACCANG]

Hey FWombat, you have something great going - good thinking guy .
I just down loaded it to my AEMLog. I will try it next week and test on 3rd gear.
I will let my friend know about your dyno log. But ever impressive work....
two thumps up .

susgestion: how about using a wheel speed sensor so that no tire calibration is needed. I think that's what the dyno uses.
I use to work at shop with a dyn. My theory what the dyno uses to meassure hp/tq. engine speed (amp probe on #1 for rmp reading) and wheel speed (dyno rollers). man if that's the case, with a wide band and your set up using a wheel sensor to meassure wheel speed and using engine speed for load - don't need to pay for dyno session anymore.

what do you think? this may work right EMS that does dyno as well...

[RCABACCANG]

hey could not wait, I down the street and tried it
set the wheel at 15+/- 0 : 205+/-0 :55+/-0
weight at 2900+/-0

hp reading 50

I think I did something wrong - would like to learn more about this set up   .

[eslai]

Note that it will only give accurate numbers for the gear you enter at the top.  So, if you enter the gear ratio for 2nd gear, only 2nd gear pulls will give you accurate number.  1st gear will read high, and 3rd and up will read low.  

Yeah, I entered in third gear then displayed one of my existing log files.  Second gear looked like it had the right output, third gear was way low.  Does it get confused if the logfile contains more than one gear pull?  This file was from a standing start through third gear.

[FWombat]

Hey FWombat, you have something great going - good thinking guy

Thanks.  

susgestion: how about using a wheel speed sensor so that no tire calibration is needed. I think that's what the dyno uses.
I use to work at shop with a dyn. My theory what the dyno uses to meassure hp/tq. engine speed (amp probe on #1 for rmp reading) and wheel speed (dyno rollers). man if that's the case, with a wide band and your set up using a wheel sensor to meassure wheel speed and using engine speed for load - don't need to pay for dyno session anymore.

what do you think? this may work right EMS that does dyno as well...

I tried the wheel speed sensor, but found that the output was too course.  The RPM (Engine Speed) signal gives much better resolution and is more accurate, so I base all of my calculations off of that.  Configuring wheel size isn't too hard, right?  Just three numbers.  

The calculations I wrote work exactly the same way as a roller dyno.  Dynos have to do these same types of calculations to calculate torque and horsepower.  The only difference is that they use the weight of the rollers for load, and I use the weight of you and your car for load.  The fundamental math is the same.  

- Brian

[FWombat]

Note that it will only give accurate numbers for the gear you enter at the top.  So, if you enter the gear ratio for 2nd gear, only 2nd gear pulls will give you accurate number.  1st gear will read high, and 3rd and up will read low.  

Yeah, I entered in third gear then displayed one of my existing log files.  Second gear looked like it had the right output, third gear was way low.  Does it get confused if the logfile contains more than one gear pull?  This file was from a standing start through third gear.

The maths won't get confused by pulls of other gears in the same log.  They'll just display accurate numbers for the gear ratios you entered at the top.  It's REALLY important to get those gear ratios correct.  I found mine by searching on the web.  Maybe you guys with other cars can search, and post the gear ratios for other people to use?

Here's a page with the gear ratios for all DSMs:  http://www.vfaq.com/mods/Trannies.html

Looks like for your car (I'm assuming you're AWD) in second gear, it should be:
GEAR_RATIO:  1.684
DRIVE_RATIO:  4.929

[eslai]

Yeah, I'm actually 2G FWD and used the values from that page.  Was trying to use third gear and it came out with that super-low number.  I'll try fussing with it again later.  I might have the weight a bit low too. Thanks!

[TDtrader]

Still no good.  FWombat, any chance you could post the equations you used and I could try plugging them in myself?

[FWombat]

For those of you having trouble getting number in the ball park of what you expect, here's how you can verify that you have your gear ratios correct:

How to verify Gear Ratios:[/i]  Make Vehicle Speed one of the parameters you log.  One of the internal calculations of the library is Vehicle_Speed_MPH.  If you have your gear ratios entered correctly, Vehicle Speed (from the AEM) and Vehicle_Speed_MPH (from my library) should be within +/- 1MPH.

- Brian

[FWombat]

Still no good.  FWombat, any chance you could post the equations you used and I could try plugging them in myself?

To be honest, I'd rather not; it's quite a bit of typing.  

What version of AEM Log are you using?  I'm running the latest; 3.06.  Try downloading the file again.  Also, try opening the file in Notepad.  It'll look like a lot of gibberish, but if it's empty that would explain the problem.   The library should be 6K in size.

- Brian