ULTM8Z

Not sure if this has been attempted before...

But I generated a mpg calculator using the injector pulse width from the scanner readout, along with vehicle speed and engine rpm. Actually fairly simple math with a bunch of unit conversions.

But it's very accurate compared to the results I get with the standard approach of measuring mpg. I measured ~23 mpg, the calculator says I'm getting 23.49.

I've attached it in the zip file. It needs Excel 2007 or higher to run though.

jakemussman

iTrader: (3)

Pretty cool. Thanks for posting it up.

junkcltr

iTrader: (1)

Why not make it a gauge or something like that in TunerPro?

ULTM8Z

Good idea...

But that's probably going to require someone with some programming skills which I don't have...

Saar

i was hoping you had cracked out an equation that would generate an accurate trip MPG..... the equations i come up with seem to work great for instant MPG calcs, but i've never gotten one to create an accurate trip value, always have significant error in either direction depending on the equation.

ULTM8Z

That wouldn't be at all difficult using a csv output from Tunerpro for a trip.

You'd simply add and formula-rize a column that looked at injector pulse width, engine rpm and vehicle speed. It would calculate an instantaneous mpg at each sample.

Then at the end of the data set, you'd run a mathematical average of all the mpg calcs for a trip average.

Send me a tunerpro .csv output file and I'll generate one.

Yeah for the spreadsheet I originally posted. I used an injector pulse width that corresponded to cruising at 65 mph constant speed on flat ground. Agreed it will not account for variability with acceleration.

Saar

i worked out my own solution a while ago..... but it's a lot more involved than math on just the PC side of things. i was just more interested to see if someone could get an accurate trip value from the existing items sent over the datastream since mine were never quite correct.....

i had to cheat a bit and create some 16-bit accumulator values in the ECM's RAM that figure out distance and fuel used this ignition cycle, then spit that out to the PC to do the final math and keep track of trip distance and fuel used(since i could otherwise have done that division on the ECM side as well and only output 1 16-bit value).

The_Punisher454

do your calcs consider injector performance?

ULTM8Z

Not sure what you mean by injector performance. It accounts for the flow rate (entered in lb/hr by the user).

junkcltr

iTrader: (1)

I tried doing calcs somewhat like this in TunerPro 4.x. I wanted to have one "pseudo" ALDL value that was made up of other real ALDL values. As an example, suppose you want to report MPG. That is a function of (BPW, RPM, Time, VSS). All of which the ECM reports. Granted that the BPW will have to be assumed to be constant over the Time period which it really isn't. It will give an averaging affect.

Does TP 5.x support mult-ALDL variable equations? I couldn't do it TP 4.x from memory.

MPG(INJ_BPW, RPM, ECM_TIME, VSS)

RBob

iTrader: (1)

Check out the $8D mask, it has VSS and injector PW accumulators in the ALDL stream. GM used this info for the trip computer (DIC). Easy to take a look and see how the data was collected on the ECM side.

They are roll over counters, 8-bit for the VSS pulses and 16-bit for the injector pulses.

RBob.

Saar

yes, V5 allows for a LOT of data manipulation that wasn't possible in V4.

maybe i'll do a mini-compare/contrast here....

mine isn't finalized since i never implimented it, just tested the code out to make sure that it works how i was expecting it to(1 mile increments after being held at 60MPH for 60 seconds, etc). now that i look at my code more.... there is at least one change i think i'm going to make since it currently does math based on how much a single injector has flowed. with a 20 gallon maximum value, it would take a multi-port engine a lot longer for increments to happen than what i was planning. a 6 injector engine would now actually be a 120 gallon max value, 8 injectors with 160 gallons..... cuts down on my fuel use resolution pretty significantly.

Cdeez

What do you plug in for injector pulse width? Plugged in 65 lb/hr for injector flow from my setup, not sure about pulse width though

7427 swapped TBI

ULTM8Z

It's the duty cycle.

For example, I got on an open stretch of road and got to steady state cruising speed, then noted the injector duty cycle on the scanner. Should be in milliseconds.

Figured it would be a good representative value for average highway fuel economy.

Cdeez

So you just note your injector base pulse width on the dash in TunerPro and plug that value in to the spreadsheet, correct???

Very cool, thank you for sharing this.

Mangus

Yes, it does. And you can create statics by creating an ADX Value with the static value as the equation (e.g. "25.8"), then reference that static value in the equation of other ADX Values.