diy mpg gauge

[curjones]

Was the name Audacity. That is what I pulled from the link you gave. Once you load the program are they using java to program to get the wave form. I know nothing about programing. I saw he had a bunch of language on a scroll down. I have seen other devices that you can hook up to the computer but they are expensive.

[curjones]

This site had some basic inf0. I believe the people here Have found a way to use a sound card and cut some cost.

http://www.aldlcable.com/

I have not got to read every thing but it looks like it has some really great info.. What do yall thiink. Think Ill make it a new thread.

[theholycow]

Audacity is a great audio editor, and was used in the link I gave you to view the waveforms...but it's not made for hooking up to fuel injection, it's just for audio. It can't do the calculations we need.

Where did you see the computer language? All I saw was a schematic for fuel injectors.

[sonyhome]

I'm too lazy to search though the forom or even this thread, but the MPG monitor was published on the forum both as a java binary and with the source code in case someone wants to edit it.
The source code is not needed to run the app.
just D/l the binary and run it.

The waev editor is just for kicks to look at the audio file.

The collection is done via the stereo microphone input of a PC/PDA or anything running java. One side collects Vss (speed sensor) and the other collects the fuel injector signal. From both you compute MPG.

Vss is a pulse AFAIK, so from its frequency you compute speed (but gotta calibrate it). FI signal is a on/off signal so ignore frequency, but compute duty cycle (how long on vs total of a cycle).

[theholycow]

Oh....it's this thread! Hahahah, I didn't even look back at earlier pages in the thread...d'oh!

There's some good stuff on the first couple pages!

This one has the compiled binary program:
http://www.gassavers.org/showpost.ph...6&postcount=43

Thanks, sonyhome!

[GasSavers_Lurch]

ummm, is this device you guys are building just for detecting the mpg??
if so its getting very complex. I like the soldered mass of diodes and resistors though. just have to wonder if he burnt himself

[itjstagame]

Wow this brings back memories. I can't believe it was over a year ago I was planning to do this and did nothing. I need to see where I put those diodes I bought or buy more. For some reason this time the circuit doesn't look as confusing or maybe I just want to jump in and test it more.

As for program, it's Java for now. Sony did you or anyone else ever use a graphics library and make anything cool? I saw a different thread in Holy Cow's thread but didn't see what code he was using.

The big thing holding me back was having no idea where my VSS signal is. I looked under the car, by the tranny and have no idea. Holy Cow you have a similar vehicle (fullsize chevy P/U), do you have any idea where VSS is or the lines run up from the tranny?

After that I need to reread the code, I remember making a lot of changes so I could calibrate easier and tell me fuel vs. acceleration and trying to build a way to automate cid calculation (but couldn't figure out how to solve the entire curve so that was a messy cludge).

[itjstagame]

Man, why did I take a year to do this, it's so easy. I found and tapped the wire and soldered the diodes up easy. I was worried since the only diodes I could find at Rad Shack said 50v, but they clamp it to .7V. I wired up and described and as MPGMetro did and I tested before I hooked to my laptop. We're producing a cycle wave so I just set my multimeter on AC and tested the voltage. Worked great and I definately had just the inside tip giving a reading and nothing hooked to the other side yet (haven't looked for VSS yet).

I made a sample recording though and I have two channels of data. Maybe my laptop just has a mono microphone jack? It doesn't have a line in like my old laptop used to, just mic.

Now I understand the fudge factors, but what are the vssthreshold and injthreshold for? Attached is a shot of my 1st record. It idled for a while (the left side) and this is a shot of right when I hit the accelerator a bit. .7V is pretty low Db, so does this mean I should lower my inj threshold a bit compared to your car?

Also whenever I start the program with no audio hooked up (and configed to not use a test wav) it keeps displaying random numbers for a while. Sometimes the whole time I'm in the program (10+ mins) and other times it'll stop after a couple mins. Does this happen to you too and any ideas?

Also I've been adding to this program like crazy. I still don't have a good way to calculate the Cid, but I have entrants for Cid, air temp, elevation, car weight and frontal area and I've added current acceleration and HP to the displays. My HP isn't quite right though, I found a good calculation for acceleration times car weight (/ by 32ft/sec^2 to get mass), but I want to add this to a drag calculation http://en.wikipedia.org/wiki/Drag_(physics). My thought being, if I'm holding at 45MPH I don't want it to say 0HP, this way it'd show the HP required for that speed due to drag and also show HP as I accelerate. Once I get this down good I want HP/gal. That way I can finally test if slowly accelerating to 45MPH is better than hot footing it to 45MPH, it should show my best efficiency of the engine (most power for gallon of gas).

So if anyone can decipher that drag calc let me know. My accerlation HP is all in ftlb/min which is standard HP measurement. But when I try even simple examples on paper with the drag calc using either ft, lb or metric I always get very large numbers and I'm not sure what the units are, certainly not HP or watts.

I'll post the code update when I'm done, but it's already been over a year and requires more debugging so who knows when .

[itjstagame]

Originally Posted by Lurch

ummm, is this device you guys are building just for detecting the mpg??
if so its getting very complex. I like the soldered mass of diodes and resistors though. just have to wonder if he burnt himself

How can you say it's complex? 2 diodes and a resistor hooked to an injector ( I just did this up in 20 mins or so) and the software works fine out of the box, I'm just adding more stuff I'd like to see. It's a simple java program that reads the injector cycles from the audio input and based on this you can approximate fuel (once you tune the fudge factor).

[itjstagame]

Ha, I was adding RPMs are 2 * injector firings / min, which makes sense because with 1 injector per cylinder each injectors gets fired every camshaft revolution, that is every 2 crank revolutions.

I just found out my TBI actually injects once for each cylinder firing! So 4 times per crankshaft revolution and 8 times per camshaft rev. Cool!