Accurately Measure MPG in Your Vehicle- $9 of parts and an old laptop

2. Locate your VSS signal and run a wire from it to the circuit and then to the Left Audio input

3. Locate an injector and run a wire from one of its signal wires to the circuit and then to the Right Audio input

4. Run a wire from the vehicle’s ground to the audio cable’s ground wire, as close to the injector and VSS connections
as possible (reduces noise on the signal)

5. Plug the audio cable into yourlaptop, and make sure you have a sound recording program (Windows comes with one if you don’t already have one)

6. Download and install the -MPG program- (also update your Java software if needed)

How to Run It:

Screen shot of the program running. Top left is the Properties File, top right is the folder with the files that make up the MPG program, middle is the readout, and the bottom is the raw feed. Note this is not connected to a vehicle, so the numbers are crazy… I wish my truck went 7,684 MPH and got infinite MPG!

1. Drive your vehicle at a constant speed for a determined distance (such as 60 MPH for 23.4 miles). Start and stop the audio recording during this interval. If you are not one of those talented people who can text on their phone, load a mag, re-organize the back seat, feed CD’s into the player, etc. while you drive, you might get an assistant to run the laptop.

2. Head back to the shop, and this time run the recorded audio file of your drive along with the MPG program. Basically you are feeding the info into the MPG program for analysis (change the properties file to point to your saved audio file).

3. Change the properties file as needed to compensate the distance traveled (compare to your odometer) and your speed reading (compared to the constant speed you were traveling). A tiny bit of math gets you calibrated for distance traveled.

4. Next you have to calibrate for fuel used. If you happen to have injector data, you can probably get there with some calculations, but most will probably not have this. Instead use the partial tank fill up method (use part of a tank of gas
while recording, then fill up noting how much gas was used). Change your fuel fudge factor in the properties file until it is correctly telling you fuel used.

5. Now that you are calibrated, you can feed the injector/VSS signals directly into the MPG program for real time data.

It’s easier than it looks, but if you get stuck, post a question here and the Build Team will get you on the right track.

Also, let us know how your build goes, or if you learned any cool new tricks to share with the group.

I’ll assume you have already gotten the Water4Gas conversion manual and hopefully are close to testing it with your new MPG software. The combination of these two simple but effective technologies can save you thousands of dollars… plus you won’t have to drive a tiny econo-box around town. If you haven’t, check it out here: Water4Gas.

I’ll talk to you soon,

* Notes on VSS (vehicle speed sensor):
The VSS is used to measure vehicle speed. It’s done differently on different vehicles, but it’s usually based on the rotation of some drive train part. If you have a manual you can usually find where this sensor is, and tap into a wire to get a good signal. It’s not to hard to make one also, just put a magnet on the driveshaft and a pickup sensor to count
rotations. You can easily calculate how many rotations equal a given distance. From there you can change the distance fudge number in the mpg properties file. Post a question if you need more detail.

** MPG software was originally posted by skewbe on gassavers.org. GasSaverGarage and GasSaverGarageBlog are
not affiliated with gassavers.org, but have tons of respect for their site, and skewbe for a great concept toward the MPG technology.

- Water4Gas Conversion -