A Deep look at Accurate Realtime Fuel Use from Data Logger (Instant MPG)

(Truck is a 2007 RCSB 5.7 4x4 for reference.)

I have spent several months decoding data signals on the CAN bus network of my 2007 Tundra. CAN (Communication Area Network) is simply the coded data communication between the ECUs of the truck. (Engine ECU, Body ECU, Instrument Cluster, Skid Control ECU, Ect.)

One of the biggest benefits of this is that I can now log real time data the ECUs are sending to each other at a VERY fast rate.

I am able to monitor Fuel Consumption (the total amount of fuel injected by the fuel injectors) in real time. The fuel flow is measured in microliters per second and the value is updated 32 times every second. That means we get almost 1900 data samples every minute. Very fast and Very accurate.

Here is about 1 minute worth of data sitting at idle in my driveway. Biggest take away here is at idle in Park the truck is burning right at 1.6 Gallons of Fuel every hour. (The spikes in the beginning of the graph are where I hit the gas and brought the RPM up, obviously this burned fuel at a faster rate)



Ok but what about while driving?
Here is a small data sample as I accelerated up from about 5Mph to a stable 70Mph on the highway. Graphs shown below.

Fuel Usage in Gallons per Hour increases as Speed goes up. More fuel needed to accelerate the truck. You can see shift points where fuel usage dips as we move to a higher gear requiring less Rpm to maintain current Speed. The Spike in Fuel Use at data sample #1700 ish is me flooring it at highway speed briefly. RPM Up = Fuel burn up yet we didn't gain much speed in this short time.

The Speed graph shows a pretty consent growth up to 70 is Mph. Gets closer to 80 near the end.

Using Speed and Fuel Used we can also show instant Mile per Gallon.(MPG) This graph is pretty accurate. The higher speed, with less fuel used equals better miles (distance) per gallon of gas burned. Around data point #1700 when I floored it, MPG drops fast, we are using more gas but didn't gain any speed in that brief time I was on the gas (about 2 Seconds.)

Overall at about 70Mph truck burns around 4.75 Gallons of Gas per Hour meaning we are getting about 14.7 Miles per Gallon (MPG) at highway speed.

 

Amazing!!! Now you can write programs for Super Chargers!!! That are totally custom. Cool info and way nice you did that!!! WOW!!! That is really cool!!

so will you be able to write something that would be useable for individual use???

 

So it would cost me about $5 bucks to idle my truck for an hour at current prices. Or, roughly $1.25 to idle for 15 minutes.

That doesn't seem bad at all to me if it keeps momma warm while I run into the store on a winter day.

However, the MPG display will scare you to death because idling for 15 minutes will destroy the "average MPG" number. Lol.

 

Yes I approximated it at about $0.08 cost per minute of idle while its about $0.25 cost per minute of driving at 70 Mph.

Also correct, Avg. MPG will suffer when you just sit and idle as it is just Total Distance Traveled/Total Fuel Used. You are burning more fuel yet not traveling an distance.

Assume Avg. Mpg is 13.5 and your trip meter is at 500 Miles meaning you have used 37.03 Gallons of gas. Now if you idle for 1 hour you have used 38.6 gal of fuel but still only traveled 500 miles... New Avg Mpg is 12.9 Mph. An hour of idle time got you a 0.6 Mpg Avg drop

 

It’s all part of my digital dash project. I monitor these values in real time on my dashboard.
You can see it here https://www.tundras.com/threads/dig...uld-you-like-to-see-speed-rpm-mpg-ect.100691/

 

I missed that one all together! That would be way nice if you could make something like that as a plug and play!

 

Amazing work. Please sell this!

 

What's your wheel tire setup and final drive ratio?

 

Truck is a 2007 RCSB 4x4 lowered 2/4 (might help somewhat aerodynamically, prob minimal)
Wheels/Tire a set of factory 2018 wheels Tires P275/55-20
Read end ratio 4:30 (Has Tow package)

 

It’s a hobby turned obsession

Almost 6 months worth of reverse engineering signals on the CAN bus to understand what they mean.

But I now have the ability to log a large amount of parameters as I drive. I plan on sharing more in the future.

Here is a quick video I did over the weekend basically controlling the entire instrument cluster from my laptop. Watch with captions to see descriptions of what is happening.

https://youtu.be/kTvmovRE8No

 

Just curious how you’re logging and deciphering this data… are you running a script?
I know there are some data loggers that connect directly to high speed CAN allowing one to read messages at 10-50 msec. But those loggers are $$$$$ (ie. vehicle spy by intrepid controls is $3k+).

 

This is cooler than the other side of the pillow.

 

Yes I essentially built my own data logger that reads the entire CAN bus into a microcontroller. The code in the microcontroller deciphers the messages into something you can understand.

Fuel consumption signal is sent every 32 milliseconds or so. Other signals with higher priority are faster while some are slower. The entire bus operates at 500kbit/sec

 

Wow. This is truly amazing. Thank you for sharing with the community.