ScanGauge II Automative Computer On A Yaris / Fuel Economy

Normally in any car, you'll be able to see how the car is doing by looking at the dashboard. For example, you can see the speed of the car, the engine RPM, the distance travelled and the approximate amount of fuel left. Now, what happens if you wish to know more about how well the car is performing? Is there any way to obtain additional information such as amount and cost of fuel used, horsepower of the engine and other information? Now why would anyone need this information anyway?! In case you're such a person, (I am), the ScanGuage II car computer is the gadget for you! I bought one from Amazon on 29 August and was delivered by vPost on 16 September. It cost US$140 and vPOST charges were around S$24. This is really a fun gadget to have.

Now, you need to make sure that your car supports the OBD2 protocol. According to the documentation, most cars have it, but please confirm this first. There's a port that can be seen around your steering wheel. On a Toyota Yaris, it looks like this. (Click photos to expand.)

This is the cable that's included in the box. It connects the OBD2 port with the ScanGauge.

After you're done with the connection, switch on the car engine and the computer will start to display information. It's updated around once every second. You can see 4 measurements on the screen. It's customisable so you can pick and choose what it displays.

On my device, KPH is 'speed in km/h', FUT is 'fuel in litres used so far on this trip'. 'TFE' is 'average fuel economy on this particular trip, in litres per hundred kilometres'. LPH is 'instantaneous TFE; what's going on now'. Sometimes I swap FUT with CST which is 'cost of fuel used on this trip'. This is very useful when I drive friends around and I need them to pay up for the fuel used. You can become an instant taxi driver this way, great! Unfortunately, my friends invariably refuse to pay when I tell them the fare. They seem to think I'm joking. Usually the cost is around fifty cents or less. Some people are really stingy with their money.

There is also other interesting information such as how long it'll take before the car runs out of petrol.

Usually people who buy this device are part of this 'secret brotherhood' who independently come to the conclusion that they can play a game while driving called 'Save As Much Fuel As Possible Disregarding Reactions From Passengers'. I've played this game ever since I started driving. It's fun and remarkably challenging and engaging. Usually, people look at the typical fuel consumption of their vehicles, say from the US Department of Energy, and try to beat the numbers.

So the numbers say that my Yaris typically does:

• 29 miles per gallon of fuel (8.1 litres per hundred kilometres or 12.33km/l) in the city
• 35 mpg (6.7 l/100km or 14.88km/l) on the expressway. 

Here are some conversions for my benefit. I've used km/litre for the past few years but it seems litres/100km is the new standard that people use.

The standard ways to improve fuel economy include not accelerating too quickly, planning your route so that you hit as few traffic lights as possible (starting a car from a complete stop uses a lot of fuel) and not driving too fast. Of course there are other considerations and the experienced player will be aware of lots more 'tricks' to save fuel. I usually get 13-14km/l and I'm interested in data which will help me answer a few questions. The ScanGauge is useful in that it can provide information that will help disprove some of my assumptions about driving and saving fuel.

Hypothesis: Try to get to 4th gear as soon as possible from a stop even if it involves braking very soon because you want to make a turn.
Busted: Not necessarily. It's very possible to avoid speeding up the car to 4th gear (60km/h) and still use less fuel. The important thing is to maintain a constant lower speed.

Hypothesis: From Wikipedia, 'the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW).' There is a sweet spot that is optimum. This sweet spot is most likely close to the point where the 4th gear engages, which is around 60-70km/h .
Busted: This is a surprising finding. The sweet spot seems to be at much higher speeds than 60km/h. In fact, while maintaining 90-93km./h, it is able to give me 4 to 5 litres/100km, better than what I get at lower speeds!

Hypothesis: The point is to try to reach optimum speeds for fuel economy.
Quite true: But there's more; the point is not only that, it's also to maintain the speed when I can see that the fuel economy is good. Increasing and decreasing speeds use more fuel that if the car is maintained at the same speed.

I'll continue to monitor the readings and see if I can be more certain of my findings. One additional benefit is that the ScanGauge constantly reminds me to be light on my feet, to imagine that I have a balloon between my foot and the accelerator pedal, to break gently, if not at all (by planning when to slow down or not to.) It makes driving more fun because sometimes I use less than 6l/100km of fuel on the expressway and that is way better than the published numbers. So if you're interested in playing the same game and me and irritating the hell out of your passengers, get the ScanGauge II now! :)