Disappointing fuel consumption

Patrick:

That's how an Air Canada Boeing 767 Flight 143 ran out of fuel over Red Lake, Ontario, while at cruising altitude. They were on their way from Montreal to Edmonton but the fuel totalizer and indicating system was inoperative. Unbelievably, Air Canada allowed the flight to leave with no working fuel indication.

Not only did they have to convert to litres, they also had to work out the conversion from U.S. gallons to Imperial Gallons first. Yes, the ground crew made a serious conversion error and put in less than half the required fuel.

So at 41,000 ft the tanks were sucked dry. Once both engines flamed out, all the screens went blank so the crew had to pretend they had gone back in time more than 50 years. The Ram Air Turbine provided minimal hydraulic boost to operate the flight surfaces and some standby instruments.

They thought they could glide all the way to Winnipeg but it was apparent given their sink rate they couldn't, with the alternative to set down in a potato field or along the Trans Canada. So they diverted to an abandoned air base at Gimli.

The front gear failed to lock down, so on landing the front gear partially retracted and the plane slid on its belly before stopping. Amazingly, only minor injuries, all of them from using the slides.

They were able to repair the Boeing enough to fly it out 2 days later to Winnipeg for more repair of the nose skin and front gear. Yes, they topped off the tanks before flying it.

 

Of course keep in mind the distinction between fuel economy (litres per km) and range (km between fillups). The Prius fuel tank with its internal bladder has become famous for holding noticeably less than the stated capacity, and trying to force in more than it wants to hold just results in spillage. I rarely get in more than 8.5 gallons at a fill.

Definitely check your tire air pressure anytime the ambient temp changes by more than about 10F or 5 C. 42/40 PSI front/rear works well for me (what th' heck is that in kiloPascals?).

 

Richard:

I noticed my fuel economy started going up especially with over 8,000km on the car. So a "break-in" really is needed.

I'm not sure if you would "gain" that much by pumping the tires up to 42F/40R for primarily city driving at 70 km/h or slower. I tried that setting for a couple of weeks with no noticeable difference in city commuting fuel economy.

On the Trans Canada at 100-110 km/h - similar road, temp, and wind conditions - the higher pressure returned 5.1 litres per 100km vs 5.3 at the recommended pressure. That's a difference of 2 miles per Imperial gallon, not worth the much harsher ride.

As far as tire pressure in kPa, I don't think anybody around here uses it. Some things like psi are impossible to get rid off.

 

That would be 289.58/275.79 kiloPascals

arubinst

 

Question:

I have noticed that when I change between kilometer and miles per hour, the corresponding Energy Monitor and Consumption screens do not change from MPG to L/100km. Are the Prii in metric countries set for L/100km? Is there a way for us to switch between the two units of measurement?
.

 

Patrick:

That would almost make sense to also change the MFD between MPG and l/100km.

The only tricky part is ... is that MPG with U.S. gallons or MPG with Imperial gallons?

Most countries that have adopted the metric system used to use the Imperial units for volume. FYI one U.S. gallon is about 3.78 litres, and one Imperial gallon is about 4.54 litres.

Since MPH is always MPH, and km/h is always km/h, it's easy to provide the button to switch between the two.

I drive enough between Canada and the U.S. to make this a God send. Have you ever tried to read the tiny inner scale on an analog speedo?

Impossible if you're near-sighted with driving glasses on. The Prius display is nice and large, just for blind b******** like me!

Of course, if you move (Canada to the U.S. or vice versa) then the THHT can be used to change the primary display.

 

Well, first of all, I hope we hear from you either way. Nice to see more Canadian PriusChat members.

Going into this winter, I only had around 2,000km on the car. If you've paid attention to the national weather forecasts, Winnipeg has been brutally cold this winter, with -40 temps for long stretches.

I still think city driving is the best way to break-in a motor (Always varied speeds), and this winter was a good way to practice stop and go driving. My MFD average fuel economy went from 10 to around 7 under similar conditions as I put on over 5,000km.

We haven't been as cold lately, usually -20 C for a low, -3 C for a high. On my normal commute when the temps reached +8 C, the MFD claimed an average of 4.5 to 4.8. This is with 8,600km on the car.

So things will improve. Just hang in there.

 

Actually, it reads "0" once you're stopped.

It's quite likely, though, that it will read 99.9 as you coast to a stop, but when you stop moving, it stays at 0, whether the ICE is running or not.

But in metric terms of fuel consumption (cL/km), if you are not moving and the ICE is on, your fuel consumption becomes infinite. It really should NOT show zero in that instance.

If anything it should show a DIVBYZERO error.
;-)

 

Bach on the CD player is nice. Otherwise, just relax - the Prius won't let you drain the battery. If it senses the charge getting low, it will turn on the ICE and goose it for a couple of minutes.

 

I noticed that while the car was coasting to a stop, and I thought "wow 99 MPG." I was more impressed with the test drive in SLC than with staring at the MFD - that's a good way to rear-end somebody.

With the l/100km display, when you come to a full stop and the ICE shuts down, the display will read 0 l/100km. The ICE is off, you're not burning any fuel, so you are consuming 0 litres of fuel.

However, if you come to a full stop at -40, and the ICE must continue running, the MFD will indicate 99.9 l/100km. As long as you're at a full stop, with the ICE running, it will indicate 99.9. Once you start moving it will settle down to a more "normal" level of 7-9 l/100km.

Remember: with the MFD displaying l/100km, "less is better."

 

aikidojoe,
I'm in Ontario, and it has not been nearly as cold as Jayman's -40. However, the yellow snowflake of doom has been on since October and has not shut off yet. It is consistently between -10 and 0 here. My mileage is also in the 8-10 L/100 km range due to the temps and my quite short commute. Basically, the ICE never has a chance to shut off. When I coast up to a stop sign and come to a complete stop, the MFD reads 99.9L/100 km (as discussed above) because the engine is trying to warm itself and I am trying to arm myself (with the heater). When spring/summer/fall comes and you can cruise with the windows down and no ac or heater needed, then you will see 3-5 L /100km. It is a guarantee. Please be patient. Nice to see another canadian Prius.

 

I actually take a somewhat longer route to avoid downtown congestion, though it takes the same time. I use *less* fuel driving further!

Around 17km at 60-70 km/h consistently, only 3 lights. Very easy to coast and feather the pedal. Sometimes the MFD will claim 3 L/100km!

I suppose I have ideal conditions then wrt commute speed.

If more inch-n-stop is involved, 5-6 L/100km is the best I can hope for in moderate temps. At closer to -40, 7-9 L/100km if a lot of inch-n-stop.