How Florence's (Italy) traffic has beaten the Prius...

Hum... surprising.

At such a low speed average, why did the ICE run that much? Heater? Very quick accelerations followed by too powerful braking for the regenerative braking to happen? No gliding at all?

 

Another positive way to see it: you might have asked the other regular petrol-engine car drivers stucked with you in the traffic what their fuel consumption was... If the Prius was at 7,8L/100km, I would not like to see theirs... "Oh mein Gott" would probably be appropriate.

 

This is normal. You never had a chance to recharge the battery, and once the SOC dropped below certain level, the car just creeped forward using ICE as any other car would. You are still better off in a Prius even under these adverse conditions, because at least the ICE does not run when you stand still. In a "normal" car of comparable size, your consumption might be well around 15l/100km in such scenario - I know from my own experience with my previous car.

Prius excells in a light city traffic - you can easily get the advertised mileage when the traffic flows continuously. But traffic jams are MPG killers.

The problem is that the ICE is extremely inefficient when operating under very low loads, such as when creeping forward at the walking pace. I developed my own driving technique for such scenarios.

If you find yourself in such situation, it is effective to force-charge the battery when standing (press the brake firmly and floor the gas pedal at the same time in order to do that) and then creep in the EV mode. once the battery depletes, simply repeat the process. When force-charging, the ICE is working more efficiently than when creeping slowly forwards and the overall efficiency of the process is better, despite inherent efficiency losses due to multiple energy conversion.

The problem is that this technique puts a lot of strain on the traction battery - you load it with extremely high current (very much on its design limit) when force-charging, and than you deplete it back to two pinks. This cannot be good for the battery longevity. That's why I am reluctant to practice this techniqe very often. But I tried it out under such traffic conditions as you describe and achieved better results than when driving "conventionally".

 

BTW, it is very convenient to resist the urge to follow the car in front of you in the usual few-meter creeps. I let him go and let a longer gap (say 15-20m) to develop in front of me, and than I catch him again with one longer leap . This allows me to accelerate very briefly and to glide for the rest of the distance.

 

Yes, I've driven in Bangalore and know the local traffic jams well .

 

Been in Florence and aside from a traffic jam coming up the Amalfi it can get pretty intense there and if you miss your turn well you have to go all the way around and start over. It was the most difficult drive for my daughter when we were there a couple years ago. You just don't get a chance to coast and sooner or later the gas has to come on to charge the engine.

 

Your Prius consumed 3.4L for this trip.

My Subaru would have consumed 4.5L merely for 4 hours of idling (English units, 0.3 gallon/hour). Add at least 5L for the actual stop-and-go movement over that distance, delete about an hour of idling that would be actual moving time, and that still totals to around 8.5L.

The Prius did provide a considerable benefit.

After having been unemployed since before buying the Prius, I finally had a rush hour interview yesterday and a real work commute today. After having watched the Subaru's daily MPG (displayed on a ScanGauge) collapse in heavy traffic last year, it is very nice to see the Prius MPG start climbing once I get into the main traffic jams. Next week I'll start mapping out what happens on the traditional alternate routes.

 

Consider yourself lucky you weren't driving in Naples. If you ever have to go to Naples, keep your Prius home and rent a tank--with its own driver.

 

lol

Why do you think cars have bumpers

 

Well my 2 litre Camry would use more fuel in free flowing traffic. I averaged around 8L/100km at an average speed of around 37km/h across Adelaide using almost every trick to keep consumption low including coasting in neutral with engine idling going down slight inclines, using 5th gear at 60km/h and using 5th gear and engine braking on slightly steeper inclines to engage fuel shut-off. Outside temperature 20 - 25c so no heater or AC. So considering the situation, your Prius did a fine job.

 

This week snowstorm has jammed highways, railways, cities and airports all over the country. It wasn't really that much snow to be honest but we are rarely prepared for emergencies and now that temperatures have risen the traffic has doubled since many have been forced/chosen to postpone their travel. Florence itself was hit by the snowstorm and that's a pretty rare event.
Rome is probabily the real driver's nightmare city as roads are vastely insufficient to handle regular daily traffic, people dislike to take public transportation and the local administration struggles to build new roads or to expand existing ones because anytime you dig a hole some ancient Roman ruin pops up and you are forced by law to turn it into an archeological site.
The worst highway is the Salerno - Reggio Calabria.
Well... welcome back, enjoy your stay!

 

LOL!
And get yourself a hangar if you plan to park it, otherwise you won't find a single screw of your beloved tank. And strangely you'll see children playing with missles, home adorned with metal plates, cannons laying around in the streets...

 

Nothing can relieve the frustration of being in a creeping, traffic jam. However, there is a slow speed range that even in a Prius can be pretty dreadful:

Your 10 km/h would be ~6 mph but definitely on the poor performance side of the "gray" line. What happens is vehicle overhead such as:

• heater and defroster operation - common in rain
• windshield wiper operation - rain
• head and tail lights - rain (US regulations in the South)
• brake and brake light operation - requires accumulator pump
• vehicle ECUs - the Prius has a lot of control units

Hind sight is small comfort but these thoughts come to mind:

1. Use "P" - when immobile, use "Park" so the brake light and accumulator pump do not have to operate. The parking pawl will hold the car stationary. Unlike "N", the engine can run and put a charge on the traction battery.
2. Cycle 'defrost' - minimizes air conditioner usage and load. Some small amounts of fogging on windows may be OK.
3. Use "Rain-X" - an exterior glass treatment, it sheds water so the windshield wipers may not be needed so much.
4. Cycle wipers as needed to minimize use.

It is my hope you'll not have to go through that mess again but I have no doubt that it will. There comes a time when walking makes more sense.

Merry Christmas!

Bob Wilson

 

A euro-Prius gets better efficiency than a usa-Prius? Ours are only rated at 51mpg city / 49mpg hwy, not the claimed 59mpg by the original post...

Also, I saw no mention of your operating conditions for your Prius... having only had mine for a 6 weeks, I have learned that cold temperatures, running the heater, heated seats, etc. will all affect the overall efficiency of your car.

I'll bet that the ICE had to basically run continuously whether moving or standing still in traffic, along with running the heater, and possibly heated seats, that would explain your performance results.

Also, traffic is traffic... whether it's LA with 3M people and thousands of miles of freeways; or Firenze with 500k people and approx 100km of streets.

 

On the very same car, our EPA rating scale produces considerably different (lower) numbers than the Euro and Japanese scales.

 

Is that not because you have a different testing procedure? Also, there is the difference between UK & US gallons (4.5 litres UK - 3.9 litres US).

Apparantly the UK test figures for the Prius indicate we should get over 70mpg on the urban/city test! Yeah right! Maybe in super ideal circumstances, crawling along at 24 mph or similar.