Driving tips to reduce fuel consumption

[kellsworthington]

Browsing Wikipedia.com, I noticed they had a nice entry for the Toyota Prius. You can see it here
http://en.wikipedia.org/wiki/Toyota_Prius

It lists how the car works, etc.

But the interesting thing is listed when you scroll down some, it lists some ways to reduce fuel consumption. I read this before I had the Prius, but now that I own one, it all makes perfect sense. Some are common sense, others are some I never thought of. Check it out.

Driving tricks to reduce fuel consumption

Stop shutdown

(Transmission mode in B, speed zero)

Often you will pull up at a stop light that has just changed. In some suburban areas this may entail a wait of several minutes, as the lights cycle through various simultaneous or sequential left turns, cross traffic, pedestrians, etc. If the gasoline engine is running when you approached the stop it will take the better part of a minute before the computer recognizes the situation and shuts off the engine. There is a trick to getting the engine to shut off promptly. If you approached the stop in B (engine assist braking), you may then when stopped with the brake on, command D (drive) - the engine will stop immediately - at least in 2004 US versions.

Off throttle shift to electric mode

(Transmission mode in D, cruising speed up to 45 mph (70 km/h), road level.)

When reaching cruising speed it is often possible to briefly go "off throttle", allowing the system to switch to electric only mode. If the road is nearly level a gentle re-application of throttle to just enough to maintain cruising speed in electric mode may enable electric cruising (depending upon road grade, wind conditions, and battery state).

Accelerate from stop to 35 to 45 mph (60 to 70 km/h)

(Transmission mode in D, cruising speed up to 45 mph (70 km/h), road level.)

When running in traffic, a brisk (but not full throttle) acceleration, followed by an off throttle attempt (see previous) will be much more effective than gentle acceleration. This is a general technique applicable to non-hybrid cars. A gasoline ICE engine is more efficient (in terms of power produced/fuel consumption) when operating at higher effort due to smaller throttle losses. This is less important for compression-ignition engines, which do not have throttles but are instead regulated by the amount of fuel provided directly to the cylinder.

Accelerate with no traffic to 25 mph (40 km/h)

Transmission mode in D, cruising speed up to 25 mph (40 km/h), road level.

With substantial patience it is possible to accelerate to cruising speed using only electric power. Owing to the slow acceleration this should not be attempted with following traffic present. Although this will temporarily reduce fuel consumption since you're driving in electric mode, it will not improve the long term fuel consumption, since you have to recharge the battery at some point later (and the generation and use of electricity involve energy conversion losses). As pointed out above, it is better to accelerate at a moderate pace.

Long uphill followed by long downhill

(Transmission mode in D, cruising speed uphill to 65 mph (105 km/h), road uphill, followed by downhill at or below 50 mph (80 km/h) with transmission mode in B.)

The controller is blind to the future; it cannot tell that it would make sense to run the battery down on a long upgrade knowing that it can be quickly recharged on a subsequent downgrade. Nor is it possible for the driver to inform the system that this condition is coming. What happens is that the system will use the engine power when going uphill to charge the battery to normal state. Then, running down hill (with "B" selected) the battery is quickly charged to the maximum before the bottom of the hill. This full charge (battery state shown in green) will then cause the system to use the motor for compressive braking. It would be far more efficient to be able to use the battery capability to assist the motor (rather than taking charge from the motor). A run up the hill at sufficient throttle to demand electric motor assist (within speed limits, both statutory and by road and traffic conditions) may improve overall efficiency in this particular circumstance.

Downhill run

When using "B" on a long (1 to 2 km) downhill (e.g. over 60 mph, 100 km/h) you may find at higher speeds that the motor is used for braking in addition to the power recovery from the generator. Unless the battery is fully charged (showing green on the monitor), this is wasting excess energy which could be stored. By briefly braking to a somewhat slower speed, say 45 to 50 mph (70 to 80 km/h), the motor will not be used to retard the vehicle, all subsequent retarding energy will go to the battery, and a longer time will be spent recovering energy, and so more energy will be recovered. This is less useful on a long mountain downgrade where the battery will become fully charged regardless of the technique used,.

Gentle rise and descent

A small amount of additional throttle will accelerate the vehicle before the rise is reached and this additional power may be maintained on most of the upgrade. Reducing throttle and paying off the excess speed before the top is reached may enable electric cruise to be entered, with energy recovery on the downgrade. Reapply cruising throttle at the bottom of the hill when reduction to normal cruise speed is obtained.

Slow steady speed

When traveling on relatively flat surfaces at approx 0 to 25 km/h (15 mph), sometimes the engine will run seemingly unnecessarily. By applying the brakes it tells the car to regenerate and is usually enough to shut it down. Sometimes it is necessary to come to a complete stop. At speeds that low, there is no real need for the gas engine. Alternatively, in the US one could re-enable the EV-Mode Button which is standard in EU and JP Prii, this feature allows the driver to request that the engine not start durring times when it may not be needed.

[rogerSC]

I'm a great believer in not doing a lot when driving, other than keeping an eye on the mpg and appropriately feathering the gas pedal when possible, anticipating lights, stop signs, and other slow downs, and not accelrating too rapidly or driving real fast on the freeway.

My gas mileage is currently over 50mpg for my work commute, and I'm happy with that.

Also, the ICE in my car stops after just a few seconds at a light or stop sign. I've come to the conclusion that my car is smarter than me, and I try to help it when I can, but basically let it do it's thing.

-Roger

[electronics_scrounger]

Draft on folks! It works for Lance Armstrong!

[bruceha_2000]

Originally posted by rogerSC@Oct 12 2005, 06:40 PM
Also, the ICE in my car stops after just a few seconds at a light or stop sign.  I've come to the conclusion that my car is smarter than me, and I try to help it when I can, but basically let it do it's thing.

It depends on the ambient and engine temp. This summer, my Prius shut down very quickly at stops but when the weather gets cold again, I expect it to return to the "I'm still thinking about it" mode where it can, in fact, take a minute or more, if at all. With the heat on, the ICE will not shut down at stops on the winter.

[Tideland Prius]

Yeah, I'm already having the "engine run at red light to keep warm". I had to shut of the climate control to get the engine to turn off. I've only set it at 22°C.