Prius Special Feature
Last Updated: Weds. 5/28/2003
Stealth is a special feature of Prius. It's the ability to drive without the engine running, using only electricity. The result is very smooth movement in total silence. The term "stealth" was coined by owners due to that quietness. This is also sometimes referring to as "stealth mode".
Below are details about how stealth works:
Reduced consumption & emissions is what people associate the word "hybrid" with. Finding out there's also an aspect of electric driving is quite a surprise. Experiencing it is a true delight.
Pure pleasure is what parking lots become when driving a Prius. The slow speeds accommodate stealth wonderfully. With the engine already warm, getting to & from a parking spot without any sound or vibration is effortless. Every press of the accelerator pedal results in a smooth, silent glide.
Stop & Slow Driving
Emissions have been growing as the population continues to grow, because highway congestion worsens. Prius deals with this situation extraordinarily well. When highway speeds slow due to heavy traffic, the engine shuts off. Those with traditional vehicles all continue to waste gas. You just roll along in silence using stored battery power. Stealth carries you along without any waste... or emissions. Short distances, like a river crossing or where traffic merges, can be traversed at city speeds without the need to run the engine.
42 MPH (68 km/h) is the fastest electric-only speed the system is capable of sustaining. Beyond that, the motor provides a boost so the engine doesn't have to work as hard.
Once you begin driving a Prius, you'll find long, flat roads with 30 or 35 MPH (48 or 56 km/h) limits to be your favorite place to drive.
With the engine warmed up and the A/C or Heater on the lowest setting (or off), smooth & silent driving is a pleasure your can invoke by simply releasing pressure on the accelerator pedal just long enough to trigger stealth. The engine will shut off. Then when you apply pressure again on the accelerator pedal, only electricity will be used for power. When you encounter a hill along the way, try to accelerate lightly. If the engine starts back up again, don't worry. It will shut back off quickly afterward you reach the top.
1/2 mile (0.8 km) stretches are what you'll find most common for stealth cruising, since it's hard driving further than that without encountering a stop or some sort or a hill in the city. And after a few of those stretches, the engine will start back up to recharge the battery-pack. Doing that avoids deep discharges, which shorten the life of the battery-pack. Losing stealth temporarily is disappointing. Thank goodness it only take a few minutes of +45 MPH (+72 km/h) driving to replenish the charge enough to return to stealth again.
You can accelerate from a stop using only the electricity, but that isn't the most efficient method. Taking advantage of the engine helps save gas overall. Stepping on the accelerator pedal generously will cause the engine to quickly startup and rev to an optimum full-power RPM. That will turn the wheels and the generator providing thrust for the wheels and electricity for the motor.
Technically, anywhere from 6 to 10 miles (9.6 to 16 km) driving solely on electricity is possible, but it's a very, very BAD thing to do. (Fortunately, the only way that's even possible if you run out of gas.) Deeply discharging the battery-pack will shorten its life, that's why the system goes out of its way to recharge even though electricity is still available. Many, many years after the purchase of your Prius, you'll be quite pleased that the battery-pack was protected from stress for you automatically.
Prius will allow you to drive 1/2 mile (0.8 km) stretches in stealth routinely. In fact, you'll find there's sometimes enough electricity available to use stealth several times during a long trip (like on a typical commute to work).
When driving at speeds faster than 42 MPH (68 km/h) with excess momentum propelling the car (like when you gain speed going down a hill), the engine will continue to pump the pistons; however, fuel won't always be supplied. This avoided waste increases overall MPG. Owners have dubbed this condition: "Warp Stealth"