Quote:
Originally Posted by JethroBodine
. . . I don't have a hybrid(yet), . . .
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The Prius plays a trick that non-hybrids would have little chance of following. When the ICE runs, it operates at a higher power level than the vehicle needs and banks the excess power in the traction battery:
- dilutes ICE mechanical overhead to insignificance - at 25-26 mph, the car only needs ~8-10 hp and the engine mechanical overhead is about 2 hp. So an ordinary car would need to generate an extra 2 hp to handle the mechanical overhead.
- the Prius engine generates 3x power, closer to 24-30 hp yet the same mechanical drag because the ICE rpm barely increased. So only 26-32 hp is generated but the 16-20 hp is banked in the traction battery.
- turn off the engine to use stored traction energy - so when the car has enough banked energy, the engine goes off and the car uses the stored battery energy to sustain motion. No more mechanical overhead from the ICE.
- the round-trip charge-discharge overhead << engine mechanical overhead
An ordinary gas engine vehicle can be turned off but if more power is generated than needed, the vehicle accelerates into higher drag regions. In effect, the aerodynamic and stirring losses increase because of the higher speed with an ordinary vehicle. The hybrid does not increase the speed since it uses cruise control and banks the extra energy in the traction battery.
During the stunt, I had a lot of time to stare at the Scangauge II fuel consumption:
- ~0.02 - engine off, fuel burn, use of 0.02 gal/hr avoid divide by zero risk. The engine shuts off automatically under hybrid control laws.
- ~0.20 gal/hr - engine idle, no load, minimum fuel burn, which does not happen in ordinary operation. The hybrid laws turn the engine off and uses the traction battery or potential energy to maintain kinetic energy (i.e., speed.)
- Shifting into "N" with the engine off lets the potential energy maintain or even let the least increase in speed while preserving traction battery charge from the earlier engine run. When the speed decreases to the cruise control speed, shifting into "D" and "resume" lets the traction battery preserve kinetic energy until the engine is needed.
- ~0.60 gal/hr - hybrid mode, lowest engine power level. Depending upon the vehicle drag load, any excess power is banked in the traction battery.
- ~1.20 gal/hr - hybrid mode, highest engine power level. Typically seen climbing a grade at 26-27 mph. Yet excess power is banked in the traction battery so the engine overhead has faded into insignificance.
When the engine runs, the control laws bank energy in the traction battery and potential energy as the car climbs gentile grades. But as soon as there is enough traction battery and/or potential energy, the ICE is off, the engine mechanical drag goes away yet the car preserves its kinetic energy at a low drag speed range.
Still, you are welcome to the effort. I found it a long and boring waste of time. I already knew I could achieve any indicated MPG over any arbitrary distance. Going a 1,000 miles was just validation.
GOOD LUCK!
Bob Wilson