About a year or so ago, I realized our NHW11 (2003) had a 30-45 second period between start and when the catalytic converter lit-off that it would run as a power EV. During this time:
- spark severely retarded - probably to increase exhaust gas temperature to heat the Cats.
- HC converter valve closed - speculation not observed, to capture the cold-engine, HC rich fumes since the Cats. are too cold to combust the HCs.
- 0-38 mph, 0.60-0.70 GPH - with gentle accelerator, the car will reach nearly 40 mph at a fixed fuel burn.
- 40-50 MPG at end - when the cats light off, the car will be at a high efficiency MPG.
- +50 MPG, 0.30 GPH in "N" - shifting into "N" drops the fuel consumption but preserves the speed on a slight downgrade or not so bad on a flat.
A similar pattern exists with the ZVW30.
This is a chart showing the effect with my wife's ZVW30:
Today I verified this same window exists in the ZVW30 even at ending speeds above 40 mph. Given normal ZVW30 EV ends at 25 mph, this is interesting.
I observed this behavior in 56 F weather with the ZVW30 but the NHW11 behavior happens at all temperatures.
Bob Wilson
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