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Questions from A.C. Propulsion about Hybrids

1080 Views 1 Reply 2 Participants Last post by  james

Hybrid Vehicles

What is the mpg at sustained 70 mph? A big advantage of hybrid-drive vehicles is the ability to recapture driving energy through regenerative braking. This has a big effect in urban driving, but only a minor effect on the highway. A public aware of the 80 mpg promises of PNGV, or the 3L/100 km objectives of some European vehicle projects, or even the 66 - 70 mpg claims for Japanese hybrid vehicles, may be disappointed at the actual highway fuel economy of hybrid vehicles which are likely to be in the 35 to 45 mpg range.

What speed can be sustained up a 6% grade? For how many miles? For example, can the hybrid sustain speed up the Grapevine Grade on Interstate 5? Extended hill climbing requires a good balance between non-fuel energy storage (battery) and the power of the onboard engine. The smaller the battery, the larger the engine required to make the Grapevine climb. The larger the engine, the less it is able to run at constant power and the more it must follow the load as in a conventional vehicle.

What are off-cycle emissions such as at full throttle acceleration to 75 mph? Air quality does not care whether emissions are on-cycle or off-cycle. If typical driving produces high emissions, then the value of low-emission certification is questionable.

What are lifetime, real-world emissions projected for this vehicle? This would include off-cycle driving, deterioration, malfunctions, negligence, tampering, and all the other things that happen over a vehicle's lifetime. Probably no one knows the answer, but it's a good question, because the answer, times the 200+ million cars in service, is what determine whether we have clean air or not.

I can answer the first question myself: I got about 60 MPG at 70 miles an hour.

-What about the climbing a 6% grade? I've never done that.
-What are off-cycle emissions such as at full throttle acceleration to 75 mph?
-What are lifetime, real-world emissions projected for this vehicle?
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"What is the mpg at sustained 70 mph?"

It will vary due to temperature, headwinds, slight grades, road surface, probably even phase of the moon. I'd say the 60 MPG is the low end of the range. I usually get between that and the occasional stretch of 100+ plus on the freeway part of my driving. Overall I'd guess 75-80 in summer, 5 mpg less in winter.

"What speed can be sustained up a 6% grade?"

It will sustain highway speeds on any stretch of road I've driven. The 6% grade ones around here have curves (and flatlanders who drive about 25 mph), so much more than 60 isn't easy, but I believe it's capable of it - you just have to get used to doing that in 2nd :)

The battery will be drained after about 1500 vertical feet if you keep trying for max assist, but the gas engine is quite capable of sustaining acceptable speed on its own.

I often drive a road that goes from 4500 ft to 8900 ft in about 12 miles. The Insight isn't a Porsche Turbo, but it's plenty fast enough to keep me cussing the flatlanders :)
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